TECHNICAL FIELD

The present disclosure relates to a method for treatment of waste comprising one or more oxidized metals. The disclosure also relates to metals in a zero oxidation state obtained by the method and to uses thereof.

BACKGROUND

The growing global population has caused increasing competition for natural resources such as metals, minerals, fuel, soil and water leading to scarcities, pollution and rising prices in several areas. Unless important changes take place the Earth ^' s limited resources will be used up resulting in significant shortage. It is well recognized that the present situation has a negative impact on the environment, and there is also an increasing awareness that measures have to be taken to transform society to function in a more sustainable and eco-friendly way.

Thus, it is clear that resources have to be managed more efficiently throughout their entire life cycle from extraction and consumption to disposal of waste. Commonly, waste is deposited in landfills. However, this is not a desired solution since the waste may be associated with environmental hazards and still contain valuable materials that could be used if extracted. Environmental concerns and legislation therefore prompt reduction of waste disposal and favor waste recycling. The recycling will then allow for reuse of materials.

In many areas, the waste being produced contains valuable metals. For instance, valuable metals may be present in residual products from the steel industry, in ash such as bottom and/or fly ash and in worn out equipment. However, the metal may not be present in a form that is suitable and/or desired for recovery and subsequent use. The method for treatment of the waste must then include a step of transforming the metal into a suitable and/or desired form.

Frequently, the waste material includes metal present in the form of for instance an oxide, hydroxide, carbonate etc. while it is desired to obtain the metal in pure metal form. In other words, the waste material contains one or more oxidized metals which should be transformed into one or more metals in zero oxidation state. The method for treatment of the waste will then have to include a reduction step in which the oxidized metal is reduced to a metal having a zero oxidation state, i.e. the metal oxidation number is zero.

US 201 1/0020663 discloses a metal reduction process, which comprises adding a mixture comprising at least one metal containing material, at least one reducing agent and at least one additive into a reactor, heating the reactor to a selected reduction temperature, moving the mixture through the reactor while stirring the mixture, allowing a reduction period to occur, and obtaining a resulting composition comprising at least one zero-valent metal and a residue. It is disclosed that the reducing agent may be chosen from coals, and anthracites and cokes. It is disclosed that the oxygen is depleted inside of the reactor. JP2001239230 discloses fused salt processing for residue from incineration of domestic waste wherein heavy metal halides are reduced in molten fused salt by contacting salt with reducer particle and separating and recovering heavy metal from salt. It is mentioned that the process involves electrolysis. From a recycling point of view it is more challenging to reduce one or more oxidized metals which are in admixture with waste materials, and also to do this on a large scale allowing for treatment of large amounts of waste material. Moreover, from both an economic and environmental point of view the use of added reagent(s) originating from virgin or refined material should be minimized or avoided. However, many reagents are only accessible in refined form or present in a form in which they are more difficult to use.

There exists a need for methods for treatment of waste including one or more oxidized metals allowing for reduction of the one or more oxidized metals into one or more metals in zero oxidation state. In particular, there is a need for such methods in which the addition of virgin or refined reagents is minimized.

It is an object of the present disclosure to overcome or at least mitigate some of the problems associated with recycling of oxidized metals in waste material. SUMMARY OF THE DISCLOSURE

In accordance with the present disclosure there is provided a method for treatment of waste material, said waste material comprising one or more oxidized metals,

said method comprising the steps of:

- ensuring that said waste material comprises a reducing agent selected from the group consisting of metallic aluminium, metallic magnesium, carbon and any combination thereof,

- ensuring that said waste material comprises one or more salts selected from the group consisting of NaCI, KCI, CaCI ₂ , MgCI ₂ , LiCI and any combination thereof, said one or more salt being present in an amount within the range of from about 1 wt% to about 20 wt% based on the weight of the waste material,

- heating said waste material to a temperature from about 700 °C to about 1600 °C in an oxidative atmosphere whereby said one or more oxidized metals are reduced into one or more metals in a zero oxidation state thereby producing treated waste material comprising said one or more metals in a zero oxidation state, and

- separating the one or more metals in a zero oxidation state from the treated waste material.

The term "about" as used herein means in reasonable vicinity of the stated numerical value, such as plus or minus 10%.

In this document, an element in zero oxidation state is understood to be an element whose oxidation number is zero. The oxidation number may be calculated or determined as known in the art.

In the method described herein, the one or more salts may be added to the waste material before, and/or during heating said waste material. Additionally or alternatively, the one or more salts may be present in an amount within the range of from about 1 wt% to about 10 wt% or from 1 about wt% to about 5 wt% based on said waste material. It will be appreciated that the amount of the one or more salts may be based on the waste material to be treated, i.e. the waste material optionally including any added salts, black dross or further added components.

