Use of active charcoal and steel slag for binding contaminants in contaminated materials and composition comprising active charcoal, steel slag and contaminated material

Field of the invention [0001] The invention relates to the use of active charcoal for binding contaminants in contaminated materials and to a composition comprising active charcoal and contaminated material.

State of the art

[0002] In many industrial processes residues are produced for which useful applications as secondary building materials are being sought. Because these residues potentially contain high concentrations of contaminants, such as heavy metals and/or organic microcontaminants, which may be able to leach out, leaching standards have been established with which these contaminated materials must comply (the Building Materials Decree in The Netherlands). If the secondary building materials do not comply with leaching standards, techniques for improving the (leaching) quality of these materials can possibly be sought. For a number of contaminated materials that are used as secondary building material the leaching standards are structurally exceeded. [0003] The current techniques for reducing leaching of contaminants from granular residues (improving the quality) are usually targeted at specific adsorption of inorganic contaminants on mineral surfaces. This is usually done by adding iron and/or aluminium salts (such as FeCl ₃ , AlCl ₃ or Fe ₂ (SCM) ₃ ) or by addition of phosphate compounds in combination with neutralisation to an approx. neutral degree of acidity (pH). Because many metals have minimum solubility in this pH range, this pH control can increase the binding efficiency. In a number of cases these techniques can indeed reduce leaching of, for example, metals from the contaminated materials to acceptable values.

[0004] Another solution for improving the quality of (mainly salt-containing) residues is washing. In this case the residue is washed with (process) water, as a result of which the relatively mobile elements (salts, oxyanions and to a certain degree organically bound metals such as copper as well) seep out. One possible method for this treatment is specified in NL 1022176 C.

[0005] The quality of a number of residues (mainly combustion residues) can also be improved by stabilisation with cement (change of granular residue to mono lite) or by vitrification (melting of residues at high temperature). This latter technique in particular is very expensive and is therefore not widely used on a large scale. [0006] Leaching of organic microcontaminants is not influenced or is hardly influenced by the use of mineral additives. The addition of mineral additives (such as FeCl ₃ , AlCl ₃ or Fe ₂ (SCM) ₃ ) can also have the adverse side effect that leaching of salts such as chloride or sulphate is substantially increased. Chloride or sulphate, inter alia, are now already critical components in a number of industrial residues. Finally, the improvement in quality on the basis of specific adsorption of contaminants on mineral surfaces is regarded as an expensive technique because primary materials are employed.

[0007] A problem with the conventional techniques for improving the quality of residues (as contaminated materials) is that these have a relatively low efficiency. There are often cases where residues remain critical with regard to the leaching standards after treatment.

Summary of the invention

[0008] Therefore, one aim of the invention is to find an alternative and preferably better solution to the immobilisation of one or more contaminants in contaminated material.

[0009] Surprisingly, it is found that a composition comprising contaminated material and active charcoal provides a material that, for example, can be used in building and in constructions and that advantageously has a reduced leaching value for heavy metals such as copper. In a specific embodiment the invention provides a composition comprising contaminated material and active charcoal, wherein the composition contains 0.1-10 wt.%, preferably 0.1 - 4.5 wt.% active charcoal, based on the total amount of the composition.

[00010] Further, it is found that a composition comprising contaminated material and steel slag provides a material that, for example, can be used in building and in constructions and that advantageously has a reduced leaching value for oxyanions like Mo or for instance SO4 ^2" , Se and Sb. Hence, in a specific embodiment the invention provides a composition comprising contaminated material and steel slag, wherein the

composition contains 5 - 20 wt.% steel slag, based on the total amount of the composition.

[00011] Further, it is surprisingly found that a combination of active charcoal and steel slag can be used to bind contaminants in contaminated material. Hence, according to a further aspect of the invention, there is provided a composition comprising contaminated material, steel slag and active charcoal, wherein the composition preferably contains 2-30 wt.% steel slag and 0.1 - 10 wt.% active charcoal, based on the total amount of the composition (i.e. including contaminated material, active charcoal and steel slag). Preferably, the composition contains 2-25 wt.% steel slag and 0.1 - 10 wt.% active charcoal, more preferably 5-20 wt.% steel slag and 0.1 - 4.5 wt.% active charcoal (the remainder being contaminated material), based on the total amount of the composition.

[00012] An advantage of the use of active charcoal and steels slag together, is that leach out of a number of contaminants can substantially be reduced, whereas the presence of these additives active charcoal and steel slag may not substantially increase the leach out of other contaminants, especially when the above mentioned amounts of active charcoal and steel slag are used. Hence, in contrast to many prior art approaches, in this embodiment not a single contaminant is targeted, but a range of contaminants is targeted. It is known in the art that by solving the problem of leach out of one component, the leach out behaviour of other contaminants may disadvantageously be increased. Here, a more integral solution is provided which surprisingly solves or reduces the leach out of a number of contaminants while not promoting the leach out of a number of other contaminants. [00013] According to another aspect of the invention an application of active charcoal is provided for the immobilisation of contaminants in contaminated material, in particular for use in building and in constructions.

[00014] According to another aspect of the invention an application of steel slag is provided for the immobilisation of contaminants in contaminated material, in particular for use in building and in constructions. [00015] According to another aspect of the invention an application of steel slag and active charcoal is provided for the immobilisation of contaminants in contaminated material, in particular for use in building and in constructions.

