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Title:
GASEOUS MERCURY CAPTURE
Document Type and Number:
WIPO Patent Application WO/2019/046882
Kind Code:
A1
Abstract:
The present invention relates to methods, systems and devices for safely and efficiently capturing gaseous mercury and removing the mercury from an environment. A device of the present invention may comprise a sorbent material, a porous body and a means of binding the sorbent material to the body. The gaseous mercury may be captured by such a device upon contact of the mercury with the sorbent material and, after use, be safely removed from the environment.

Inventors:
MCCARTHY, Damien (Macquarie University, c/- Balaclava RoadNorth Ryde, NSW 2109, AU)
EDWARDS, Grant (Macquarie University, c/- Balaclava RoadNorth Ryde, NSW 2109, AU)
Application Number:
AU2018/000169
Publication Date:
March 14, 2019
Filing Date:
September 07, 2018
Export Citation:
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Assignee:
MACQUARIE UNIVERSITY (Balaclava Road, North Ryde, NSW 2109, AU)
International Classes:
C02F1/28; B01D15/00; B01D53/02; B01D53/14; B01J20/02; B01J20/22; B01J20/30; B09C1/10; C02F3/34
Attorney, Agent or Firm:
SPRUSON & FERGUSON (GPO Box 3898, Sydney, New South Wales 2001, AU)
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Claims:
CLAIMS

1. A device for capturing gaseous mercury, comprising:

- a body of sufficient porosity to permit passage of gaseous mercury;

- a sorbent material that retains the gaseous mercury upon contact; and a binding means for associating the sorbent material with at least a portion of a surface of the body.

2. The device of claim 1 , wherein the body is a fibrous body.

3. The device of claim 2, wherein the body is produced from natural fibres.

4. The device of claim 3, wherein the body is produced from coconut fibres or coir matting.

5. The device of claim 2, wherein the body is produced from synthetic fibres.

6. The device of any one of claims 1 to 5, wherein the device is flexible.

7. The device of any one of claims 1 to 6, wherein the sorbent material is selected from the group consisting of metal halide crystals, coconut pith bio char or activated char.

8. The device of claim 7, wherein the metal halide crystals are copper(l) iodide crystals.

9. The device of claim 7 or claim 8, wherein the metal halide crystals are present at between about 200 g/m2 and about 1200 g/m2.

10. The device of claim 9, wherein the metal halide crystals are present at between about 200 g/m2 and about 300 g/m2.

1 1. The device of claim 9, wherein the metal halide crystals are present at between about 500 g/m2 and about 600 g/m2.

12. The device of claim 9, wherein the metal halide crystals are present at between about 450 g/m2 and about 800 g/m2.

13. The device of any one of claims 1 to 12, wherein the binding means is a polymeric material.

14. The device of claim 13, wherein the polymeric material comprises silicone or natural rubber.

15. The device of claim 14, wherein the polymeric material consists of silicone.

16. The device of any one of claims 1 to 15, wherein the binding means is gas-permeable.

17. The device of any one of claims 1 to 16, wherein the ratio of sorbent material to binding means is between about 3: 1 w/w and 1 :3 w/w.

18. The device of claim 17, wherein the ratio of sorbent material to binding means is about 1 : 1 w/w.

19. A method of producing a device of any one of claims 1 to 18, the method comprising the steps: applying the binding means to the body; applying the sorbent material to the body; and allowing the binding means to dry or cure on the body.

20. The method of claim 19, further comprising the step of pre-treating the body before applying the binding means and the sorbent material to the body.

21. The method of claim 20, wherein the pre-treating step comprises treating the body with at least one of the group consisting of: a solvent, water, an acid, and a base, or combinations thereof.

22. The method of claim 20 or claim 21 , wherein when the body comprises fibres, the step of pretreating the fibres comprises:

a) Solvent extraction of raw fibres in 100% acetone for about24 hours;

b) Washing the fibres with distilled water;

c) Solvent extraction of the fibres in a 1 :2 mixture of 70% ethanol and 100% benzene for about 24 hours;

d) Washing the fibres with distilled water;

e) Drying the fibres;

f) Soaking the fibres in a 5% NaOH solution for about 1 hour; and

9) Washing the fibres with distilled water.

23. The method of any one of claims 19 to 22, further comprising the step of adding a solvent to the binding means before application of the binding means to the body.

24. The method of claim 23, wherein the solvent is selected from the group consisting of ethyl acetate, ethanol, isopropyl alcohol, xylene and mineral spirits.

25. The method of claim 23 or claim 24, wherein the solvent is ethyl acetate.

26. The method of any of claims 23 to 25, wherein the ratio of binding means to solvent is between about 1 :2 w/w and 1 :8 w/w.

27. The method of claim 26, wherein the ratio of binding means to solvent is about 1 :5 w/w.

28. The method of any one of claims 19 to 27, wherein the steps of applying the binding means to the body and applying the sorbent material to the body are performed simultaneously.

29. The method of any one of claims 19 to 28, wherein the binding means and the sorbent material are combined in a mixture before application to the body.

30. The method of any one of claims 19 to 29, wherein each of the applying steps are performed by spraying, rolling or dipping or combinations thereof.

31. A method of removing mercury from an environment, comprising: exposing the device of any one of claims 1 to 18 to the environment, such that the device contacts and captures gaseous mercury from the environment.

32. The method of claim 31 , wherein the environment is selected from the group consisting of: an atmosphere or a gaseous mixture; a body of water; contaminated soil; a waste site contaminated with mercury; a mine; a mining waste site; sediment, or a construction site.

33. The method of claim 32, wherein the atmosphere or gaseous mixture is a gaseous waste stream, a gaseous product stream or a gaseous discharge stream.

34. The method of any one of claims 21 to 33, further comprising the step of volatilizing the non-volatile mercury in the environment.

35. The method of claim 34, wherein the volatilizing step comprises: applying to the environment microbial cells that volatilize non-gaseous mercury forms.

36. The method of claim 35, wherein the microbial cells are bacteria or microalgae.

37. The method of claim 36, wherein the bacteria include the merA gene.

38. The method of claim 36 or claim 37, wherein the bacteria are selected from the Pseudomonas genus

39. The method of any one of claims 36 to 38, wherein the bacteria are selected from the Pseudomonas fluorescens group.

40. The method of any one of claims 36 to 39, wherein the bacteria are Pseudomonas veronii.

41. The method of claim 35, wherein the microbial cells are applied to the environment as a composition comprising: microbial cells that volatilize the non-gaseous mercury in the environment, wherein the microbial cells are immobilized by a polymer.

42. The method of claim 41 , wherein the polymer is a biopolymer.

43. The method of claim 41 or claim 42, wherein the polymer is water-soluble such that on contact with water said microbial cells are mobilized.

44. The method of any one of claims 41 to 43, wherein the biopolymer is selected from the group consisting of alginate and xanthan gum.

45. The method of any one of claims 41 to 44, wherein the composition further comprises: a particulate substrate, wherein the microbial cells are immobilized by a polymer, and the polymer is fixed to a surface of the particulate substrate.

46. The method of claim 45, wherein the particulate substrate is inert.

47. The method of claim 45, wherein the inert particulate substrate comprises a zeolite-based material.

48. The method of any one of claims 41 to 47, wherein the composition further comprises a water soluble nutrient.

49. The method of any one of claims 31 to 48, wherein the device is arranged to partially or completely surround, cover or overlay the environment.

50. The method of any one of claims 31 to 49, further comprising the step of removing captured mercury from the device.

51. The method of claim 50, comprising: exposing the device comprising captured mercury to a solvent capable of dissolving the binding means for a time and under conditions to dissociate the binding means and captured mercury from the body and collecting the captured mercury.

52. A method of producing the composition defined in any one of claims 41 to 51 , the method comprising the steps: inoculating the polymer with the microbial cells; and applying the inoculated polymer to the particulate substrate.

53. The method of claim 52, wherein the applying step includes adding the inert particulate substrate to the inoculated polymer.

54. The method of claim 53, wherein the applying step includes spraying the inert particulate substrate with the inoculated polymer.

55. A method of treating a solid and/or liquid contaminated with mercury, the method comprising: i) encapsulating microbial cells adapted to volatilize mercury with a polymer; ii) attaching the encapsulated microbial cells to an inert particulate substrate; iii) mixing the encapsulated microbial cells and substrate with the contaminated solid and/or liquid;

iv) releasing said microbial cells from said biopolymer to volatilize mercury; and v) positioning the device of any one of claims 1 to 17 in gaseous contact with the contaminated solid and/or liquid.

56. The method of claim 55, wherein the contaminated solid comprises soil.

57. The method of claim 55 or claim 56, wherein the inert particulate substrate comprises a zeolite-based material.

58. The method of any one of claims 55 to 57, wherein the biopolymer is water soluble and the microbial cells are released on contact with water.

59. The method of any one of claims 55 to 58, further comprising the step of adding suitable nutrient to the contaminated solid and/or liquid.

