AU617166B2 - Hydrometallurgical effluent treatment - Google Patents

Description

OPI DATE 16/10/89 w, AOJP DATE 09/11/89 APPLN. ID 33649 89

PCT

PCT NUMBER PCT/AU89/00144 INTERNATIONAL APPLICATION PUB EdB6 UNDER THE P&N OOPERATION TREATY (PCT) (51) International Patent Classification 4 C02F 1/62 S(1 InternitionjubllAon Number: WO 89/ 09192 Al (43) International Publication Date: 5 October 1989 (05.10.89) (21) International Application Number: PCT/AU89/00144 (22) International Filing Date: (31) Priority Application Number: (32) Priority Date: (33) Priority Country: 31 March 1989 (31.03.89) PI7564 31 March 1988 (31.03.88) (71) Applicant (for all designated States except US): COM- MONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION [AU/AU]; Limestone Avenue, Campbell, ACT 2601 (AU).

(72) Inventors; and Inventors/Applicants (for US only) DIXON, David, Roger [AU/AU]; 31 Eustace Street, Blackburn, VIC 3130 HA, Tiong, Chee [Ai/AU]; 13 Bennett Parade, East Kew, VIC 3102 (AU).

(74) Agents: CORBETT, Terence, G. et al.; Davies Collison, 1 Little Collins Street, Melbourne, VIC 3000

(AU).

(81) Designated States: AT (European patent), AU, BB, BE (European patent), BF (OAPI patent), BG, BJ (OAPI patent), BR, CF (OAPI patent), CG (OAPI patent), CH (European patent), CM (OAPI patent), DE (European patent), DK, FI, FR (European patent), GA (OAPI patent), GB (European patent), HU, IT (European patent), JP, KP, KR, LK, LU (European patent), MC, MG, ML (OAPI patent), MR (OAPI patent), MW, NL (European patent), NO, RO, SD, SE (European patent), SN (OAPI patent), SU, TD (OAPI patent), TG (OAPI patent), US.

Published With international search report.

Before the expiration of the time limit for amending the claims and to be republished in the event of the receipt of amendments.

(54) Title: HYDROMETALLURGICAL EFFLUENT TREATMENT (57) Abstract A method for removing metal ions from solution, which comprises contacting the solution with a particulate mineral or clay material, in the presence of an alkali or alkaline earth metal oxide, hydroxide, carbonate or sulphide and a polyelectrolyte, whereby the particulate material becomes coated with a precipitate of the oxide, hydroxide, carbonate or sulphide of the metal(s).

2 i WO 89/09192 PCT/AU89/00144 -1- HYDROMETALLURGICAL EFFLUENT TREATMENT This invention relates to a method for the recovery and/or removal of metal ions from aqueous solutions, 27 especially effluents from mining and ore treatment processes.

29 Hydrometallurgy has evolved as firstly an art and 31 now a science dedicated to the production of metals from mineral ores using solution (usually aqueous) processes 33 rather than the high temperature approach of pyrometallurgy. There are three fundamental aspects: dissolution or leaching by chemical or biological means to solubilize the metals; concentration and/or separation of 37 unwanted components; and recovery of the desired metal.

39 Methods of solution purification include cementation, crystallization, and precipitation as 41 hydroxides, sulphides or carbonates. More recently used 7 WO 89/09192 PCT/AU89/00144 -2- 1 processes include ion exchange, solvent extraction and membrane processes such as reverse osmosis. Most of the 3 latter require a preliminary solid-liquid separation to remove suspended matter and if possible some of the unwanted metal species.

7 The most common precipitation technique used is hydroxide treatment because of its relative simplicity, 9 low cost of precipitant (lime), and ease of automatic pH control. In small plants, simpler and less expensive 11 batch systems are more feasible, but a continuous treatment system can be used when flow rates are larger.

13 The metal hydroxide precipitates tend to be colloidal and amorphous in nature, causing the resultant sludge to be voluminous and difficult to de-water. The other limitation associated with hydroxide treatment is that the 17 presence of complexing agents severely inhibits hydroxide formation and precipitation.