[00016] According to yet another aspect of the invention a method is also provided for the immobilisation of contaminants in contaminated material, comprising mixing the contaminated material with active charcoal.

[00017] According to yet another aspect of the invention a method is provided for the immobilisation of contaminants in contaminated material, comprising mixing the contaminated material with steel slag.

[00018] According to yet another aspect of the invention a method is also provided for the immobilisation of contaminants in contaminated material, comprising mixing the contaminated material with steel slag and active charcoal.

Brief description of the figures

[00019] Figures 1-5 show leaching of Cu, Mo, SO4 ^2" , and Ba as a function of pH in untreated ("fresh") and artificially aged ("aged") MSWI (municipal solid waste incinerator) bottom ash and after the addition of various percentages of active charcoal thereto and/or steel slag.

Detailed description of the invention

[00020] In one embodiment, the invention relates to the addition of active charcoal to contaminated materials such as, for example, industrial residues, dredged material, residues from the clean-up of soil and contaminated soil which, in terms of leaching, are critical for heavy metals and/or organic microcontaminants. Active charcoal can be used as an additive to these materials (for example "in situ") in order to reduce leaching and the risk of spreading of contaminants. Surprisingly it is found that by use of the invention the contaminants in, for example, contaminated soil or bottom ash, etc., are immobilised. Because active charcoal does not degrade, or does not degrade to a significant extent, in the environment, this is a method that will also retain a permanent effect in the long term. Furthermore, one advantage of the use according to the invention can be that active charcoal has little to no effect on the pH of the contaminated material of the composition (in contrast to the method according to the state of the art where minerals are added). [00021] In another embodiment the invention relates to the addition of steel slag (either alone or in combination with active charcoal) to the contaminated materials. Steel slag can be used as an additive to these materials (for example "in situ") in order to reduce leaching and the risk of spreading of contaminants. Surprisingly it is found

that by use of the invention the contaminants, such as S, Se, Mo and Sb, in, for example, contaminated soil or bottom ash, etc., are immobilised (i.e. decrease of leach out).

[00022] Specific contaminated materials that can be treated according to the invention and provide a suitable constituent in the composition for, for example, use in building and in constructions are, inter alia, bottom ash (such as WI bottom ash), contaminated soil, dredged material and residues from clean-up of soil. Therefore, the contaminated material in the composition according to the invention is preferably a solid material, such as a solid granular material, or a viscous mass. Preferably the contaminated material comprises one or more materials selected from the group consisting of industrial residues (preferably bottom ash, in particular WI bottom ash and more in particular MSWI bottom ash), dredged material, residues from clean-up of soil and contaminated soil. In one embodiment polluted water does not fall under the contaminated material for use in the composition according to the invention. However, the invention may be applied to any solid contaminated material with risk of leach out of contaminants as especially herein indicated.

[00023] An important residue that can be used as contaminated material for improving the quality is WI bottom ash (this is the ash that is produced in the case of incineration in a waste incinerator) (especially MSWI bottom ash (this is the ash that is produced in the case of waste incineration in a municipal solid waste incinerator)). In The Netherlands approx. 1.1 million tonnes of this are produced annually; virtually 100 % of this residue is utilised as fill/base material in road in building and in constructions. An important sticking point here is the leaching of, inter alia, copper. This issue also arises at a European level. In The Netherlands a special category of leaching standards has currently been established for MSWI bottom ash in the Building Materials Decree, in which broader standards for, inter alia, copper have been incorporated. With effect from 1 January 2006 all MSWI bottom ash in The Netherlands must comply with the current leaching standards in the Building Materials Decree. Therefore, in one embodiment of the invention, contaminated material is understood to be industrial residues, in particular bottom ash, in particular WI bottom ash, in particular MSWI bottom ash.

[00024] Preferably, the composition, in particular a composition comprising bottom ash and active charcoal, contains less than 10 wt.% fly ash, more preferentially less

than approx. 5 wt.% fly ash, and the industrial residue consists mainly of bottom ash, preferably WI bottom ash.

[00025] Furthermore, the industrial residue is preferably WI bottom ash from domestic waste (obtained from a WI for domestic waste, i.e. MSWI). [00026] In another embodiment the industrial residue as source of contaminated material for the composition can also contain bottom ash that is obtained from the incineration of biomass, such as green waste.

[00027] Dredged material is understood to be the sediment that is removed from rivers, estuaries, lakes, canals and ditches, etc., by dredging work and can be severely contaminated with contaminants (metals and organic microcontaminants).

[00028] In the case of clean-up of soil there are often one or more fractions that remain that cannot be cleaned up or are too polluted to be re-used. This is usually the fine fraction of the soil (such as clay), which also does not have any good characteristics from the civil engineering standpoint. This material is referred to as "residue from the clean-up of soil". According to the invention, this material, in combination with active charcoal, is preferably used in combination with the addition of cement or cement-like binder material (= stabilisation).

[00029] Of course, combinations of materials can also be used. For instance, the composition according to the invention can contain, for example, bottom ash, (contaminated) soil and active charcoal, for example 0.1 - 4.5 wt.% active charcoal and 95.5 - 99.9 wt.% bottom ash and (contaminated) soil. In yet another embodiment, the composition according to the invention can contain, for example, bottom ash, (contaminated) soil and active charcoal, for example 0.1 - 4.5 wt.% active charcoal, 5- 20 wt.% steel slag and 75.5 - 94.9 wt.% bottom ash and (contaminated) soil.

