Abstract: The invention relates to a method for the treatment of fluoboric electrolyte resulting from the processes of electro-extraction of metals such as copper and lead comprising a leaching stage with fluoboric acid, in order to recycle said fluoboric acid to be recirculated to said leaching stage devoid of impurities of metals such as Me=Fe, Zn, Ca, Mg, Cd, characterized in that it comprises the stages of: a) treating said fluoboric electrolyte comprising Cu(BF4)2 or Pb(BF4)2 with H2S in order to precipitate CuS or PbS respectively in accordance with the reactions Cu(BF4)2+H2S=>CuS+2HBF4  (1) Pb(BF4)2+H2S=>PbS+2HBF4  (2) thus obtaining a solution of HBF4 containing the fluoborates of said metals Me, said solution being separated, b) treating said Me fluoborates with H2SO4 in accordance with the reaction 2 Me(BF4)n+n H2SO4=>Me(SO4)n+2n HBF4  (3) (where Me=Fe, Zn, Ca, Mg, Cd) it being possible for said sulp

Abstract: Provided herein is a method for the removal of soluble metal species consisting of lead, cadmium, zinc and mixtures thereof, present in an aqueous effluent, the method comprising the steps of: a) contacting the aqueous effluent with a organophosphorus salt selected from sodium di-(n-octyl) phosphinate and sodium di-(n-dodecyl) phosphinate or mixtures thereof; b) achieving precipitation of said soluble metal species by reaction with said organophosphorus salts to yield a precipitate; and c) recovering said precipitate by filtration. Preferably, the mole ratio of organophosphorus salt is about 1.5 to 2.5 and most preferably about 2, in relation to the total mole ratio of the said soluble metal species. Preferably, prior to step a), the pH of the aqueous effluent to be treated is adjusted to at least about 3 and most preferably at least about 4.

Abstract: The invention relates to a method of treating germanium-containing gaseous waste coming from a unit for manufacturing an optical fiber preform, the method comprising the following steps:a liquid effluent is formed from the gaseous waste; andthe germanium is precipitated in the liquid effluent. According to the invention, the precipitation is performed by adding magnesium MgO to the liquid effluent.

Abstract: A process for the preparation of a fire-retardant material which comprises a particulate inorganic filler (other than a tin compound) coated with a layer of divalent metal hydroxystannate or a divalent metal stannate, which process comprises the steps of: (i) forming a slurry of the particulate inorganic filler in an aqueous solution of an alkali hydroxystannate, also containing a divalent metal oxide dissolved therein; (ii) reacting the slurry from step (i) with a hydrolysing agent, or a water-soluble source of a divalent metal, to form a layer of a divalent metal hydroxystannate on the surface of the filler, and (iii) optionally, heating the filler coat with hydroxystannate in step (ii) in order to convert it to the corresponding divalent metal stannate.

Abstract: A lead-containing complex oxide containing substantially no alkali metal is produced under hydrothermal conditions in the absence of alkali metals using a Pb source which serves also as a mineralizer for precipitating the lead-containing complex oxide. Preferred Pb source acting as the mineralizer is lead oxide.

Abstract: A hydrometallurgical method involves treating a dross source containing typically both antimony and tin and treating the dross to a series of chemical operations to yield a soft lead precursor, suitable for making soft lead for lead-based alloys for batteries or other applications, which method includes utilizing sulfuric acid to decompose the dross source to provide a slurry in which the liquid contains the principal tin values and the solid phase contains the antimony and lead values, followed by treating of the separated solid phase so as to either separate the lead values from the antimony values via an antimony leach and a solid/liquid separation or by desulfurizing the solid phase, carrying out a solid/liquid separation, treating the solid phase with a lead leach to solubilize the lead values and carrying out a further solid/liquid separation to recover the lead-rich phase as the filtrate, separated from the antimony-rich solid phase.

Abstract: Herein disclosed is 6 indium tin oxide (ITO) fine powder whose crystal form is a corundum type one and which has a true specific gravity of not less than 6.5 g/cc, a green density of not less than 3.0 g/cc, and a Seebeck coefficient of less than 30 .mu.V/cc at ordinary temperature and less than 80 .mu.V/cc after heating at 200.degree. C. The ITO fine powder can be prepared by a method which comprises the steps of neutralizing an aqueous solution containing an indium salt and a tin salt with ammonia to thus control the pH of the reaction solution to the range of from 6.8 to 7.5; separating the resulting neutralized precipitates through filtration; drying and washing the precipitates; calcining the precipitates in the air at a temperature ranging from 550 to 700.degree. C.; and then reducing-burning at a temperature ranging from 350 to 450.degree. C. in a reducing atmosphere.

