A composite material for the containment and use of hazardous waste products and methods for the production thereof

Abstract

The invention relates to a composite material comprising a binder capable of cross-linking and a filler. In particular, the composite material comprises a matrix of cross-linked polymer material comprised of polymer chains and a series of cross-links therebetween, and a filler material that is encapsulated by the cross-linked polymer material. The invention also provides a method for making a composite material including combining a binder capable of cross linking and a filler. In particularly preferred embodiments the filler includes bauxite residue, also known as red mud.

Description

A COMPOSITE MATERIAL FOR THE CONTAINMENT AND USE OF HAZARDOUS WASTE PRODUCTS AND METHODS FOR THE PRODUCTION THEREOFTECHNICAL FIELD

[0001] The present invention relates to the field of composite materials and in particular composite materials and methods for producing a composite material. The invention is particularly suited for use as an inert material for road construction or in the remedial maintenance of a substrate, such as an item of infrastructure such as a road surface or for use in the form of construction products, dam and irrigation lining, mine and oil well remediation, fluid infrastructure and pipes and for containment of other hazardous materials. However, it is to be appreciated that the invention may have broader application.BACKGROUND OF THE INVENTION

[0002] Red mud is a name for bauxite residue which is an industrial waste generated during the processing of bauxite into alumina. It is composed of various oxide compounds, including iron oxides which give red mud its red colour. In addition to iron oxide, the other dominant components include silica, unleached residual aluminium compounds, and titanium oxide.

[0003] However, the constituents of red mud vary depending on the quality and nature of the bauxite ore and the extraction process and conditions. The composition ranges for common chemical constituents or red mud include: Fe2O3 -5-60%; AI2O3 - 5-30%; TiO2 - 0-15%; CaO - 2-14%; SiO2 - 3-50%; and Na2O - 1-10%.

[0004] Red mud can be hazardous environmentally because of its alkalinity, which makes the material extremely corrosive, and because of its species components. The alkalinity of red mud, of about pH 13, means it carries a highcontamination risk and its is classified as hazardous waste. Furthermore, red muds often include heavy metal elements which can be toxic, including arsenic (As), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), and vanadium (V) among others.

[0005] Every tonne of alumina produced generates approximately 1.5 to 2.5 tonnes of red mud. Global annual production of alumina is about 150 million tonnes resulting in the generation of about 225 to 375 million tonnes of red mud. The global stockpile of red mud is currently estimated at 3 billion tonnes.

[0006] Presently, red mud is turned into a slurry with water and is stored in lagoons or ponds which are sometimes created in former bauxite mines or disused quarries or which are constructed with dams or levees. Up until fairly recently, red mud was also discharged into rivers and seas but this practice has generally ceased.

[0007] Other processes have been developed to dry out or filter red mud from water and to treat the resulting red mud to remove some of its alkalinity before transporting the red mud for further processing. Attempts have been made at extracting the remaining oxides from red mud. However, thus far, these processes have been only modestly successful or not cost effective.

[0008] To date, there are no known uses for red mud on a large scale and there is no known option for using red mud in a way that prevents leaching of toxins into the surrounding environment and which is cost competitive with simply storing the red mud.

[0009] Accordingly, a need exists for a way to dispose of red mud or to use it for some other purpose that contains or encapsulates the hazardous constituents of the red mud to prevent those constituents from leeching into the surrounding environment. A need also exists for a way to dispose of or to use other bulk materials, which may contain the hazardous substances, in a manner that contains or encapsulates the hazardous constituents and prevents them from leeching into the surrounding environment. Examples of other such bulkmaterials include the bi-products of tyre manufacturing and reclamation, mining minerals and metals processing such as waste foundry sand and soft plastics.SUMMARY OF THE INVENTION

[0010] In one aspect, the present invention relates to a composite material comprising: a binder capable of cross-linking; and a filler.

[0011] Advantageously, embodiments of the composite material are operable for encapsulating a hazardous material such as red mud and has sufficient structural integrity to be used for some other purpose. Furthermore, it has been found that the binder contains or encapsulates the hazardous constituents of a material such as red mud to prevent those constituents from leeching into the surrounding environment.

