GB2456645A

GB2456645A - Extraction from an ore using a redox reagent, a pH adjuster and a dissolution promoter

Info

Publication number: GB2456645A
Application number: GB0801378A
Authority: GB
Inventors: John William Carson
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-25
Filing date: 2008-01-25
Publication date: 2009-07-29
Anticipated expiration: 2028-01-25
Also published as: GB0801378D0; GB2456645B

Abstract

A process for the extraction of a reactive element from ore by feeding a redox reagent, a pH adjusting entity (including buffers) and a reactive element dissolution promoter into the proximity of the ore via at least one bore hole and recovering reaction products from at least one bore hole. The redox reagent, pH adjusting entity and reactive element dissolution promoter can be fed separately or together as a single reagent composition with each constituent dissolved or suspended in water. The reactive element dissolution promoter may be a secondary oxidant, a secondary reductant, a secondary acid, a secondary base, dual valency transition metal coordination compounds, chelating agents, (poly)oxo anions, complex anions/cations, zero charge complexes, organometallics, organic ligand complexes, enzymic complexes, protein inorganic metal complexes, crown structures and cryptstands.

Description

IMPROVED EXTRACTION FROM ORES

The present invention relates to a process by which elements can be extracted from ores, and a substrate specific reagent composition for use in the process.

In particular, the invention relates to a process which utilises substrate specific reagents applied to ore bodies in situ, that is in locations within the geological strata wherein they are contained.

Such substrate specific reagents may be percolated through strata containing the ore body of the element or elements to be extracted.

An advantage of the present invention is that the process may be applied to a wide range of minerals and native elemental entities, without the need for extensive mining or other conventional extraction procedures.

The present invention provides both a range of novel substrate specific reagents and a process by which they may be applied in the extraction of ranges of elements from specific ores.

In this specification the ore body is the substrate to be reacted.

Whereas it is known that certain acids, alkalis, oxidants and reductants may dissolve or partially dissolve specific ores, so as to facilitate the extraction of certain elements, it has now been discovered that this effect can be significantly improved by the application of these reactants in the form of the substrate specific reagent compositions of the present invention.

By substrate specific reagents, in this specification, we mean reagents that act preferentially on a reactive element in the ore body.

By reactive element in the ore body we mean a specific element present in the ore, which may or may not be the targeted element.

By targeted element we mean the valuable element present in the ore, which is the subject of the main commercial aim of the extractive process.

By way of an explanation, it has now been discovered that targeted elements may be extracted from ores via the dissolving effect caused by substrate specific reagent compositions. This dissolution process may solubilise either the reactive element or the targeted element or both. The dissolution process suitably de-structures the ore body and allows for the removal of the targeted element in a freed physico- chemical format.

The physico-chemical function achieved by the substrate specific reagent composition of the present invention may be for example, an accelerated form of acid dissolution, alkali, dissolution, oxidative dissolution, reductive dissolution or any known chemical combination of the above, of the reactive element, which may or may not be the targeted element.

The physico-chemical format produced by the substrate specific reagent composition may be a solubilised or suspended form of acidified, basified, oxidised or reduced form or any known chemical combination, of the reactive element which may or may not be the targeted element.

In simple terms we may describe the overall effect of the process of the present invention as kinetically breaking the ore body so as to release elements that can then be freed for extraction.

The present invention provides a process for the extraction of various elements from their ore bodies without the need for conventional mining via the application of substrate specific reagents which solubilise components of the ore and render them recoverable as pumpable solutions or suspensions.

The process may provide for the chemical extraction of metal, transition metal and non-metal elements from ore bodies.

According to a first aspect of the present invention, there is provided a substrate specific reagent composition comprising: a redox reagent; a pH adjusting entity; and a reactive element dissolution promoter.

The substrate specification reagent composition is

preferably an aqueous composition. Suitably the redox reagent, pH adjusting entity and reactive element dissolution promoter are dissolved or suspended in water.