[00030] In one embodiment the contaminated material is pretreated. In one embodiment this is effected by a method where the pretreatment comprises carbonation of the contaminated material in the presence of a CC>2-containing gas, such as, inter alia, described in US 5 928 128 (incorporated here for reference). As a result of this pretreatment the pH of the contaminated material (that is to say the pH of a suspension in which the contaminated material is suspended to determine the pH), and thus also of the composition, can change and the pretreated contaminated material can acquire a pH of approx. 8 - 10, preferably less than 10, more preferentially approx. 8 - 9. If this is

brought into suspension with water (at a liquid to solid ratio of 10 L/kg, as common in this field), untreated contaminated material as starting material, for example untreated freshly produced WI bottom ash, gives a pH of 10 to 11.5. Laboratory results indicate that the pH of the composition of bottom ash and active charcoal can change up to 0.5 units at 10 wt.% addition of charcoal. Because the addition of active charcoal has little or no influence on the pH, these pH values also apply to the composition that contains the (pretreated) material, that is to say if the composition according to the invention is brought into suspension with water, in one embodiment a pH of 10 to 11.5 is obtained if the contaminated material has not been treated with CO ₂ and a pH of 8 - 10, preferably less than 10, more preferentially approx. 8 - 9 is obtained for the composition according to an embodiment according to the invention (if brought into suspension (at a liquid to solid ratio of 10 L/kg)) if the contaminated material, for example bottom ash, has been treated with CO ₂ . Of course, other additions to the composition can have an influence on the pH. [00031] In another embodiment the contaminated material is first washed before it is mixed with active charcoal. In a preferred embodiment this washing is carried out by means of the process that is described in NL 1022176 (incorporated here for reference). [00032] Such a CO ₂ treatment and/or an optional washing treatment can be carried out before mixing the contaminated material with the active charcoal. In one embodiment the invention therefore provides a composition where the contaminated material has been pretreated.

[00033] In practice, however, the natural carbonation process will also be able to neutralise the pH by the uptake of CO ₂ from air and a composition according to the invention will be obtained which has a pH value of below 10 (if a portion of the composition, for example from a fill, has been removed from the construction after a specific period (for example a number of months or years) and were to be brought into suspension with water (at a liquid to solid ratio of 10 L/kg)).

[00034] Therefore, in one embodiment a composition is provided where the composition (which may or may not be used product), if put in water, gives a pH of 8 - 11.5 and in a specific embodiment a composition is provided where the latter, if put in water, provides a pH of 8 - 10, preferably less than 10 (either as a result of pretreatment or in a natural manner), preferably 8 to 9 (at a liquid to solid ratio of 10 L/kg).

[00035] In one embodiment the contaminants in the contaminated material are contaminants taken from the group consisting of metals and organic microcontaminants.

[00036] Organic microcontaminants are understood to be, for example, one or more from the group consisting of poly cyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and dioxins. In particular these contaminants can be immobilised surprisingly well by the addition of active charcoal. In this way the abovementioned materials in the composition according to the invention can still be advantageously utilised, whilst otherwise the material would possibly have to be stored, or could possibly be used only under specific safety measures.

[00037] Leaching of organic microcontaminants is not influenced, or is hardly influenced, by the use of mineral additives. It is found to be advantageous that these contaminants (which may or may not be bound to humic and/or fulvic acids) do bind strongly to active charcoal. This application is therefore also relevant in connection with possible future leaching standards.

[00038] In another embodiment the contaminated material contains one or more metals taken from the group consisting of lead, cadmium, iron, gold, copper, manganese, nickel, platinum, mercury, silver, zinc, tin, thorium and tungsten. In particular metals such as copper, nickel, zinc, lead and cadmium, and more particularly copper, can be immobilised. Whereas usually these metals (or elements) are leached out (and disseminated in the environment) or relatively expensive and/or inefficient removal or immobilisation methods have to be used, the composition according to the invention contaminated with these metals (or elements) may usefully and advantageously be utilised as, for example, building material. In this context the term metal in principle includes all bound forms thereof, both the free metal, the inorganically complexed metal and the organically complexed metal (for example bound to humic and/or fulvic acids), in particular organically complexed contaminants. Of course, the contaminated material can contain combinations of contaminants, such as copper and PAHs, copper and nickel, etc. [00039] The addition according to the state of the art of mineral additives (such as FeCl ₃ , AlCl ₃ or Fe ₂ (SOzI) ₃ ) can also have the adverse side effect that leaching of salts such as chloride or sulphate is substantially increased. These are now already critical components in a number of industrial residues.

[00040] Other relevant contaminants are contaminants selected from the group consisting of S (in the form Of SO ₄ ^2" ), Se and Sb and Mo.