[0012] In embodiments of the composite material the binder is an epoxy.

[0013] Preferably the binder includes a first part and a second part. Preferably the first part includes epichlorohydrin (ECH) and preferably the second part includes a bisphenol, such as bisphenol A, bisphenol F or a brominated bisphenol.

[0014] In other embodiments, the binder includes a thermosetting polymer preferably including any one of polyurethane, polyester, polyurea or a vinyl ester resin.

[0015] In embodiments, the filler includes bauxite residue (i.e. red mud).

[0016] Preferably, the filler material includes mining waste or tailings, zeolite, limestone, potash, inorganic mined materials or reclaimed demolition materials or combinations thereof.

[0017] In embodiments, the composite materials includes a substance to encourage cross linking between the binder constituents. Preferably thecomposite material includes a substance to encourage cross linking between the binder and the filler. Preferably, the substance to encourage cross linking includes any one or more of carbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

[0018] In embodiments, the composite material includes 10 wt% to 20 wt% of the binder material and 80 wt% to 90 wt% of the filler material.

[0019] In embodiments, the composite material further includes a reinforcement material. Preferably, the composite material includes 3 wt% to 90 wt% of the reinforcement material. The reinforcement material preferably comprises glass, carbon, steel, wool, or hemp or fibrous plant material.

[0020] In another aspect, the invention provides a method for making a composite material including combining: a binder capable of cross linking; and a filler.

[0021] In embodiments, the method includes mixing the binder and the filler together using any one or more of a blender, a tumble mixer, injection, spray or sublimation.

[0022] Preferably, the binder includes is an epoxy derived from mixing epichlorohydrin (ECH) and a bisphenol or a thermosetting polymer comprising any one of polyurethane, polyester, polyurea or a vinyl ester resin.

[0023] The method preferably includes adding a substance to encourage cross lining between the binder constituents including any one or more of carbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

[0024] Preferably, the method includes combining 10 wt% to 20 wt% of the binder material and 80 wt% to 90 wt% of the filler material.BRIEF DESCRIPTION OF THE FIGURES

[0025] The present invention will now be described in more detail with reference to preferred embodiments illustrated in the accompanying figures, wherein:

[0026] Figure 1 is a flowchart illustrating an embodiment of a method of making a composite material in accordance with an embodiment of the invention including combining a mixture of a binder capable of cross-linking and a filler material;

[0027] Figure 2 illustrates a schematic representation of a cross-linking binder used for encapsulating and bonding a filler together in accordance with an embodiment of the invention; and

[0028] Figure 3 illustrates a method for forming a road surface from a composite material in accordance with an embodiment of the invention.DETAILED DESCRIPTION

[0029] The present invention relates to a composite material and methods to manufacture a composite material. The composite material described herein is suitable for applications including road and pavement construction, road and pavement repair including filling of holes in roads and pavement surfaces, containment of waste including hazardous wastes such as e-waste, medical waste or nuclear waste.

[0030] In other embodiments, the composite material of the invention is suitable for use as a construction product, for dam construction and irrigation lining, mine and oil well remediation, fluid infrastructure construction and remediation and for rapid construction of roads and infrastructure, such as for disaster recovery.

[0031] Referring to Figure 2, the present invention relates to a composite material 1 . The composite material 1 comprises a matrix of cross-linked polymer material 40 comprised of polymer chains 50, 55 and a series of cross links 60 therebetween. The composite material 1 also comprises filler material 70 that is encapsulated by the cross-linked polymer material 40.

[0032] In embodiments, deposits of the filler 70 and the cross-linked polymer 40 are homogenously blended, alleviating bonding weaknesses between polymer chains 50, 55 and between the polymer 40 and the filler 70.

[0033] Preferably, the filler comprises bauxite residue which is commonly referred to as red mud. Red mud is the industrial waste generated during the processing of bauxite into alumina. It is composed of various oxide compounds, including iron oxides which give red mud its red colour. In addition to iron oxide, the other dominant components include silica, unleached residual aluminium compounds, and titanium oxide. The constituents of red mud varies depending on the quality and nature of the bauxite ore and the extraction process and conditions.

