Abstract: A process for recovering copper from heap leach residues containing residual copper, includes identifying a production zone within the heap leach residues for secondary leaching, drilling wells into the heap at locations suitable for delivering leach solution into the production zone, injecting the leach solution including ferric ions through the wells and aerating the production zone to facilitate oxidative reactions within the production zone, and collecting effluent from the heap for copper recovery therefrom.

Abstract: The present invention provides a process for extracting noble metals from anode slime, comprising: mixing sodium carbonate, quartz and coke powder and impurity-removed anode slime, and subjecting the mixture to smelting and converting to obtain alloys of noble metals. The present invention avoids problem of lead pollution by using metallic bismuth to collect noble metals; meanwhile, metallic bismuth has low melting point, high specific gravity, and formation heat of bismuth oxide of 45.6 kcal/g atomic oxygen, thus it is easy to be reduced and the reduction temperature is low, which are beneficial for saving energy consumption and reduction time; the much smaller amounts of copper, nickel, antimony and arsenic entering noble bismuth in a slightly reductive smelting atmosphere than those entering noble lead make the converting of noble bismuth become simple, thereby decreasing smelting time and increasing the direct recovery rate of noble metals in anode slime.

Abstract: This invention provides a fine particle composite comprising fine powder of a sulfide or sulfide complex comprising a given element. The fine particle composite is obtained by a method for producing a fine particle composite comprising fine powder of a sulfide or sulfide complex comprising at least one element selected from the group consisting of molybdenum (Mo), rhodium (Rh), ruthenium (Ru), and rhenium (Re). Such method comprises steps of: preparing a solvent mixture from at least one compound containing an element selected from among molybdenum (Mo), rhodium (Rh), ruthenium (Ru), rhenium (Re), and sulfur (S); and subjecting the solvent mixture to a hydrothermal or solvothermal reaction. The resulting fine particle composite comprises fine particles of a sulfide or sulfide complex comprising at least one element selected from the group consisting of molybdenum (Mo), rhodium (Rh), ruthenium (Ru), and rhenium (Re).

Abstract: Various embodiments provide a process roasting a metal bearing material under oxidizing conditions to produce an oxidized metal bearing material, roasting the oxidized metal bearing material under reducing conditions to produce a roasted metal bearing material, leaching the roasted metal hearing material in a basic medium to yield a pregnant leach solution, conditioning the pregnant leach solution to thrill a preprocessed metal bearing material; and leaching the preprocessed metal bearing material in acid medium.

Abstract: The present invention relates to a process of gold and copper recovery from gold-containing copper ores obtained from mixed oxide-sulfide copper ore bodies by a series of flotation stages. More specifically, the present invention relates to a process of gold and copper recovery whereby gold-containing ores obtained from mixed oxide-sulfide copper ore bodies, and/or copper flotation by-products thereof, are subjected to at least one flotation step following a dewatering step. In particular, it recovers copper and gold from the oxidized zone of porphyry and other mixed ore deposits. Likewise, the present process allows recovery of copper and gold from the tailings and scavenger concentrates which, in conventional process are no longer viable for further treatment.

Abstract: Provided is a method for separating and recovering iodine ingredients from acid solution containing iodide ions and iron (II) ions and for efficiently producing iron (III) ions. Said method is for treating acid solution containing the iodide ions and the iron (II) ions. Said method comprises a step of oxidizing the iron (II) ions in said solution into iron (III) ions with iron-oxidizing microorganisms, the step being performed in the presence of activated carbon.

Abstract: A method of recovering copper from chalcopyrite concentrate by chemical leaching, using pyrite and silver. The catalytic properties of pyrite in the chalcopyrite leaching process are significantly enhanced by pretreating the pyrite with silver ions. Particulate pyrite is exposed to a solution containing silver ions to form silver-treated pyrite. Particulate chalcopyrite and the silver-treated pyrite are mixed in an acidic sulfate leach solution. The copper is leached from the concentrate in the leach solution in the presence of an oxygen-containing gas, under conditions whereby the pyrite is substantially unoxidized. The leached copper is recovered from the solution by conventional methods. The used silver-treated pyrite is recycled to the leaching process.

Abstract: The invention relates to a method for leaching copper oxide without using sulfuric acid, comprising the following steps consisting in: impregnating the copper oxide using a non-polluting organic leaching agent consisting of an aqueous solution formed by tricarboxylic acid (C6H807) combined with water in a mixture having an acidity varying between a pH of 1 and 5; obtaining copper citrate; and, optionally, again irrigating the copper oxide impregnated with the non-polluting organic leaching agent, thereby obtaining a more concentrated copper citrate.

Abstract: A process for leaching an ore containing sulfidic copper-containing minerals includes carrying out an aerated oxidizing leach of a part of the ore and producing an acidic leach liquor containing ferrous ions, ferric ions, and copper ions in solution. The process also includes carrying out a leach of another part of the ore using the leach liquor under conditions that minimize reactions with a source of iron in the ore and producing a leach liquor containing copper ions in solution. The process further includes recovering copper from the leach liquor.

Abstract: Disclosed is a method of efficiently leaching copper not only from a readily-soluble copper ore but also a poorly-soluble copper sulfide ore partially containing or consisting of chalcopyrite and/or covellite by means of ore heap leaching under versatile conditions for actual operation. Also disclosed is a method of leaching copper from a copper sulfide ore, including leaching copper from an ore including a copper sulfide ore by heap or dump leaching with the use of a sulfuric acid solution containing ferric (III) ions and iodide ions at a total iodine concentration of 8 to 100 mg/L as a leaching solution.

Abstract: Disclosed is a method of copper leaching without reducing the growth of iron-oxidizing bacterium and the iron-oxidizing capacity when leaching copper from a copper sulfide ore with the use of a sulfuric acid solution to which iron-oxidizing bacteria and silver have been added. Also disclosed is a method of leaching copper from a copper sulfide ore, including adding a naturally occurring nitrogen-containing organic component to a leaching solution upon copper leaching from a copper sulfide ore with the use of, as the leaching solution, a sulfuric acid solution to which iron-oxidizing bacteria and silver have been added is provided.

Abstract: A method of recovering copper from a copper sulfide concentrate comprising a copper arsenic sulfosalt or a copper antimony sulfosalt, using pyrite as a catalyst. The concentrate and pyrite are added to an acidic sulfate leach solution. The copper is leached from the concentrate, in the presence of an oxygen-containing gas, under conditions whereby the pyrite is substantially unoxidized. The pyrite:copper sulfide ratio of the pyrite being added to the copper sulfide present in the concentrate being added is at least 1:3. The pyrite may be maintained at a concentration in the leach solution of at least 9 grams per liter. The leached copper is recovered from the solution by conventional methods.

Abstract: The invention relates to a method for leaching bulk concentrate of chalcopyrite-type by means of an aqueous solution containing sulphuric acid and an oxygen feed at atmospheric pressure and at a temperature between 75° C. and the boiling point of the solution. It is typical of the method that the particle size of the concentrate to be fed into leaching is in the region of 80% below 60-100 ?m and that the concentrate is leached with an aqueous solution, the acid concentration of which is regulated to be around 20-90 g/l.

Abstract: A system for cooling and recuperative heating of a slurry in a metallurgical process which includes heat exchangers, pumps and autoclaves is described herein. The heat exchangers use a non-scaling common liquid heat transfer medium. Preferably, the heat exchangers are tube-in-tube heat exchangers with 3 to 7 slurry tubes in each heat exchanger. An advantage of this system is that it does not use flash tanks. To minimize abrasive wear on impinged surfaces, the velocity of the slurry is not more than 5 meters per second. The slurry comprises a solids concentration of 25% to 50%. Preferably, the pumps in the system are float-type pumps in which the driven liquid from the discharge pumps is also used as the drive liquid for the feed pumps.

Abstract: Processes are provided for recovering precious metals from refractory materials using thiosulfate lixiviants. The processes can employ heap leaching or lixiviants that include one or more blinding agents.

Abstract: A heap leaching method to recover copper from a primary copper sulphide mineral wherein the mineral is leached in an acidic chloride/sulphate solution in the presence of oxygen with the surface potential of the mineral below 600 mV (vs. SHE) to cause dissolution of the copper sulphide.

Abstract: The present invention is directed to a multi-compartment autoclave using inter-compartment dividers having one or more underflow openings for passing a feed stream between compartments.

Abstract: A hydrometallurgical process for the treatment of complex silver-bearing sulfide ores and concentrates that recovers substantially all silver, lead, antimony, zinc, copper and sulfur, along with the chemical reagents utilized during the process. Finely ground ores and concentrates are leached under heat and pressure with water, sulfuric acid, nitric acid, oxygen, and a catalyst, and are further treated to recover silver in the form of silver chloride; iron in the form of iron hydroxide; copper and all traces of soluble toxic metals as sulfides; zinc as zinc ammonium sulfate and specifically nitric acid, sulfuric acid, oxygen, ammonia, and ammonium compounds as valuable fertilizer products.

Abstract: There is provided a method for leach extraction of copper/iron/sulphur ores and concentrates including leaching the mineral with an aqueous stream containing ferric ions and sulphuric acid in the presence of oxygen, the aqueous stream including a solution formed by reaction of basic ferric sulphate with excess suphuric acid. Integrated methods of forming and releaching basic ferric sulphate are also described.

Abstract: Methods and systems for removing copper minerals from a molybdenite concentrate. One embodiment provides leaching copper from the molybdenite concentrate with a leaching solution comprising ferric chloride, removing molybdenite from the leaching solution, introducing an acid into the leaching solution and introducing O2, O3, or a combination of both, into the leaching solution. A method for regenerating ferric chloride in a leaching solution is also provided. One embodiment provides adding a leaching solution comprising Fe(II) ions, Fe(III) ions, or a combination of both, to a mixture of mineral sulfides, introducing an acid into the leaching solution, and introducing O2, O3, or a combination of both, into the leaching solution.

Abstract: A chemical process to leach copper concentrates in the presence of a concentrated solution of sulfates and chlorides. The process includes forming a high reactivity chemical paste containing a high concentration of ions in the liquid phase of the paste which react with copper ores and forms a series of soluble salts. The salts are extracted by a simple wash. Mixing equipment for handling high viscosity liquids is used. The total mixing time is about 5 minutes, after which the paste is poured into a rectangular mold, of several hundred meters per side, and is left to settle and breathe. During settling, water and sulfuric acid are added at intervals to replace that consumed by the reactions taking place during the aeration, until the reactions have virtually end. This treatment results in a dry, very resistant mass, containing the copper extracted in form of chlorine salts, and sulfate.

Abstract: Spent, acidic solutions comprising cupric chloride and hyrdrochloric acid from the copper etching process are regenerated by a process in which the acid is subjected to distillation with sulfuric acid. In one embodiment, the process comprises (a) providing a spent etchant comprising at least about 10% by weight chloride and at least about 5% dissolved copper; (b) adding at least about 2 moles of sulfuric acid per mole of dissolved copper to the spent etching solution, thereby converting copper chloride into hydrochloric acid and precipitated copper sulfate; (c) distilling the mixture from step (b) to vaporize at least a portion of the hydrochloric acid; (d) condensing at least a portion of the vaporized hydrochloric acid; (e) separating at least a portion of the precipitated copper sulfate from the residual liquid, wherein said residual liquid comprises sulfuric acid; and (f) reusing at least a portion of the residual liquid as a sulfuric acid source in step (b).

Abstract: A copper concentrate obtained by flotation of a high grade copper ore containing chalcopyrite as a main mineral constituent is leached at a temperature of 100° C. or higher, and under a pressure greater than atmospheric pressure yielding a copper leachate containing ferric ions of at least 5 g/L and sulfuric acid, and this copper leachate is used in heap leaching or vat leaching of a low grade copper ore, whereby a method of recovering copper economically from a material containing copper is provided.

Abstract: The invention provides a hydrometallurgical process for treating metal-containing sulfide ores and concentrates, comprising reacting said metal-containing sulfide with concentrated sulfuric acid at a temperature of between about 300° C. and 400° C. in the presence of oxygen to produce a solid metal sulfate product and a gaseous product which is primarily SO3, wherein said metal is selected from the group consisting of iron, copper, zinc, nickel, cobalt and manganese. Said metal sulfate product is then leached with dilute sulfuric acid to form a metal-containing solution, from which the metal values are separated by precipitation at raised H2SO4 concentrations obtained by saturating the solution with the gaseous SO3 from the sulfatization reaction step.

Abstract: A process for recovering metal values from a metal containing material including the metal values comprising digesting the metal containing material in a sulfuric acid solution comprising sulfuric acid, a reducing agent, and a carbon source, heating the digestion mixture and separating the resulting solution from the remaining solids. The sulfuric acid solution may additionally include hydrofluoric acid (HF) as a source of fluoride ion.

Abstract: The heap leaching of copper bearing ores is improved by using sodium nitrate as an oxidizing chemical reactive in a sulphuric acid leaching solution. In particular, the ore is crushed to <6 mm and stored in heaps less than twelve meters high. The heaps are irrigated with a dilute solution consisting essentially of sulphuric acid and sodium nitrate to produce a leach product. The leach product is recovered from the heap and copper is recovered from the leach product by electrolysis. The pH of the heap is preferably maintained at ≦1.7 pH.

Abstract: Precious metal values, e.g., platinum, palladium and rhodium, and, optionally, other valuable elements, e.g., one or more rare earths and cerium in particular, are recovered from a wide variety of compositions of matter and articles of manufacture, for example waste or spent catalysts such as vehicular postcombustion catalysts, by (i) optionally comminuting such composition/article into a finely divided state, (ii) intimately admixing the composition/article with sulfuric acid, (iii) calcining the resulting admixture at a temperature ranging from 150° to 450° C., and (iv) leaching the calcined admixture in an aqueous medium, whether simultaneously or separately, with H+ ions and chloride ions, whereby obtaining (1) a solid residue substantially depleted of such precious metal values and, optionally, of such other elements, and (2) at least one liquid solution comprising such precious metal values and, optionally, such other elements.

Abstract: A process for the extraction of copper from a sulphide ore or concentrate comprises the steps of subjecting the ore or concentrate to pressure oxidation in the presence of oxygen and an acidic solution containing halide and sulphate ions to obtain a resulting pressure oxidation slurry. The slurry is subjected to a liquid/solid separation step to obtain a resulting pressure oxidation filtrate and a solid residue containing an insoluble basic metal sulphate salt. The basic metal sulphate salt is leached in a second leaching with an acidic sulphate solution to dissolve the basic metal salt to produce a leach liquor containing a metal sulphate, e.g. copper sulphate, in solution and a resulting solid residue. The leach liquor is separated from the solid residue and subjected to a solvent extraction process to produce metal concentrate solution and a metal depleted raffinate. At least a portion of the raffinate is recycled to the pressure oxidation after being subjected to evaporation.

Abstract: Methods for enhancing the leaching of copper from copper bearing ores with an aqueous sulfuric acid leach solution are disclosed wherein an antifoam formulation stable at a solution pH of about 1 to 2 is added. A preferred antifoam formulation comprises a glycol ester and an alkyl phenol ethoxylate in a paraffinic oil solvent added to the aqueous sulfuric acid leach solution.

Abstract: A process for the separation of metals from a ferrite or a roasted metal sulphide ore is carried out by leaching the ferrite or roasted ore with peroxysulphuric acid (Caro's acid) and separating therefrom a solution containing metals. The roasted ore may contain ferrite and/or ferrite may be added to the ore, either before or after roasting. The leaching with peroxysulphuric acid may be carried out in the presence of gaseous chlorine. The metal sulphide ores may contain substantial proportions of copper and zinc sulphides.

Abstract: A process for recovering a base metal from a material, the base metal being selected from cobalt, copper, nickel and zinc, the process comprising the steps of reacting the host material with a ferric ion species in a leach solution, at conditions sufficient to cause at least a portion of the base metal to be oxidized by the ferric ion species, thereby causing the ferric ion species to be converted to a ferrous ion species, and oxidizing the ferrous ion species with an oxidation mixture of SO2 and oxygen to form the ferric ion species for subsequent reaction with the material.

Abstract: A process is provided for the leaching of copper from chalcopyrite using ferric sulfate in which acceptable rates of leaching are achieved by controlling the surface potential of the chalcopyrite to an empirically determined “window” within the broad range of 350 to 450 mV. The most effective process conditions involve the selection of the said surface potential; the leach temperature; the pH of the leach solution; and the fineness of the grind of the chalcopyrite. The invention may be applied to both tank leaching and heap leaching processes.

Abstract: A method for recovering gold from gold-loaded fine carbon residue from a coarse carbon gold recovery process is disclosed. The gold-loaded fine carbon residue is mixed with activated coarse carbon and an aqueous solution of a transfer reagent to form a slurry. In the slurry the reagent promotes transfer of gold from the fine carbon to the coarse carbon. After allowing time for the transfer, gold-loaded coarse carbon is separated from the slurry. Gold can then be recovered from the separated coarse carbon, for example by cyanide leaching followed by electrowinning. More gold can be recovered by adding further coarse carbon and repeating the transfer of gold to that coarse carbon. In one example 66% of gold was transferred from the fine carbon to the coarse carbon in one transfer cycle. About 89% and 96% of gold can be recovered after respectively second and third transfer cycles.

Abstract: Disclosed is a process for leaching copper from copper sulfide using bacteria, which ensures that the rate of leaching of copper increases to reduce the leaching time period and that the rate of leaching of primary copper sulfide contained in ores is increased. The process comprises using an acid leaching solution that includes both or any one of iron oxidizing bacteria and sulfur oxidizing bacteria in a concentration of 106 microbes/mL, the acid leaching solution having a redox potential of from 550 to 750 mV and 5 g/L or more of iron, the ratio of trivalent iron ions to bivalent iron ions (Fe3+/Fe2+) in the acid leaching solution being 50 or more.

Abstract: A process for oxidation of ferrous ions in solution, and more particularly a process for improved base metal and/or uranium leaching from ores, concentrates or tailings using ferric ion as an oxidizing agent. A reaction vessel (10) holds a ferrous ion-containing solution, for example, a copper sulphide leach slurry or concentrate. An agitator (12) may be provided to promote leaching of the base metal into solution. Some of the ferrous ion-containing solution is drawn off from the reaction vessel (10) and pumped through an in-line mixer (14) via a feed pump (16). Oxygen is injected into the reactor (14) to facilitate oxidation of the ferrous sulphate to form ferric sulphate. The ferric ion-containing solution is then recirculated back to the reaction vessel (10) where the ferric ions are reused in the dissolution of copper sulphide into soluble copper sulphate.

Abstract: The present invention is directed to a process for recovering copper from a copper-containing material by pressure oxidation followed by solvent extraction and electrowinning. The copper-containing solution formed by pressure oxidation is diluted before solvent extraction and the raffinate solution from solvent extraction is neutralized to reduce the acid levels in the raffinate solution.

Abstract: A process for the extraction of a metal from an ore or concentrate comprises subjecting the ore or concentrate to pressure oxidation in the presence of oxygen and an acidic solution containing halogen ions and a source of bisulphate or sulphate ions, such as H.sub.2 SO.sub.4. The metals which can be extracted by the process comprises copper, as well as non-cuprous metals, such as zinc, and precious metals, such as gold and silver.

Abstract: A process for the extraction of zinc from a sulphide ore or concentrate containing copper and zinc includes subjecting the concentrate to pressure oxidation in the presence of oxygen and an acidic halide solution to obtain a resulting pressure oxidation slurry and subjecting the slurry to a liquid/solid separation step to produce a liquor containing copper and zinc in solution. The liquor containing the copper and zinc is subjected to a first solvent extraction with a copper extractant to remove copper from the solution and to produce a copper depleted raffinate. The copper depleted raffinate is subjected to a second solid extraction with a zinc extractant to produce a zinc depleted raffinate and the zinc depleted raffinate is recycled to the pressure oxidation step.

Abstract: A method for improving the recovery of gold and silver from precious metal ore is disclosed. The method comprises contacting precious metal ore with an aqueous solution containing certain fluoroaliphatic surfactants.

Abstract: An aqueous phase oxidization process for the oxidization of any nonoxidized feed material using a mixture of a feed material, an oxidizing acid, such as nitric acid; oxygen gas, water and preferably a stabilizing acid, such as sulfuric acid. The mixture is pressurized in a reactor and maintained at a temperature no greater than about 210.degree. C. Sufficient oxygen gas is added to increase the pressure beyond the pressure resulting from any gases formed during the oxidation process and to ensure that a substantial portion of reduction products of nitric acid formed during oxidation of the feed are substantially reoxidized to nitric acid.

Abstract: There is provided a novel hydrometallurgical process for the extraction of copper from sulphidic concentrates involving an oxidizing pressure leach using dilute sulphuric acid and a carbonaceous additive. The leaching step is carried out preferably at temperatures above the melting point of sulphur but below about 200.degree. C.

Abstract: The present invention is directed to a process for recovering copper from a copper-containing material by pressure oxidation followed by solvent extraction and electrowinning. The copper-containing solution formed by pressure oxidation is diluted before solvent extraction and the raffinate solution from solvent extraction is neutralized to reduce the acid levels in the raffinate solution.

Abstract: Provided is a process for treating refractory precious metal-containing ores, particularly gold-bearing ores, which are refractory due to the presence of organic carbon, to reduce the ability of organic carbon to interfere with recovery of the precious metal. The ore may also contain sulfide materials with which the gold is associated and from which the gold is difficult to separate. The ore is comminuted to a size at which at least about 80 weight percent of the ore is smaller than about 40 microns in size. The comminuted ore is then slurried and subjected to pressure oxidation at severe operating conditions. The treating temperature is greater than about 190.degree. C. When sulfide minerals are present, substantially all of the sulfide sulfur must first be oxidized prior to obtaining significant benefit from the treatment of the organic carbon. Greater than about 96% of the sulfide sulfur must be oxidized.

Abstract: A continuous hydrometallurgical process for conversion of ore derived copper and zinc sulfides into recoverable water soluble sulfates is provided. The process comprises:i) contacting the ore derived copper and zinc sulfides with sulfuric acid and with nitric acid to form a reaction mixture in an acidic solution,ii) maintaining the reaction mixture at a temperature in the range of 110.degree. C. to 170.degree. C. while continuously mixing the reaction mixture,iii) adding sufficient sulfuric acid and nitric acid to the reaction mixture to form a light precipitate and a dark precipitate in the reaction mixture, the light precipitate comprising water soluble sulfate salts of copper sulfate, zinc sulfate and iron sulfate, and the dark precipitate being water insoluble and comprising mainly elemental sulfur and gangue,iv) introducing a source of oxygen to the reaction mixture to promote oxidation in the presence of the nitric acid, of the sulfides to sulfates and to oxidize gaseous NO.sub.

Abstract: A method for the recovery of copper from copper-containing materials, for example, scrap, ores or dust. An aqueous cupric tetrammine sulfate lixiviant is contacted with the copper-containing material to produce a leachate containing cuprous, nickel, and zinc ions, ammonium sulfate and free ammonia. Copper can be recovered from the leachate by electrolysis. Nickel and zinc can be precipitated from the resulting spent electrolyte by oxidizing substantially all of the cuprous ions in the copper ammine sulfate solution to cupric ions and lowering the pH of the solution to a range from about pH 7.5 to about pH 8.0 in order to form a precipitate. Alternatively, copper sulfate can be added to the cupric ammine sulfate-containing solution in order to form nickel and/or zinc containing precipitate.

Abstract: A process for recovering at least one precious metal from an ore containing carbonaceous material is disclosed. The process involves the use of promoting amounts of certain metal redox couples and/or metal components, in particular, certain metal complexes with ligands.Preferred metal compositions comprise at least one of (1) redox cyclable vanadium (5+) ligand complex, (2) redox cyclable iron (3+) ligand complex, and (3) redox cyclable manganese (3+) ligand complex. In the process, the use of at least one regenerable component capable of maintaining the complexed metal in the desired oxidation state provides for integrated process synergy.

Abstract: A process for recovering at least one precious metal from an ore containing carbonaceous material is disclosed. The process involves the use of promoting amounts of certain metal redox couples and/or metal components, in particular, certain metal complexes with ligands.Preferred metal compositions comprise at least one of (1) redox cyclable vanadium (5+) ligand complex, (2) redox cyclable iron (3+) ligand complex, and (3) redox cyclable manganese (3+) ligand complex. In the process, the use of at least one regenerable component capable of maintaining the complexed metal in the desired oxidation state provides for integrated process synergy.

Abstract: A method of increasing the extraction of tellurium from copper electrorefining slime comprises leaching the slime with dilute sulphuric acid in a reactor under a partial oxygen pressure of up to 150 psi and at an elevated temperature between about 100.degree. and 200.degree. C. until copper, nickel and substantially all of the tellurium is dissolved, thereby forming a leach slurry, and contacting the slurry with an appropriate reducing agent immediately after the leaching operation has been halted and the leaching reactor brough back to atmospheric pressure to reprecipitate any excessive quantities of silver and selenium solubilized during the leaching operation.

Abstract: A process for separating precious metals from an MnO.sub.2, sulfidic or carbonaceous refractory ore or refractory feed such as tailings is provided. The process includes the step of leaching a feed with a leach liquor that includes an acid selected from the group of HCl and H.sub.2 SO.sub.4 in the presence of MnO.sub.2 and a reductant. A source of chloride ion is added to the leach sufficient to dissolve at least about 50% of the precious metals present in the ore. A portion of the leach is removed and precious metals are recovered from the removed portion. A portion of the chloride carrier is recycled to the leach to carry chloride values to the leach. In one embodiment, HCl is regenerated by pyrohydrolysis, which minimizes harmful waste products. The present process can advantageously avoid the use of noxious reagents.

Abstract: A process for recovery of copper from a copper residue obtained during purification of a zinc sulfate solution comprises leaching the copper residue in a concentrated sulfuric acid solution in the presence of an oxidant at a temperature of between 60.degree. and 80.degree. C. and separating the solids from the leach solution, electrowinning copper from the leach solution, returning the electrolyte solution to the initial leaching stage to initiate dissolution of the copper residue, and bleeding a portion of the electrolyte solution to reduce the concentration of impurities in the solution.