Metal leach and recovery process

Patent metadata

Field	Value
Publication number	US-9657368-B2
Application number	US-201314416748-A
Country	US
Kind code	B2
Filing date	Aug 7, 2013
Priority date	Aug 10, 2012
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

The present invention relates to a metal leach and recovery process. The process involves subjecting a metal bearing material to a reactive process by combining said metal bearing material with a leaching agent to liberate at least one metal value and forming a first aqueous leach pulp. This first aqueous leach pulp is subjected to a solid liquid separation step thereby providing a first clarified aqueous leach solution and a second aqueous leach pulp. The first clarified aqueous leach solution is then subjected to solvent extraction thereby obtaining the first aqueous raffinate. The second aqueous leach pulp is subjected to at least two further solid liquid separation steps of which some or all are in a counter current decantation (CCD) arrangement. Each of the solid liquid separation steps of the CCD arrangement results in an aqueous liquor and aqueous suspension of solids wherein each aqueous suspension of solids resulting from each solid liquid separation step of the CCD arrangement is passed to the subsequent solid liquid separation step and the suspension of solids resulting from the final solid liquid separation step is removed from the process. Further, each aqueous liquor resulting from each solid liquid separation step of the CCD arrangement is passed to the previous solid liquid separation step. The further solid liquid separation steps result in at least one further clarified aqueous leach solution. The at least one further clarified aqueous leach solution is/are subjected to solvent extraction thereby obtaining at least one further aqueous raffinate. At least a portion of the one or more of the at least one further aqueous raffinates is fed into the final solid liquid separation is of the CCD arrangement. The process provides a flocculation system comprising either: (i) addition of an organic polymeric flocculant to or prior to at least one solid liquid separation step, which polymeric flocculant is formed from 2-acrylamido-2-methylpropane sulphonic acid (ATBS) or salts thereof as a homopolymer or copolymer with at least one water-soluble ethylenically unsaturated monomer; or (ii) addition of an organic polymeric flocculant and at least one support agent to or prior to at least one solid liquid separation step, which at least one support agent is selected from at least one of the group consisting of oxidizing agents, reducing agents, irradiation and free radical producing agents. The process provides significantly improved metal extraction and recovery.

First claim

The invention claimed is:

1. A metal leach and recovery process comprising:
(a) subjecting a metal bearing material to a reactive process by combining said metal bearing material with a leaching agent to liberate at least one metal value from said metal bearing material and obtain a first aqueous leach pulp comprising a mixture of leached solids and an aqueous leach solution comprising at least one metal value, a leaching agent and water;
(b) subjecting the first aqueous leach pulp to a solid liquid separation step to provide a first clarified aqueous leach solution and a second aqueous leach pulp, wherein the second aqueous leach pulp comprises a greater solids content than the first aqueous leach pulp;
(c) subjecting the first clarified aqueous leach solution to solvent extraction thereby obtaining a first aqueous raffinate;
(d) subjecting the second aqueous leach pulp to at least two further solid liquid separation steps of which some or all of the further solid liquid separation steps are in a counter current decantation (CCD) arrangement in which each solid liquid separation step of the CCD arrangement results in an aqueous liquor and an aqueous suspension of solids, wherein each aqueous suspension of solids resulting from each solid liquid separation step of the CCD arrangement is passed to the subsequent solid liquid separation step of the CCD arrangement and the aqueous suspension of solids resulting from the final solid liquid separation step of the CCD arrangement is removed from the process and wherein each aqueous liquor resulting from each solid liquid separation step of the CCD arrangement is passed to the previous solid liquid separation step, in which at least one further clarified aqueous leach solution results from at least one of the further solid liquid separation steps;
(e) subjecting the at least one further clarified aqueous leach solution to solvent extraction thereby obtaining at least one further aqueous raffinate;
(f) feeding at least a portion of the one or more of the at least one further aqueous raffinates into the final solid liquid separation step of the CCD arrangement;
wherein at least one of the solid liquid separation steps is subjected to a flocculation system in which the flocculation system comprises either:
(i) addition of an organic polymeric flocculant to or prior to at least one solid liquid separation step, which polymeric flocculant is formed from 2-acrylamido-2-methylpropane sulphonic acid (ATBS) or salts thereof as a homopolymer or copolymer with at least one water-soluble ethylenically unsaturated monomer; or
(ii) addition of an organic polymeric flocculant and at least one support agent to or prior to at least one solid liquid separation step, which at least one support agent is selected from at least one of the group consisting of oxidising agents, reducing agents, irradiation and free radical producing agents.

2. A process according to claim 1 in which the organic polymeric flocculant is a copolymer of ATBS and either acrylamide or methacrylamide.

3. A process according to claim 1 in which the organic polymeric flocculant is a copolymer of sodium acrylate and either acrylamide or methacrylamide and used in conjunction with the support agent.

4. A process according to claim 1 in which the organic polymeric flocculant is used in conjunction with an oxidising agent, preferably hydrogen peroxide or ozone.

5. A process according to claim 1 in which the organic polymeric flocculant is used in conjunction with irradiation, preferably ultrasonic irradiation.

6. A process according to claim 1 in which the support agent is used in conjunction with at least one control agent, in which the at least one control agent consists of iia) at least one activator component and/or iib) at least one suppressor component, in which the at least one activator component increases the activity of the oxidising agent and the suppressor component decreases the concentration of the activator component.

7. A process according to claim 1 in which the organic polymeric flocculant exhibits an intrinsic viscosity of at least 4 dl/g.

8. A process according to claim 1 in which the flocculation system is applied to either or both of the final or penultimate solid liquid separation stages of the CCD arrangement.

9. A process according to claim 1 in which the first clarified aqueous leach solution and the at least one further clarified aqueous leach solutions are both/all fed to a solution extraction plant comprising at least two solution extractors and at least one stripping unit.

10. A process according to claim 1 in which the second leach pulp is subjected to a further leach stage and then passed to further solid liquid separation stages in which the further solid liquid separation stages comprise an intermediate solid liquid separation stage which is not part of the CCD and subsequent solid liquid separation stages which are part of the CCD arrangement,
wherein two further clarified aqueous leach solutions are produced comprising a second clarified aqueous leach solution resulting from the intermediate solid liquid separation stage which is not part of the CCD arrangement and a tertiary clarified aqueous leach solution resulting from the first of the solid liquid separation stages of the CCD arrangement,
in which the second and the third clarified aqueous leach solutions are both subjected to solvent extraction to produce a second raffinate and a third raffinate.

11. A process according to claim 10 in which at least a portion of the second raffinate is fed into either or both of the second aqueous leach pulp or the first aqueous leach pulp.

12. A process according to claim 10 in which essentially all of the second raffinate is fed into the second aqueous leach pulp.

Assignees

• Basf Se

Inventors

• Nisbett Andrew
• Adkins Stephen
• Flanagan Ian John
• Berger Alexsandro

Classifications

• C22B15/0084

  Treating solutions (with organic compounds C22B3/20) · CPC title

• C22B3/44 Primary

  by chemical processes (treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42) · CPC title

• C22B3/04

  by leaching (C22B3/18 takes precedence) · CPC title

• B01D21/01 Primary

  using flocculating agents (for purifying water C02F1/52; for liquid radioactive waste G21F9/10) · CPC title

• C22B3/205

  using adducts or inclusion complexes · CPC title