[0034] Red mud is highly alkaline (pH of about 13) which makes the material extremely corrosive. Red mud often includes heavy metal elements which can be toxic, including arsenic (As), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), and vanadium (V) among others.

[0035] In other embodiments, the filler material includes other bulk materials such as mining waste or tailings which can comprise hazardous compounds. In other embodiments, the filler material may include zeolite, limestone, potash, inorganic mined materials or reclaimed demolition materials that may contain the aforementioned materials or combinations thereof.

[0036] The binder comprises a material that is capable of cross-linking such as a cross-linked polymer 40. In embodiments, the cross-linked polymer 40 is comprised of an epoxy. The epoxy resin may be reacted (cross-linked) either through catalytic homopolymerisation, or with a co-reactant including apolyfunctional amine, acid, phenol, alcohol or thiol. Such co-reactants are referred to as a hardener or a curative and the cross-linking reaction is referred to as curing.

[0037] Preferably, the binder includes a first part and a second part. The first part is comprised of epichlorohydrin (ECH) and the second part includes a bisphenol, such as bisphenol A, bisphenol F or a brominated bisphenol.

[0038] In another embodiment, the binder includes a thermosetting polymer. Preferably, the thermosetting polymer includes any one of polyurethane, polyester, polyurea or a vinyl ester resin.

[0039] Preferably the composite material 1 includes 80 wt% to 90 wt% of the binder material and 10 wt% to 20 wt% of the filler material.

[0040] Advantageously, embodiments of the composite material are operable for encapsulating a hazardous material such as red mud. It has been found that the binder contains or encapsulates the hazardous constituents of a material such as red mud to prevent those constituents from leeching into the surrounding environment. The advantageous properties of the composite material are likely ability of the cross-linking binder (e.g. epoxy or other thermoset) to be adapted to bond with the surface of the materials used as fillers. The composite material will encapsulate and bond the inert fillers together, in particular entities containing aluminum, silica, iron, and titanium oxides along with pure metals.

[0041] Accordingly, embodiments of the invention are advantageous in that they provide a process of containing, via chemical cross linking, and therefore neutralising the toxic elements of finely ground residues from mineral processing, in particular Red Mud, as a product of that cross linking.

[0042] An advantage of embodiments of the invention are that pull strength of the cross-linking binder is increased due to the nature of the irregular shapedparticles of the Red Mud and the often porous nature of the material in its raw state.

[0043] In embodiments, the composite material 1 further includes a substance to encourage cross linking between the binder constituents. The substance to encourage cross linking is preferably adapted to encourage crosslinking between the binder 40 and the filler 70. The substance to encourage cross linking preferably includes any one or more of carbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

[0044] The addition of carbon black for example, introduces more opportunities for cross linking into the material and improves the overall gel and cure rates between 5 and 10 times.

[0045] Accordingly, in embodiments, the properties of the Red Mud and the carbon black, for example, can be used to control the gel and cure rates of the binder. This control can be conducted and fine-tuned on a batch by batch basis.

[0046] In embodiments, calcium carbonate is included in the composite as a chemical neutraliser.

[0047] In embodiments, the composite material 1 further includes reinforcement material, preferably a fibre. The reinforcement fibre comprises at least one fibre selected from glass, carbon, steel, wool, hemp or fibrous plant material or a combination thereof. The reinforcement fibre is present in the composite material 1 in a concentration of 3 wt% to 90 wt%.

[0048] In a further aspect, the invention relates to a method for manufacturing a composite material. The method involves combining 80 wt% to 90 wt% of filler material, 10 wt% to 20 wt% of binder material to form a mixture. In embodiments, a substance to encourage cross linking between the binder constituents is added. The components are then thoroughly mixed for 5 to 30 minutes.