Abstract: A continuous system recovers germanium (Ge) from a chemical vapor deposit. A chemical vapor deposit scrubber scrubs a chemical vapor deposit to form a chemical vapor deposit scrubber solution. An equalization and neutralization mixer adds a caustic soda to the chemical vapor deposit scrubber solution to form an equalization and neutralization mixer solution having a pH above 12.0 to maintain the solubility of silicon oxide (SiO.sub.2) and hypochlorite (ClO.sup.-). A hypochlorite reduction mixer adds a peroxide to the equalization and neutralization solution to form a hypochlorite reduction solution to reduce hypochlorites. A precipitant and neutralization mixer adds a metal cation such as Epsom Salts (MgSO.sub.4) and a caustic soda, such as sodium hydroxide (NAOH), to the hypochlorite reduction solution to form a precipitant and neutralization solution to precipitate magnesium germanate (MgGeO.sub.3) and magnesium metasilicate (MgSiO.sub.3).

Abstract: A method for producing an indium oxide-tin oxide powder, which comprises supplying to react an aqueous solution of an indium salt, an aqueous solution of a tin salt and an aqueous alkaline solution into water at 40.degree. C. or more and less than 100.degree. C. so that the pH during the reaction is maintained within the range from 4 to 6, forming a precipitate, washing the formed precipitate after solid-liquid separation, and calcining the precipitate at 600.degree. C. or more and 1300.degree. C. or less.

Abstract: The invention relates to electrically conductive pigments which as a conductive layer on a platelet-shaped or needle-shaped substrate have a niobium- and/or tantalum-doped tin oxide or titanium dioxide layer.

Abstract: A sol having dispersed in a liquid medium particles of a hydrated zinc stannate having a primary particle diameter of from 2 to 200 nm and represented by the formula xZnO.ySnO.sub.2.zH.sub.2 O wherein the molar ratio of x:y:z is 1:0.83 to 1.43:1.00 to 5.00.

Abstract: According to the method, an aqueous salt solution containing either tin, indium or both, are mixed with an alkali to produce a slurry containing precipitated particles. Then, the slurry is maintained at a predetermined temperature range for a time sufficient to convert the precipitated particles to larger size particles by coagulation or agglomeration. The resulting slurry is then dried and calcined to produce a mixed power. The mixed power is ball milled, press molded and/or cold isostatic press (CIP) molded. The molded body is then sintered to form an ITO sintered body. The ITO sintered body obtained by this process offers superior sinterability whose theoretical density can reach more than 95%.

Abstract: The present invention relates to an improved process for producing lead oxide in a pure state from a spent paste resulting from exhausted acid batteries. The spent paste is first calcined and desulfurized, then leached by a concentrated solution comprising an alkali hydroxide at a temperature above 100.degree. C. The separated solution is contacted with a ketone resulting in a suspension from which the .alpha.-lead oxide constituent is recovered. The solutions of alkali and ketone are recycled in the process. The preferred alkali constituents are selected from sodium hydroxide or potassium hydroxide, preferably containing also a small amount of sulfate of the respective alkali metal of the hydroxide used.

Abstract: Solution precipitation processes for preparing antimony doped tin oxide having improved volumetric efficiency and improved wash efficiency involving use of concentrated base and metal salt solutions are disclosed.

Abstract: The invention provides acicular electroconductive tin oxide fine particles which has a mean diameter of 0.005-1 .mu.m and a mean length of 0.05-10 .mu.m and an aspect ratio of 3 or higher. The invention further provides a process for producing the acicular electroconductive tin oxide fine particles, which comprises firing a starting material containing tin, silicon and an alkali metal halide at 700.degree.-1200.degree. C and removing soluble salts from the resulting fired product.