[00041] This problem is in an embodiment at least partially prevented by adding active charcoal. In a preferred embodiment the invention provides an application of active charcoal in order to immobilise one or more of the abovementioned metals, lead, cadmium, iron, gold, copper, manganese, nickel, platinum, mercury, silver, zinc, tin, thorium and tungsten, in particular metals such as copper, nickel, zinc, lead and cadmium, as contaminants in contaminated material (materials) as well as the composition(s) obtained therewith. In a specific embodiment the contaminated material contains at least 1 mg/kg of one or more of the elements cadmium, copper, nickel, lead and zinc. In another specific embodiment the contaminated material contains at least 10 mg/kg of one or more of the elements cadmium, copper, nickel, lead and zinc. In yet another specific embodiment the contaminated material contains at least 100 mg/kg of one or more of the elements cadmium, copper, nickel, lead and zinc. A person skilled in the art will understand that these values relate to the total amounts of the elements but that the contaminants can be present in the form of free metal, the inorganically complexed metal and the organically complexed metal (for example bound to humic and/or fulvic acids). In one embodiment use can be made of contaminated materials such as, for example, industrial residues, dredged material, residues from the clean-up of soil and contaminated soil, which contain one or more of the following contaminants: 0.1 - 100 mg/kg Cd, 5 - 10000 mg/kg Cu, 7 - 5000 mg/kg Ni, 10 - 20000 mg/kg Pb and 1 - 10000 mg/kg Zn, based on the total amount of contaminated material. [00042] This problem is in an another embodiment at least partially prevented by adding steel slag. In a preferred embodiment the invention provides an application of steel slag in order to immobilise one or more of the abovementioned elements S (in the form of SO ₄ ^2" ), Se, Sb and Mo, as contaminants in contaminated material (materials) as well as the composition(s) obtained therewith. In a specific embodiment the contaminated material contains at least 500 mg/kg SO ₄ ^2- . In yet another specific embodiment, the contaminated material contains at least 0.1 mg/kg Se. In yet another embodiment, the contamination material contains at least 0.2 mg/kg Mo. In another embodiment, the contaminate material contains at least 0.1 mg/kg Sb. In yet a specific embodiment, the contaminated material contains one or more of the following

contaminants: 500 - 50000 mg/kg SO ₄ ^2" , 0.01 - 50 mg/kg Se, 0.2 - 200 mg/kg Mo and 0.1 - 500 mg/kg Sb, based on the total amount of contaminated material.

[00043] The contaminated material can also contain one or more organic compounds from the group consisting of humic acid (HA), fulvic acid (FA) and the smaller and more hydrophilic compounds (hydrophilic fraction, Hy, such as a wide variety of water-soluble organic compounds, for example sugars, proteins, amino acids or carboxylic acids). In addition to the possible initial presence of these organic compounds in the contaminated material, these compounds can also be produced and/or the quantity thereof can increase during use of a composition according to the invention. For example, in the composition according to the invention used as fill/base materials for roads, dikes, embankments, etc., organic acid can be produced by microbial processes for the degradation of vegetable and animal material in the vegetation possibly present above and possibly present alongside the composition and seep into the composition. In one embodiment the composition according to the invention contains 0.001-10 wt.%, preferably 0.01 - 10 wt.%, more preferably 0.001-5 wt.%, even more preferably 0.1 - 5 wt.%, of one or more organic acids, based on the total amount of the composition. In particular the invention is targeted at a composition containing, in addition to active charcoal, one or more compounds taken from the group consisting of humic acid and fulvic acid. Bottom ash, contaminated soil, residue from the clean-up of soil and dredged material, etc., can contain a certain amount of reactive compounds, such as humic and fulvic acids and inert carbon (specific surface area « 50 m ² /g, for example < 5 m ² /g). However, the presence of active charcoal (specific surface area of > 270 m ² /g, preferably > 300 m ² /g,) on its own provides in an embodiment one or more of the advantages of the invention.

[00044] In one embodiment of the invention a composition is provided containing 0.1 - 10 wt.%, more preferentially 0.1 - 4.5 wt.%, active charcoal, based on the total amount of the composition. Specifically, with these amounts a material is obtained where contaminants, such as copper, are immobilised well and where a material is obtained that can be used to economic advantage and with good physical properties in building and in constructions. In one embodiment it is found that with the addition of between approx. 0.1 and 10 wt.%, more preferentially 0.1 - 4.5 wt.% active charcoal to

WI bottom ash, or one of the other contaminated materials mentioned above, the leaching of copper can be reduced to approximately 2 orders of magnitude. The conventional techniques usually achieve a reduction of at most 1 order of magnitude, but usually less. The immobilisation efficiency (degree to which in particular metals, but also organic micro contaminants are immobilised) in the case of the addition of active charcoal for improving the quality is higher than in the case of the use of mineral additives. These conventional techniques for improving the quality bind only the inorganic metal complexes and the free metal ion. As a result the efficiency of this application is much lower than in the case of the method and application according to the invention where active charcoal is used as additive. With this method and application primarily the metals (and possibly organic microcontaminants) bound to dissolved humic and fulvic acids are immobilised; these are also frequently the dominant binding forms of a number of heavy metals (in particular copper), but also radionuclides and rare earths. The phrase "wherein the composition contains 0.1-10 wt.% active charcoal" and similar phrase refers to compositions comprising contaminated material and active charcoal, wherein the composition at least contains 0.1-10 wt.% active charcoal. The remainder will then be contaminated material (and optionally steel slag). [00045] In one embodiment active charcoal with a specific surface area greater than about 270 m ² /g, preferably greater than approx. 300 m ² /g, more preferably greater than approx. 500 m ² /g, and even more preferentially between approx. 700 and 1500 m ² /g (BET surface area) is used. The determination of the BET surface is known in the art and herein especially refers to the N ₂ adsorption at 200 ⁰ C. Furthermore, an active charcoal with a weighted average particle size of 0.05-10, more preferably 0.1 - 10 mm, preferably 0.2 - 5 mm, more preferentially less than approx. 5 mm, more preferentially less than approx. 2 mm, yet more preferentially less than approx. 1 mm, yet more preferentially less than 0.5 mm and yet more preferentially less than approx. 0.2, even more preferentially less than about 0.1 mm is used. Preferably the pore size is approx. 0.1 - 50 nm, preferably 0.2 - 20 nm.