The reducing agent selected from the group consisting of metallic aluminium, metallic magnesium, carbon and any combination thereof may be provided at least partly by at least one of a recyclable product, a recycled product, waste material. The reducing agent may comprise further reducing agents in addition to the metallic aluminium, metallic magnesium and/or carbon. In this document, metallic aluminium is understood to comprise or consist of aluminium in a zero oxidation state. Further, metallic magnesium is 5 understood to comprise or consist of magnesium in a zero oxidation state. The carbon may be present in organic compounds, plastic materials etc. which may provide carbon upon pyrolysis. Further, the carbon may be present as bituminous coal or black coal, and/or as coke. In this document, carbon as a reducing agent intends carbon that may reduce a metal oxide to a corresponding metal in a zero oxidation state. When carbon is 10 used as a reducing agent it may be oxidized to carbon monoxide and/or carbon dioxide.

As used herein, a recyclable product is any item or material that is suitable to use in recycling. For instance, a raw or refined material of aluminium is a recyclable product. Further, in this document a recycled product is understood to be any item or material that

15 is being reused in original or altered form. As an example, a collected and recovered

aluminium can is a recycled product. It will thus be appreciated that a recyclable product may comprise a recycled product and/or an item or material suitable for use in recycling. Further, waste material is understood to comprise or consist of discarded and/or discharged material. Waste material that is to be subjected to the method described

20 herein may include any material.

As used herein, recycling is understood to be a process of converting waste material into reusable items or materials. The method described herein may be considered a recycling method.

25

Surprisingly, in the method described herein the oxidative atmosphere substantially does not oxidize the metallic aluminium, metallic magnesium and/or carbon thereby allowing said metallic aluminium, a metallic magnesium and/or carbon to reduce the metal oxide(s) of the waste material. While not wishing to be bound by any specific theory, it is believed

30 that when the method is performed the one or more salts vaporize and/or melt during heating thereby preventing the reducing agent from being oxidized by the oxidative atmosphere. For instance, when the reducing agent is metallic aluminium the one or more salts prevent its oxidation by the oxidative atmosphere to aluminium oxide. The amount of salt used in the method described herein may be within the range of from about 1 to about

35 20 weight % such as from about 1 to about 10 weight % such as about 1 to about 5 weight % such as from about 1 to about 3 weight % based on the waste material to be treated. An oxidative atmosphere is an advantage since inter alia heating may take place directly within the furnace without flushing with inert gas, which is more efficient and simple. For instance, the heating may take place using an oxy-fuel burner as described herein. In a further example, all of the steps of the method described herein may be performed under an oxidative atmosphere.

The method described herein uses about 20 wt% or less of the one or more salts based on the weight of the waste material including said one or more salts. Therefore, it will be appreciated that the method described herein does not involve molten salt technology. Further, the method described herein does not comprise electrochemistry such as electrolysis.

As used herein, molten salt technology intends a process wherein a reaction is performed in molten salt, i.e. all or substantially all of the reaction mixture of the process is constituted by molten salt. The molten salt may function as reactant, reagent, medium and/or electrolyte.

The one or more salts of the waste material may be selected from the group consisting of NaCI, KCI, CaCI ₂ and any combination thereof.

In this document, an oxidative atmosphere is understood to be an oxidizing atmosphere. The expressions "oxidative atmosphere" and "oxidizing atmosphere" are used

interchangeably.

The waste material to be treated in the method described herein may contain no, little or sufficient amounts of a reducing agent comprising or consisting of metallic aluminium, metallic magnesium and/or carbon. In order to ensure that the waste material to be treated comprises a reducing agent as described herein, a person skilled in the art may measure and/or estimate the amount of said reducing agent present in the waste material using ordinary methods in the field of waste management. Further, knowledge of the origin of the waste material may be helpful in measuring and/or estimating the amount of the reducing agent present. When considered necessary, a reducing agent as described herein may be added in amounts considered appropriate or sufficient. An appropriate or sufficient amount of the reducing agent may be an amount that may reduce part of, all or substantially all of the one or more oxidized metals of the waste material in the method described herein. The appropriate or sufficient amount of the reducing agent may be sub- stoichiometric, stoichiometric or in excess with respect to the one or more oxidized metals of the waste material. Accordingly, the method step of ensuring that the waste material comprises a reducing agent as described herein may comprise or consist of:

- measuring and/or estimating the amount of reducing agent as described herein in the waste material, and/or

- adding a reducing agent as described herein to the waste material comprising one or more oxidized metals so that said waste material comprises said reducing agent in a desired amount.

