USOO896.1911 B2 (12) United States Patent (10) Patent No.: US 8,961,911 B2 Dahal (45) Date of Patent: Feb. 24, 2015 (54) SELECTIVE LEACH RECOVERY OF ZINC 5,523,066 A 6/1996 Geisler et al. FROMA COMPOSITE SULPHIDE ORE g R: 1358. R et al DEPOSIT, TAILINGS, CRUSHED ORE OR W - oyes et al. MINE SLUDGE FOREIGN PATENT DOCUMENTS (75) Inventor: Madhav Dahal, Toronto (CA) CN 1414121 A 4/2003 CN 1456692. A 11, 2003 (73) Assignee: Yava Technologies Inc., Toronto, RU 2006 141445 5, 2008 Ontario (CA) WO WO 98.36102 8, 1998 WO WOO3,O23.077 3, 2003 (*) Notice: Subject to any disclaimer, the term of this OTHER PUBLICATIONS patent is extended or adjusted under 35 U.S.C. 154(b) by 4 days. Translation of RU2352652, Apr. 2009.* Translation of CN 1456692, Nov. 2003.* (21)21) AppAppl. No.: 13A876,9019 Translation of CN 1414121 Apr.p 2003.* International Search Report of PCT/CA2011/001094, date of mail (22) PCT Filed: Sep. 30, 2011 ing Jan. 6, 2012. International Preliminary Report on Patentability of PCT/CA2011/ (86). PCT No.: PCT/CA2O11AOO1094 001094, dated Apr. 2, 2013, with Written Opinion of the International Searching Authority, dated Dec. 8, 2011. S371 (c)(1), Chinese Office Action dated Apr. 14, 2014 in Chinese Application (2), (4) Date: Apr. 22, 2013 No. 201180057747.5 with English translation. Panamanian Examination Report datedMar. 18, 2014 in Panamanian (87) PCT Pub. No.: WO2012/040829 Registration No. 89635-01. PCT Pub. Date: Apr. 5, 2012 * cited by examiner (65) Prior Publication Data Primary Examiner — Steven Bos US 2013/0216456A1 Aug. 22, 2013 (74) Attorney, Agent, or Firm — Collard & Roe, P.C. Related U.S. Application Data (57) ABSTRACT (60) Provisional application No. 61/404.244, filed on Sep. Zinc and lead are usually concomitantly present in Zn-Pb 30, 2010. ores and tailings. A novel non-polluting hydrometallurgical process for selectively leaching and recovering Zinc (Zn) (51) Int. Cl. from a composite lead (Pb) and Zinc sulphide containing COIG 9/00 (2006.01) mineral, crushed untreated rock or unconsolidated mineral C22B 9/02 (2006.01) particles, mill tailings and/or agglomerated or unagglomer C22B3/00 (2006.01) ated Sulphidic Zinc containing waste material without neces (52) U.S. Cl. sitating Smelting and refining operation has been developed. CPC ................. C22B 19/02 (2013.01); C22B 19/24 A combination of selected oxidant and alkali metal hydroxide (2013.01) has been found effective. A leachant consisting of e.g. a USPC ............ 423/101; 42.3/102:42.3/105. 42.3/100 mixture of sodium hydroxide (NaOH) and Sodium hypochlo (58) Field of Classification se arch s s rite (NaOCl) is employed to selectively dissolve zinc sulphide None at high pH at standard temperature and pressure (STP). The kinetics of leaching along with the effect of varying concen S ee appl1cauonlication fileIlle fIor completelet searcnh historv.n1Story tration (preferably of sodium hydroxide and sodium (56) References Cited hypochlorite) were systematically investigated. Feedore con taining diverse set of minerals e.g. Sulphides and carbonates U.S. PATENT DOCUMENTS can also be conveniently treated to selectively and almost quantitatively recover Zinc as high purity Zinc carbonate. This 3,515,510 A * 6/1970 Satterwhite et al. .......... 423.109 3,927,170 A 12/1975 Dixon et al. technology can be employed either in-situ or ex-situ based on 4,153,522 A * 5/1979 Arbiter et al. ................. 205,580 the amenability of a particular type of mineral depositor feed 4,272,341 A 6, 1981 Lamb O. 4.331,635 A * 5/1982 Arbiter et al. ................... 423.33 4,500,398 A 2/1985 Cole, Jr. et al. 10 Claims, 3 Drawing Sheets U.S. Patent Feb. 24, 2015 Sheet 1 of 3 US 8,961,911 B2 uZ()d??S U.S. Patent Feb. 24, 2015 Sheet 2 of 3 US 8,961,911 B2 1200 ---------------------- ------------------------------------------ 1000 - ---------------------u-uu-------------------------------------............-------------- Time (h) -- 0.24MNaOCl; 0.675M NaOH -- 0.24MNaOC; 1.35M NaOH 0.48M NaOH; 0.675MNaOH -- a-- 0.48MNaOH: 1.35M NaOH 15 % 10% 5% -- wwww.uuv. 0% - 70 80 Time (h) -0- 0.24MNaOCl; 0.675M NaOH -- 0.24MNaOCl, 1.3MNaOH 0.48MNaOCl; 0.675M NaOH.-- 0.48MNaOCl; 1.3MNaOH U.S. Patent Feb. 24, 2015 Sheet 3 of 3 US 8,961,911 B2 FIG. 4 100% - 90% 80% 70% 60% 50% | 40% 30% 20% 10% - O% - alo O 2O 40 60 8O Time (h) -0-0.24MNaOCl; 0.675M NaOH -- 0.24MNaOCl, 1.35M NaOH -A-0.48MNaOCl; 0.675M NaOH --0.48MNaOCl, 1.35M NaOH US 8,961,911 B2 1. 2 SELECTIVE LEACH RECOVERY OF ZINC Turner in U.S. Pat. No. 6,726,828, describe use of in-situ FROMA COMPOSITE SULPHIDE ORE leach mining utilizing a mixture of acetic acid and hydrogen DEPOSIT, TAILINGS, CRUSHED ORE OR peroxide (for sulphide oxidation) to recover Ca, Mn, Pb and MINE SLUDGE Zn as a combined leachate from a permeable geological host. Both methods employ hydrogen peroxide as an oxidant. The CROSS REFERENCE TO RELATED decomposition of hydrogen peroxide with time and its effect APPLICATIONS on the overall recovery process is left unexplained. U.S. Pat. No. 4,500,398 uses fluosilicic acid with an oxidant to dissolve This application is the National Stage of PCT/CA2011/ sulphides. Neither of these methods suggests selective leach 001094 filed on Sep. 30, 2011, which claims priority under 35 10 ing of Zinc from composite lead-zinc Sulphidic minerals pro U.S.C. S 119(e) of U.S. Provisional Application No. 61/404, posed herein. 244 filed on Sep. 30, 2010, the disclosure of which is incor porated by reference. The international application under SUMMARY OF THE INVENTION PCT article 21(2) was published in English. 15 A new hydrometallurgical method has been found for BACKGROUND OF THE INVENTION selective dissolution of Zinc from composite Zinc sulphidic minerals. Lead and Zinc Sulphides generally undergo similar oxida The invention comprises a process for selective leaching of tion-reduction reactions. As a result, there is no known Zinc from mixtures and ores containing Zinc Sulphide, com method to leach and recover zinc selectively from composite 20 prising: lead-zinc sulphidic minerals. This invention deals with a a. contacting the mixture or ore with an aqueous leachant selective leaching and recovery of Zinc from composite Zinc comprising: 1) an oxidant selected to oxidize the Sulphur and usually lead-bearing Sulphides, which are either in the present only to elemental Sulphur, and 2) alkali metal form of complex Zinc and lead metal containing Sulphidic hydroxide in amounts sufficient to form soluble alkali minerals, or in the form of zinc Sulphide concentrates, in-situ- 25 metal Zincate; or ex-situ in an economic and environmentally friendly man b. extending the contact time between leachant and Solids . to give the desired zinc recovery and selectivity in the Zinc is the fourth most common metal in use, trailing only leachate while maintaining operative reagent concentra iron, aluminium, and copper. It is normally found in associa tions; tion with other base metals such as copper and lead in natu- 30 c. separating the desired leachate from the residual Solids; rally occurring ores. Zinc has a low affinity for oxides and and prefers to bond with sulphides. Sphalerite, which is a form of d. recovering zinc from the leachate. Zinc sulphide, is the most heavily mined zinc-containing ore. The oxidant may be selected from the group consisting of The major uses of Zinc are anti-corrosion coatings on Steel an oxygen-containing gas, a water-soluble peroxide, a water (galvanizing), precision components (die casting), construc- 35 soluble perchlorate and a water-soluble hypochlorite. tion material, brass, dry batteries, pharmaceuticals and cos Preferably the oxidant is a hypochlorite in a concentration metics and micronutrient for humans, animals and plants. The sufficient to oxidize all of the sulphides present. oxide is used in the manufacture of paints, rubber products, When the starting solids also contain lead sulphide, the floor coverings, plastics, printing inks, soap, textiles, electri resulting leachate is substantially free of lead after an cal equipment, and other products. 40 extended contact time. Conventional extractive metallurgical process generally The desired oxidation potential of the leachant for steps a) involves pyrometallurgical methods for recovering Zinc Val and b) is maintained by reagent addition. The desired alkali ues from Zinc Sulphides. Known recovery process mostly metal hydroxide content of the leachant is maintained involves grinding the ore, froth flotation (which selectively throughout the leaching steps a) and b). The contact time in separates minerals from gangue by taking advantage of dif- 45 steps a) and b) is extended for up to about 24 hours to attain ferences in hydrophobicity) to get an ore concentrate, roast desired recovery and selectivity. ing and reduction with carbon or electrowinning. However, The invention includes an aqueous leachant composition Such treatment often entails expensive mining and beneficia selected to solubilize Zinc selectively from Zinc sulphide tion process steps to concentrate the Sulphides. In addition, containing Sulphidic minerals and mixtures, comprising: the production of Zinc employing the known technology from 50 1) an oxidant selected to oxidize the sulphur from the Sulphidic Zinc ores produces large amounts of Sulfur dioxide, Sulphides only to the elemental Sulphur stage; and carbon dioxide and cadmium vapor. Smelter slag and other 2) an alkali metal hydroxide selected to form soluble alkali residues of process also contain significant amounts of heavy metal Zincates from Zinc Sulphide oxidation products. metals. The dumps of the past mining operations leach sig In a preferred aspect the composite Sulphides are treated nificant amounts of Zinc and cadmium.