[00046] Preferably an attempt is made to use industrial residues with a high content of active charcoal as the source of active charcoal in order to prevent primary materials having to be used for improving the quality of residues. In this context a distinction is

therefore made between industrial residue as contaminated material and industrial residue as source of active charcoal. This possible component of the composition is also referred to, inter alia, as industrial residue containing active charcoal. [00047] Therefore, an industrial residue with an active charcoal content can also be used instead of pure active charcoal. Preferably, the industrial residue contains at least 20 - 80 wt. %, more preferentially at least 40 - 90 wt.% active charcoal, based on the total amount of this industrial residue. In a preferred embodiment a composition is provided where the industrial residue comprises coke. If, for example, coke (such as A-coke; i.e. active cokes (see also below)) or fly ash from gasification of biomass is added as an alternative for active charcoal, the composition can contain up to approx. 60 wt.% of this coke, preferably approx. 0.5 - 30 wt.% of the industrial residue containing active charcoal, because this material can have a negative residual value (for example in The Netherlands). [00048] If use is made of such an industrial residue as the source of active charcoal, the active charcoal content can then optionally also be higher than, for example, 4.5 wt.% (as mentioned above). In one embodiment the invention is targeted at a composition containing 0.5 - 60 wt.% of the industrial residue containing active charcoal, more particularly 0.5 - 30 wt.%, based on the total amount of the composition, and 99.5 - 40 wt.%, more particularly 99.5 - 70 wt.% of the contaminated material (possibly including industrial residues such as bottom ash), respectively. Preferably the ratio of organic acids to active charcoal is approx. 1:1000, more preferentially approx. 1:100 and even more preferentially approx. 1:10 (mass ratios). [00049] In a specific embodiment the invention also provides a composition and method where the industrial residue containing active charcoal, such as coke, is pretreated, wherein the pretreatment comprises heating the industrial residue containing active charcoal at between approx. 800 and 1000 ⁰ C (for example 950 ± 30 ⁰ C) for approx. 2 hours (excluding heating-up time) in the presence of a water-containing gas. The specific surface area of the industrial residue can increase as a result of the pretreatment. A CC> ₂ -containing gas can also be chosen instead of or in combination with the water-containing gas in the case of a treatment at temperatures of between approx. 800 and 1000 ⁰ C. CO ₂ forms CO and creates new surface. CO must preferably be converted to CO ₂ in an after-treatment of the gas phase. In yet another embodiment a chemical pretreatment is used. The pretreatment of the industrial residue containing

active charcoal can optionally also include a grinding step. Preferably the material is pretreated in one or more ways so that the industrial residue containing active charcoal is provided that contains an active charcoal with a specific surface area of at least about 270 m ² /g, preferably at least about 300 m ² /g, preferably greater than approx. 500 m ² /g, and more preferentially between approx. 700 and 1500 m ² /g. It also possible that the industrial residue initially contains no or hardly any active charcoal, but does so after the pretreatment. Such an industrial residue, which is used as a source of active charcoal and which has to be pretreated, is also referred to as industrial residue containing active charcoal. [00050] Various types of cokes can be used. In one embodiment A-coke is used, i.e. brown coal coke that is used as flue gas purifier, in, for example, MSWI installations. After use, in a possible pretreatment, for example activation and/or removal or reduction of pollutants such as dioxin, a coke can be obtained (regained) which has a suitable active charcoal content. A-coke, also indicated as active cokes, is based on brown coal coke. Advantageously, this waste stream may usefully be applied in the invention as additive to bottom ash (and optionally steel slag).

[00051] Brown coal coke or pit coal coke, or other suitable cokes known to those skilled in the art, can also be used. In one embodiment the invention provides a composition where the coke containing active charcoal (as source of active charcoal) comprises one or more cokes selected from the group consisting of brown coal coke or pit coal coke. Preferably the composition contains 0.1 - 30 wt.%, more preferentially 0.5 - 10 wt.% and even more preferentially 0.5 - 4.5 wt.% of one or more of these types of coke, such as A-coke, brown coal coke or pit coal coke. Preferably the coke for use in the invention is a coke with a specific surface area of about 270 m /g or more, preferably greater than approx. 300 m /g, more preferentially greater than approx. 500 m ² /g, and even more preferentially between approx. 700 and 1500 m ² /g (BET surface area). Furthermore, a coke is preferably used as active charcoal that has a weighted average particle size of 0.1 - 10 mm, preferably 0.2 - 5 mm, more preferentially less than approx. 5 mm, more preferentially less than approx. 2 mm, even more preferentially less than approx. 1 mm, even more preferentially less than 0.5 mm and even more preferentially less than approx. 0.2 mm. For instance, for example, activated brown coal coke is used which has a particle size less than or equal to 0.2, more

preferentially less than or equal to 0.125 mm. Preferably, the pore size is approx. 0.1 - 50 nm, preferably 0.2 - 20 nm.