Similarly, the waste material to be treated in the method described herein may contain no, little or sufficient amounts of the one or more salts as described herein. In order to ensure that the waste material to be treated comprises one or more salts as described herein a person skilled in the art may measure and/or estimate the amount of said one or more salts present in the waste material using ordinary methods in the field of waste

management. Further, knowledge of the origin of the waste material may be helpful in measuring and/or estimating the amount of the one or more salts being present. When considered necessary, the one or more salts as described herein may be added in amounts considered appropriate or sufficient. An appropriate or sufficient amount of the one or more salts may be an amount allowing for performing the method described herein in such a way that at least one of the method steps such as the heating step may be performed in an oxidative atmosphere. As an example, all method steps may be performed under oxidative atmosphere. Accordingly, the method step of ensuring that the waste material comprises one or more salts may comprise or consist of:

- measuring and/or estimating the amount of one or more salts as described herein in the waste material, and/or

- adding one or more salts as described herein to the waste material comprising one or more oxidized metals so that said waste material further comprises said reducing agent in a desired amount.

Further, the method described herein may comprise a step of at least partially mixing the waste material to be treated optionally in the presence of added salt. Such a mixing step may ensure that the one or more salts as described herein are present throughout the entire mixture or at least one part thereof. The mixing of the waste material optionally together with the one or more salts may be performed using a device including a rotating screw.

In case a reducing agent and/or one or more salts is/are added to the waste material to be treated in the method described herein, the addition may be performed in one or more steps before and/or during the heating step of the method. Further, it will be appreciated that addition of the reducing agent and/or one or more salts may be accompanied by mixing such as mixing during and/or after the addition. Such mixing may ensure that the added reducing agent as described herein is present throughout the entire waste material to be treated or at least part of said waste material to be treated.

The heating taking place in the method described herein leads to melting of the waste material and any added salts. As the reduction of the one or more metals of the waste material precedes at least two phases will form one of which will contain the treated waste material and the other one will contain the one or more metals in zero oxidation state. The at least two phases may be separated from one another using means known in the art.

The method described herein may further comprise a step of cooling. The cooling may be performed after the heating and separating steps. The cooling may be performed in such a way that the treated waste material of the method described herein is partly or entirely in an amorphous state. This may be achieved by rapid cooling such as cooling to about room temperature in ten minutes or less. The treated waste material in amorphous state may be used as an additive in concrete. Thus, there is provided a use of the treated waste material of the method described herein as a concrete additive. Further, the method described herein may be a method for producing a concrete additive.

The method described herein may further comprise a step of collecting the one or more metals in zero oxidation state, which may be used further. Additionally, any remainder of the treated waste material may be collected and optionally used further.

The method of the present disclosure allows for obtaining one or more metals such as a plurality of metals in zero oxidation state, for instance as a metal alloy, from waste material in which the corresponding metal was present in oxidized form. In this way, previously inaccessible and valuable metal(s) in waste material may be converted to pure metal(s) and/or a metal alloy that may conveniently be collected from the treated waste material for further use. Frequently, more than one oxidized metal is present in the waste material and as a result the method described herein produces several metals in zero oxidation state. Thus, the method may result in a mixture of metals in zero oxidation state. The mixture of metals in zero oxidation state may occur as an alloy. Accordingly, there is provided one or more metals in zero oxidation stage obtainable by the method described herein. The one or more metals in zero oxidation state may be a mixture of different metals such as an alloy. The purity of the one or more metals in zero oxidation state may vary depending on inter alia the origin of the waste material. In some cases, the one or more metals in zero oxidation state may be contaminated with waste material and therefore purification may be necessary. The need for purification will depend on the end use of the one or more metals in zero oxidation state resulting from the method described herein.

There is also provided a method as described herein, wherein said waste material optionally in combination with added salts as described herein before heating is subjected to a treatment selected from the group consisting of crushing, sieving and at least partial removal of iron, copper and/or aluminium. The crushing, sieving and/or at least partial removal of iron, copper and/or aluminium may be performed as commonly known in the field of waste management. For instance, the removal of magnetic material, such as iron, may be performed using a magnet such as a ferromagnet, electromagnet and/or a neodymium magnet. The removal of copper and/or aluminium may be performed using an eddy current magnet.

The waste material of the method described herein may be selected from the group consisting of metal hydroxide sludge, metallurgical waste, ash, mine waste, sludge from polluted water, landfill material, shredder light fraction and any combination thereof. For instance, the waste material may comprise or consist of metal hydroxide sludge. The metal hydroxide sludge may originate from the steel industry. In a further example, the waste material may comprise or consist of shredder light fraction (SLF). The SLF may originate from manufacturing and/or recycling of automobiles and/or household

appliances. The SLF may comprise plastics, rubber, glass, sand, textiles, leather, wood, paint, metals and any combination thereof. The metals of the SLF may include metals in zero oxidation state and/or metals in oxidized form. The recyclable and/or recycled product comprising aluminium, magnesium and/or carbon of the method described herein may be selected from the group consisting of packaging material, black dross, white dross, cutting process scrap, landfill material and any combination thereof. The packaging material may be provided by food packaging, candy packaging, blister pack, a carton for liquid and any combination thereof.