60. A method of treating a solid and/or liquid contaminated with non-volatile mercury, the method comprising: mixing the composition defined any one of claims 41 to 51 with the contaminated solid and/or liquid; positioning the device of any one of claims 1 to 18 in gaseous contact with the contaminated solid and/or liquid; wherein the device of any one of claims 1 to 18 captures the gaseous mercury emitted from the contaminated solid and/or liquid.

61. A kit for removing mercury from a solid and/or liquid contaminated with non-volatile mercury, comprising: a composition defined in any one of claims 41 to 51 ; and a device of any one of claims 1 to 18.

62. Use of the kit of claim 61 in the method of claim 60.

Description:
GASEOUS MERCURY CAPTURE

Technical Invention

[0001] The present invention relates to methods and systems for capturing gaseous mercury. Background

[0002] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

[0003] Various chemical forms of mercury enter the natural environment due to anthropogenic emissions from activities such as burning fossil fuels, mining and other industrial activities. The release of mercury-containing compounds from such industrial processes into the environment, either via liquid discharge or gaseous release, may result in substantial contamination of natural areas such as soil and rivers. Such mercury pollution can impact how that land or water is then used. For instance, in order to expand residential areas, remediation of these areas prior to any approval for residual housing may be required.

[0004] Significant mercury levels in the environment are of particular concern, as mercury, known to be toxic to humans and animals in all its forms, is a potent neurotoxin that bioaccumulates in marine and terrestrial food webs. Mercury accumulation can have serious consequences for human health and indeed other organisms and natural ecosystems. Humans may be exposed to mercury in a variety of forms, such as lipophilic methyl mercury compounds as well as other small molecule mercury-containing compounds, including elemental mercury vapour. The toxicity of these mercury-containing compounds is largely due to mercury's strong affinity for sulphur-containing organic compounds at the cellular level, such as enzymes or proteins, and for lipophilic mercury species to accumulate in fatty tissues, such as the myelin sheaths surrounding the central nervous system neurons.

[0005] Acute mercury toxicity can have adverse effects throughout the body, including on the central nervous and renal systems, as well as the cardiovascular, digestive, immune, endocrine and reproductive systems and may result in death. The effect of mercury poisoning on humans is well known. There have been many notable historical mercury pollution disasters. In the 1800's, the hat making industry used mercury in the curing of animal pelts. Poor ventilation in workshops led to inhalation and accumulation of mercury in the body of workers and subsequent toxicity. At the time the symptoms were poorly understood and were thus diagnosed as insanity, leading to the term "mad as a hatter" being coined. In the 1970's, Iraqi grain contaminated with mercury impacted wildlife, water supplies, and subsequently human health, leading to 6500 poisoned and 450 dead. From 1932-1968, in Minamata Japan, Chisso Corporation dumped an estimated 27 tons of methyl mercury in local waters. The local population's diet consisted largely of fish. It took years for symptoms to show, with the first indications being seen in cats, then in humans. 10,000 people have been diagnosed with Minimata disease, of which 3,000 died. The recently promulgated United Nations Environmental Program (UNEP) treaty on Mercury is a global treaty to protect human health and the environment from the adverse effects of mercury was named the Minamata Convention as a result.

[0006] Interestingly, it has been found that certain bacteria, fungi and plants have evolved mechanisms for resisting the toxic effects of mercury and metabolizing certain chemical forms of mercury in the environment. Significantly, these bacteria, fungi and plants play a major role in the global cycling of mercury in the natural environment. Accordingly, the ability of these bacteria and fungi to remove mercury from soil and water have been previously investigated and they have been found to volatilize the mercury contamination, thereby removing it from the soil or water, but it remains in the overall mercury cycle.

[0007] Remedial decontamination of environments, such as soil, to remove mercury is an extremely costly and, in many cases, inconsistent process. In terms of in-situ bio-remediation strategies, whereby soil is treated at the site without being removed for treatment, the transport and mixing of suitable bacterial or fungal cultures into the soil for treatment is extremely difficult. Further, the bacteria and/or fungi added to the site merely removes the mercury from being bound in the soil and volatilizes it as elemental mercury, rather than removing it from the mercury cycle.

[0008] Therefore, there is a need for a device or method for the capture of mercury in its gaseous form in a cheap and efficient manner. Preferably, the device or method would safely remove the mercury from the mercury cycle.

Summary of the Invention

[0009] In a first aspect of the present invention, there is provided a device for capturing gaseous mercury, comprising: a body of sufficient porosity to permit passage of gaseous mercury; a sorbent material that retains the gaseous mercury upon contact; and a binding means for associating the sorbent material with at least a portion of a surface of the body. [0010] The following options may be used in conjunction with the first aspect, either individually or in any suitable combination.

[001 1] The body may be fibrous. When the body is fibrous, it may be produced from natural and/or synthetic fibres. Natural fibres suitable for producing the body may include coconut fibres or coir matting.

[0012] The device of the first aspect may be, and for certain application is preferably, flexible.

[0013] The sorbent material may be selected from the group consisting of metal halide crystals, coconut pith bio char or activated char. When the sorbent material is metal halide crystals, they may be copper(l) halide crystals. Metal halide crystals may be present in the device at amounts between about 200 g/m 2 and about 1200 g/m 2 , or between about 200 g/m 2 and about 300 g/m 2 , or between about 500 g/m 2 and about 600 g/m 2 , or between about 288 g/m 2 and about 576 g/m 2 , or between about 450 g/m 2 and about 800 g/m 2 .

[0014] The binding means may be a polymeric material. When the binding means is a polymeric material, it may comprise silicone or natural rubber, or it may consist of silicone. The binding means may be gas permeable. The ratio of sorbent material to binding means may be between about 3: 1 w/w and about 1 :3 w/w, or it may be about 1 : 1 w/w.

[0015] In an embodiment, the device of the present invention efficiently captures gaseous mercury. In this embodiment, the body comprises a fibrous body produced from natural fibres. The sorbent material comprises crystals of a copper(l) halide which has been applied at the rate of 288 g/m 2 . The binding means comprises a gas-permeable silicone which is applied to the body so that the device, once the silicone is cured, remains flexible. The ratio of sorbent material to binding means in this embodiment is about 1 : 1 w/w.

[0016] In a second aspect of the present invention, there is provided a method of producing a device of the first aspect, the method comprising the steps: applying the binding means to the body; applying the sorbent material to the body; and allowing the binding means to dry or cure on the body.

[0017] The following options may be used in conjunction with the second aspect, either individually or in any suitable combination. [0018] The method of the second aspect may also comprise an additional step of pre- treating the body before applying the binding means and the sorbent material to the body. This pre-treating step may comprise treating the body with at least one of the group consisting of a solvent, water, an acid, a base or combinations thereof. When the body comprises fibres, the step of pretreating the fibres may comprise:

a) Solvent extraction of the fibres in 100% acetone for 24 hours;

b) Washing the fibres with distilled water;

c) Solvent extraction of the fibres in a 1 :2 mixture of 70% ethanol and 100% benzene for about 24 hours;

d) Washing the fibres with distilled water;

e) Drying the fibres;

f) Soaking the fibres in a 5% NaOH solution for about 1 hour; and

g) Washing the fibres with distilled water.

[0019] The method of the second aspect may also comprise an additional step of adding a solvent to the binding means before application of the binding means to the body. When used, the solvent may be selected from the group consisting of ethyl acetate, ethanol, isopropyl alcohol, xylene and mineral spirits. The solvent may be ethyl acetate. The ratio of binding means to solvent may be between about 1 :2 w/w and about 1 :8 w/w. The ratio of binding means to solvent may be about 1 :5 w/w.

[0020] The steps of applying the binding means to the body and the sorbent material to the body may be performed sequentially or they may be performed simultaneously. When the sorbent material and the binding means are to be applied simultaneously, the two components may be applied to the body individually or they may be combined in a mixture before application to the body. The applying steps may be performed by spraying, rolling or dipping or any other suitable means.

[0021] In an embodiment, the device of the present invention may be produced by mixing the binding means with ethyl acetate at a ratio of about 1 :5 w/w, effectively diluting the binding means, when the binding means is a polymer. A sorbent material may be added to the polymeric binding means and the resultant mixture applied by spraying to the body, rolling or dipping the body in the mixture, or any other suitable means. [0022] In a third aspect of the present invention, there is provided a method of removing mercury from an environment, comprising: exposing the device of the first aspect to the environment, such that the device contacts and captures gaseous mercury from the environment.

[0023] The following options may be used in conjunction with the third aspect, either individually or in any suitable combination.

[0024] The environment to be treated by the device of the present invention may be selected from the group consisting of: an atmosphere or a gaseous mixture; a body of water; contaminated soil; a waste site contaminated with mercury; a mine; a mining waste site; sediment; or a construction site. When the environment is an atmosphere or gaseous mixture, it may be a gaseous waste stream, a gaseous product stream or a gaseous discharge stream. The device may be arranged so as to surround the waste site. The atmosphere may be a gaseous waste stream or it may be a gaseous product stream.