Abstract: The invention provides acicular electroconductive tin oxide fine particles which has a mean diameter of 0.005-1 .mu.m and a mean length of 0.05-10 .mu.m and an aspect ratio of 3 or higher. The invention further provides a process for producing the acicular electroconductive tin oxide fine particles, which comprises firing a starting material containing tin, silicon and an alkali metal halide at 700.degree.-1200.degree. C. and removing soluble salts from the resulting fired product.

Abstract: This invention relates to novel crystalline molecular sieves having the pharmacosiderite structure and having germanium and M metals as framework elements. Optionally, titanium and silicon can also be a framework element. The M metals can be any metal which has octahedral coordination and has a valence of +2, +3, +4 or +5. Illustrative of these M metals are niobium, tin, antimony, aluminum, gallium and tantalum.

Abstract: A fine metal oxide powder is prepared by a method comprising the steps of (1) preparing a hydroxide precursor of a metal oxide, (2) mixing the precursor with an inorganic compound having a melting point lower than the crystallization temperature of the metal oxide, and (3) subjecting the resulting mixture to a high temperature thermal treatment to form the fine metal oxide powder.

Abstract: A process for the preparation of ceramic material Lithium stannate doped with a transition metal for a humidity sensor mixes a salt of Lithium with SnO.sub.2 in dry condition, thereafter mixes in wet conditions using an organic solvent, adds a transition metal compound to the resulting mixture, mixes the mixture thoroughly, drys and compacts the mixture in the range of 5000 to 8000 lbs and heats the pellets so formed at a temperature in the range of 600.degree. to 800.degree. C. for a period in the range of 6 to 12 hours followed by slow cooling to room temperature.

Abstract: The invention relates to a method for removing calcium ions and silicon compounds from various liquors produced or obtained in an alkali metal chlorate process, thereby reducing the operating cost and improving the possibility to close the process further. The calcium ions and silicon compounds are removed by addition of carbonate ions for precipitating calcium carbonate and by addition of an iron-containing compound for forming and precipitating a complex of iron ions and a silicon compound, whereupon the precipitates are co-separated from the liquor. The removal of calcium and silicate ions is substantially facilitated by the simultaneous separation of the precipitates. Subsequently, the excess of carbonate ions can be reduced by acidifying the electrolyte for releasing carbon dioxide.

Abstract: In the process of removing heavy metals from aqueous solutions (groundwater) by precipitation of a salt thereof, an oxidizing agent is optionally used to increase the valence of said metal, and a precipitation-enhancing agent is added to maximize particle size of the precipitate and to facilitate its separation from said solution.

Abstract: The present invention is directed to improved methods for processing battery wastes, battery casing debris and other lead contaminated materials. The improved processes of the present invention provide less environmentally stressful methods for recovering lead from such materials while at the same time producing scrap or recyclable ebonite and plastics having reduced and environmentally acceptable lead and leachable lead levels. Most of the lead is first removed by trammel scrubbing. In another aspect of the present invention ebonite and other hard surface materials to which are adhered lead contaminants are mixed with water and abraded in a high energy scrubber to remove the adhered contaminants prior to separation of the cleaned ebonite from solution. This simple and environmentally preferred hydromechanical process provides clean scrap or recyclable ebonite.

Abstract: The present invention describes a method of making metal stannates by reacting a solid metal oxide, hydroxide or carbonate with an aqueous stannate solution and recovering the precipitated metal stannate, the solid component being added in an amount which is stoichiometrically not substantially more then the amount of tin.

Abstract: The present invention is directed to improved methods for processing battery wastes, batter casing debris and other lead contaminated materials. The improved processes of the present invention provide less environmentally stressful methods for recovering lead from such materials while at the same time producing scrap or recyclable ebonite and plastics having reduced and environmentally acceptable lead and leachable lead levels. Most of the lead is first removed by trommel scrubbing. In another aspect of the present invention ebonite and other hard surface materials to which are adhered lead contaminants are mixed with water and abraded in a high energy scrubber to remove the adhered contaminants prior to separation of the cleaned ebonite from solution. This simple and environmentally preferred hydromechanical process provides clean scrap or recyclable ebonite.

Abstract: The thallium content of lead bullion is decreased in that iron chloride is stirred into the lead bullion so as to form a salt slag which contains thallium.

Abstract: Bismuth impurity is removed from copper electrolyte by contacting the electrolyte with an effective amount of finely divided lead oxide.