It is a significant advantage of the method described herein that the reducing agent comprising or consisting of metallic aluminium, metallic magnesium and/or carbon may be provided by at least one of a recyclable product, a recycled product, waste material which otherwise may have been disposed of. In particular, the method described herein envisages using metallic aluminium and/or magnesium that is present in waste material such as packaging material, black dross, white dross, cutting process scrap, landfill material and/or any combination thereof. As an example, aluminium is frequently present in laminates, films and/or foils in packages. Although the individual components of laminates, films and foils are technically recyclable, the difficulty in sorting and separating the material components makes recycling and remelting considerably more difficult and less attractive from an economic point of view. Advantageously, when used in the present method the individual components of the waste material do not have to be separated. The reducing agent of the method described herein may be used in a stoichiometric amount or in excess with respect to the one or more oxidized metals. Alternatively, the reducing agent described herein may be used in a sub-stoichiometric amount. When a reducing agent is added to the waste material, addition of a sub-stoichiometric amount may be sufficient if the waste material being treated and/or the material providing the reducing agent comprise(s) material including further reducing agents. As an example, a packaging material may comprise a laminate of aluminium and plastics. The amount of reducing agent may be measured and/or estimated using methods known in the field of waste management allowing a person skilled in the art to determine whether or not a reducing agent as described herein should be added.

The one or more salts of the method described herein may be selected from the group consisting of NaCI, KCI, CaCI ₂ and any combination thereof. It will be appreciated that these salts are commonly present in waste material such as black dross, and are cheap and easily available. Thus, the method of the present disclosure may conveniently be performed using these salts which optionally may be provided by black dross.

The heating of the waste material of the method described herein may take place at a temperature from about 700 °C to about 1600 °C such as from about 800 °C to about 5 1600 °C or from about 900 °C to about 1600 °C. As an example, the heating temperature may be about 800 °C, about 900 °C, about 1000 °C, about 1 100 °C, about 1200 °C, about 1300 °C, about 1400 °C, about 1500 °C or about 1600°C.

The method described herein may be performed in a furnace known to the person skilled in the art. For instance, the furnace may be a Kaldo furnace.

0

The one or more oxidized metals of the waste material of the method described herein may be provided by a compound comprising or consisting of at least one of an oxide, hydroxide, carbonate, sulphide, sulphite, sulphate, chloride, bromide, fluoride, phosphate, phosphide, carbide, silicate, aluminate, chromate, iodide, vanadate of a metal selected5 from iron, copper, lead, nickel, molybdenum, tungsten, vanadium, zinc, chromium, manganese, cobalt, silver, palladium, platinum, cadmium, tin, iridium, gold, osmium, rhodium, ruthenium, tantalum and/or bismuth.

The compound providing the one or more oxidized metals of the waste material described0 herein may be selected from the group consisting of FeO, Fe ₂ 0 ₃ , Fe ₃ 0 ₄ , FeOOH, FeC0 ₃ , FeCI ₂ , FeCI ₃ , FeS0 ₄ , Fe ₂ (S0 ₄ ) ₃ , Cu ₂ 0, CuO, NiO, PbO, Pb0 ₂ , Pb ₂ 0, Pb ₂ 0 ₃ , Pb ₃ 0 ₄ , PbS, NiCI ₂ , NiF ₂ , ZnO, ZnCI ₂ , ZnS0 ₄ , Zr0 _2, Sb ₂ 0 ₃ , Sb ₂ 0 ₄ , Sb ₂ 0 ₅ , As ₂ 0 ₃ , As ₂ 0 ₅ , As ₂ S ₃ , CdC0 ₃ , CdCI ₂ , CdF ₂ , Cd(OH) ₂ , CdO, CdS0 ₄ , CrCI ₂ , CrCI ₃ , CrF ₂ , CrF ₃ , Cr(OH) ₂ , Cr ₂ 0, CrO, Cr ₂ 0 ₃ , CrS0 ₄ . CrS, Cr ₂ S ₃ , CoC0 ₃ , CoCI ₂ , CoCI ₃ , CoF ₂ , CoF ₃ , Co(OH) ₂ , CoO, Co ₂ 0 ₃ , Co ₃ 0 ₄ ,5 CoS0 ₄ , CoS ₂ , Cu ₂ C0 ₃ , CuCI ₂ , CuF, CuF ₂ , Cu(OH) ₂ , CuS0 ₄ , Cu ₂ S0 ₄ ,Cu ₂ S0 ₃ , FeF ₂ ,