[0025] The method of the third aspect may further comprise the step of volatilizing the mercury in the environment. Once volatilized, the mercury can be captured by a device of the first aspect. When used, this volatilization step may comprise applying to the environment microbial cells that volatilize non-gaseous mercury forms. The microbial cells may be bacteria or they may be microalgae. When the microbial cells are bacteria, the bacteria may possess the merA gene. The bacteria may be selected from the Pseudomonas genus, for instance it may be a member of the Pseudomonas fluorescens group. It may be Pseudomonas veronii.

[0026] The microbial cells may be added to the environment to be treated in any suitable manner. In one example, the microbial cells may be in the form of a composition. The composition may comprise the microbial cells which are immobilized by a polymer. The polymer may be water-soluble, such that on contact with water, the microbial cells are released or mobilized. The polymer may be a biopolymer. The biopolymer may consist of alginate or xanthan gum.

[0027] The composition may be fixed to the surface of a particulate substrate. The substrate may be an inert particulate substrate. The inert particulate substrate may comprise a zeolite- based material, or it may be zeolite.

[0028] The composition may further comprise a water soluble nutrient. [0029] The device of the first aspect of the device used in the method of the third aspect of the present invention may be produced, configured or arranged to partially or completely surround, cover or overlay the environment. The device may be arranged so that all, or substantially all, of the gaseous mercury is captured from the environment.

[0030] The method may further comprise the step of removing the captured mercury from the device. This step may comprise soaking the used device in a solvent capable of dissolving the binding means, and removing the body from the solvent, thereby retaining the binding means and the sorbent material in the solvent. This allows for safe disposal of the mercury and reuse of recycling of the clean device body.

[0031] The composition described above may be produced by a method comprising the steps: inoculating the polymer with the microbial cells; and applying the inoculated polymer to the inert particulate substrate. The applying step may include adding the inert particulate substrate to the inoculated polymer, or it may include spraying the inert particulate substrate with the inoculated polymer

[0032] In a fourth aspect of the present invention, there is provided a method of treating a solid and/or liquid contaminated mercury, the method comprising: i) encapsulating microbial cells adapted to volatilize mercury with a polymer; ii) attaching the encapsulated microbial cells to an inert particulate substrate; iii) mixing the encapsulated microbial cells and substrate with the contaminated solid and/or liquid; and iv) releasing said microbial cells from said polymer to volatilize mercury; and v) positioning the device of the first aspect in gaseous contact with the contaminated solid and/or liquid.

[0033] The following options may be used in conjunction with the fourth aspect, either individually or in any suitable combination.

[0034] The contaminated solid may comprise soil. The inert particulate substrate may comprise a zeolite-based material. The polymer may be water soluble and the microbial cells may be released on contact with water.

[0035] The method of the third or fourth aspects may further comprise the step of adding a suitable nutrient to the contaminated solid and/or liquid or to the composition comprising the immobilized cells. The addition of a nutrient may produce a self-sustaining microbial cell colony. [0036] In a fifth aspect of the present invention, there is provided a method of treating a solid and/or liquid contaminated with non-volatile mercury, the method comprising: mixing the composition described in the third aspect with the contaminated solid and/or liquid; positioning the device of the first aspect in gaseous contact with the contaminated solid and/or liquid; wherein the device captures the gaseous mercury emitted from the contaminated solid and/or liquid.

[0037] In a sixth aspect of the present invention, there is provided a kit for removing mercury from a solid and/or liquid contaminated with non-volatile mercury, comprising: a composition described in the third aspect; and a device of the first aspect.

[0038] The kit of the sixth aspect may be used in the method of the fifth aspect.

[0039] The present invention also discloses a method of treating gaseous mercury from a waste site comprising providing a body sufficiently porous to permit passage of said gaseous mercury, binding to said body a compound adapted to capture and render said mercury inert, and applying said body to the site to contact said gaseous mercury emitting from said waste site.

[0040] The present invention also discloses a means for treating gaseous mercury comprising a body of sufficient porosity to permit passage of gaseous mercury or mercury vapour with a compound adapted to capture and render said mercury inert being bound to the body whereby upon contact with said gaseous mercury or mercury vapour, said compound binds and reacts with said mercury.

[0041] In one embodiment, the body is a blanket or mat of fibres. In one embodiment, the compound bound to the mat is copper(l) iodide most preferably in crystalline form. The copper(l) iodide can be bound to the mat in various forms but in one embodiment it is embedded in a silicone matrix. On contact with the mercury gas or vapour the mercury is stripped from the gas/vapour and binds/reacts with the copper iodide crystal to form copper tetra iodide mercurate. This is understood to be due to the copper(l) iodide bound to the fibres of the mat catching and chemisorbing the mercury atoms as the gas passes there through.

[0042] In another embodiment, the present invention discloses a method of treating contaminated waste to be optionally used with the aforementioned method of capturing the gaseous mercury or mercury vapour, said method comprising: i) encapsulating within a biopolymer, microbial cells adapted to volatilize mercury included in said waste;

ii) attaching said encapsulated microbial cell to a inert particulate substrate; iii) mixing said cells and substrate with said waste; and

iv) releasing said microbial cells from said biopolymer to volatilize mercury in said contaminant.

[0043] In another aspect, the present invention provides a means for treating waste contaminated with mercury comprising microbial cells adapted to volatilize said mercury in the waste, encapsulated in a biopolymer and fixed to an inert particulate substrate such that upon mixing with the body of waste and release of said microbial cells into said waste, said mercury is volatilized to escape from said waste.

[0044] In a particularly preferred embodiment, these microbial cells are encapsulated and immobilised in a suitable biopolymer and supported on a zeolite substrate. Xanthan gum is shown to be a particularly suitable biopolymer for this purpose.

[0045] In a particularly preferred embodiment, it is preferred that sufficient microbial cells are applied to the soil such that the self-sustaining population is established. Generally, the bacterial and fungal colonies all face competition within the soil environment. Preferably, suitable nutrients or other soil conditioning methods may be applied to ensure long term survival of the colony.

[0046] In one preferred embodiment, the strain of microbial cells used could be quite unique such that their nutrient source is one which only the unique cells can metabolise. This would avoid competition with other organisms and potentially ensure long term survival of the colony.

[0047] In another broad aspect, the present invention comprises a system of treating mercury contaminated waste comprising applying to the waste the aforementioned means for treating waste contaminated with mercury, and applying the abovementioned means for capturing gaseous mercury to capture and render inert mercury emissions from said waste.

[0048] The present invention therefore provides a holistic approach for treatment of mercury contaminated soil comprising the aforementioned zeolite particulate substrate with bacteria/fungal cells supported thereon and the aforementioned fibrous body for placement over the waste to capture and render inert said mercury emissions. Description of the Drawings

[0049] The present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a comparative graph of total mercury content of various fibrous bodies before and after exposure to gaseous elemental mercury;

Figure 2 is a graph showing the mercury capture ability of three replicates of coir matting, coated with silicone and copper(l) iodide crystals, in a stream of between 4000 and 6000 ng/m 3 gaseous mercury over 45 hours;

Figures 3 and 4 are SEM images of fibres coated with a material to treat gaseous mercury in accordance with a further embodiment of the present invention;

Figures 5 and 6 are SEM images of raw coconut fibre for use with the present invention;

Figures 7 and 8 are SEM images of pre-treated fibres in accordance with the present invention;

Figure 9 is a graph of the release of gaseous elemental mercury (GEM) over time from soils contaminated with mercury, wherein one sample is not inoculated with microbes capable of volatilizing mercury, and one sample is inoculated with mercury-volatilizing Pseudomonas veronii.

Figure 10 is a graph of the functionality of microbial cells in a composition as described in the third aspect when applied to soils contaminated with mercury;

Figure 1 1 is a comparative graph of gaseous oxidized mercury omissions for soil both with and without treatment according to the present invention;

Figure 12 is a graph showing the ability of coir matting treated with three different concentrations of copper(l) iodide to capture gaseous elemental mercury (GEM). This graph shows:

A: baseline levels of GEM in apparatus; B: the effect of coir matting only on the GEM flux, where no appreciable effect on GEM flux is detected;

C: coir matting treated with silicone and 4g of copper(l) iodide is inserted into the GEM stream for 2 hours, retarding substantially all of the GEM through sorption over this time;

D: 4g treated coir matting removed from GEM stream, GEM returns to baseline;

E: coir matting treated with silicone and 2g of copper(l) iodide is inserted into the GEM stream for 12 hours, retarding substantially all of the GEM through sorption over this time;

F: 2g treated coir matting removed from GEM stream, GEM returns to baseline; and

G: coir matting treated with silicone and 1g of copper(l) iodide is inserted into the GEM stream for 18 hours, retarding substantially all of the GEM through sorption over this time.

Definitions

[0050] As used herein, the term "gaseous mercury" refers to any mercury-containing chemical species that is gaseous, or a vapour, under usual environmental conditions, including elemental mercury and oxidized mercury. This term may be used interchangeably with the term "mercury vapour".