19 Sulphide precipitation is an effective alternative 21 to the above, with attractive features such as precipitation at lower pH values, lower sensitivity to the 23 interference from complexing agents, greater selectivity with the possibility of recovery of specific metals, and less gelatinous sludges. However there are several disadvantages, including the potential for H 2 S gas 27 evolution, environmental concern for sulphide toxicity and the problems associated with sulphide contamination of the 29 mine circuit waters, which need to be recycled and used elsewhere on the mining site. The use of sodium carbonate 31 to precipitate metals is another alternative.

33 Despite nearly three hundred years of success in mineral processing, there is increasing pressure to -3improve the efficiency of hydrometallurgical treatment. This arises from a need to treat more complex and lower grade ores such as tailings and also from the need to protect our environment. Further, many Australian mines are in dry regions where water is a precious commodity which must be conserved both in quantity and in quality. The effects of water recycling with its attendant contamination problems on the efficiency of the different hydrometallurgical processes must also be considered.

We have now found that the problems associated with collecting and handling precipitates of metal hydroxides and other compounds can be at least minimised by the addition to suspensions of such precipitates of a particulate mineral or clay material and a polyelectrolyte.

0 #0 By appropriate adjustment of the process conditions, the hydroxides or o other compounds flocculate and collect around the particles to create flocs oo .which are more readily separated from the suspension, e.g. by settling or filtration.

According to one aspect of the present invention, there is provided a method for removing metal ions from solution, especially effluents from mining and ore treatment processes, which comprises the steps of: *0 9 S. 25 contacting the solution with a magnetic or magnetisable particulate Smaterial, in the presence of an alkali or alkaline earth metal oxide, -1y 4 4dioAde. carbonate or sulphide and polyelectrolyte, whereby the particulate material becomes coated with a precipitate of the oxide, hydroxide, carbonate or sulphide of the metal; and separating the coated particulate material from the solution.

910613,dabnc.001,33649.res,3 -4- In a preferred embodiment of this invention, the magnetic or magnetisable particulate material is an iron oxide such as gamma iron oxide or magnetite. Ferrites, such as barium ferrite or spinel ferrite, can be used.

Chromite (CrO 2 can also be used. All of these oxides may be of natural or synthetic origin.

For use in the method of the present invention, the particle size of the particulate material is not critical, but most usefully will be in the range of from 1 ;o 100 microns, usually about 50 microns. The particles should not be 15 so small as to present handling problems. Particles which are too large may tend to fall through the flocs.

The method of the invention may be used for the removal of a wide variety of unwanted metal ions from 9I 9 9, .9.

iqe@ 9 9 *991, *J 9 9. 9 09

S

9

I:

s i i t ~los I 910613,dabcmr-001,33649.res,4 WO 192 PCT/AU89/00144 1 mining and ore treatment effluents or for the extraction of wanted metal values from such solutions.

3 The metals to be removed or recovered may be present in solution as free (or solvated) metal ions or may be in the form of complex ions, e.g. chloride or cyanide 7 complexes.

9 The amount and type of alkali or alkaline earth reagent oxide, hydroxide, carbonate or sulphide) 11 needed to produce the required precipitate will depend on the nature and concentration of the metals to be recovered 13 and/or removed from solution.

Suitable reagents are sodium hydroxide, carbonate or sulphide, lime, magnesium oxide or calcined dolomite.

17 Mixtures of these reagents may also be used.

19 The volume of the flocs produced may vary considerably with the choice of reagent, and thus the 21 choice of reagent will be influenced by this consideration. A fourfold or greater variation in settled 23 floc volume may result when different reagents are used.

The pH required for the precipitation of the metal by the hydroxide, sulphide or other reagent is usually in 27 range 3-12 and will be determined principally by the known chemistry of the metal or metals in the solution to be 29 treated. However, the exact pH at which precipitation occurs may vary from the theoretical value because of the 31 influence of other factors, such as the presence of other metal ions and/or differing metal ion concentrations, or 33 the presence of complexing agents. Tests should always be carried out, therefore, to determine the optimum

I

WO 89/09192 PCT/AU89/00144 -6- 1 parameters. For example, precipitation of copper hydroxide can be effected at pH 7, when the concentration 3 of copper ions is about 2000 ppm. At 200 and 20 ppm, the pH required is 8 and 9, respectively.