[00052] The advantage of the use of coke is that two (or more) residue streams may be combined in a composition that can advantageously be used in constructions instead of the starting materials having to be tipped, or possibly being able to be used, with specific protective measures. In addition, the use of active charcoal produced as a primary product is avoided by an embodiment using coke (e.g. spent A-cokes from flue gas cleaning of WI gas). [00053] The term "coke" is known in the art and may refer to a solid carbonaceous residue derived from bituminous coal such as pit coal and brown coal or other organic material such as lignite, wood, peat, coco-nut shells, etc. The volatile constituents of the coal (including water, coal-gas and coal-tar) may for instance be driven off by baking in an airless oven (i.e. pyrolysis / dry distillation) at temperatures as high as 1,000 ⁰ C (or higher) so that the fixed carbon and residual ash are fused together. Due to the heat treatment volatile components are removed and a porous structure is obtained (cokes). In this way, brown coal cokes, pit coal cokes, lignite coal cokes, etc. can be obtained from, brown coal, pit coal, lignite, etc., respectively. The specific areas of these cokes depend upon the kind of heat treatment. Active charcoal may be obtained, as known in the art, by a further chemical and/or steam treatment of the cokes. According to an aspect of the invention, as active charcoal, one or more of the materials selected from the group consisting of active charcoal, brown coal cokes, pit coal cokes and lignite coal cokes are used. The average energy density may be about 2-12 kWh/kg. [00054] Steel slag is a product of the steel making process. Once scorned as a useless byproduct, it is now accepted and, often, preferred and specified as it is known to be a valuable material with many and varied uses. A steel slag such as Blast Furnace Slag is formed when iron ore or iron pellets, coke and a flux (either limestone or dolomite) are melted together in a blast furnace. When the metallurgical smelting process is complete, the lime in the flux has been chemically combined with the aluminates and silicates of the ore and coke ash to form a non-metallic product called blast furnace slag. During the period of cooling and hardening from its molten state, BF slag can be cooled in several ways to form any of several types of BF slag products. A steel slag such as Steel Furnace Slag is produced in a (BOF) Basic Oxygen Furnace

(Basic Oxygen Steel making: BOS) or an (EAF) Electric Arc Furnace. Hot iron (BOF) and/or scrap metal (EAF) are the primary metals to make steel in each process. Lime is injected to act a fluxing agent. The lime combines with the silicates, aluminium oxides, magnesium oxides, manganese oxides and ferrites to form steel furnace slag, commonly called steel slag. Slag is poured from the furnace in a molten state. After cooling from its molten state, steel slag is processed to remove all free metallics and sized into products. BOF steel slag is also known as LD (Linz-Donawitz) steel slag. Steel slag from an Electric Arc Furnace is also known as EAF steel slag (or ELO ElektroBogenOfen steel slag). Steel slag may be applied herein with weight averaged particle sizes below about 10 mm, preferably below about 6 mm, more preferably below about 2 mm. Preferably, the steel has slag has a weight averaged particle size in the range of 0.1-10 mm, more preferably in the range of 0.2-6 mm, even more preferably in the range of 0.5-2 mm. [00055] The advantage of the use of steel slag is that two or more residue streams are combined in a composition that can advantageously be used in building and in constructions instead of the starting materials having to be tipped, or possibly being able to be used, with specific protective measures. Steel slag, bottom ash and optionally active charcoal (e.g. in the form of cokes) can be combined to provide useful materials.

[00056] The composition according to the invention contains in an embodiment a composition of active charcoal (or an industrial residue that can serve as a source for active charcoal) and contaminated material such that the composition preferably meets the Category 2 standard according to the Building Materials Decree, more preferentially the Category 1 standard according to the Building Materials Decree or other future European legislation in this field for the use of alternative building materials without restriction. These categories are described in the Dutch Building Materials Decree (Bulletin of Acts, Orders and Decrees of the Kingdom of The Netherlands, no. 567, pp 1-92, 1995) in which standards are specified for both granular materials (such as bottom ash) and shaped materials (for example after stabilisation with cement).

[00057] The composition according to the invention can be provided by means of a method comprising mixing the contaminated material with active charcoal (optionally using coke containing active charcoal as the source of the active charcoal). In one

embodiment the contaminated material and the active charcoal, optionally in the form of industrial residue containing active charcoal, can be mixed "on site" or "off site" using mobile mixing equipment. The addition of active charcoal and mixing can be operated either batchwise or completely continuously, a completely continuous process being preferred. The process can be operated either off site or on site because use can be made of mobile mixing equipment. The contaminated material and/or active charcoal (for example a coke containing active charcoal as the source of the active charcoal) can also be pretreated using the techniques described above, for example before mixing the components of the composition (comprising the components contaminated material and active charcoal). Likewise, steel slag can be mixed to the contaminated material, with or without the addition of active charcoal. [00058] Possible fields of application in the building and construction industry are, for example, as road base, as a replacement for sand in the case of fills, for stabilisation with cement/binders, after which the composition can be used as, for example, road base, and as lightweight fill material. The contaminated material preferably used as lightweight fill material (for example for fills in regions that are sensitive with regard to the relative density, for example on boggy ground, inter alia to prevent "settling" in the construction) is dredged material and/or residue from the clean-up of soil; bottom ash, contaminated soil, dredged material and residues from the clean-up of soil can be used for the other applications. Likewise, steel slag can be used in these applications, either alone or together with active charcoal.