Fe(OH) ₂ , PbCI ₂ , PbCI ₄ , PbF ₂ , PbFCI, Pb(OH) ₂ , PbO, PbS0 ₃ , PbS0 ₄ , MnCI ₂ , MnCI ₃ , MnF ₂ , MnF ₃ , Mn ₂ 0 ₇ , MnO, Mn ₂ 0 ₃ , Mn0 ₃ , MnS0 ₄ , Mn(S0 ₃ ) ₂ , MnS, MnS ₂ , MoCI ₂ , MoCI ₃ , MoCI ₄ , M0CI ₅ , MoF ₆ , Mo(OH) ₃ , Mo0 ₂ , Mo0 ₃ , Mo ₂ 0 ₃ , Mo ₂ 0 ₅ , MoS ₂ , MoS ₃ , MoS ₄ , NiC0 ₃ , NiS, NiS0 ₄ , NiS0 ₃ , PtCI ₂ , PtCI ₃ , PtCI ₄ , PtF ₂ , PtF ₄ , PtF ₆ , Pt(OH) ₂ , PtO, Pt0 ₂ , Pt0 ₃ , Ag ₂ S0 ₃ ,0 AgO, AgCI, Ag ₂ C0 ₃ , AGF, Ag ₂ S0 ₄ , Ag ₂ S, SnCI ₂ , SnCI ₄ , SnF ₂ , SnF ₄ , SnO, Sn0 ₂ , SnS0 ₄ , SnS, SnS ₂ , WCI ₂ , WCI ₄ , WCI ₅ , WCI ₆ , WF ₆ , W0 ₂ , W ₂ 0 ₅ , WS ₂ , WS ₃ , ZnF ₂ , Zn0 ₂ , Zn(OH) ₂ , ZnS, VCI ₂ , VCI ₃ , VCI ₄ , VF ₃ , VF ₄ , VF ₅ , VO, V0 ₂ , V ₂ 0 ₃ , V ₂ 0 ₅ , VS0 ₄ , VS, V ₂ S ₅ , V ₂ S ₈ , PdCI ₂ , PdF ₂ , PdF ₃ , PdO, Pd0 ₂ , PdS0 ₄ , PdS, and PdS _2;

or a combination of any one of the foregoing compounds with crystal water or any

5 combination thereof. For instance, the compound may be selected from the group consisting of CuO, PbO, NiO, Pb0 ₂ , Pb ₂ 0, ZnO, Zn(OH) ₂ , CrO, Cr ₂ 0, Cr ₂ 0 ₃ , CoO, Co(OH) ₂ , Co ₂ 0 ₃ , CoCOs, Co ₃ 0 ₄ , Cu ₂ C0 ₃ , CuS0 ₄ , Pb(OH) ₂ , PbS0 ₄ , MnO, Mn ₂ 0 ₃ , Mn0 ₃ , MnS0 ₄ , Mo0 ₂ , Mo0 ₃ , Mo ₂ 0 ₃ , Mo(OH) ₃ , NiC0 ₃ , NiS0 ₄ , SnO, Sn0 ₂ , SnS0 ₄ , ZnS0 ₄ , VO, V0 ₂ , V ₂ 0 ₃ and any combination thereof.

Additionally or alternatively, the one or more oxidized metals of the waste material described herein may be provided by one or more organometallic compounds comprising a metal selected from at least one of iron, copper, lead, nickel, molybdenum, tungsten, vanadium, zinc, chromium, manganese, cobalt, silver, palladium, platinum, cadmium, tin, iridium, gold, osmium, rhodium, ruthenium, tantalum and/or bismuth. The organometallic compound may originate from plastics, flame retardants, rubber, insecticides, pesticides, weedkillers, catalysts etc. In a further example, the organometallic compound may be provided by shredder light fraction such as automotive shredder residue. As used herein, an organometallic compound is understood to be a compound containing at least one bond between a carbon atom of an organic compound and a metal.

The one or more metals in a zero oxidation state of the method described herein may be selected from the group consisting of Fe ⁽⁰⁾ , Cu ⁽⁰⁾ , Ni ⁽⁰⁾ , Pb ⁽⁰⁾ , Zn ⁽⁰⁾ , Zr ⁽⁰⁾ , Mo ⁽⁰⁾ , Cr ⁽⁰⁾ , Mn ⁽⁰⁾ , Co ⁽⁰⁾ and any combination thereof.

The waste material of the method described herein may further comprise one or more metals in a zero oxidation state. In case the waste material to be treated in the method described herein further comprises one or more metals in zero oxidation state, the method described herein will provide said one or more metals in zero oxidation state together with the one or more metals in zero oxidation state originating from the one or more oxidized metals of the waste material being treated. Thus, the origin of the one or more metals resulting from the method described herein may be one or more metals in zero oxidation state present in the waste material to be treated and/or the one or more oxidized metals of the waste material.

All method steps of the method described herein may be performed in an oxidative atmosphere. The oxidative atmosphere may comprise air optionally in admixture with additional oxygen gas. Further, at least one of the steps of the method described herein may take place in a rotating converter or a Kaldo converter. Additionally or alternatively, at least one of the steps of the method described herein may comprise stirring and/or mixing.