According to a second aspect of the present invention, there is provided a process for the extraction of a reactive element from an ore body, the process comprising applying to the ore body a redox reagent, a pH adjusting entity and a reactive element dissolution promoter.

In the process of the second aspect, each of the redox reagent, pH adjusting entity and reactive element dissolution promoter may be applied alone or in combination with one or more of the other components.

Each component may optionally comprise a mixture of reagents. For example the process may comprise applying a mixture of one or more redox reagents and/or one or more pH adjusting agents and/or one or more reactive element dissolution promoters. Thus the redox reagent, pH adjusting entity and reactive element dissolution promoter may be applied concurrently or sequentially. Preferably the process of the second aspect comprises applying to the ore body a composition of the first aspect.

The nature of the substrate specific reagent composition that is the subject of the present invention will now be defined.

The redox reagent (also referred to herein as redox entity) is suitably an oxidant or a reductant. A mixture of two or more oxidants and/or reductants may be used.

Hydrogen peroxide contained in an aqueous solution is an example of a suitable oxidic ingredient for use as a redox reagent in the substrate specific reagent composition.

Nascent hydrogen derived from, for example, the reaction between powered zinc and a strong inorganic acid, may be used as a redox reagent and is an example of a suitable reductive entity in the substrate specific reagent composition.

The pH adjusting entity (or pH controlling entity), may be an acid, an alkali, a buffering salt or a mixture thereof.

Suitable examples of useful pH adjusting entities include strong inorganic acids, strong inorganic alkalis and chemical buffering salts. Chemical buffering salts are typically either salts based on strong acids and weak bases, or weak acids and strong bases. The overall result of the addition of such buffers is to alter and then maintain a specific mid range pH.

The substrate specific reagent composition also comprises a reactive element dissolution promoter.

By reactive element dissolution promoters we mean specific complex chemical substances that act so as to accelerate the effect of the other two components in the substrate specific reagent composition.

Suitable reactive element dissolution promoters include secondary oxidants, secondary reductants, secondary acids and secondary bases. Advantageously these may also contain secondary buffering agents, and complexing agents that maintain either or both the reactive and the targeted element in solubilised form.

Though not catalysts in the chemical sense of the term, these reactive element dissolution promoters suitably work with the redox and pH adjusting chemicals so as to promote and accelerate the desired reaction on the ore.

Though as yet not fully understood it is believed that these reactive element dissolution promoters function by providing oxidative or reductive chemical bridges for the desired reactions on the targeted element in the ore body.

The reactive element dissolution promoters may be selected from complex chemical entities for example, coordination compounds of dual valency transition metals, chelating agents, oxo and poly oxo anions, complex cations, complex anions, zero charge complexes, organometalics, organic ligand complexes, enzymic complexes, protein inorganic metal complexes, crown structures, cryptands and other advanced chemicals.

The reactive element dissolution promoters may confer chemically distinguishing features as specific extracted elements from the core bodies treated, via approaches such as coordinate compound formation, complexation, chelation and crypstand formation.

It is a feature of the present invention that a wide range of highly specific reactive element dissolution promoters have been discovered and can be made available for the treatment of many commercial and currently mined ore bodies.

These reactive element dissolution promoters may accelerate the solubilisation of the reactive element in the ore body and may also serve to maintain the dissolved substances in solution.

It is believed that the solubility maintaining function of the above grouping of types of reactive element dissolution promoters is that they provide linkage points with specific ionic radii. In this way they may be targeted for the abstraction of specific elements contained in specific form in specific ores.

It is a feature of the present invention that relatively small quantities of reactive element dissolution promoter are needed to effect the accelerated dissolution and solubility maintenance of reactive elements in specific ores on which they are targeted.

Preferably the substrate specific reagent composition of the present invention is an aqueous composition comprising significant quantities of a redox reagent, significant quantities of a pH adjusting entity, and smaller quantities of a reactive element dissolution promoter.