[0051] As used herein, the term "capturing" refers to a process whereby a chemical species, usually in a gaseous or vapour phase, is preferentially retained by the capturing material, by absorbing, adsorbing, chemisorbing, reacting or otherwise being immobilised and retarded from passage through the material, and is not easily released or desorbed therefrom.

[0052] The term "environment" as used herein refers to immediate surroundings, and is not necessarily limited to natural features or locations. In other words, "environment" is used to refer to the "local environment" such as the solids, liquids, gases, and mixtures thereof in the general vicinity, rather than a broader definition of "environment" to include places, locations or natural features.

[0053] The term "atmosphere" as used herein refers to "any gaseous envelop or medium", or generally any mixture of gasses, rather than referring to any special or particular construct. [0054] As used herein, the term "sorbent material" refers to any material that is capable of strongly absorbing, adsorbing or chemisorbing a particular chemical species. In the present invention, it is understood that the sorbent material is capable of absorbing, adsorbing or chemisorbing gaseous mercury. "Chemisorbing" is understood in the art to refer to a process whereby a chemical reaction occurs on the surface of the sorbent in order to retain the adsorbate.

[0055] As used herein, the term "polymeric" refers to a material formed from polymer chains, wherein "polymer chain" refers to a chemical species that is formed from the linkage of smaller chemical compounds into a larger compound. Similarly, the term "biopolymer" used herein refers to a polymeric material that is produced by a biological source, such as a microbial cell or higher organism such as a fungus or a plant.

[0056] As used herein, "silicone" refers to a polymeric material formed from the

polymerisation of siloxane compounds. This term may be interchangeably used with

"polysiloxane".

[0057] As used herein, the term "between", when used in reference to a range of values, includes the stated end points. Thus, for example, "between" 1 and 6 includes 1 , 2, 3, 4, 5 and 6.

[0058] The term "comprises" means "includes". Variations on the word "comprises", such as "comprising" and "comprise", have corresponding meanings. As used herein, the terms "including" and "comprising" are non-exclusive. As used herein, the terms "including" and "comprising" do not imply that the specified integer(s) represent a major part of the whole.

[0059] The term "consists of as used herein means "to the exclusion of other additional components purposefully added", or "only the following recited elements are intended to be present". Additional components may be present in the defined composition or device provided that they are not intentionally present.

Description of Embodiments

[0060] The present invention relates to the capture of gaseous mercury or mercury vapour and rendering it inert. The gaseous mercury may be emitted from a contaminated waste site, or it may be found in an industrial waste or product stream, or any other environment that comprises gaseous mercury. It is envisaged that the capturing of gaseous mercury is performed by use of a device that comprises a body of sufficient porosity to permit passage of gaseous mercury, a sorbent material for retaining the gaseous mercury upon contact, and a binding means for associating the sorbent material with at least a portion of a surface of the body. The inventors have discovered that this combination is effective in capturing gaseous mercury and it is advantageously adaptable for application to a wide range of mercury contaminated sites.

[0061] In one form, the device may be a fibre mat or blanket to capture and treat gaseous mercury emissions from a site of environmental mercury contamination. The term "fibres" herein does not refer to material made solely or only of fibres. Any material which allows the passage of a mercury gas or vapour is envisaged. In another form, the device may be a filter or similar for use in an industrial process, whereby the filter removes gaseous mercury from a gaseous stream. The following detailed description conveys exemplary embodiments of the present invention in sufficient detail to enable those of ordinary skill in the art to practice the present invention. Features or limitation of the various embodiments described do not necessarily limit other embodiments of the present invention or the present invention as a whole. Hence, the following detailed description does not limit the scope of the present invention, which is defined only by the claims.

Mercury Capture I Sorbent Material

[0062] The present invention relates to the capture of gaseous mercury forms, including gaseous elemental mercury as well as gaseous oxidized forms of mercury. This capture may be achieved by any chemical or physicochemical process that results in gaseous mercury being strongly bound and hence removed from the atmosphere or environment that is contaminated with the gaseous mercury. Whilst it may be anticipated that the bulk of the gaseous mercury would be captured by the sorbent material described herein, other components of the device that are in contact with the gaseous mercury may also

absorb/adsorb some of the mercury. For instance, due to the known tendency of oxidised mercury to readily deposit onto a surface, some of the oxidised mercury may adsorb directly onto the binding means and/or body material in use.

[0063] The sorbent material used in the device of the present invention, which is

responsible for capturing most of the gaseous mercury when in contact, may be any suitable sorbent material which selectively binds to, or strongly associates with, gaseous mercury. In this regard, an effective sorbent material is any material capable of binding to gaseous mercury, but which does not readily release said mercury, thereby resulting in substantial mercury capture from a gaseous mercury source.

[0064] The sorbent material may be substantially organic or carbon-based, or substantially inorganic, in nature. For instance, a carbon-based sorbent material may be an activated charcoal. The activated charcoal may be sourced from a renewable source, such as coconut pith bio char, bamboo charcoal, or activated char, or it may be from a fossil or non-renewable source, such as petroleum pitch. Alternatively, the sorbent material may be substantially inorganic or it may be partially inorganic. For instance, halogens, sulfur-containing compounds and transition metal-halide complexes are known to react with, or strongly bind to, gaseous mercury. In some embodiments, the sorbent material may comprise a combination of organic sorbent material and inorganic sorbent material. For example, it is known in the art that doping an activated carbon material with sulfur can increase the affinity of the doped activated carbon for mercury when compared to the activated carbon without sulfur.

[0065] As it is known in the art, halogens, sulfur-containing groups and transition metal-halide complexes are known to react with or bind to gaseous mercury. Accordingly, chemical species such as these are candidates for use as a sorbent material in the device of the present invention. Importantly, however, in order to act as a sorbent material, the material must be capable of binding to, and remaining in contact with, the body of the device. Any sorbent material that evaporates, sublimates, becomes liquid and drops from, is water soluble and may leach from the body of the device, or is removed or separated from the binding means in any way, either before or after mercury capture, would not be appropriate for use. Hence, diatomic halogens (e.g., bromine, iodine and chlorine) would likely not be useful as sorbent materials as they may leach from the device before or after mercury capture. However, transition metal halides of general formula [M n+ X n ], wherein M is a transition metal atom, X is a halogen and n is both the oxidation state of the transition metal and number of halogens, may be suitable for use as a sorbent material. One preferred example is copper(l) iodide, which is known in the art as being both water insoluble and reactive with gaseous mercury. Contact between copper(l) iodide and elemental mercury is believed to form the insoluble cuprous tetraiodide mercurate ([Ci^UHg]) complex, however other similar metal halide complexes could also be utilised. Generally, the metal halides are used in the device of the present invention as crystals, due to the preferred aqueous insolubility required of the sorbent material to produce an environmentally stable device. [0066] As mentioned above, copper(l) iodide crystals are the preferred compound for capturing and rendering the gaseous mercury or mercury vapour inert but other compounds could be used including coconut pith bio char and activated charcoal. It is known in the art that activated charcoal for instance is an efficient mechanism for capturing mercury vapour. Other compounds are usable but since it is preferred that the desired product is to be insoluble, stable and environmentally safe, copper(l) iodide is preferred. Copper(l) iodide also has a greater affinity for mercury compared to activated charcoals, meaning that less sorbent material can be applied for an equivalent outcome.

[0067] When metal halide crystals are used as the sorbent material, they may be present at a coverage of between about 200 g/m 2 and about 1200 g/m 2 , such as between about 200 and about 400 g/m 2 , about 400 and about 600 g/m 2 , about 288 and about 576 g/m 2 , about 300 and about 500 g/m 2 , about 350 and about 550 g/m 2 , about 450 and about 800 g/m 2 , about 600 and about 1200 g/m 2 , about 900 and about 1200 g/m 2 , about 500 and about 1 100 g/m 2 , about 600 and about 1000 g/m 2 , about 250 and about 750 g/m 2 , about 300 and about 900 g/m 2 , or about 300 and about 600 g/m 2 , such as about 200, 250, 288, 300, 350, 400, 450, 500, 550, 576, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1 100, 1 150, or 1200 g/m 2 .

[0068] The mechanism of action for the sorbent material to capture the mercury may vary depending on the sorbent material. For example, and without being bound to theory, when the sorbent material comprises an activated charcoal, the gaseous mercury may adsorb to the charcoal in a physicochemical manner (i.e., without a substantial chemical reaction, although there may be chemical-based interactions). Alternatively, when the sorbent material comprises a metal halide, the gaseous mercury may react with the metal halide to form a different inorganic complex, thereby chemically absorbing, or chemisorbing, the mercury. As an example, when copper(l) iodide is the metal halide sorbent material, it is theorised that upon contact with gaseous mercury, a red or brown copper(l) iodide mercurate complex is formed, although the precise reaction between copper(l) iodide and gaseous mercury is poorly understood.