[0049] Figure 1 is a flowchart illustrating an embodiment of the method 10 of making a composite material in accordance with an embodiment of the invention. The method 10 includes a step of adding constituents into a mixer 12, namely the filler material and the cross-linking binder material and any reinforcement. The constituents are then mixed to provide a homogenous mixture 14. The mixture is removed from the mixer 16 and allowed to cure. In the method 10 of Figure 1 , the mixture is placed in a mould 18 in which the mixture is allowed to cure 20. Alternatively, the mixture may be placed into another receptacle or form in which the mixture is allowed to cure and harden.

[0050] In embodiments, other blending or mixing apparatus including a blender, tumble mixer, injection, spray and sublimation can be used to blend or mix the constituents.

[0051] In embodiments, the mixture is created on-site and is deposited onto roads for use as a filler for road maintenance. In other embodiment, the mixture is deposited into forms or moulds to form roads and pavements, construction products and dam and irrigation lining to name a few.

[0052] In other embodiments, the mixture is created on-site and is deposited for fluid infrastructure construction and remediation, rapid construction of roads and infrastructure services, for example in disaster recovery.

[0053] In other forms, the mixture derived from the method 1 is deposited into moulds or forms for the containment of other toxic materials such as e- waste, medical waste or nuclear waste.

[0054] In the abovementioned embodiments, after the mixture is placed into the mould or form, the mixture is allowed to cure 20 to thereby form the final composite material.

[0055] The present invention includes a composite material comprising: a binder capable of cross linking; and a filler. Preferably, the composite materialincludes a reinforcement material such as glass, carbon, steel, wool, hemp or fibrous plant material.

[0056] In embodiments, the invention relates to a composite material comprising: 80 wt% to 90 wt% of the filler material; 10 wt% to 20 wt% of the binder material. In embodiments, 3 wt% to 90 wt% of reinforcement material is dispersed within the composition.

[0057] In embodiments, the filler material is bauxite residue (i.e. red mud). In other embodiments, the filler material includes other bulk materials such as mining waste or tailings, zeolite, limestone, potash, inorganic mined materials or reclaimed demolition materials that may contain the aforementioned materials or combinations thereof.

[0058] The binder includes a matrix of cross-linked polymer material comprised of polymer chains and a series of cross links therebetween. The reinforcement material is a fibre, glass, carbon, steel, wool, hemp or fibrous plant material.

[0059] In some embodiments, the composite material further includes a substance to encourage cross linking between the binder and the filler, preferably any one or more of carbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

[0060] Referring to Figure 3, there is shown a method and apparatus for the deposition of the composite material to form a road surface in accordance with an embodiment of the invention.

[0061] The method includes providing the binder and filler into a mixing chamber 82 and thoroughly mixing the constituents. The resulting mixture 85 is deposited onto a surface. A compactor machine 90 compresses the mixture 85 which then cures to form a road surface 80. In other embodiments, the composite material is self levelling and does not need to be compacted.

[0062] The mixture 85 is comprised of 80 wt% to 90 wt% of filler material and 10 wt% to 20 wt% of binder material. Preferably a substance to encourage cross linking between the binder constituents is added to the mixing chamber 82 and thoroughly mixed along with the other constituents.

[0063] Preferably, the filler which is added to the mixing chamber 82 comprises bauxite residue (i.e. red mud). In other embodiments, the filler material includes other bulk materials such as mining waste or tailings, zeolite, limestone, potash, inorganic mined materials or reclaimed demolition materials that may contain the aforementioned materials or combinations thereof.

[0064] The materials added to the mixing chamber 82 that are to be reacted (cross-linked) to provide the binder include a first part and a second part. The first part is comprised of epichlorohydrin (ECH) and the second part includes a bisphenol, such as bisphenol A, bisphenol F, or a brominated bisphenol. In another embodiment, the binder includes a thermosetting polymer, preferably any one of polyurethane, polyester, polyurea or a vinyl ester resin.

[0065] Preferably the composite material 85 includes 80 wt% to 90 wt% of the filler material and 10 wt% to 20 wt% of the binder material.

[0066] The method enables the deposition, in batches, of a homogenous composite mixture on-site to form a road surface.