Typically, the substrate specific reagent composition contains: 5% to 95% w/w of a redox reagent; 5% to 95% wlw of a pH adjusting entity; and -% to 5% w/w of a reactive element dissolution promoter.

Preferably, the substrate specific reagent composition contains: 50% to 90% w/w of a redox reagent; 5% to 50% w/w of a pH adjusting entity; and 0.0001% to 0.1% w/w of a reactive element dissolution promoter.

By applying a substrate specific reagent composition, as defined herein, to specific ores the reactive element, which may or may not also be the targeted element, may be abstracted into the aqueous phase via an accelerated process.

The targeted element, if it is not also the reactive element, may then be extracted from the ore body either as a solution or a suspension.

The result of using a substrate specific reagent composition, as defined herein, is to significantly reduce the current difficulties associated with the mining of certain specific elements.

The scope for the use of the substrate specific reagent approach to mining will now be defined, firstly in general terms.

Substrate specific reagents may be applied in the extraction of a wide range of elements.

Any element may be extracted from an ore in which it is contained if either the target element or the reactive element, or both, are capable of chemical existences in two or more valencies. Thus both native element and mineral ores may be so treated.

Also it will be recognised that a wide range of metal and metal containing ores may be so treated.

Rare elements contained in small quantities in ores may also be recovered.

Additionally many non-metallic elements can be so treated.

Many rarer metals and elements contained in small quantities in ores together with less rare metals or elements may be treated as to first solubilise the less rare element. The effect of dissolving the less rare element from the ore matrix frees or aids the release of the rarer element.

The use of substrate specific reagents is believed to amount to a significant commercial improvement, in the form of an alternative to conventional mining. This assertion stems from the recognition that substrate specific reagent compositions may be used in-situ i.e. via pipelines or bore holes to the proximity of the ore body rather than massive excavation, as is current practice.

These aspects of the current invention will be described later in this patent application.

The scope for the use of substrate specific reagent compositions will now be defined in terms of a limited number of specific examples of types of reagent developed for the treatment of a specific ore.

To date we have discovered and are developing many substrate specific reagents, as described herein, for the in-situ treatment of many specific ores, and our research continues. The following are therefore only examples of the types of substrate specific reagents we have developed, together with definitions of appropriate ore bodies.

We have chosen the following two examples because they are based on commercially available reactive element dissolution promoters.

The first quoted example is a form of alkaline oxidative extraction.

The second quoted example is a form of acidic reductive extraction.

Example 1

A suitable substrate specific reagent for the extraction of chromium from chromite ore, may comprise a water based solution of hydrogen peroxide an alkaline, buffering agent such as sodium citrate together with sodium hydroxide and a small quantity of a manganese complex based on nine member ligand rings known as "Gandor". Gandor is a commercially available reagent used in the peroxide bleaching of cellulosics for example cotton and wood pulp.

The result of applying the above substrate specific reagent is the oxidation of both iron, the reactive element and chromium, the target element, and their removal from the spinal structure of the chromite ore, in dissolved form.

Example 2

A suitable substrate specific reagent for the extraction of chromium from chromite ore may comprise a water based solution of nascent hydrogen produced in-situ via reaction of hydrochloric acid on finely divided zinc powder, together with the aforementioned acid and a small quantity of a vanadium complex based on picolinate ligands known as a LOMI reagent.

LOMI (Low Oxidation Metal Ion) reagents are commercially available heater circuit descaling agents used in the nuclear power generation industry. The result of applying the above substrate specific reagent is the reduction of the chromium, which in this case is both the reactive and the target element, and its removal from the spinal structure of the chromite ore, in dissolved form.

Many other substrate specific reagents both based on currently commercially available reactive element dissolution promoters and further types currently under development, have been shown to be effective in the improved ore extraction procedure which is the subject of the current invention.