Body

[0069] The structural basis for the device of the present invention is the portion described herein as the body. [0070] The body of the device of the present invention may be porous, such that the gaseous mercury may pass through the body. This porosity allows for a greater surface area of the device to contact the gaseous mercury and hence provides more efficient mercury capture. This porosity also allows other gasses that are not adsorbed by the sorbent material (i.e., gasses other than gaseous mercury) to pass through the body of the device, allowing the device to act like a filter, or to allow gasses on either side of the device to exchange. For example, if the device is placed over soil, the porosity of the body will allow gas to freely leave the soil, and for atmospheric gasses such as oxygen to access the soil underneath.

[0071] The body of the device may comprise a single active layer or region, or it may comprise multiple active layers or regions. The term "active" refers to a layer or region of sorbent material that is capable of adsorbing, absorbing or chemisorbing a chemical species from the gasses passing through the porous body (i.e., may be active in capturing a gaseous chemical species). Each layer or region may sorb the same chemical species, or they may each sorb different species. When present, the layers may be arranged so as to be

substantially parallel relative to each other, or the regions may be arranged so as to be distinct areas along the length and/or breadth of the device. For instance, it is envisioned that a device of the present invention may be effective in cleaning flue gases resulting from the combustion of coal, by combining mercury capture (as disclosed herein) with other active layers or regions that each sorb, for example, NO x and SO x species. Such a combination device may provide a cost-effective solution to the remediation of such flue gases.

[0072] The porous body of the present invention may be fibrous. The fibrous body can be made of any natural or synthetic material which allows the passage of the gaseous mercury or mercury vapour to contact the compound such that it can capture and render said mercury inert. In other words, it may be formed wholly or substantially from fibres or fibrous material. The fibres may be naturally occurring fibres, such as fibres produced from coconut husk (i.e. , coir), flax, hemp, jute, bamboo, pine, silk and cotton. In a particularly preferred embodiment, coconut fibres or coir matting/mulch may be used. The fibres may be synthetic fibres, or fibres that are not naturally occurring. Examples of synthetic fibres includes, but is not limited to, nylon, acrylic, polyester, glass or metallic fibres.

[0073] The fibrous body may be in any suitable form including a mat or blanket of material. Various forms of fibrous body other than mats or blankets can also be used, such as tubular pipe inserts or other three-dimensional shapes. One of the advantages of a mat or blanket produced from natural fibres is that the fibres are cheap, renewable, very tough and have the desired mechanical characteristics. Additionally, natural fibres such as coir degrades in the environment after several years, meaning that used devices, once cleaned of mercury, are not expected to contribute significantly to landfill and can advantageously biodegrade or be reused or repurposed, such as use as a geotextile.

[0074] The fibrous body according to the present invention may, in certain embodiments, be uniquely adapted to capture and treat gaseous mercury leaving a waste product. As will be discussed below, the present invention also involves a technique for releasing such gaseous elemental mercury from waste. However, it will be appreciated by the skilled addressee that the method and means of treating mercury emissions according to the present invention can also be used in other environments, for instance where mercury is emitted in its gaseous elemental form or gaseous oxidised form.

[0075] The body of the present invention may be rigid or it may be flexible, depending upon the conditions that the device is to be deployed under and/or the materials used in producing the body. For example, if used as an industrial filter, a rigid body may be preferred, whereas when used as a ground covering in soil remediation, a flexible body may be preferred for ease of transport (i.e., can be rolled up) and/or use (i.e., easier to cover non-flat surfaces).

[0076] Preferably the fibres of the body, when used, undergo a pretreatment step to assist in attachment of the binding means and sorbent material. Natural fibres, such as coconut fibre, can be used in their raw form, however in some instances some natural fibres have a coating of wax or oils which may interfere with binding of the sorbent material and binding means to the fibre. To enhance adhesion of the binding means, for instance a silicone gel, to the fibre, it is preferred that the fibres are pre-treated, such as by the methods described herein, to remove wax and oil from the surface of the fibre prior to coating with the binding means.

Binding Means

[0077] The device of the present invention is designed to be deployed in an atmosphere or environment of gaseous mercury contamination or production, such that the device captures the gaseous mercury, and the device can then be removed from that environment for disposal of the mercury residue. In order to achieve this, the sorbent material of the present invention must be bound to, or in fixed relationship to, the body of the device. Hence, the present invention includes a binding means for associating the sorbent material with at least a portion of a surface of the body. [0078] As defined above, a binding means may be a physical element or a process used to achieve the result of associating the sorbent material with the body. For instance, the binding means may be a material which binds to the surface of the body and also to the sorbent material, embedding or partially embedding the sorbent material into the binding material. The binding means may be a gas-permeable material, which would allow the gaseous mercury to access any embedded sorbent material. The binding means may be a polymeric material, such as silicone, natural rubber, natural latex, polyethylene, polypropylene, or polyamide. Preferably, when the binding means is a polymeric material, the polymer is not cross-linked. This allows the captured mercury to be recovered.

[0079] The mercury can be recovered by any suitable means. According to one aspect, the device of the present invention is exposed to or treated with a solvent. As the polymeric binding means is not crosslinked, it is amenable to be dissolved in or by solvent. As long as a solvent is used that is capable of dissolving the polymeric binding means, the mercury dissociates from the body of the device in bound crystalline form along with the polymeric binding means, leaving the body substantially devoid of sorbent material and binding means (i.e., cleaned). The cleaned body is then removed and can be dried and recoated with sorbent material and used again, recycled or repurposed, such as installed as a geotextile, or disposed of. Once exposed to solvent, the binding means may separate or detach from the body in any suitable manner. For instance, the polymeric binding means may slough from the body by gravity or some other passive means, or it may be removed actively via centrifugation or some other active means. The solvent may then be evaporated off (or extracted), and the small amount of polymeric material which is heavily impregnated with the mercury may then either be disposed of or further treated to separate the metal species from the polymer through known techniques. This recovery process is particularly suited to devices that utilise silicone as the binding means, although any non-cross-linked polymer capable of being redissolved after curing could be utilised for this mercury recovery process.

[0080] The binding means may also conceivably be a process, rather than a material. For instance, metal halide crystals could be grown on the surface of the body, wherein the binding means is the crystallisation of the sorbent material on the surface of the body. Alternatively, the binding means could be adsorbed or absorbed by the body material itself, such as a fibrous body absorbing an iodine solution.

[0081] The ratio of sorbent material to binding means may be between about 3: 1 w/w and about 1 :3 w/w, such as between about 3: 1 and about 1 : 1 w/w, about 1 : 1 and about 1 :3 w/w, about 2: 1 and about 1 :2 w/w, about 2: 1 and about 1 : 1 w/w, or about 1 : 1 and about 1 :2 w/w, for example about 3: 1 w/w, 2: 1 w/w, 1 : 1 w/w, 1 :2 w/w or 1 :3 w/w. The ratio will depend upon the properties of the sorbent material and the binding means, whereby the sorbent material must be present in an amount to effectively capture mercury, yet must fall within any inherent limitation of the binding means to bind both the sorbent material and the body. For instance, as exemplified below, copper(l) iodide and silicone may be present in a 1 : 1 w/w ratio for effective gaseous mercury capture.

[0082] In a particular embodiment, a mat or blanket made of coconut fibre or coir is treated with a compound such as copper(l) iodide crystals, which are adapted to capture the gaseous mercury and render it inert. In the example of copper(l) iodide crystals, these may be bound to the coconut fibre mat using a silicone or natural rubber. The mat or blanket is placed over the soil to trap and treat the gaseous elemental mercury leaving the soil by contact with the copper iodide crystals.

Manufacture

[0083] Also herein described is a method for producing the device described above.

[0084] The method for producing a device comprises the steps of applying the binding means to the body, applying the sorbent material to the body, and allowing the binding means to dry or cure on the body, thereby retaining the sorbent material in association with the body. As would be evident to the skilled person, the sorbent material must be bound to, or held in association with, the body of the device. This association is achieved by either the use of a binding material, or some other binding means as described above.

[0085] In most embodiments, it is envisaged that the binding means is a material capable of binding to both the body and the sorbent material. In these embodiments, the binding material is applied to the body. To assist in the application of the binding material to the body, such as to reduce the viscosity or density of the binding material and to optimise the coverage of the binding material over the body, a solvent may be added to the binding material before application to the body. The solvent added to the binding material preferably only acts to dilute or dissolve the binding materials, rather than change the chemical properties of the material, although the skilled person would appreciate that certain chemical modifications, such as to improve the adhesion of the binding means to the sorbent material, may be beneficial. For example, when the binding means is silicone, solvents for addition to the silicone include, but are not limited to, ethyl acetate, ethanol, isopropyl alcohol, xylene and mineral spirits.

[0086] When adding solvent to the binding material before application to the body, the solvent may be added in a ratio of between about 1 :2 w/w and about 1 :8 w/w, for instance between about 1 :2 w/w and about 1 :5 w/w, about 1 :3 w/w and about 1 :6 w/w, about 1 :4 and about 1 :8 w/w, about 2:5 and about 1 :7 w/w, about 1 :4 and about 1 :5 w/w, or about 1 :6 and about 1 :7 w/w, such as about 1 :2 w/w, 1 :3 w/w, 1 :4 w/w, 1 :5 w/w, 1 :6 w/w, 1 :7 w/w, or 1 :8 w/w.