The principal function of the polyelectrolyte is to 7 trap traces of flocs which do not become attached to the particulate material. The polyelectrolyte may be selected 9 from a wide range of commercially-available materials.

Laboratory tests with a range of commercial flocculants 11 including those based on polyacrylamides and substituted polyacrylamides, polyamines and quaternary ammonium 13 polyelectrolytes indicate that the main prerequisite for satisfactory performance is molecular weight; in general, the higher the molecular weight, the better the performance. The "Magnafloc" LT series of flocculants 17 from Allied Colloids, which are based on poly(acrylamide) are of appropriate molecular weight (about 106) and 19 experiments with various types of polymers of about the same molecular weight but different charge shows a slight 21 advantage for anionic flocculants such as LT 23 The amount of polyelectrolyte required will generally depend on the nature and concentration of the metal(s) present in solution, and should not be such as to affect sludge density o7 interfere in the regeneration 27 process. Amounts of 1 to 2 ppm have been found to be satisfactory, but larger or smaller amounts may also be 29 used, again as determined by preliminary experiment.

31 The method of the invention can be perfomed using any suitable known apparatus.

WO 89/09192 PCT/AU89/00144 -7- 1 Stirring must be maintained to ensure that the particulate material is suspended in contact with the 3 flocs for a sufficient time to allow the attachment.

Vigorous stirring should generally be avoided because it may tear the flocs.

7 Separation of the loaded particulate material from the treated solution can be effected by any suitable known 9 method, such as sedimentation or filtration. When magnetic materials are used, separation by magnetic means, 11 e.g. in a magnetic separator, is particularly effective.

13 Regeneration f the particulate material is achieved by treating the 4--eS4ed material with an acidic solution.

By appropriate selection of the acid concentration, a low volume effluent can be produced which contains a high 17 concentration of the metallic components. If the recovered metal is the valuable material then acid 19 treatment will not only regenerate the added particulate material prior to recycle, but also provide a subsequent 21 metal recovery stage, for example; electrowinning and cementation. If the precipitated material is waste then 23 it can quickly be separated from the clarified product water and treated for metal recovery in a subsequent stage, if desired.

27 The following examples further illustrate the S principles and practice of the invention. It will be 29 understood, however, that the invention is not limited by these examples.

31 WO 89/09192 PCT/AU89/00144 -8- 1 Example 1 3 One litre of a simulated cooling tower and filter cloth effluent, containing 50 mg/l Zn, 560 mg/l Ca and 12500 mg/1 Na was contacted with 10 g of magnetite (1-10 p) at pH 9.0 for fifteen minutes (pH was adjusted 7 with sodium hydroxide). The product water contained 0.9 mg/l of Zn ions as determined by atomic absorption 9 spectroscopy. Acid regeneration of the loaded magnetite at pH 6.0 achieved a 100% recovery of Zn ions.

11 Example 2 13 In similar laboratory tests, 10 g of magnetite was contacted with one litre of Yarra River water (Colour Pt-Co units and Turbidity 14 NTU), spiked with 50 mg/1 Cu 17 at pH 7.0 (pH was adjusted with sodium hydroxide). The product water was of colour, <1 Pt-Co unit and of 19 turbidity 0.8 NTU and had a Cu concentration of 0.5 mg/l.

21 Example 3 23 One litre of ore dump leachate containing 108 mg/l Cu, 89 mg/1 Ca, 182 mg/l Mg, 17.2 mg/1 Mn, 40.0 mg/1 Na, 9.4 mg/1 Al, 25 mg/1 Si and 4.8 mg/l Zn, was treated with g of magnetite and 0.1 mg/l of the nonionic 27 polyelectrolyte, LT 20 at pH 8.0 (pH was adjusted with sodium hydroxide). The product water contained 0.34 mg/1 29 of Cu. Acid regeneration, of the loaded magnetite at pH for 2.5 minutes achieved 100% recovery of the cupric 31 ions.