[00059] The invention can, for example, be used for, for example, contaminated materials such as residues which are used as (secondary) building material, where leaching does not meet the valid leaching standards. The materials concerned here are, in particular, residues for which the leaching of contaminants (copper, nickel, zinc, lead, and cadmium) does not meet the criteria. In The Netherlands requirements as specified in the Building Materials Decree apply for these. At the European level work is currently being carried out on the Construction Products Directive (CPD); this will be the European equivalent of the Building Materials Decree. Likewise, steel slag can be used in these applications, either alone or together with active charcoal.

[00060] In addition, in The Netherlands contaminated soil (that cannot be cleaned) is stabilised with cement so that it can then be used as road foundation. Leaching of copper is also a sticking point here. Partly for this reason, the market for this is (still)

small. The invention therefore also provides a solution to this, because a composition containing contaminated material, active charcoal and cement can be used, with suitable leaching values. Likewise, steel slag can be used in these applications, either alone or together with active charcoal. When mixing contaminated material, especially contaminated soil, with one or more of active charcoal (or an active charcoal comprising material such as brown coal cokes, etc.) and steel slag, preferably first the active charcoal and/or steel slag is added to the contaminated material, before adding cement, especially before adding water as component of cement. [00061] Finally, there are possibilities within the framework of the Dutch Disposal Act or within the European Landfill Directive. Residues that have to be disposed also have to comply with leaching standards for landfills in order to meet the requirements for disposal. The invention provides a solution for this purpose as well, because active charcoal can be used to immobilise heavy metals and/or organic microcontaminants. As described herein, also steel slag may be used to immobilise heavy metals and/or organic microcontaminants, either alone or in combination with active charcoal.

[00062] The invention therefore provides an application of active charcoal for the immobilisation of contaminants (metals in one embodiment) in contaminated material and in particular an application of the compositions based on this in the construction industry, such as when laying road foundations or as fill material, etc.

[00063] The invention therefore also provides an application of steel slag for the immobilisation of contaminants (metals in one embodiment) in contaminated material and in particular an application of the compositions based on this in the construction industry, such as when laying road foundations or as fill material, etc. [00064] The invention therefore provides an application of active charcoal and steel slag for the immobilisation of contaminants (metals in one embodiment) in contaminated material and in particular an application of the compositions based on this in the construction industry, such as when laying road foundations or as fill material, etc. [00065] Characteristic applications of the composition of the invention may be as material for use in embankments, noise barriers, road foundations, etc.

Example 1

[00066] In the example a pure active charcoal from Merck (cat. no. 9631, grain size 0.3 - 0.5 mm, for gas chromatography, BET surface is 1283 m /g) is used (this active charcoal is also used in the examples shown in figure 2). In addition, a carbon-rich fly ash (60 % C) (from gasification of biomass) is also used as a possible alternative for the addition of pure active charcoal (not depicted). The effect of active charcoal was tested on samples of MSWI bottom ash. In this case leaching experiments were carried out where active charcoal (between 1 and 50 wt.% (wt.% also known as % (m/m))) was added to bottom ash. The composition was then brought into suspension with water (liquid/solid ratio of 10) and leached out at various pH values (between 7 and 12). After equilibration for 48 hours the suspensions were filtered and the copper concentrations and the concentrations of dissolved FA were determined.

[00067] The results of the leaching tests with MSWI bottom ash and various active charcoal dosages are given in Figure 1. The "fresh" sample is the fresh and untreated bottom ash. The "aged" sample is MSWI bottom ash for which the quality has been improved by accelerated ageing (blowing through a CCh-rich gas mixture, as specified above). In addition, tests were carried out using active charcoal additions of 1, 5, 7 and 50 wt.%. In order to make the effect of dissolved organic carbon on Cu leaching clear, a bottom ash sample was heated at 550 ⁰ C in the laboratory for 24 hours before leaching the material. This sample shows the leaching behaviour of Cu if no organic material is present. Finally, the standards in the Building Materials Decree (Cat. 1 and 2) have been added and the detection limit (DTL) of the analytical technique is shown. If the leaching of Cu from bottom ash is above the Cat. 2 standard the material may not be re-used. If Cat. 2 is met, the material may then be used as building material, but there is an obligation to apply isolating facilities (sheeting) to prevent the material leaching out. Category 1 means that the material may be used freely. Therefore the invention also provides an embodiment in which the composition meets the Category 2 standard and the material is used as building material in combination with protective measures. [00068] The provisional measurements show that after the addition of active charcoal to bottom ash the leaching of copper decreases. The addition of 1 wt.% active charcoal to bottom ash reduces leaching to approximately the same level as that of aged bottom ash. However, leaching of copper can still remain critical compared with

Category 2 standards in the Building Materials Decree. The addition of up to approx. 5 wt. % active charcoal to bottom ash reduces leaching to such an extent that the Category 2 standard that is specified in the Building Materials Decree is met. It can thus be seen from the results that the addition of active charcoal, for example approx. 0.1 - 4.5 wt.% is very promising in order, in any event, to meet the Category 2 standards.

Example 2

[00069] Below an example is given of brown coal cokes that can be used in the composition and application of the invention. Rheinbraun ultra fine brown coal cokes (< 0.125 mm)

C: 87.9 wt.%;

H: 0.4 wt.%;

O: 0.6 wt.%;

N: 0.4 wt.%; S: 0.6 wt.%;

Others: about 10 wt.% (SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , SO ₃ , CaO, MgO, Na ₂ O, K ₂ O).