[0087] The binding material may be applied to the body separately from the sorbent material, for example the binding means may be applied to the body and, before curing or drying of the binding material, the sorbent material is applied and adheres to the binding material. Alternatively, the binding material and the sorbent material may be applied to the body simultaneously. This may involve applying both the binding and sorbent materials at the same time but with separate applications (i.e., both materials sprayed on to the body via separate nozzles but at the same time), or it may involve premixing the binding and sorbent materials together and then applying the mixture. Whether applied separately or simultaneously, any suitable application steps may be performed to apply the materials to the body. Preferably, the binding means and sorbent material are applied in such a way so as to achieve an even distribution of materials over the maximum surface area on the surfaces of the porous body. For instance, the binding material, the sorbent material or a mixture thereof may be applied by spraying or rolling the body with the material or by dipping the body in the material, or any combination thereof.

[0088] Once the sorbent material, and the binding material when used, is applied to the body, the material(s) may be left to dry or cure on the body before the device can be used. This ensures that the materials are not inadvertently removed from the device before use and hence reducing the efficiency of the device.

Use

[0089] One of the uses for the device of the present invention, as described above in detail, is in removing gaseous mercury from an atmosphere. This may be achieved by exposing the device to an atmosphere that comprises gaseous mercury. As described above, when the sorbent material comes into contact with the gaseous mercury, the mercury may be retained by the sorbent material and hence removed from the other gasses passing through the porous body of the device, or it may be otherwise retained by the device, such as by forming deposits on the surface of the device. The sorption method may be dependent on the chemical form of the mercury. For instance, gaseous elemental mercury may preferentially chemisorb to the sorbent material, whereas the oxidized forms of mercury may form deposits on any available surface, due to the tendency of oxidized mercury to do so. Either way, it is anticipated that both elemental mercury and oxidized mercury, when in gaseous form, would be retained by a device of the present invention.

[0090] Whilst the atmosphere to be treated does not need to be under any particular pressure or experience any particular velocity through the device, it must nonetheless be passed through the device for the most efficient usage. However, this transport can be achieved passively, for instance by placing the device over a gaseous mercury source, such as contaminated soil, and allowing the gaseous mercury to diffuse up and out of the soil and through the device. Where the device is used under increased velocity or pressures, the thickness of the device may likewise need to be increased to ensure optimal capture of the mercury. Alternatively, there may be uses for the device whereby the gaseous mercury-containing atmosphere is under pressure or velocity when passing through, such as when the atmosphere is an industrial gaseous waste stream. It is not anticipated by the inventors that the device would fail to operate under such conditions, so long as the materials of the device are chosen to withstand the conditions of the atmosphere being treated.

[0091] It follows that a method of using the device of the present invention may include the step of exposing the device to an atmosphere comprising gaseous mercury. It is envisaged that, once exposed to the gaseous mercury-containing environment, mercury capture will occur. The mercury-containing environment may be any gaseous mixture that includes gaseous mercury, irrespective of the concentration of said mercury. For example, the atmosphere may be found immediately above a site contaminated with mercury, such as a building site or a waste site, or some other mercury-contaminated site that emits gaseous mercury. In this example, the device may be placed over the contaminated site on an upper surface of the site, surrounding a solid waste site, or suspended above a liquid waste site. Whilst the skilled person could conceive of other uses for the device, such uses would be obvious so long as the device is in contact with the gaseous mercury emitted from the contaminated site.

[0092] Another potential use for the device of the present invention is in the capture of industrial sources of gaseous mercury, such as fossil fuel power plants or in the manufacture of a range of goods, such as electrical devices, cement and automotive parts. In such industrial settings, one potential use for the device described herein is as a filter component to remove gaseous mercury from gasses generated during operation. The mercury-containing gasses may be waste gases, such as the flue from a coal-fired power plant, or the mercury may be present in a product stream, whereby the gaseous mercury is present alongside the desired product of the process. These mercury-containing gasses may be passed through the device of the present invention and capture the emitted mercury, without the use of wet scrubbing techniques as currently used in the art.

Bioremediation

[0093] As described above, one potential use for the device of the present invention is in the capture of gaseous mercury emitted from environmental sites contaminated with mercury, such as waste sites (i.e., landfill) or building and construction sites whereby the soil is contaminated with mercury. Generally, sustained mercury contamination of soil or other solid contaminated sites is due to the presence of non-volatile mercury forms, such as methyl mercury, or the mercury being bound in larger bioinorganic complexes including, for example, organic acids or biopolymers naturally found in soils. Current techniques for rehabilitating sites contaminated with mercury are generally expensive, time-consuming and inefficient, particularly if removal of the contaminated material from the site, for decontamination off-site, is required. Accordingly, cheap and efficient in situ techniques for removing mercury from a contaminated site are highly desirable.

[0094] As it is known in the art of bioremediation, there are naturally occurring microorganisms and fungi that are capable of volatilizing non-gaseous forms of mercury. Whilst this approach has been used previously to successfully volatilise mercury, the current approach does not remove the mercury from the global mercury cycle. Rather, the mercury is merely removed from the contaminated site and discharged to the atmosphere, where it is oxidized and returned to ground and water sources and the cycle continues. It is therefore desired to remove the volatilized mercury at the site of volatilization to reduce the local environmental mercury load. The inventors propose that the device of the present invention may be suitable for this purpose, in combination with the pre-treatment of the site with appropriate microbial cells. As will be clear to the skilled addressee, remediation time (deployment) is quite variable - depending on starting concentration and very site-specific variables.

[0095] To achieve the aim of bioremediation using the device of the present invention, a suitable method for preparing, transporting and inoculating the contaminated site for treatment is required. However, as the transport of large quantities of liquid can be expensive and the contaminated sites may be hard to reach by heavy machinery, transport of aqueous cultures of the mercury-volatilizing bacteria, and the equipment required to inoculate the site with the microbes, may be undesirous and prohibitive. Instead, a more compact preparation of microbial cells which can easily be applied to the site for remediation is required.

[0096] In one solution to this problem, the inventors have created a composition combining microbial cells adapted to volatilize the non-gaseous mercury forms present in the contaminated site with a biopolymer to encapsulate the microbial cells. The microbial cells encapsulated with biopolymer may then fixed to the surface of an inert particulate substrate, or they may be prepared as beads or other shapes and used without a particulate substrate. In either form, this composition is advantageous as it may be easily stored and transported, may be stable for extended periods of time as the biopolymer protects the microbes, and may be easily applied to a contaminated site.

[0097] The particulate substrate, to which the biopolymer and microbe cells may be affixed, may be any suitable material that may be easily mixed through a soil or waste that is contaminated with mercury, but will not cause further pollution of the site being remediated and may even be beneficial to the soil once remediated. In one example, the particulate substrate is inert and may be particulate zeolite or a zeolite-based material. Zeolites are preferred as they are naturally occurring minerals that are generally beneficial to soils, are inert (i.e., chemically unreactive), are not particularly dense and can be easily mixed through soils using conventional methods. The inert particulate substrate may be an organic material that is capable of biodegrading in situ and/or providing nutrients to the encapsulated microbes.

[0098] The use of the substrate is a significant advantage as it provides for fast and reliable mixing of the microbial cells throughout the soil to be treated. As will be clear to a person skilled in the art, it is extremely difficult to provide thorough treatment in the soil unless the cells are adequately mixed through. Use of the zeolite particulate substrate allows the cells to be mixed through the soil by conventional means.

[0099] The microbial cells to be used in this composition may be bacteria or fungal cells and are adapted to volatilize mercury contaminated waste, particularly soil. Various bacterial or fungal cells may be used so long as they can achieve the volatilization of non-gaseous mercury and can be grown under laboratory conditions to allow efficient production of the composition for use. Without being bound to theory, it is preferred that the microbial cells harbour the merA gene or mer operon, which is believed to provide the microbial cells with the ability to metabolise and volatilize mercury.

[00100] The microbial cells may be bacterial cells. They may be species of Klebsiella or Pseudomonas or any other suitable bacterial species. The microbial cells may be Klebsiella pneumoniae. The microbial cells may belong to the Pseudomonas fluorescens group. They may be selected form the group consisting of P. azotoformans, P. brenneri, P. cedrina, P. congelans, P. corrugate, P. costantinii, P. extremorientalis, P. fluorescens, P. fulgida, P. gessardii, P. libanensis, P. mandelii, P. marginalis, P. mediterranea, P. migulae, P. mucidolens, P. orientalis, P. poae, P. rhodesiae, P. synxantha, P. tolaasii, P. trivialis and P. veronii.

[00101 ] In a particular embodiment, Pseudomonas veronii may be used.