-Now WO 89/09192 PCT/AU89/00144 -9- 1 Example 4 3 One litre of a dump leachate containing 269.8 mg/1 Al, 777 mg/l Ca, 80.9 mg/l Cd, 538.7 mg/l Cu, 73.6 mg/l Fe, 1493 mg/I Mg, 282.9 mg/1 Mn, and 10.88 g/l Zn along with various amounts of trace elements was treated with 7 20 g of magnetite at pH 5.4 and 1.0 mg/l of anionic polyelectrolyte LT 25 (pH was adjusted with a lime 9 slurry). The product water contained 7.45 mg/l Al, 94.5 mg/l Cu, 0.05 mg/1 Fe and 10.26 g/l Zn. Whilst there has 11 been some loss of Zn and Cu, the primary objective was achieved, namely, the removal of Al and Fe.

13 Example One litre of a highly concentrated leachate 17 containing 17.7 g/l of Zn, 130 mg/l Cu, 84.0 mg/l Cd, 950 mg/l Fe, 25.7 mg/1 Al, and 460 mg/l Ca was contacted with 19 40 g of magnetite and 20 mg/l of LT 25 at pH 6.0 (pH was adjusted with a lime slurry) to produce a clear water with 21 the following metal ion concentrations: 14.0 g/l Zn, 0.17 mg/1 Cu, 71.6 mg/1 Cd, 560 mg/1 Fe, 0.8 23 mg/l Al and 461 mg/1 Ca. To cope with the high level of chelated Fe in this leachate, in subsequent tests 20 ml of 20 volume hydrogen peroxide was added initially, which lowered the Fe level to 0.4 mg/l. The use of peroxide as V 27 an oxidant to break the Fe-organic complex is an option available in those instances where almost total Fe removal 29 from a concentrated effluent is essential.

31 Example 6 33 One litre of dump leachate containing 24.3 mg/l Al, 30.7 mg/l Fe, and 543 mg/l Zn at pH 3.77 was treated with 1 20 g of magnetite and 1.0 mg/l LT 25 at pH 6.5. pH control was .achieved using three different alkalies, 3 caustic soda, a lime slurry and a saturated solution of sodium carbonate. In each case greater than 99% of the Al was removed, but the results with sodium carbonate were vastly different for Fe and Zn: there being less removed 7 than with the other alkalies. This raises the possibility of using different alkalies for treatment of different 9 effluents.

11 Example 7 13 One litre of a leachate containing 6.2 mg/l Al, 27.1 mg/l Fe, 1.0 mg/l Cu and 288 mg/1 Zn at pH 3.70 was treated with 20g of magnetite, 1.0 mg/l LT 25 and 0.6g of sodium sulphide at pH 7.5. The alkali used in for pH 17 control was a lime slurry. In this instance, the objective was the removal of virtually all metal ions to 19 provide a clean water for use elsewhere in the mining circuit.

21 The water obtained contained 20 mg/l Zn and 23 mg/l Al, Fe and Cu.

Example 8 27 The experiment of Example 7 was repeated using a slurry of magnesium oxide for pH control.

29 The product water was of similar composition to that 31 obtained in Example 7, but the settled volume of loaded magnetite floc was about half that observed when using 33 lime for pH control.

i' WO 89/09192 PCT/AU89/00144 -11- 1 Example 9 3 One litre of a leachate containing 850 mg/1 Al, 125.9 mg/l Fe, 83.7 mg/l Cu, 13.9 mg/l Cd, 0.17 mg/l Cr, 9.62 mg/l Ni, 85.5 mg/l Mn and 22.60 mg/1 Zn at pH 2.50 was treated with 20 g of magnetite and 1 mg/l LT 25 at the 7 following pH values 7.95, 9.00, 10.42 and 11.60. The alkali used was caustic soda. The objective was the 9 removal of all metals to below desired concentration levels, such as concentration levels specified by 11 environmental authorities for discharge into natural water courses. Table 1 displays the composition of the water 13 obtained at each pH.

TABLE 1 pH CONCENTRATION (mg/1) Al Fe Cu Cd Cr Ni Mn Zn 7.95 0.11 0.16 0.02 3.44 0.03 0.14 39.0 6.38 9.00 0.09 0.18 0.01 0.23 0.01 0.02 1.35 0.08 10.42 0.55 0.18 0.01 0.08 0.01 0.02 0.00 0.01 11.60 5.10 0.22 0.04 0.10 0.03 0.01 0.01 0.53

Claims (4)

12- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method for removing metal ions from solution, which comprises the steps of: contacting the solution with a magnetic or magnetisable particulate material, in the presence of an alkali or alkaline earth k droxide. metal oxide, hrdi~Exide carbonate or sulphide and polyelectrolyte, whereby the particulate material becomes coated with a precipitate of the oxide, hydroxide, carbonate or sulphide of the metal; and separating the coated particulate material from the solution. 2. A method as claimed in Claim 1, which further comprises: regenerating the particulate material; and recycling the particulate material to step 3. A method as claimed in Claim 1 or Claim 2, wherein the particulate material is gamma iron oxide, magnetite or ferrite. e o0* 25 4. A method as claimed in any one of the preceding claims wherein the coated particulate material is separated from the solution by magnetic means. 5. A method as claimed in any one of Claims 2 to 4, wherein the particulate material is regenerated by treating the coated pardculate material with an acidic solution. 910613,dabcm.001,33649.res,12 ;M4 V I L: -13- 6. A method as claimed in any one of Claims 1 to 5, wherein the particle size of the particulate material is from 1 to 100 microns. 7. A method as claimed in Claim 6, wherein the particle size of the particulate material is about 50 microns. 8. A method as claimed in any one of the preceding claims wherein the metal ions to be removed from solution are 4 n free, solvated or complexed form. S 5 o 5 S S OS S. a 9. A method as claimed in any one of the preceding claims, wherein the metal ions to be removed from solution are in the form of chloride or cyanide complexes. 10. A method as claimed in any one of the preceding claims, wherein the alkali or alkaline earth metal oxide, hydroxide, carbonate or sulphide is sodium is hydroxide, carbonate or sulphide, lime, magnesium oxide, calcined dolomite or mixtures thereof. 11. A method as claimed in any one of the preceding claims, wherein the polyelectrolyte has a molecular weight of about 106. 12. A method as claimed in any one of the preceding claims, wherein the 25 polyelectrolyte is anionic.

13. A method as claimed in any one of the preceding claims wherein the amount of polyelectrolyte added is 1 to 2 ppm. S 55 S @58 S 1 A~ 9106l3,dabcmc.O01,33649.res,13 14

14. A m~tbod as claimed in any one of the preceding claims, wherein the amount of the alkali or alkaline earth metal oxidde, hydroxide, carbonate or sulphide added to the solution is such that the pH of the solution is 3 to 12.