Abstract: A method of precipitating metals from a spent geothermal brine containing the same comprises admixing the geothermal brine with a condensate of steam, derived from the brine, in a volume ratio of brine to condensate of 1:2 to 1:10. The invention is particularly applicable to geothermal brine processes for the production of electric power, such as are practiced at the Salton Sea.

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: A method of treating solid hazardous wastes containing unacceptable levels of leachable metals such as lead, cadmium and zinc includes mixing the solid waste with a buffering agent selected from the group consisting of magnesium oxide, magnesium hydroxide, reactive calcium carbonates and reactive magnesium carbonates, and with an additional agent which is an acid or salt containing an anion that forms substantially nonleachable forms of the metals, which additional agent is selected from the group consisting of triple superphosphate, ammonium phosphate, diammonium phosphate, phosphoric acid, boric acid and metallic iron so that under both acidic and nonacidic leaching conditions the metals in the mixture will be converted to substantially nonleachable forms.

Abstract: A process for the preparation of a superconductor of the type AB.sub.2 Cu.sub.3 O.sub.7-x, wherein A is a mixture of rare earths, B is an alkaline earth metal and x is less than one, comprising the treatment of xenotime to obtain a rare earths oxide therefrom and mixing the oxide with an alkaline earth metal compound and a copper compound and heat treating the mixture to obtain the superconductor. The treatment of the xenotime comprising melting the xenotime with a 1:1 mixture of Na.sub.3 CO.sub.3 and K.sub.2 CO.sub.3, dissolving a solid obtained therefrom in HCl, treating the resulting solution with NH.sub.4 OH to precipitate the rare earths, dissolving the precipitate in HCl, treating the resulting solution with H.sub.2 C.sub.2 O.sub.4 to precipitate the rare earths aned calcinating the precipitate to obtain a rare earths oxide.

Abstract: A process for the heavy-metal decontamination of contaminated substances such as natural and industrial sludges, thermal residues and soils. The contaminated starting substance is treated with an acid and the dissolved metal salts are precipitated as metal hydroxides in the pH range of about 3.5-11. The exact control of the pH value makes it possible to isolate individual metal fractions which can be used as raw materials in the metallurgical industry.

Abstract: Aqueous effluent solutions containing metal cations may be treated with an extractant comprising an organophosphinic acid, a di-2-ethylhexyl phosphoric acid and/or an aliphatic amine to selectively separate chromium, nickel, cobalt, copper and lead cations from the aqueous solution. Typical extraction techniques include liquid-liquid extraction employing either mixer settlers or columns, liquid membrane extraction and selective supported membrane extraction.

Abstract: Precipitation (conversion) of dissolved heavy metals in waste effluents is achieved with the addition and mixing of a solution of sodium polythiocarbonate with a solution containing dissolved heavy metals. The solution of sodium polythiocarbonate has been pH buffered to a pH of 12.5 or less in the manufacturing process. Precipitation of the dissolved heavy metals with the buffered sodium polythiocarbonate is complete by the formation of a stable, unleachable [as defined in 40 CFR 190.01, Part 261 Appendix II (Code of Federal Regulations)], extremely insoluble metallic polythiocarbonate particle.

Abstract: Refining of either niobium hydroxide or tantalum hydroxide containing transition metals as impurities is accomplished easily and economically by dissolving the metal hydroxide in an aqueous solution of either hydrofluoric acid or oxalic acid, adjusting the pH of the solution to 1 to 4 and adding ammonium pyrrolidinedithiocarbamate (APDC) to the solution while maintaining the temperature of the solution below 60.degree. C. The addition of APDC causes the transition metals to simultaneously precipitate as coordination compounds. The minimum amount of APDC is 0.05 wt % of Nb.sub.2 O.sub.5 or Ta.sub.2 O.sub.5 that can be formed from Nb or Ta contained in the solution. After the treatment with APDC the pH of the solution is raised to 6 or above to precipitate the refined metal hydroxide.

Abstract: Transparent conductive coatings excellent in transparency are provided on substrates such as glass, plastics, etc. by the use of conductive coating materials obtained by maintaining aqueous solutions of hydrolyzable tin containing or indium containing compounds at pH of 8-12, and gradually hydrolyzing said compounds in the solutions to form sols containing colloidal particles, followed by drying and calcining.