The scope of the current invention will now be further demonstrated via a listing of proven examples of ores that can be treated via selected substrate specific reagent compositions for the extraction of the targeted element: Copper via an acidic reductive version on malachite.

Tin via an acidic reductive version on cassiterite.

Titanium via an acidic oxidatative version on ilmenite.

Manganese via either an alkaline oxidative version on rhodochrosite, or an acidic reductive version on pyrolusive.

Chromium via an alkaline oxidative version on chromite, or an acidic reductive version on the same ore.

Nickel via an acidic oxidative version on suiphide ores, or an acidic reductive version on divalent ores.

Molybdenum via an alkaline or buffered oxidative version on molybdenite, or an acidic reductive system on higher valency ores.

Tungsten via an alkaline or buffered oxidative version on wolframite, or an acidic reductive version on woiframite or scheelite.

Cobalt via an acidic oxidative version on cobaltite, or an acidic reductive version on trivalent ores or nickel/copper tailings.

Uranium via an alkaline oxidative version on uraninite ie pitchblend, or an acidic reductive version based on ores containing one or more higher valency.

Zirconium via an acidic reductive version on zircon sands.

Vanadium via an alkaline oxidative version on vanadinite or carnotite, or an acidic reductive version on higher valency ores.

Cerium via an alkaline or buffered oxidative version on monozite sands, or an acidic reductive version on bastnasite.

Niobium via an alkaline oxidative version on niobite or columbite.

Tantalum via an alkaline oxidative version on tantalite or colurnbite.

Platinum group via alkaline or acid oxidative versions on native metals or suiphide ores.

Nobel metals via alkaline or acid oxidative versions on native metal or suiphide ores.

Additionally, our work continues on the development of substrate specific reagent compositions for treatment of the following ores: Carbonate-based oil shales for oil extraction.

Magnetite, hematite, siderite for iron extraction.

Bauxite, boehmite, diaspore and gibbsite for aluminium extraction.

Sphalerite and hemimorphite for zinc and associated rarer metals.

Galena, anglesite for lead and associated rarer metals.

Cinnabar, for mercury.

Basalt, for a wide range of rarer elements.

Granite, for a wide range of rarer elements.

Ways in which the substrate specific reagent compositions, as defined herein, may be applied to ore bodies will now be described.

Typically a substrate specific reagent composition is pumped or fed into the proximity of the ore body via a hole or bore holes and, after reaction, the reaction products are recovered in a similar manner.

In a relatively simple embodiment of the current invention the substrate specific reagent composition may be applied and the reaction products recovered via a single concentric bore hole. The composition may be transported to the ore body down the annulus and the reaction products recovered via the central pipe.

Alternatively, two simple bore holes may be used. These are to be positioned one upstream of the ore body, in terms of natural subterranean water flowing through the strata, and the other downstream of the ore body. The composition is supplied through the upstream bore and the reaction products recovered through the downstream bore.

In a further embodiment a single reactant bore hole may be surrounded or partially surrounded by a ring of reaction product extraction bore holes.

In some situations a single bore hole can be used for the composition, and the reaction products recovered from natural springs issuing from the ore body.

Using any of the above four examples or any further currently applied bore hole mining technologies, substrate specific reagent compositions may conveniently be applied to ore bodies.

In the case of some alluvial deposits, bore holes are not required and the ore sands may be treated in lined lagoons or tanks.

A similar system may be applied in the cases of previously mined ores and ore tailings.

In many situations the simple provision of the substrate specific reagent composition and the recovery of the reaction products will yield the targeted element.

However, in more sophisticated embodiments of the current invention, extraction efficiencies may be increased by any one or combinations of the following: In a further embodiment of the current invention the substrate specific reagent compositions may be heated prior to use.

In a further embodiment of the current invention the pH of the substrate specific reagent composition may be progressively changed during the application of the substrate specific reagents.