The heating of the heating step of the method described herein may be provided by a burner such as an oxy-fuel burner as known in the art. The fuel of the oxy-fuel burner may be provided by any suitable fuel such as fossil fuel, gas such as natural gas, oil, waste containing organic residues such as combustible waste and/or plastic material. The use of an oxy-fuel burner in the context of the method described herein is a significant benefit since it is easy to use and allows for generating heat with the aid of a fuel originating from waste such as combustible waste. Thus, the method described herein allows for treating waste material comprising one or more oxidized metals optionally in combination with black dross, which is a hazardous by-product generated during secondary aluminium production, with the aid of an oxy-fuel burner using waste as fuel. As an overall effect, different kinds of waste and by-products are recycled into valuable metals making the method environmentally sustainable and economically profitable.

Further, there is provided a use of a packaging material comprising a laminate, film and/or foil including aluminium as a reducing agent for reduction of oxidized metal(s) of waste material.

The amount of waste material that may be subjected to treatment in the method described herein may be very large making it useful on an industrial scale. For instance, the amount of waste material subjected to treatment may be from about 1 ton to about 50 tons such as from about 1 ton to about 30 tons or from about 5 tons to about 30 tons. However, it will be appreciated that the method described herein may be performed on any scale that is compatible with the equipment used. The process described herein may be performed batchwise or in a continuous way.

It will be appreciated that the at least one or more oxidized metals are more prone to reduction than aluminium, magnesium and/or carbon. An Ellingham diagram may be used to determine which oxidized metals may be reduced. For instance, a metal oxide may be reduced by aluminium if its curve lies above the curve for aluminium in the Ellingham diagram. The invention is illustrated by the following non-limiting examples. EXAMPLES

The following experiments were performed in a chamber furnace allowing for heating up to 1200 °C. In all experiments, the crucibles used were made of Al ₂ 0 ₃ . Example 1. Reduction of Fe ₂ 0 ₃ using metallic aluminium at 1200°C

Three experiments were performed as indicated below. In all experiments, metallic aluminium and Fe ₂ 0 ₃ were mixed and added to a crucible. The crucible was placed in a furnace at room temperature. Thereafter, the temperature was raised to 1200 °C at a speed of 10 °C/minute. The temperature of 1200 °C was maintained for 30 minutes, and then lowered to room temperature at a speed of 10 °C/minute.

a) Comparative example with pure iron powder and metallic aluminium

Pure iron powder mixed with metallic aluminium was added to a crucible, and heated to 1200 °C as described above.

XRPD analysis of the resulting powder showed that the iron powder had oxidized to Fe ₂ 0 ₃ .

b) Treatment of Fe?Q with metallic aluminium in the presence of SiO?

A layer of Si0 ₂ was added to the bottom of a crucible followed by a mixture of Fe ₂ 0 ₃ , metallic aluminium and a small magnesium flake. Finally a layer of Si0 ₂ was added to cover the mixture. The crucible was heated to 1200 °C as described above. After cooling, it was difficult to entirely separate the formed product from the Si0 ₂ . XRPD analysis of the formed product indicated a large number of components and that the formed product was amorphous to a large extent. There was no indication of formation of metallic iron.

c) Treatment of Fe?Q with metallic aluminium in the presence of AI?Q

A mixture of Fe ₂ 0 ₃ , metallic aluminium, a small magnesium flake and ethanol were formed into a small ball. A layer of Al ₂ 0 ₃ was added to the bottom of a crucible followed by the ball formed mixture. Finally a layer of Al ₂ 0 ₃ was added to cover the ball formed mixture. The crucible was heated to 1200 °C as indicated above. After cooling, a lump having a brittle outer layer and an inner unbreakable ball was collected. XRPD analysis indicated that the brittle outer layer comprised Al ₂ 0 ₃ . The unbreakable ball was magnetic indicating formation of metallic iron. The formation of the brittle outer layer appears to be due to sintering. It is believed that that brittle outer layer prevents oxidation of the metallic aluminium thereby allowing it to reduce the Fe ₂ 0 ₃ into metallic iron. Example 2. Reduction of Fe ₂ 0 ₃ using metallic aluminium in the presence of CaCI ₂ at 900°C

Metallic aluminium was used to reduce Fe ₂ 0 ₃ in the presence of CaCI ₂ x 2 H ₂ 0 at a temperature of 900 °C. Three experiments were performed. In all experiments, 0.715 g of Fe ₂ 0 ₃ (corresponding to about 0.5 g of iron) was used and the amount of metallic aluminium was varied. Further, in all experiments the total amount of CaCI ₂ x 2 H ₂ 0 was about 10 g. In this document, "g" stands for grams.

a) Sub-stoichiometric amount of metallic aluminium

The molar amount of metallic aluminium was half of that of Fe ₂ 0 ₃ . A layer of CaCI ₂ x 2 H ₂ 0 was added to the bottom of a crucible followed by a mixture of Fe ₂ 0 ₃ and metallic aluminium. Finally a layer of CaCI ₂ x 2 H ₂ 0 was added.