Abstract: A process is provided for working up dusts which have been precipitated electrostatically from the gas mixture composed essentially of carbon monoxide and phosphorus vapor produced in the electrothermal production of yellow phosphorus, which process comprises converting the dusts into a calcinate at 300.degree. to 800.degree. C. under oxidizing conditions in a first step, leaching the calcinate with phosphoric acid in a second step, adjusting the pH of the solution in phosphoric acid to 0 to 1.5 with sodium hydroxide solution in a third step, precipitating the sulfides of lead, copper and cadmium from the partially neutralized solution in phosphoric acid by adding sulfide and filtering them off in a fourth step, adjusting the pH of the filtered, partially neutralized solution in phosphoric acid to about 1.5 to 5.

Abstract: The invention provides a hydrometallurgical process for recovering lead in essentially pure form from a sulphurized compound containing at least lead as a non-ferrous metal. The process involves treating the sulphurized compound with an aqueous lixiviating solution containing at least one chloride of a metal selected from the group consisting of copper, bismuth, antimony, arsenic, and silver, preferably cupric chloride, the quantity of said at least one chloride being less than or equal to that which is stoichiometrically required for the complete dissolution of the lead contained in the sulphurized compound, thereby to obtain a solution containing lead chloride and the chlorides of metals nobler than lead as impurities if originally present in the sulphurized lead compound, and an insoluble residue containing the sulphide of the metal of said at least one chloride, the sulphides of the non-ferrous metals originally present in the sulphurized compound, and free sulphur.

Abstract: A process for the treatment of flue dust from copper and lead smelters includes the steps of subjecting a slurry (10) of water and flue dust to a first caustic leach (12) to form a first liquids soluble sulfate solution (14) and a first solids portion (15), subjecting the solids portion to a second caustic leach (16) to solubilize lead and arsenic in a second liquid portion (22) and, selectively extracting the arsenic from the second liquid portion by precipitation (23).

Abstract: Process for the recovery of germanium from solutions that contain it, in particular from solutions diluted by the addition of tartaric acid and extraction with an organic solution of a tertiary amine. In the reextraction with sodium hydroxide there is obtained a concentrate of germanium.

Abstract: An elastic bar member is coupled to an orbiting mass oscillator and the entire assembly is suspended from a cable or the like such that the bar member has freedom of lateral motion and is nakedly immersed in a slurry having particulate material contained therein such as a mineral ore reject from which metal has been extracted. The rotor of the orbiting mass oscillator is driven at a speed such as to generate cycloidal sonic energy in the bar preferably at a frequency such as to set up resonant standing wave vibration of the bar in a cycloidal quadrature pattern. The cycloidal vibrational energy tends to set the surrounding fluid material into a whirling rotation or rotary traveling wave which facilitates the agglomeration or coagulation of the particles in the material and enhances the settling operation to make for more complete separation of the particles from the liquid.

Abstract: An elastic bar member is clamped to an orbiting mass oscillator and the entire assembly is suspended from a cable or the like such that the bar member has freedom of lateral motion and is nakedly immersed in a leachant having a material contained therein such as a mineral ore from which metal is to be extracted. The rotor of the orbiting mass oscillator is driven at a speed such as to generate cycloidal sonic energy in the bar preferably at a frequency such as to set up resonant standing wave vibration of the bar in a cycloidal nutating pattern. The cycloidal vibrational energy tends to set the surrounding fluid material into a whirling rotation or rotary traveling wave which facilitates the mixing of the ore and leachant and enhances the leaching operation to make for more complete separation of the mineral from the ore.

Abstract: This invention can treat a uranium-containing solution of high or low concentration and/or the waste generated from uranium conversion processes, etc. It is characterized by the use of acorns, nuts of oak tree, which can be easily obtained in our botanical system. By coprecipitating the uranium or other heavy metal elements with the extract of acorns, this invention can not only recover the uranium of other heavy metal elements but also can reduce them before being discharged to the environmental radioactivity level.