In a further embodiment of the current invention a sequence of two or more substrate specific reagent compositions may be introduced, with differing redox potentials, in sequence or concurrently.

In a further embodiment of the current invention two or more reactive element dissolution promoters may be used, in sequence or concurrently.

In a further embodiment of the current invention, an electric current may be established between bore hole systems.

In a further embodiment of the current invention a two stage extraction process may be used which can involve firstly an oxidative phase followed by a reductive phase, or, firstly a reductive phase followed by an oxidative phase.

By applying any one or a combination of the above embodiments, the extraction rate of targeted elements may be improved.

The result obtained is suitably a flow of reaction products containing the extracted targeted element together with other entities derived from the dissolution process and residues from the pH adjusting and redox components and reactive element dissolution promoter.

The target element may be recovered from this water based mixture by any appropriate standard chemical separation procedure, for example as is currently applied to the element concerned.

These recovery processes are well known in mining chemistry and may involve the application of any one or a sequence of the following: pH alteration; precipitation; solubilisation; ion exchange; solvent extraction; froth floatation; chelation; electrochemical reaction; evaporation; crystallisation; oxidation; reduction, and smelting.

The resulting product will be the targeted element in the form of either the metal or non-metal or commercially usable chemicals derived from the same.

It is an advantage of the current invention that the separation of the targeted element from the reaction products may be simplified or improved in terms of efficiency because of the specific nature of the reactive element dissolution promoter used in the substrate specific reagent. This effect stems from the ability of the reactive element dissolution promoter to selectivity abstract specific targeted elements. Specifically, we believe, this is achieved on the basis of ionic radii, although other mechanisms may also be involved.

The result is that the targeted element entities produced differ chemically, and are therefore easier to separate from, the other reaction products.

In some cases valuable dissolved co-products may also be recovered via the above techniques.

In still further cases at least some part of the reactive element dissolution promoter may also be recoverable.

The overall result achieved by the process of the present invention is the economic extraction of a wide range of commercially important elements from their ores.

Moreover, the present invention permits much energy to be saved because of the significant reduction in extractive effort. Far less overburden and non-ore rock needs to be excavated than in conventional mining.

This reduction in the generation of mine spoils also has a beneficial effect on the local scenery, the local ecology and the environment generally.

Taken together, we believe the above improvements constitute a major breakthrough in the extractive industry Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A substrate specific reagent composition comprising: a redox reagent; a pH adjusting entity; and a reactive element dissolution promoter.

2. A composition according to claim 1 wherein the redox reagent, pH adjusting entity and reactive element dissolution promoter are dissolved or suspended in water.

3. A composition according to claim 1 or claim 2, wherein the reactive element dissolution promoter is selected from a secondary oxidant, a secondary reductant, a secondary acid and a secondary base.

4. A composition according to claim 1 or claim 2, wherein a reactive element dissolution promoter is selected from coordination compounds of dual valency transition metals, chelating agents, oxo and poiy oxo anions, complex cations, complex anions, zero charge complexes, organometallics, organic ligand complexes, enzymic complexes, protein inorganic metal complexes, crown structures and cryptstands.

5. A composition according to any preceding claim which comprises: 50% to 90% w/w of a redox reagent; 5% to 50% w/w of a pH adjusting entity; and 0.0001% to 0.1% w/w of a reactive element dissolution promoter.

6. A process for the extraction of a reactive element from an ore body, the process comprising applying to the ore body a redox reagent, a pH adjusting entity and a reactive element dissolution promoter.

7. A process according to claim 6, which comprises applying to the ore body a composition as claimed in any of claims 1 to 5.

8. A process as claimed in claim 6 or claim 7 in which the redox reagent, a pH adjusting entity and a reactive element dissolution promoter are pumped or fed into the proximity of the ore body via a bore hole or bore holes and reaction products are recovered via a bore hole or bore holes.

9. A composition or process substantially as hereinbefore described with reference to the examples.