The crucible was placed in a furnace at room temperature, and the temperature of the furnace was raised to 900 °C at a speed of 10 °C/minute. The temperature of 900 °C was maintained for 10 hours after which it was lowered to room temperature at a speed of 10 °C/minute.

The sample was added to deionized water in order to dissolve the salt. The magnetic components were removed using a neodymium magnet, exposed to nitrogen gas to allow for drying and weighed. A magnetic phase containing the magnetic components was studied using XRPD. A non-magnetic phase was collected. In this document, XRPD stands for X ray powder diffraction.

b) Stoichiometric amount of metallic aluminium

The molar amount of metallic aluminium was the same as that of Fe ₂ 0 ₃ . A layer of CaCI ₂ x 2 H ₂ 0 was added to the bottom of a crucible followed by a layer of Fe ₂ 0 ₃ , a layer of CaCI ₂ x 2 H ₂ 0 and then a layer of metallic aluminium.

The sample was heated and analysed as described for experiment a).

c) Excess of metallic aluminium

The molar amount of metallic aluminium was twice that of Fe ₂ 0 _3. The sample was added to the crucible, heated and analysed in the same way as for a). When the sample was added to the crucible, a layer of CaCI ₂ x 2 H ₂ 0 was added to the bottom of the crucible followed by a mixture of Fe ₂ 0 ₃ and metallic aluminium. Finally a layer of CaCI ₂ x 2 H ₂ 0 was added.

The following results were obtained.

For a) no unreacted aluminium was observed. Most of the Fe ₂ 0 ₃ had been converted to Fe ₃ 0 ₄ . Some unreacted Fe ₂ 0 ₃ was observed. Most of the metallic aluminium appeared to be present in the non-magnetic phase since only a small amount of CaAI ₄ 0 ₇ was observed in the magnetic phase.

5 For b) both the magnetic phase and the non-magnetic phase contained metallic iron and unreacted Fe ₂ 0 ₃ .

For c) substantially all Fe ₂ 0 ₃ was reduced to metallic iron. Formation of some FeO was also observed. The aluminium mainly formed aluminium oxide, but some

10 CaAI ₄ 0 ₇ was also observed. The excess of aluminium formed an alloy with the iron.

Some unreacted aluminium may be present in the non-magnetic phase.

It was concluded that metallic aluminium reduced Fe ₂ 0 ₃ to metallic iron in the presence of the oxidative atmosphere of the furnace. Further, from experiment b) it 15 was concluded that lack of mixing of the metallic aluminium and the Fe ₂ 0 ₃ had a negative impact on the extent of reduction of the Fe ₂ 0 ₃ . It was also concluded that the CaCI ₂ prevented oxidation of the metallic aluminium.

Example 3. Reduction of Fe ₂ 0 ₃ using metallic aluminium in the presence of KCI at 20 800°C

Metallic aluminium was used to reduce Fe ₂ 0 ₃ in the presence of KCI at a temperature of 800 °C. Two experiments were performed. In a first experiment, aluminium was added in excess (the molar amount of metallic aluminium being twice that as Fe ₂ 0 ₃ ). In a second experiment, aluminium was added in a stoichiometric amount. In both experiments, 0.715

25 g of Fe ₂ 0 ₃ (corresponding to about 0.5 g of iron) was used and the amount of metallic aluminium was varied. In both experiments, a layer of KCI was added to the bottom of a crucible, followed by a mixture of Fe ₂ 0 ₃ and metallic aluminium and then a further layer of KCI on top of said mixture. The amount of KCI was about 10 g. The crucible was placed in a furnace having a temperature of 800 °C, kept in the furnace for one hour and then

30 allowed to cool on a grid. The sample was then added to deionized water, and the

magnetic components forming a magnetic phase removed using a neodymium magnet dried using nitrogen gas and weighed. A magnetic phase comprising the magnetic components was analysed using XPRD. Further, a non-magnetic phase was collected. XRPD analysis of the magnetic phase of the samples from both experiments showed that the samples contained metallic iron, iron-aluminium alloys, unreacted aluminium and partly reduced iron oxides (Fe ₃ 0 ₄ and FeO). The experiment run with an excess of metallic aluminium also provided a non-magnetic phase comprising essentially metallic aluminium. Aluminium oxides were not detected in the magnetic or non-magnetic phases, which was presumably due to their fine particle size making them prone to stay in the deionized water. This indicated that a reaction time of one hour was not sufficient to achieve complete reaction. It was concluded that the metallic aluminium reduced Fe ₂ 0 ₃ to metallic iron in the presence of the oxidative atmosphere of the furnace. Further, it was also concluded that the KCI prevented oxidation of the metallic aluminium.