Abstract: There is disclosed a process and an apparatus for beneficiating a mineral ore, such as phosphate-containing ore, in a substantially vertical column. The feed subjected to the benefication preferably has a particle size of less than 20 mesh. The feed is introduced into the column, containing at least one baffle, into which there is also introduced a gas at the bottom portion thereof and a liquid through at least one column inlet at the top of the column. The baffle and the rates of introduction of the feed, the gas, and the liquid are such as to create relatively high turbulence conditions within the column. The enriched, beneficiated product is removed at the top of the column, while the waste products, such as silica-containing material, in the case of a phosphate ore, are recovered at the bottom of the column.

Abstract: Modified starch compositions and their use for flocculating mineral waste residues, particularly the red mud containing alumina liquors from bauxite residues, comprising the addition to an alumina liquor of a flocculating amount of a methylated starch which, optionally, may be hydrolyzed, or a methylated starch which is also sulfonated and, optionally, may be hydrolyzed. Preferably, the methylated starch compositions are potato and dasheen starch derivatives prepared at temperatures of about 50.degree. to about 85.degree. C.

Abstract: A process is disclosed for recovering metals from chromium bearing material comprising one or more or the metals of cobalt, nickel, molybdenum, tungsten, iron, tin, aluminum. The process comprises atomizing the material to produce a flowable powder which is then fused in an oxidizing atmosphere with sufficient alkali metal hydroxide at a temperature sufficient to form a nonmagnetic fused material in which the chromium, tungsten and molybdenum are present as water soluble salts. The resulting fused material is then slurried with a sufficient amount of water to dissolve the water soluble compounds. The pH is adjusted to from about 9.2 to about 9.6 with an acid to allow insolubles to form which contain any cobalt, and nickel and the major portion of any iron, tin and aluminum followed by separating the insolubles from the resulting first liquor.

Abstract: A ceramic composition represented by the following general formula:Pb.sub.1-x La.sub.x (Zr.sub.y Ti.sub.1-y).sub.1-x/4 O.sub.3wherein O<x<1, O<y<1) is produced by a method which comprises adding a mixed solution of a titanium alkoxide and a zirconium alkoxide to an aqueous solution containing lead nitrate and/or lead acetate and lanthanum nitrate and/or lanthanum acetate thereby simultaneously effecting hydrolysis of said alkoxides and coprecipitation of lanthanum components, further adding an alkaline substance to the resultant system thereby effecting substantially thorough precipitation of lead and lanthanum components, and heating the produced precipitate.

Abstract: Solid residues arising from the burning of solid wastes have lead and cadmium sufficiently insolubilized to pass the EPA toxicity test only where the pH in the EPA test is between 7.5 and 12.0. Addition of water soluble phosphate, especially phosphoric acid, increases the immobilization of lead and cadmium so as to make such residues in compliance with the toxicity tests over a substantially broader pH range.

Abstract: Iron is recovered from an iron-containing dust obtained in processing iron or steel by dissolving iron and bivalent metals present in the dust in an acid. Subsequently the iron is precipitated as iron hyroxide by adding an alkaline substance or ammonia to adjust the pH to 5 to 8. Before or during precipitation of any iron the bivalent metal ions present, such as zinc, cadmium and lead, are converted into a soluble complex by the addition of a complexing agent, preferred complexing agents being polyamines, particularly triethylene tetramine. The process may be conducted more than once in the same solution, thereby providing a final solution containing considerable amounts of zinc, cadmium, or other bivalent metals, which may be separated by boiling or precipitation.

Abstract: A method is provided for the removal of lead contaminants from ores and mineral concentrates, comprising leaching the concentrates, at elevated temperatures, with an aqueous solution containing an aminopolycarboxylic acid. After separating the solution from the concentrates, lead can be precipitated by treating the solution with a sulfide; the solution can be recycled for use as a leachant.

Abstract: This is a method for the complete leaching of the valuable metals in a metal sulphide material which contains copper, zinc, lead, silver and iron by the use of a solution which essentially contains cupric chloride/sulphates. After the valuable metals have been recovered, the solution is regenerated whereby ferrous chloride and cuprous chloride/sulphate is oxidized to a ferric hydroxide solid and a cupric chloride solution respectively. The regenerated solution is split into two part-solutions and returned to the process.One part-solution goes to a metathesis stage where the fresh metal sulphide material is added in large excess with respect to the part-solutions's content of copper. The result is that only the valuable metals like zinc, lead and silver are leached while copper and iron remain in the residue.The other part-solution goes to a leach stage where the residue from the metathesis stage is added.