[00102] The biopolymer that is used to encapsulate the microbial cells, and/or to fix the microbial cells to the surface of the inert particulate substrate, may be water soluble. Release of the cells into the soil can be accomplished by watering of the soil or by simply allowing rain or other precipitation to permeate the soil. Again, by thorough mixing of the microbial cells through the soil, remediation can commence immediately. A water insoluble biopolymer could be used for this purpose, although rupturing of the biopolymer and subsequent release of the microbial cells into the contaminated site will need to be achieved by other means, such as mechanical abrasion. A water-soluble biopolymer may also have additional advantages, such as being used by the microbes as an energy source in situ, leading to colonisation of the contaminated soils and/or increasing the viability of the microbial cells. If the viability of the microbial cells can be maintained for extended periods of time, this may lead to more complete volatilization of the mercury in the contaminated site. The biopolymer may be a polysaccharide or another polycarbohydrate, or a derivative thereof. It may be selected from the group consisting of alginate, xanthan gum, starch, guar gum, gum arabic and carrageenan. In one embodiment, the biopolymer is xanthan gum.

[00103] There are a number of significant advantages arising from immobilisation or encapsulation of the functional mercury volatilizing microbial cells, as they can be stored for long periods and efficiently and reliably transported to the treatment site. This has been a problem in the past where live cells have been used. [00104] As described above, the composition disclosed in the present invention provides an efficient and reliable mechanism for storage and transportation of functional mercury reducing microbial cells to mercury contaminated terrestrial sites for treatment.

[00105] The composition, comprising the microbial cells and the biopolymer, and optionally the inert particulate substrate, may further comprise a separate microbial nutrient. As described above, the addition of a nutrient to the composition may increase the activity or longevity of the mercury-volatilizing microbial cells, or may encourage or lead to colonisation of the contaminated site. This may result in more complete mercury volatilization (i.e., more of the total mercury present is removed).

[00106] The composition as described herein may be produced by inoculating the biopolymer with the microbial cells, and then applying the inoculated biopolymer to the inert particulate substrate. The inoculated biopolymer may be produced by mixing a culture of microbial cells with the biopolymer. The biopolymer may be powered and added to the culture, or the biopolymer may be in aqueous solution and added to the culture. The biopolymer may be made and exuded by the microbial cells themselves during culturing, resulting in an inoculated biopolymer mixture.

[00107] Once the inoculated biopolymer is mixed, it can be formed into beads or other shapes, or it may be coated onto the surface of the inert particulate substrate. Any suitable coating means can be used that results in a coating of viable microbe cells encapsulated by the biopolymer and fixed to the surface of the substrate. For instance, the inert particulate substrate can be added to a viscous inoculated biopolymer solution and shaken or stirred to coat the particles with the biopolymer. Spraying the inert particulate substrate with the inoculated biopolymer may also be performed, although the high pressures and/or temperatures that may be required to carry out this method may result in damage to the microbial cells and a drop in their overall viability, depending on the conditions used.

[00108] Also disclosed herein is a method of treating a solid and/or a liquid contaminated with mercury. Essentially, any site that is contaminated with mercury may be treated by this method. The method comprises encapsulating microbial cells, adapted to volatilize mercury, within a biopolymer and either forming small beads or the like, or attaching the encapsulated microbial cells to an inert particulate substrate. The encapsulated cells and substrate are then mixed through the contaminated solid and/or liquid, and the microbial cells are then released from the biopolymer so that they can volatilize the mercury. The volatilized mercury is then captured by a device as described herein, which is positioned so as to be in gaseous contact with the treated site. The release of the microbial cells may be achieved by rupturing the biopolymer encapsulating the microbial cells. This release may be achieved by applying water if the biopolymer is sufficiently water soluble, or by any other means, such as mechanical or chemical means, so long as the microbial cells are viable when they enter the contaminated environment. The mixing of the encapsulated cells and substrate with the solid and/or liquid to be treated may be performed using conventional means, for example spreading over the surface using a mechanical spreader, mixing through the contaminated solid with a plough or similar apparatus, or a combination thereof. Non-limiting examples of environments to be treated using this method may include dry soil, swamps, industrial sites, mining sites, natural waterways (i.e., lakes, rivers, creeks and the like) and the surrounding land, and waste sites such as landfills, mining tailings or runoff, or evaporation ponds.

[00109] In this method, the selection of biopolymer, inert particulate substrate and microbial cells are the same as those considered above in regards to the microbe-based composition and the same considerations may be equally applied here.

[001 10] An alternative method for treating a solid and/or liquid contaminated with non-volatile mercury comprises mixing a composition as described above, which comprises an inert particulate substrate, a biopolymer and microbe cells adapted for volatilizing mercury, with the contaminated solid and/or liquid, and positioning a device as described above so as to be in gaseous contact the contaminated solid and/or liquid. The device, being in gaseous contact with the contaminated site being treated, may then capture the mercury being volatilized by the microbial cells upon contact with the sorbent material of the device, thereby removing the mercury from the environment.

[001 1 1 ] In order to carry out this method, it is envisaged that a kit may be produced, wherein the kit comprises a microbial composition as described above and a mercury capture device as described above.

Examples

Example 1 - Mercury capture concept

[001 12] Figure 1 shows the effects of various treatments on the ability of coconut husk fibres to capture gaseous elemental mercury (GEM) emissions. The treatments, described below, include no treatment (i.e., raw fibres), silicone applied to raw fibres, fibres cleaned of their outer waxy layer (pre-treated), and pre-treated fibres coated in silicone and copper(l) iodide crystals.

[001 13] A plume of constant concentration gaseous elemental mercury (GEM) was created by heating a small bead of liquid mercury in a 100 ml glass vessel secured in a waterbath held at constant temperature of 50°C. Fibres were bundled together such that when placed in the plume, they were snugly secured within the opening rim of the glass vessel. Fibres were exposed for 60 mins, then removed and placed in sealed sterile glass containers and stored securely until testing.

[001 14] Various pre-treatments of the fibres were tested for their efficiency in sorbing mercury from GEM. Four treatments are presented below.

1 ) Untreated fibre - no treatment other than cutting fibres to sufficient size

2) A solution of 8% w/v silicone gel dissolved in THF was made and raw fibres

submerged, then THF evaporated off over 24 hrs under fumehood

3) Solvent extraction of raw fibres using double solvent of 100% acetone for 24 hours followed by 1 :2 70% ethanol/100% benzene for 72 hours with rinsing with dH 2 0 between extractions. Fibres were then air dried and soaked in 5% NaOH solution for 1 hour and rinsed with dH20.

4) The above (3), followed by a suspension of roughly 1 : 1 : 1 w/w/w 100% silicone caulking gel and ethyl acetate solvent and Cul crystals such that a pasty consistency is formed and then fibres are simply mixed through this paste and removed and excess removed and allowed to dry. This is known as treatment [R2SiO] n + Cul in Figure 1.

[001 15] Fibres for this example were derived from pre-manufactured coir (coconut fibre) mat. Any treatment prior to this experiment was unknown. In fact, the "raw" fibres seem to have quite high pre-existing mercury content at several hundred ppb (see Table 1 ). The fibres that underwent solvent extraction (see treatment 3 above) as a pre-treatment saw a tenfold decrease in mercury content hence they have a much lower starting "before" reading (see Table 1).

[001 16] Figure 1 provides data on mercury content before and after one hour exposure for the four treatments. It will be noted that testing determined mercury content on fibres before and after exposure using a pre-calibrated Milestone Direct Mercury Analyser. [001 17] It can be seen from Table 1 that for the [R2SiO]„ + Cul treatment, there is a large increase in mercury attached to the fibre, a figure 194 times higher than it's starting concentration. This compares very favourably to the other treatments although all samples showed an increase in mercury content. In terms of mercury capture, efficiency is measured simply by a ratio of mercury content before and after exposure to GEM (see Table 1 below), where the following is noted: - [R2SiO] n + Cul > NaOH > Untreated > 8% silicone.

Table 1

[001 18] In this particular experiment, we were unable to continue measurements past the 1 hour mark. However, of note is that the fibres coated with silicone and copper iodide crystals after this 1 hour exposure do not show any noticeable change in colour, although they show a greatly increased mercury content. This is significant, as the copper(l) iodide forms a red complex upon chemisorption of mercury. With no discernible colour change after 1 hour exposure, this indicates that the [R2SiO] n + Cul material has capacity for capturing mercury that extends significantly beyond the 1 hour exposure of the present experiment. Further, as the 8% silicone was ineffective as a sorbent material on its own, the increase in mercury in the [R2SiO]„ + Cul sample must be due to the chemisorption by copper(l) iodide.