Example 4. Treatment of Ti0 ₂ and Zr0 ₂ with metallic aluminium in the presence of KCI at 800 °C

Experiments with Ti0 ₂ and Zr0 ₂ , respectively, were performed in analogy with Example 3. However, the metallic aluminium was added in excess (the molar amount of metallic aluminium being twice that of Ti0 ₂ and Zr0 ₂ , respectively) and the temperature in the furnace was maintained for four hours instead of one hour. After cooling, the sample was placed in water to dissolve the salt and to allow for collection of a lump containing the sample. XRPD analysis for the experiment run with Ti0 ₂ indicated no formation of metallic titanium. XRPD analysis for the experiment run with Zr0 ₂ indicated formation of metallic zirconium. It was also concluded that the KCI prevented oxidation of the metallic aluminium by the oxidative atmosphere of the furnace thereby allowing the metallic aluminium to reduce the Zr0 ₂ . Example 5. Reaction of hydroxide slag with metallic aluminium in the presence of KCI or black dross.

The hydroxide slag used was obtained from water treatment in metallurgical process and consisted mainly of CaO (about 40 wt%), and Fe ₂ 0 ₃ (about 25 wt%). The hydroxide slag also contained Si0 ₂ (about 1 -2 wt%), MgO (about 1 -2 wt%), MnO (about 1 -2 wt%), CrO (about 1 -2 wt%), NiO (about 1 -2 wt%), and S0 ₄ (about 1 -2 wt%).

The black dross used was obtained from a process of remelting of aluminium scrap, and consisted mainly of AI203 (about 40 wt%), Na/KCI (about 30 wt%), MgO (about 10 wt%) and CaO (about 10 wt%). The black dross also contained about 1 wt% to about 2 wt% of Fe ₂ 0 ₃ , Si0 ₂ , MgO, MnO, Al ⁽⁰⁾ .

The metallic aluminium, Al ⁽⁰⁾ , was provided by a laboratory supplier in the form of a finely divided powder having a particle size of < 0,1 mm.

The crucible in these experiments was made of aluminium oxide (Al ₂ 0 ₃ ).

Hydroxide slag was reacted with metallic aluminium in the presence of KCI or black dross at 800 °C in the presence of air in a box furnace. Generally, the hydroxide slag, the metallic aluminium and the KCI or black dross were crushed and mixed in a mortar to provide a homogenous mixture, which was then transferred to a crucible. The crucible containing said mixture was then put in the hot box furnace. The reaction time was 10 minutes for all but one sample as this was determined to be sufficient for full reaction (see below). After reaction the crucible was taken out from the hot furnace and allowed to cool to room temperature in ambient air.

The amounts of the hydroxide slag, the metallic aluminium and the KCI or black dross were varied as described below. a) Hydroxide slag and KCI being present in a weight ratio of 1 :1 (1 g of each), heating at 800 °C for both 10 minutes and 1 hour. The amount of metallic aluminium was 0.3 g.

After the reaction it was observed that the mixtures had sintered. A part of the sintered mixtures was subjected to X-ray powder diffraction analysis (XRPD), which revealed the presence of iron aluminium silicide. Thus, iron oxides in hydroxide slag had been reduced to iron. No iron oxides were detected with XRPD, which was taken as an indication that most of or all of the iron oxides had be fully reduced to metallic iron. No difference was observed between the sample that had been allowed to react for 10 minutes and the sample that reacted for 1 hour. This indicated that 10 minutes was sufficient for the reaction to finish. Therefore all subsequent experiments were done with a reaction time of 10 minutes. b) Hydroxide slag and KCI being present in a weight ratio of 2:1 (2 g of slag and 1 g of KCI), heating at 800 °C for 10 minutes. The amount of metallic aluminium was 0.3 g. The experiment was performed as for a) except that the weight ratio between the hydroxide slag and the KCI was 2:1 . After cooling it was observed that the mixture had sintered only partly. No iron oxides were detected with XRPD, which was taken as an indication that most of or all of the iron oxides had been fully reduced to metallic iron. c) Hydroxide slag and black dross being present in a weight ratio of 2:1 (10 g of slag and 5 g of black dross), heating at 800 °C for 10 minutes. The amount of metallic aluminium was 0.15 g.

Hydroxide slag, black dross and aluminium powder were crushed and mixed in a mortar. The resulting mixture was placed in a crucible, heated to 800 °C and kept at 800 °C for 10 minutes. After cooling it was observed that the mixture had sintered. A part of the sintered mixture was subjected to XRPD analysis, but the NaCI originating from the black dross overlapped with the reduced products rendering direct monitoring of formation of iron difficult. Therefore, the reduction reaction was monitored by observing the remainder of unreacted compounds of the hydroxide slag. No unreacted compounds such as iron compounds were observed. Thus, iron oxides in the hydroxide slag had been reduced to iron. It was concluded that the black dross prevented the metallic aluminium from being oxidized by the oxidative atmosphere of the furnace thereby allowing the metallic aluminium to serve as a reducing agent. Thus, black dross may be used as an alternative to a salt such as CaCI ₂ or KCI or a mixture of salts.