[0067] In another example, the composite mixture is deposited into a mould to form a containment vessel adapted for containing hazardous materials such as toxic and low-level radioactive wastes. The containment vessel is adapted as an alternative to existing waste containment systems that often comprise cements that are prone to degradation and cracking overtime from the waste.

[0068] An advantage of embodiments of the invention is doing away with the need to separate different materials from the aggregate filler, for example metal, glass or other minerals. Embodiments of the invention enable the useof mixed waste aggregates and is therefore more cost effective and has an inherent lower carbon footprint.

[0069] Weight percentages (wt %) of a particular component are given with reference to any material of which the particular component forms a constituent part. Unless stated otherwise, weight percentages refer to “dry weights”, and suitably exclude any solvents (e.g. water) used to slurry ingredients to assist in the mixing thereof. It will be understood by those skilled in the art that the summation of wt % values for all components with a material (including both stipulated and unstipulated components) should total 100 wt %. It will be understood by those skilled in the art that stipulation of a weight percentage for a particular component does not necessarily limit the potential weight percentage values allowed for other components (whether such other components are stipulated or not), except where a stipulated minimum wt % for the particular component will naturally limit the maximum wt % for other components (whether stipulated or otherwise) given that the total wt % values for all components (including any unstipulated ingredients) will inevitably total 100 wt %.

[0070] Particle size relates to the length of the longest dimension of a given particle. Particle size may be measured by a variety of methods well-known in the art, including sieving, laser diffraction, and so forth.

[0071] Herein, the term “consists essentially of’ or “essentially consists of’ means a given material primarily consists of a given component, suitably at least 75%, suitably at least 90%, suitably at least 97%, suitably at least 99%, and suitably substantially 100% of the given component.

Claims

CLAIMS:

1. A composite material comprising: a binder capable of cross linking; and a filler.

2. The composite material of claim 1, wherein the binder is an epoxy.

3. The composite material of claim 1 , wherein the binder includes a first part and a second part.

4. The composite material of claim 3 wherein the first part includes epichlorohydrin (ECH).

5. The composite material of claim 3, wherein the second part includes a bisphenol, such as bisphenol A, bisphenol F or a brominated bisphenol.

6. The composite material of claim 1, wherein the binder includes a thermosetting polymer.

7. The composite material of claim 6, wherein the thermosetting polymer includes any one of polyurethane, polyester, polyurea or a vinyl ester resin.

8. The composite material of claim 1, wherein the filler includes bauxite residue (i.e. red mud).

9. The composite material of claim 1, wherein the filler material includes mining waste or tailings, zeolite, limestone, potash, inorganic mined materials or reclaimed demolition materials or combinations thereof.

10. The composite material of claim 1, further including a substance to encourage cross linking between the binder constituents.

11. The composite material of claim 1 , further including a substance to encourage cross linking between the binder and the filler.

12. The composite material of claim 10 or claim 11 , wherein the substance to encourage cross linking includes any one or more of carbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

13. The composite material of claim 1 , including 10 wt% to 20 wt% of the binder material and 80 wt% to 90 wt% of the filler material.

14. The composite material of claim 1 , further including a reinforcement material.

15. The composite material of claim 14, including 3 wt% to 90 wt% of the reinforcement material.

16. The composite material of claim 14, wherein the reinforcement material comprises glass, carbon, steel, wool, or hemp or fibrous plant material.

17. A method for making a composite material including combining: a binder capable of cross linking; and a filler.

18. The method of claim 17, including mixing the binder and the filler together using any one or more of a blender, a tumble mixer, injection, spray or sublimation.

19. The method of claim 17, wherein the binder includes is an epoxy derived from mixing epichlorohydrin (ECH) and a bisphenol or a thermosetting polymer comprising any one of polyurethane, polyester, polyurea or a vinyl ester resin.

20. The method of claim 17, including adding a substance to encourage cross linking between the binder constituents including any one or more ofcarbon black, calcium carbonate, organic peroxides, amines or amides, silanes, epoxies, free radical and Ultra Violet cure monomers or isocyanates.

21. The method of claim 17, including combining 10 wt% to 20 wt% of the binder material and 80 wt% to 90 wt% of the filler material.

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