[001 19] Fibres were also exposed to a GEM plume for 24 hours although no measurement of mercury content was conducted. The stripping and capture of mercury from the plume is actually visible on the 24 hour exposed fibres as they had changed colour to a reddish tinge. This is the colour of the expected compound copper(l) tetra iodide mercurate arising from the predicted reaction between the mercury and copper iodide crystals. At this point it was not clear what is the precise mercury content at this point but it is assumed that it would be significantly (orders of magnitude) higher than 9718 (see [R2SiO]n+Cul above). Example 2 - High concentration mercury capture

[00120] In this example, fibres were treated as outlined in Example 1 above, and exposed to GEM at a higher mercury flux. In this experiment, about 3ml liquid mercury was placed in a Teflon bottle housed in a water bath and held at constant temperature to create a gaseous mercury plume. The gas was fed to a Tekran Mercury vapour analyser which had been pre- calibrated. A coir fibre filter (47mm diameter, 6mm thickness, weighing 1.4 g prior to addition of silicone and copper iodide) was added to the apparatus. A mixture of 5: 1 ethyl acetate to silicone (by weight) was homogenized so that silicone was fully dissolved. The coir fibre was then soaked in the solution and allowed removed and allowed to dry for 30 mins. Copper(i) iodide (1g) was then applied to the partially dry disc.

[00121 ] The treated coir fibre disc sample was placed such that the mercury stream passed wholly through the disc. This was done at the 3 hour mark of Figure 2, and as seen, the mercury level reaching the Tekran instrument drops to zero. This disc was kept in the stream for 45 hours. Two more replicates were then tried, both for 45 hours.

[00122] At around 141 hours, untreated coir fibre was tried. As can be seen, this has no effect on mercury levels.

[00123] Whilst it is noted that the background levels of mercury fluctuated between 4000 and 6000 ng/m 3 , it is not expected that this fluctuation significantly impacted the result obtained, as all three samples did not reach saturation after 45 hours in the mercury stream.

Example 3 - Fibres

[00124] Figures 3 and 4 are SEM images of the fibres before the exposure. The magnification of Figure 3 is 350x where the general surface morphology is clear, and for Figure 4 magnification is at 1000x where the copper iodide crystals can be seen as a dense outer coating. (No change in morphology at this scale was noted in the "after" exposure to GEM images.)

[00125] Figures 5 to 8 are SEM images to show why the solvent extraction and 5% NaOH bath treatment are preferred. As shown in Figs. 5 and 6 coconut fibres naturally have a coating of wax and oils that may interfere with the binding of silicone gel to the fibre. To enhance adhesion, wax and oil is removed from the surface of the fibre prior to silicone coating as shown in Figures 7 and 8. Example 4 - Microbial composition

[00126] Referring to Figures 9 and 10, these graphs show the release of gaseous elemental mercury (GEM) from soil contaminated with mercury. In these experiments, soil samples of contaminated mine tailings were obtained. For each replicate, two trays of the same size were prepared with soil sampled from the contaminated mine tailings. Both trays had the same volume of water added, either 50% or 15% v/v, as a pre-treatment. One tray was then treated by mixing through zeolite that had bacterial cells fixed to the surface, whilst the other (control) had an equivalent amount of zeolite added that was not coated in bacteria. The trays were continuously monitored for mercury levels using a Tekran 2537 Automated mercury analyser, which was attached to a mercury flux chamber situated directly above the sample and control trays. Gaseous elemental mercury levels were monitored using the Tekran 2537 analyzer, whilst oxidized mercury levels were monitored using appropriate CEM filters appropriately attached to the apparatus. Background levels were continuously monitored during this time.

[00127] Figure 9 shows the results for the 50% v/v water added experiment, and Figure 10 shows the results for when 15% v/v was added to the soil as a pre-treatment. Each graph shows a comparison of soil treated with zeolite-immobilised Pseudomonas veronii, against a controlled experiment without application of such microbial cells, only zeolite. In each of Figures 9 and 10 background emissions were a positive flux of 2 ng Hgm 2 p/h, and only the GEM results are shown.

[00128] The zeolite particles with suitable microbial cells affixed thereto are mixed with the soil and the gaseous elemental mercury (GEM) emission is measured. The effect of the microbial cells on GEM emission was substantial. It can be seen in Figure 9, there is a substantial increase in the level of GEM emissions using the immobilised Pseudomonas veronii cells. Indeed at around 80 hours into the experiment the level of GEM emission was so high it could not be adequately measured.

[00129] Figure 10 also shows a substantial increase in GEM emissions over the control though not as marked as Figure 9. Although it is not entirely clear why this occurs, it is hypothesised that release of the cells in Figure 9 may be more marked due to the increase in water content.

[00130] In both experiments, it can be seen that there is a substantial increase in gaseous elemental mercury (GEM) emissions for the soil/waste treated with these zeolite-immobilised cells. Example 5 - Inert particulate substrate

[00131 ] Turning now to Figure 1 1 , this diagram is a comparison between mercury contaminated soils and the result of gaseous oxidised mercury emissions in soil treated with zeolite versus the zeolite-immobilised cells according to the present invention.

[00132] To explain, mercury is mainly found in its oxidised form in soil. Some of this is oxidised mercury naturally emitted via volatilisation in a gaseous form (GOM). Pseudomonas veronii cells are able to take up oxidised mercury when in the soil, reduce it via a redox reaction to elemental form and then emit it as gaseous elemental mercury (GEM). Accordingly, it can be seen in Figure 10 that soil treated according to the present invention reduces the naturally occurring gaseous oxidised mercury (GOM) because the pseudomonas cells veronii with which the soil is treated take up oxidised mercury and thus reduce the overall load of oxidised mercury in the soil that could be emitted as GOM.

[00133] The present invention provides a method and means for capturing gaseous mercury or mercury vapour from waste. In particular it is useful for capturing and treating elemental mercury escaping from soil. In conjunction with the above-described zeolite immobilised cells, the system in accordance with the present invention can treat mercury contaminated soil or waste rapidly and relatively inexpensively.

[00134] It is expected that using the present inventive approach, mercury contaminated soil or waste could be treated to liberate large quantities of any mercury contained therein. While remediation time for the present invention is highly variable due to starting concentration and site specific conditions, the aforementioned method and means for capturing and treating the thus released mercury by way of a fibrous body can then be used in a safe and reliable manner to capture the thus emitted mercury.

[00135] Once the mercury leaves the soil and is captured in the fibrous mat or blanket, the mercury can be recovered via solvent extraction and the mat or blanket can be reused.

Example 6 - Gaseous mercury capture

[00136] Figure 12 shows the ability of a device of the present invention to capture gaseous elemental mercury (GEM). In this series of experiments, a testing apparatus similar to that used in Example 2 above was used to measure the effect of the treated coir matting on GEM emissions. [00137] As can be seen in Figure 12, a background level of between about 410 and 450 ng Hg/m 3 /hr was measured (indicated as A in Figure 12), and maintained throughout the experiment. Once a relatively stable background was identified, an untreated coir matting sample was inserted into the GEM stream (indicated as B in Figure 12) and the flux of mercury passing through the matting was detected. As shown in this figure, there is no noticeable effect on the GEM concentrations reaching the detector, indicating that the matting alone is not capable of sorbing the GEM emissions.

[00138] At point C of Figure 12, the untreated coir matting is replaced with a device according to the present invention (sample #1). Sample #1 is an identical coir matting sample as used at timepoint B, except that has been treated first with silicone, then 4g of copper(l) iodide is added before the silicone is fully cured. The copper(l) iodide is hence bound to the coir matting by the silicone and retained in place as the silicone cures. As the area of the matting sample is 17.5cm 2 , this is equivalent to 1 , 152g/m 2 of copper(l) iodide.

[00139] The effect of sample #1 is complete elimination of the GEM flux through the treated coir matting. It is believed that this significant reduction in mercury flux is attributed to the presence of copper(l) iodide chemisorbing the mercury, rather than simple occlusion. This is supported by the data at time point D, which shows that, after 2 hours of sample #1 being in the GEM stream, the background levels returned immediately to the previous background, indicating that mercury was removed from this system by the treated coir matting.

[00140] At time point E, another device according to the present invention (sample #2) is placed into the testing apparatus. Sample #2 is prepared in the same manner as sample #1 , but with only 2g of copper(l) iodide added, resulting in an equivalent coverage of 576g/m 2 copper(l) iodide. As can be seen from Figure 12, for the full 12 hours following the insertion of sample #2, complete occlusion of the GEM flow in the analyser is again recorded. Notably, complete sorption of the mercury is recorded over the entire testing period for this sample, indicating that sample #2 had not reached mercury saturation. Following this 12 hour exposure to the gaseous mercury, at time point F sample #2 is removed from the analyser and baseline levels of GEM are quickly returned.

[00141 ] Sample #3, prepared in the same manner to samples #1 and #2 but with only 0.5g copper(l) iodide, equivalent to 288g/m 2 , was inserted into the GEM stream at point G of Figure 12. As can be seen from this figure, complete removal of the GEM stream was achieved by this sample for the full 18 hours of exposure. Again, no sign of saturation was seen, indicating that maximum mercury removal was not reached, even after 18 hours of exposure to 410-450 ng/m 3 GEM.

[00142] It will be appreciated that the present invention can be embodied in other forms without departing from the spirit or scope of the invention as defined.