15. A method for removing metal ions from solution substantially as hereinbefore described with reference to the Examples. Dated this 13th day of June, 1991. COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION By Its Patent Attorneys DAVIES COLLISON e 0 4 910613,ciabanc.001,33649.res14 IN"ERNATIONAL SEARCH REPORT International Application No. PCT/AU 89/00144 I. CLASSIFICATION OF SUBJBET MATTER (if several classification symbols apply, indicate all) 6 According to International Patent Classification (IPC) or to both National Classification and IPC 7 4I I Int. Cl. CO2F 1/62 I r II. FIELDS SEARCHED IMinimum Documentation Searched 7 I Classification System Classification Symbols IPC I C02B 1/23, 1/26, C02F 1/48, 1/62, 1/64 I I Documentation Searched other than Minimum Documentation Sto the Extent that such Documents are Included in the Fields Searched 8 SA: IPC as above I SIII. DOCUMENTS CONSIDEREDTO BE RELEVANT 9 Category* I Citation of Document, with indication, where appropriate, Relevant to I of the relevant passages 12 Claim No 13 I X,Y US,A,3171800 (RICE et al) 2 March 1965 (02.03.65) See column 2 1,2,5,10-14) line 39-62, column 3 lines 10-13 and 40-42. 10-17) I Y US,A,3259571 (MARSHALL et al) 5 July 1966 (05.07.66) See column (1,2,4,10-17) I 3.lines 28-43, column 4 lines 32-41. I Y US,A,3340187 (BELL) 5 September 1967 (05.09./67) See claim 7 (1,2,5,10-14) I; Y US,A,3931007 (TSUJI et al) 6 January 1976 (06.01.76) See column 2 6, 10-16) I lines 43-48, column 3 line 61, column 4 line 9. I Y US,A,4465597 (HERMAN et al) 14 August 1984 (14.08.84) See column 4 (1-2,5-7,10-15) !i lines 54-60, column 6 lines 11-18. SY,P US,A,4802993 (KATOH) 7 February 1989 (07.02.89) See claim 1 (1,2,5,10-14) i Y GB,A,2089335 (ANIC SpA) 23 June 1982 (23.06.82) See page 2 II lines 5-53. II (continued....) Special categories of cited documents: 10 later document published after the international filing date or priority date S"A' document defining the general state of the and not in conflict with the application but S art which is not considered to be of cited to understand the principle or theory I particular relevance underlying the invention earlier document but published on or document of particular relevance; the after the international filing date claimed invention cannot be considered novel I "L document which may throw doubts on priority or cannot be considered to involve an S claim(s) or which is cited to establish the inventive step publication date of another citation or document of particular relevance; the S other special reason (as specified) claimed invention cannot be considered to |i document referring to an oral disclosure, involve an inventive step when the document S use, exhibition or other means is combined with one or more other such I! document published prior to the documents, such combination being obvious to S international filing date but later than a person skilled in the art. S the priority date claimed document member of the same patent family IV. CERTIFICATION |i Date of the Actual Completion of the Date of Mailing of this International I' International Search I Search Report 14 July 1989 (14.07.89) ,Z JLc International Searching Authority Signature ,"'uthorized Officer I ji Australian Patent Office A. 1 Form PCT/ISA/210 (second sheet) (January 1985) -cl i International Appl .tion No. PCT/AU 89/00144 I FURTHER NFORMATION CONTINUED FROM THE SECOND SHEET I Y ly Y V. Patents Abstracts of Japan, C222, Page 26 JP,A,59-16590 (NIHON DENKI KANKIYOU ENGINEERNG K.K.) 27 January 1982 (27.01.82) Patents Abstracts of Japan, C547, page 102 JP,A,63-175686 (NIPPON DENKI KANKYO ENG K.K.) July 1987 (20.07.87) (1-4,10-14) (1-3,10-14,16) OBSERVATIONS WHERE CERTAIN CLAIMS WERE FOUND UNSEARCHABLE 1 I I This international search report has not been established in respect of certain claims under Article 17(2)(a) for the following reasons: 1.C1 Claim numbers because they relate to subject matter not required to be searched by this Authority, namely: 2. Claim numbers because they relate to parts of the international application that do comply with the prescribed requirements to such an extent that no meaningful international search can be carried out, specifically: Claim numbers because they are dependent claims and are not drafted in accordance wi h the second and third sentences of PCT Rule 6.4 VI. OBSERVATIONS WHERE UNITY OF INVENTION IS LACKI 2 I I This International Searching Authority found multiple inventions in this international application as follows: 1.l]As all required additional search fees were timely paid by the applicant, this international search report covers all searchable claims of the international application. 2. As only some of the required additional search fees were timely paid by the applicant, this international search report covers only those claims of the international application for which fees were paid, specifically claims: S3.E[No required additional search fees were timely paid by the applicant. Consequently, this international search report is restricted to the invention first mentioned in the claims; it is covered by claim numbers: 4. l[ As all searchable claims could be searched without effort justifying an additional fee, the International Searching Authority did not invite payment of any additional fee. Remark on Protest [I The additional search fees were accompanied by applicant's protest. [3 Ko protest accompanied the payment of additional search fees. Form PCT/ISA/210 (supplemental sheet (January 1985) I. i I1I 1 ANNEX TO THE INTERNATIONAL SEARCH REPORT ON INTERNATIONAL APPLICATION NO. PCT/AU 89/00144 This Annex lists the known publication level patent family members relating to the patent documents cited in the above-mentioned international search report. The Australian Patent Office is in no way liable for these particulars which are merely given for the purpose of information. Patent Document Cited in Search Patent Family Members Report US 3931007 CA 1017083 DE 2363291 FR 2210574 GB 1457528 JP 49083257 JP 49084050 JP 49127469 NL 7404782 US 4465597 AU 86975/82 CA 1183974 ?EP 72012 JP 58040192 ZA 8205411 GB 2089335 CH 652707 DE 3147549 DK 5453.81 ES 508225 ES 8300646 FR 2496083 GB 2089335 IT 1134671 NL 8105594 NO 814193 SE 8107419 US 4802993 EP 168752 JP 61025691 JP 61025692 JP 61025693 END OF ANNEX 5,25/119/1