[00070] The material may also be characterized by the following data:

Moisture: 0.5 wt.%;

Ash (loss on ignition): 10 wt.%; Volatiles: 3.0 wt.%;

Fixed carbon: 86.5 wt.%;

BET (200 ⁰ C): 292 m ² /g (this is the BET surface of the spent cokes after service life in a WI as flue gas cleaner);

BET* (200 ⁰ C): 394 m ² /g (this is the BET surface of the same material but after a treatment process; this material is applied in the experiments depicted in figures 2-5, wherein this material is indicated as "cokes");

Bulk density: 400-650 kg/m ³ .

[00071] The cokes was tested in the composition of the invention both before and after regeneration.

Example 3

[00072] Below an example is given of the main components of steel slag (BOF) that can be used in the composition and application of the invention, both as mean

value and as ranges of a preferred embodiment (data taken from http ://www.tfhrc . gov/hnr20/recycl e/waste/ssa 1.htm and "Hergebruik bouwstoffen, GWW-boekje, te Riele, J.L.M., Hendriks, G.J.J., Schwartz, A.B.E.M. (Eds.), 2002, H.J.M. Klein Gunnewiek, Doetinchem, The Netherlands):

Example 4

[00073] To contaminated soil active cokes or coal fly ash was added in amounts of 0, 1, 3 and 10 wt.%. It appears that the addition of active cokes reduces the leach out of Cu, whereas coal fly ash increases the leach out of Cu (see also figure 2). This shows that the use of cokes is especially suitable for reduction of the leach out of for instance Cu. Addition of about 3 wt.% of active cokes leads to a material of category 1 of the Dutch standards in the Building Materials Decree with respect to Cu or to a material close to this level. Addition of steel slag seems to improve the features of the composition in that the leach out of Cu from the bottom ash is even further reduced. This effect is larger than expected based on the contribution of the individual components steel slag and active charcoal (be it active cokes or coal fly ash, etc.)

Example 5

[00074] To bottom ash active cokes and steel slag were added in amounts of 3-10 wt.% and 2-50 wt.%, respectively. Leaching of Cu and Mo are reduced (see also figures 2 and 3). Amongst others, a 77 wt.% bottom ash, 20 wt.% steel slag and 3 wt.% active cokes composition, a 70 wt.% bottom ash, 20 wt.% steel slag and 10 wt.% active cokes, a 80 wt.% bottom ash, 20 wt.% steel slag, a 90 wt.% bottom ash, 10 wt.% steel slag, and a 98 wt.% bottom ash, 2 wt.% steel slag were applied. The reduction in Mo leach out is about 2 times lower than without the addition of steel slag (and optionally cokes). This applies especially to the pH range of 8-12.5. Samples were also made

wherein only steel slag was added to the bottom ash. Also these samples showed a decrease in leach out of Mo from the bottom ash, but no substantial reduction in leach out of Cu was found.

[00075] It further appears that the leach out of SO4 ^2" is substantially reduced by the presence of steel slag (see figure 4). The bottom ash sample does not fulfil the category 1 criteria, but when steel slag is added, the composition may fulfil the category 1 criteria with respect to SO ₄ ^" . Here it appears that the addition of active charcoal (such as active cokes) further reduces the leach out of SO4 ^2" . The use of the combination of active charcoal and steel slag seems therefore advantageous for the immobilisation of contaminants in contaminated material.

[00076] In addition, the leach out of Sb is reduced (not depicted). For instance, the presence of 20 wt.% steel slag in the composition reduces the leach out of Sb about 10 times with respect to bottom ash which is not mixed with steel slag. Likewise, the leach out of Se seems to be reduced by the addition of steel slag. Moreover, the use of the combination of steel slag and active charcoal seems also beneficial for the reduction of the leach out of Se from bottom ash.

[00077] From the experiments it appears that the addition of steel slag is beneficial for the reduction of the leach out of Cr, Cu, Mo, Pb, SO4 ^2" , Sb and Se. It further appears that an increase of the amount of steel slag above about 20-25 wt.% seems to have a detrimental effect on the leach out of some elements, such as Ba (see also figure 5). Hence, preferably not more than 20 wt.% steel slag is present in the composition.

Example 6

[00078] To bottom ash and contaminated soil active cokes were added in amounts ranging from 1-10 wt.%. It surprisingly appeared that the leach out of Cu (leached concentrations are approximately the same in both materials) is substantially more reduced in case of the bottom ash than in case of the contaminated soil. Addition of about 10 wt.% active cokes leads to a reduction in the leach out of Cu from bottom ash of about 90% and for contaminated soil of about 50%.

Example 7 [00079] Below an example is given of MSWI bottom ash that can be used in the composition and application of the invention as ranges of a preferred embodiment. Typical grain sizes are usually in the range of 32 mm or smaller or 40 mm or smaller.

For instance, the weighed average particle size may be in the ranges of about 0.1-32 mm or 0.1-40 mm. Data taken from: Chandler, A.J., Eighmy, T. T., Hartlen, J. Hjelmar, O., Kosson, D. S., Sawell, S.E., van der Sloot, H.A., Vehlow, J., Municipal solid waste incinerator residues, studies in environmental science 67, Elsevier, 1997.

[00080] Hence, in general MSWI bottom ash may comprise at least the following (main) components in the following amounts: