Abstract: The invention relates to a method for recovering zinc from a zinc oxide bearing material containing silicates. According to the method, the leaching of zinc compounds is carried out in circumstances where the silicates remain undissolved and consequently do not cause filtering problems. The silicate bearing residue is treated in a Waelz process, so that the major part of the silicic acid contained in the silicates is combined in the iron silicate slag formed in the Waelz process, and the zinc is returned into leaching mainly in oxidic form.

Abstract: The invention relates to a hydrometallurgical process for decontaminating soils 1 which are polluted with metallic elements, comprising a stage of basic leaching I so as to bring about the dissolution of the metallic elements to be removed, a cementation stage II bringing about the precipitation 6 of said elements in metal form, performed by electrochemical exchange with a zinc powder 5 produced by a stage of electrolysis III of the solution 7 originating from the cementation stage. In accordance with the invention a complementary addition of zinc is performed, preferably at the exit of the leaching stage in the form of a leachate 17 of waste from iron and steel manufacture, especially of dust 13 from electrical steel manufacture 15.

Abstract: Fly ash from incineration plants is treated with an acidic aqueous solution for the purpose of removing heavy metals. The residual solid matter is filtered. The filtration residue is treated with a precipitating agent for heavy metals. The thereby obtained inert residue can be directly dumped.

Abstract: Heavy metals are efficiently removed from contaminated soil by a process which comprises leaching or washing the soil with a mild leachant solution comprised of an aqueous solution of an acid and a salt. Heavy metals are also efficiently removed from paint chips by washing with an aqueous acid. The heavy metals are recovered from the leachant be cementation.

Abstract: Heavy metal values can be removed and separated from a substance having a suitable amount of the heavy metal values by contacting the substance with a fluid containing sulfur trioxide to prepare a corresponding heavy metal sulfate, which is followed by leaching the sulfate therefrom and separating the leached sulfate. For example, mercury metal, oxide or sulfide, or methyl mercury, such as can be found in used fluorescent lamps and household batteries, in industrial flue sands, fly ash, contaminated soils, etc., can be removed by contact of crushed lamps or batteries, samples of the flue sands, fly ash, or contaminated soils, etc., with a mixture of sulfur trioxide in air to form mercuric sulfate, which is leached with a suitable leaching agent such as water, aqueous hydrochloric acid, hot dilute sulfuric acid, or concentrated sodium chloride solution, and sequestered by use of an ion exchange resin or precipitated as sulfides for further isolation of mercury value.

Abstract: To remove lead, cadmium and zinc from dusts produced in the electrostatic precipitator in the electrothermal production of yellow phosphorus, the dusts are first digested by phosphoric acid having a content of at least 25% by weight of P.sub.2 O.sub.5 at temperatures above 60.degree. C. in a ventilated reaction zone. The digest solution is then separated in a filter zone into an essentially lead-, cadmium- and zinc-free solid residue and a phosphoric acid containing dissolved lead, cadmium and zinc.

Abstract: Impurity streams generated during the pyrometallurgy of copper are hydrometallurgically processed at ambient pressure for recovery of primary values in an energy-efficient manner and with the capture and conversion of metallic impurities to states that are acceptable for disposal into the environment. Hallmark features of the various embodiments of this invention include the water leach of flue dust, the extraction of water-soluble copper as a separate product, a controlled acid leach stage in which bismuth is solubilized, the return of copper to the smelting process as a sulfide, the ability to operate the various process stages at essentially ambient pressure, and the gradual reduction in temperature over the course of the process without the use of indirect heating or cooling operations.

Abstract: A process for the recovery of a metal, in particular, cadmium contained in scrap, in a stable form. The process comprises the steps of mixing the cadmium-containing scrap with an ammonium carbonate solution, preferably at least a stoichiometric amount of ammonium carbonate, and/or free ammonia, and an oxidizing agent to form a first mixture so that the cadmium will react with the ammonium carbonate to form a water-soluble ammine complex; evaporating the first mixture so that ammine complex dissociates from the first mixture leaving carbonate ions to react with the cadmium and form a second mixture that includes cadmium carbonate; optionally adding water to the second mixture to form a third mixture; adjusting the pH of the third mixture to the acid range whereby the cadmium carbonate will dissolve; and adding at least a stoichiometric amount of sulfide, preferably in the form of hydrogen sulfide or an aqueous ammonium sulfide solution, to the third mixture to precipitate cadmium sulfide.

Abstract: A process for recycling a zinc phosphating system sludge comprising forming a mixture of the sludge with water and phosphoric acid. The mixture is formed at an elevated temperature and a pH of between 1.5 and 2.4. The sludge substantially dissolves in the mixture and iron phosphate precipitates out. The resultant liquid comprises a substantially zinc ion and phosphate ion solution suitable for use as a make-up feed in zinc phosphating system.

Abstract: There is proposed a process for recovering lead, comprising the steps of: feeding molten caustic soda, lead-containing feed and an oxygen-containing gas into a reaction some having a temperature of 600.degree. to 700.degree. C. as a result of which there are obtained lead metal withdrawn from the process and a melt containing sodium sulphate, zinc and copper sulphides, and gangue. The melt is discharged from the reaction zone of subjected to a first leaching operation to obtain, as a result, a slurry representing a mixture of solid particles of sodium sulphate, zinc and copper sulphides, gangue and an aqueous solution containing essentially caustic soda. Further on, the slurry is filtered to produce a concentrated aqueous solution containing essentially caustic soda and a solid residue. The concentrated caustic soda solution is subjected to thickening by evaporation and the resulting caustic soda melt is fed into the reaction zone.

Abstract: A process is disclosed for recovering zinc, lead, copper and precious metals from zinc plant residue, said process comprising leaching the residue with return zinc spent electrolyte, neutralizing residual acid and reducing ferric iron in the solution by addition of zinc sulphide concentrate in the presence of a limited quantity of oxygen, flotation of the resulting slurry to separate unreacted zinc sulphide, treatment of flotation tailings with sulphur dioxide and elemental sulphur to further leach iron, zinc and impurity elements and precipitate copper, flotation of the resulting slurry to separate a copper sulphide concentrate, thickening, filtering and washing of the flotation tailings followed by addition of lime and sodium sulphide to activate lead sulphate and flotation of a lead concentrate from the residue.

Abstract: The present invention relates to the decontamination of soil and the like and, in particular, soils which are contaminated with metal as a result of the activities of human beings. The invention provides a physical and a chemical means for treating soil aggregate so as to obtain a product aggregate having a relatively low metal content. The physical means is characterized by the classification of a soil aggregate into portions of differing size and metal content. The chemical means is characterized by contacting a soil aggregate with an aqueous lixiviant comprising an organic acid component to lift metal from the aggregate. The physical and chemical means may be used in a combined process for decontaminating soil aggregate.

Abstract: A process for recovering zinc/rich and iron-rich fractions from the baghouse dust that is generated in various metallurgical operations, especially in steel-making and other iron-making plants, comprises the steps of leaching the dust by hot concentrated sulfuric acid so as to generate dissolved zinc sulfate and a precipitate of iron sulfate, separating the precipitate from the acid by filtration and washing with a volatile liquid, such as methanol or acetone, and collecting the filtered acid and the washings into a filtrate fraction. The volatile liquid may be recovered distillation, and the zinc may be removed from the filtrate by alternative methods, one of which involves addition of a sufficient amount of water to precipitate hydrated zinc sulfate at 10.degree. C., separation of the precipitate from sulfuric acid by filtration, and evaporation of water to regenerate concentrated sulfuric acid.

Abstract: A method for the continuous treatment of air pollution control residues from various resource recovery systems whereby the air pollution control residue is treated with a dilute salt extracting solution at a pH chosen to maximize the recovery of lead, for a reaction time chosen to maximize the recovery of lead, and for a number of recycles chosen to maximize the recovery of lead from the particular residue being treated. Other metals and dissolved salts can also be recovered from the extracting solution. Thus by monitoring these three variables for each batch of residue, and adjusting the extracting solution accordingly, residue from various sources and of varying composition can be treated efficiently and continuously to remove hazardous metals and dissolved salts from the residue. Bottom residue fines, alone or admixed with air pollution control residues, can also be treated in accordance with the process of the invention.

Abstract: A process is described for recovering metal values, e.g., gallium, contained in an aqueous solution by extraction comprising the steps of contacting the aqueous solution with a water immiscible organic phase comprising a water-insoluble substituted 8-hydroxyquinoline whereby the metal values are transferred into the organic phase; separating the organic phase from the aqueous solution and recovering the metal values from the organic phase. The novel feature comprises recovering the metal values by contacting the organic phase containing metal values with an aqueous solution of a strong base whereby metal values are removed from the organic phase to the aqueous solution with the aqueous solution containing the recovered metal values having a concentration of at least 4.6 moles per liter total hydroxide, and then separating the metal values from the aqueous phase.

Abstract: A quaternary ammonium trihalide, a novel compound, represented by the formula:[A--R'].sup.+ .multidot.X.sub.3.sup.-(wherein A stands for a trialkyl-amino radical or a pyridyl radical, R' for an alkyl radical of 6 to 22 carbon atoms, and X for a halogen atom) and a method for the dissolution of a metal with a liquid consisting essentially of an organic solvent and the quaternary ammonium trihalide.

Abstract: A process is disclosed for the two-phase extraction of metal ions from phases containing solid metal oxides, which is characterized in that the solid metal oxides are brought into contact with a hydroxamic acid, known per se, dissolved in a hydrophobic organic solvent, the phases containing the solid metal oxides and the organic phase are intensively intermixed over a sufficient contact time, after phase-splitting, the organic phase is separated and the metal ions are re-extracted from the organic phase in a manner known per se and processed.The extracting agent used therein and the use of this extracting agent are also disclosed.

Abstract: A process and apparatus for leaching metal values from a particulate mineral ore containing metal values employs a fluidized bed of the particles; a leaching agent solution containing dissolved oxygen flows upwardly of the bed in a lower leaching zone, to an upper clarification zone; a velocity profile is maintained to promote settling of particles so that the particulate solids remain in the leaching zone and a clarified leachant-containing liquid low in suspended solids rises and collects in the clarification zone; the process is carried out with a minimum of undissolved gas and avoids the need for mechanical agitation, but the kinetics of the chemical leaching reaction is improved and heat loss via escaping gases is avoided.

Abstract: Methods are disclosed for treating smelter flue dust and other smelter by-products so as to recover non-ferrous metals therefrom and convert arsenic and sulfur in the flue dust into non-leachable compounds. The methods allow the flue dust and other smelter by-products such as smelter sludges to be disposed of in a natural environment without subsequent leaching of heavy metals, sulfur, and arsenic. The smelter by-products are mixed with hydrated lie, formed into agglomerates, and roasted at an optimal temperature of about 650.degree. C. to form oxidized arsenic and sulfur which react with the lime in the agglomerates to form non-leachable compounds. The roasted agglomerates are contacted with a basic lixiviant comprising dissolved ammonia and an ammonium salt to dissolve non-ferrous metals such as copper from the roasted agglomerates. Used lixiviant can be boiled to precipitate the non-ferrous metals dissolved therein and vaporize the ammonia, thereby regenerating the lixiviant.

Abstract: A process is provided for obtaining high quality high surface area zinc oxide from a roasted zinc sulphide concentrate by leaching with an ammoniacal ammonium carbonate solution. The process utilizes optional preliminary oxidation and water leaching steps to remove soluble impurities and an optional aqueous sulphur dioxide leaching step to selectively remove readily soluble zinc oxide. The process includes an improved source of roasted zinc sulphide concentrate. The process also includes an optional reduced pressure calcining step to produce zinc oxide with further increased surface area.

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.

Abstract: A process for recovery of metal values from a mixed metal chloride containing leach solution by contacting the leach solution with a water immiscible solution of a complexing agent selective for the neutral chloride of the metal to be recovered and a chelating agent having affinity for the cation of the metal to be recovered. The chloride ion is washed from the water immiscible solution by contact with a chloride ion washing solution. The water immiscible solution containing the chelated metal ion is stripped with an aqueous stripping solution. The metal is recovered from the aqueous stripping solution.

Abstract: A method of thermal disposal of sewage sludge. The sludge is dried and incinerated. The flue gases from the incineration are washed. The flue gas dust resulting from the incineration and the sludge resulting from washing of the flue gases are treated together with high temperature combustion which includes melting of solids.

Abstract: A metal is dissolved by a method which comprises establishing contact of the metal with a quaternary ammonium compound and a halogenated hydrocarbon or with a quaternary ammonium compound, a halogenated hydrocarbon, and a polar solvent.

Abstract: Caustic dezincing galvanized steel scrap. A dezincing plant includes a plurality of tanks interconnected in series with steel scrap sequentially being moved through each of the tanks. The tanks contain a caustic leaching solution including an oxidant with the leaching solution being circulated through each of the tanks in a direction opposite to the movement of the scrap. Fresh scrap initially is exposed to a partially depleted leaching solution with the oxidant concentration of the leaching solution increasing as the scrap moves through the series of tanks. Leaching solution depleted of its oxidant is transferred to an electrolytic cell where zinc is removed and plated as metallic zinc powder onto a cathode. The leaching solution is recycled by removing zinc. The chemistry of the leaching solution is controlled so that sufficient free caustic is present to prevent passivating zinc coating on the scrap.

Abstract: A method and apparatus for treating mineral-bearing ores and, more particularly, for treating ores containing precious metals, base metals and the like values by providing a means to extract the metal or other values from a particulated ore by classifying the ore to separate values from the gangue, and by continuously chemically leaching the said values from the ore. In accordance with an embodiment of the invention, particulated ore is fluidized and intermittently moved through a tank to classify the ore particles into strata according to size, shape and density to beneficiate values, either heavier or lighter than the gangue, for recovery of concentrated values.

Abstract: A method for selectively separating Zn from an acidic aqueous solution containing ions of Zn and Fe obtained by leaching of blast furnace dust using hydrochloric acid comprises first precipitating Fe from the solution and then treating the resultent Zn-containing solution with an alkali to precipitate Zn.The Zn-containing solution is treated in two stages; in the first precipitation step the pH is adjusted to from 4.0 to 4.3.

Abstract: A process for the removal of cadmium ions by liquid-liquid extraction from wet process phosphoric acid, which had been obtained from crude phosphate ores by dissolution with sulfuric acid, uses salts of long chain alkyl amines or ammonium bases with the chlorocomplexes of polyvalent metal ions, which are dissolved in an inert organic solvent.

Abstract: A process for treatment of incinerator ash typically including heavy metals and both water soluble and insoluble fractions. The insoluble fraction is first removed from the fly ash. The soluble fraction is treated to precipitate heavy metal compounds. Preferably, the heavy metal precipitates are incorporated in a vitrifiable batch. In a separate vitrifiable batch, the insoluble fly ash portions may also be incorporated. Most preferably, bottom ash from the incinerator is also incorporated in a glass batch. The bottom ash glass batch may also incorporate the insoluble fraction from the fly ash.Precipitation of the heavy metal constituents in the soluble portion of the fly ash is preferably accomplished by raising the pH of the solution, most preferably above 10 by addition of alkali metal or alkaline earth metal hydroxides.

Abstract: The invention is a process for the removal of high concentrations of impurities including antimony (Sb), bismuth (Bi), arsenic (As), lead (Pb), zinc (Zn), cadmium (Cd), selenium (Se) and tellurium (Te) contained in flue dusts produced during the smelting of copper. To effect the separation, the flue dust is slurried to about 10-30 weight percent solids. Then slurry is fed to gravity separation equipment, where the lighter impurities fraction segregates from the heavier revenue metals fraction. The segregated high copper concentrate is then washed while the tailings are neutralized by lime milk, dewatered and recovered as tailings cake. The wash solution together with the thickener overflow is subjected to copper cementation to recover the dissolved copper in the solution. The lighter impurities fraction can be subjected to acid leaching in order to further recover copper therefrom.

Abstract: Disclosed is a process for leaching selected metal compounds (e.g. gallium arsenide) from integrated circuits containing those compounds. The method includes placing the integrated circuits into a culture medium containing bacteria. Bacteria capable of leaching the metal compounds from the integrated circuits leach the metals from the integrated circuits. The bacteria preferably used will be ATCC 53921 and mutations and recombinants thereof. The integrated circuits are generally crushed to between 20 and -400 mesh before placement into theThis invention was made with Government support under Contract No. F33615-87-C-5303 awarded by the United States Air Force. The Government has certain rights in this invention.

Abstract: Disclosed is a high temperature process (e.g.>60.degree. C.) for leaching selected metal compounds e.g. gallium or germanium from ore containing those compounds. The method includes placing the ore into a culture medium containing bacteria. Bacteria capable of leaching the metal compounds from the ore leach the metals from the ore. The bacteria preferably used will be bacteria ATCC 53921 and mutations and recombinants thereof. The ore is generally crushed to between 20 and -400 mesh before placement into the culture medium cThis invention was made with Government support under Contract No. F33615-87-C-5303 awarded by the United Stated Air Force. The Government has certain rights in this invention.

Abstract: A process of refining zinc oxide from roasted zinc sulphide bearing concentrates comprises leaching the concentrate in an aqueous sulphur dioxide solution under controlled conditions providing selective separation of zinc from other elements contained in the concentrate. The zinc bisulphite solution so obtained is separated from the remaining solids and is heat treated, preferably with steam, to precipitate zinc monosulphite crystals, possibly after first adding zinc dust to the solution to cement out residual copper and cadmium. The zinc monosulphite is then separated from the solution, possibly washed with water, and calcined to yield purified zinc oxide.

Abstract: A process for the biological oxidation of sulfide in sulfide-containing ore. Preferably, the ore is then subjected to cyanide leaching. The resulting leach tail solution can be subjected to cyanide precipitation, employing ferric sulfate which is generated during the biological oxidation step of the process. Furthermore, a process for efficiently aerating the ore slurry during the biological oxidation step is provided.

Abstract: A process for the hydrometallurgical recovery of metal value, particularly copper, from copper-containing sulphide materials in which the material is conventionally ground and reacted with a solution containing less than 3 moles per liter of chloride ion, and optionally as little as 15 g/liter, together with sulphate ions with continuous oxygen injection and vigerous agitation. The reacting may be carried out at a pH in the range of 0.5-4, at moderate pressure as low as atmospheric pressure and at a moderate temperature below the boiling point of the solution such as 85.degree. C.

Abstract: A metal is dissolved by being brought into contact with at least one halogenated hydrocarbon in the presence of a cationic surfactant.

Abstract: A process and apparatus for the recovery of metals such as silver from phosphate flue dust. The process includes the steps of blending chloride salt and the flue dust to produce a blended material, roasting the blended material in an oxygen bearing atmosphere to oxidize carbon in the blended material producing a gas and to react chloride salt with the metal in the blended material producing a water soluble metallic salt, dissolving the metallic salt in water to produce a solution, filtering the solution to remove solids, and precipitating metals from the filtered solution with the precipitate ready for conventional smelting. The preferred embodiment of the apparatus includes a flue dust hopper and mill and a salt hopper and mill for feeding the dust and salt to a radiant tube dryer and a radiant tube asher for blending and roasting the materials, and a spray chamber at the outlet of the asher for separating solids and gases, where certain of the solids go into solution.

Abstract: An improved hydrometallurgical process for extracting metals from ocean-mined ferromanganese nodules. The process includes the steps of contacting the ferromanganese nodules in an extraction zone with an aqueous solution containing effective amounts of chloride ions and nitrate ions necessary to displace metal values in the ore at an elevated temperature and continuing the contact to form an extraction mixture slurry including a liquid component comprising an aqueous solution containing extracted metal values from the ferromanganese nodules dissolved therein and a solid tailing component; and, separating the liquid and solid components of the extraction mixture slurry.

Abstract: The present invention relates to an aqueous ferric chloride leach process for the extraction of metal values from a metal-sulphide bearing material, the leach being carried out in the presence of a leaching aid chosen from among salts of diesters of sulphodicarboxylic acids. It, in particular, relates to the enhanced recovery of metal values from complex, metal-sulphide bearing materials such as, for example, fine grained, polymetallic sulphide ores, their concentrates or the like.

Abstract: Iron-containing zinc sulfide concentrate is processed to recover zinc values therefrom. The concentrate is roasted to convert zinc sulfide and iron sulfide to their oxides while adequate sulfide-sulfur is retained to maintain the iron values in the ferrous state and thereby avoid ferrite formation. Zinc oxide and iron oxide values are recovered from the roast, simultaneously or sequentially, and residual zinc sulfide may be recycled to the roasting step.

Abstract: A method for removing and recovering toxic heavy metal contaminants from an iron-bearing sludge is provided. The method comprises one or more cycles of a two step, controlled chloride leach comprising a first non-acidic chloride leaching solution and a second acidic chloride leaching solution, wherein said toxic heavy metals are separated from said sludge and said iron-bearing sludge is a substantially non-hazardous material.

Abstract: A process for the recovery of zinc from zinc-containing sulphidic material which also contains iron and from zinc oxide containing material, at least one of the materials containing lead and/or silver values. The process includes leaching zinc-containing sulphidic material and zinc oxide containing material under pressurized oxidizing conditions at a temperature in the range of from about 130.degree. to about 170.degree. C. in aqueous sulphuric acid solution with a stoichiometric excess of sulphuric acid relative to the zinc content of the materials of from about 40 to about 100% to produce a residue containing a major proportion of lead and/or silver values and a leach solution containing a major proportion of the zinc and iron. The residue is separated from the leach solution and treated to recover lead and/or silver values.

Abstract: A process is described for the controlled oxidation roasting of zinc bearing sulphidic ores and concentrates by adjusting the furnace temperature and residence time together with the oxygen availability to the sulphide retention requirements in the calcine. The obtained calcine is subsequently subjected to various physical and chemical process steps to separate the unreacted sulphides which are then dead roasted and treated for zinc recovery, according to one embodiment of the process. In another embodiment the separated, unreacted sulphides are returned to the controlled oxidation roasting step.The chemical separation process steps include sulphur dioxide leaching. In one embodiment zinc is preferentially dissolved as sulphite and the solution obtained is further treated for zinc recovery. In other embodiments sulphuric acid, or ammonical ammonium carbonate or similar leaching reagents are used for the preferential dissolution of the zinc oxide present in the calcine.

Abstract: A process comprises leaching zinc oxide either separately or in conjunction with iron oxides from a partially desulfurized zinc bearing sulfide ore of concentrate. The ore is pretreated to eliminate in a controlled manner sulfur-sulfur-sulfide in the ore yet leaving sufficient residual sulfur-sulfide in the material such that iron values are maintained substantially wholly in the ferrous state, while converting zinc sulfide to zinc oxide without formation of FeO-ZnO complexes. The partially desulfurized material may be selectively leached with a sulfuric acid containing solution under neutral leach conditions to dissolve thereby preferentially the zinc oxide over the iron oxide. Alternatively the material may be leached with a higher concentration of sulfuric acid containing solution to dissolve preferentially zinc oxide and iron oxide simultaneously. The leach liquor may be subsequently treated to electrolytically remove zinc.

Abstract: Metal ions contained in trace in an aqueous solution are extracted, for quantitative analysis by an ICP emission spectrometer, with an organic solvent supplemented by chelate compounds in an extraction vessel having a thin cylindrical upper portion, to form an organic layer containing the extracted metal ions over an aqueous layer. After extraction, water is supplied from the bottom of the vessel in an amount so that the interface between the organic and aqueous layers is positioned at a predetermined position of the thin, upper portion where a liquid withdrawal port is provided. The organic layer is recovered from the withdrawal port.

Abstract: A process for treating a first metal, manganese-containing ore comprising contacting the manganese-containing ore with an aqueous, acidic composition and a material containing at least one metal sulfide at conditions effective to (1) chemically reduce at least a portion of the manganese, (2) solubilize at least a portion of the metal from the metal sulfide, and (3) at least partially liberate the first metal from the ore; and recovering the first metal from the ore. The use of Thiobacillus ferrooxidans and/or added ferric ion in the contacting step are also disclosed.

Abstract: A process for recovering at least one first metal from a metal sulfide-containing ore comprising contacting the ore with an aqueous, acidic composition and at least one reducible manganese-containing material at conditions effective (1) to chemically reduce the manganese, (2) solubilize at least a portion of the metal from the sulfide, and (3) at least partially liberate the first metal from the ore; and recovering the first metal from the ore. The use of added ferric ion and/or Thiobacillus ferrooxidans bacteria in the above-noted contacting is also disclosed.

Abstract: In this invention sulfide compounds are added to mercury and precious metal-containing carbonaceous ore slurries prior to the slurry being processed by a carbon-in-pulp system. The sulfide compound inhibits the mercury from being adsorbed onto the activated carbon by reacting with the mercury to form mercuric sulfide and by inhibiting the dissolution of mercury from the ore. The mercuric sulfide precipitate displays no activity toward the activated carbon. The sulfiding procedure is performed with a sufficient amount of sulfide-providing compound to provide at least about 30 times the stoichiometric amount of sulfide ions required to react with the mercury in the ore slurry.

Abstract: This invention is a process for removing mercury from the desorption or cyanide liquor of a precious metal recovery, cyanide leach system. A sulfide ion-producing compound and a flocculating agent are added to the desorption liquor to form and flocculate mercuric sulfide. The desorption liquor typically has a cyanide concentration of between about 0.5 percent and about 2.0 percent by weight. The flocculated mercuric sulfide is separated from a substantially mercury-free precious metal-containing, cyanide solution.

Abstract: Mercury can be recovered from nitric acid-containing fluids by reacting the fluid with aluminum metal to produce mercury metal, and then quenching the reactivity of the nitric acid prior to nitration of the mercury metal.