Abstract: Processes for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof. Systems for regenerating alkali process streams are disclosed herein, including streams containing sodium hydroxide, magnesium hydroxide, and combinations thereof.

Abstract: The invention relates to a method and a recovery system for obtaining/recovering metallic iron and/or iron compounds, in particular iron chloride, from ores and/or ore tailings, especially from pyrite tailings, preferably from roasted pyrites produced during sulphuric acid manufacture.

Abstract: The invention relates to a method and a recovery system for obtaining raw materials from ores and/or ore tailings, in particular a method and a recovery system for recovering metals from ores and/or ore tailings, especially a method and a recovery system for recovering metals from pyrite tailings, preferably from roasted pyrites produced during sulphuric acid manufacture.

Abstract: The present invention relates to a system and method for remediating contaminated soil through separation and process of highly contaminated coarse soil, the system including: a screen adapted to separate the contaminated soil introduced into soil having given particle sizes; multiple hydrocyclones adapted to re-separate the soil having particle sizes of more than the given values by particle size from the soil having the given particle sizes separated through the screen; a remediating unit adapted to wash the soil separated through the multiple hydrocyclones by particle size; and a filtering unit adapted to separate water from the soil washed through the remediating unit.

Abstract: Zinc and lead are usually concomitantly present in Zn—Pb ores and tailings. A novel non-polluting hydrometallurgical process for selectively leaching and recovering zinc (Zn) from a composite lead (Pb) and zinc sulphide containing mineral, crushed untreated rock or unconsolidated mineral particles, mill tailings and/or agglomerated or unagglomerated sulphidic zinc containing waste material without necessitating smelting and refining operation has been developed. A combination of selected oxidant and alkali metal hydroxide has been found effective. A leachant consisting of e.g. a mixture of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl) is employed to selectively dissolve zinc sulphide at high pH at standard temperature and pressure (STP). The kinetics of leaching along with the effect of varying concentration (preferably of sodium hydroxide and sodium hypochlorite) were systematically investigated. Feed ore containing diverse set of minerals e.g.

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: A method for separating nickel, cobalt and a rare earth element from a material containing positive and negative electrode active materials of a nickel-metal hydride battery includes mixing a material containing positive and negative electrode active materials with a sulfuric acid solution and dissolving therein, and then separating a leachate from a residue; adding an alkali metal sulfate to the leachate to obtain a mixed precipitate of double sulfate of rare earth elements, and a rare-earth-element-free solution; and adding a sulfurizing agent to the rare-earth-element-free solution to separate a nickel and cobalt sulfide raw material and a residual solution.

Abstract: A method for recycling of thin film Cadmium Telluride photovoltaic modules at the end of their life, and manufacturing scrap, has been developed. This method allows for minimum glass fine generation, requires little or no acid compared to other methods, and generates a pure cadmium and tellurium product at recoveries in excess of about 80 percent. In addition, the process allows for the recovery of a clean soda-lime plate glass product.

Abstract: A method for recovering a metal, capable of recovering a metal easily without requiring the use of an organic medium, is provided. A complex between a chelating agent and a metal present in a sample is formed in a mixture prepared by mixing the chelating agent and the sample under pH conditions where the chelating agent can be insoluble in an aqueous medium. Then, the complex is recovered from the mixture, and further, the metal is recovered by dissolving the recovered complex in an aqueous medium under pH conditions that are different from the pH conditions where the chelating agent can be insoluble in an aqueous medium. By this method, a metal can be recovered easily without requiring the use of the use of an organic medium.

Abstract: A method of selectively leaching a metal such as nickel from an ore or ore processing intermediate comprising the metal and cobalt. The ore or ore processing intermediate is contacted with an acidic leach solution comprising an amount of an oxidising agent sufficient to oxidise a major portion of the cobalt to thereby cause it to be stabilised in the solid phase while a major portion of the metal is dissolved for subsequent recovery.

Abstract: The present invention relates to methods for recovering precious metals including silver and gold, rare metals including indium and gallium, base metals including copper, lead and zinc or a combination of precious, rare and base metals from complex oxide ores, sulfide ores or oxide and sulphide ores using an acid chloride oxidizing leach.

Abstract: The invention relates to a method for separating nickel and other valuable metalsparticularly from material having low nickel content, which contains iron and magnesium in addition to nickel and other valuable metals. The material havinglow nickel content is subjected to pulpingand atmospheric leaching in acidic and oxidising conditions, in which the majority of the metals in themate-rialdissolve and the iron is partially precipitated. The precipitated iron is sepa-rated from the solution, after which nickel and the other dissolved valuable metalsare precipitated as sulphides.

Abstract: A process for separating zinc from a feedstock containing a mixture of metals and metal compounds. The process includes leaching a zinc-containing feedstock with a concentrated basic solution, optionally diluting the slurry with an amount of water sufficient to reduce the viscosity of the slurry thereby facilitating separation of a pregnant liquor containing dissolved zinc from insoluble materials, separating the insoluble materials from the pregnant liquor, and precipitating zinc oxide from the pregnant liquor by adding an anti-solvent to the pregnant liquor. The described process also provides for recycling of the basic solution and the anti-solvent.

Abstract: Calcium (Ca), manganese (Mn) and magnesium (Mg) carbonate plus lead (Pb) and zinc (Zn) sulphide minerals in a permeable host, crushed ore, concentrates or as mine discharge tailing are selectively solution mined (in-situ or ex-situ) with a selected acid e.g. acetic acid to extract Ca, Mn, and Mg followed by multivalent oxidizing salts e.g. ferric salts to extract Pb and Zn sequentially. For in-situ leaching, an inter relationship has been identified between pressure, temperature, target depth and leachate concentration such that carbonate leaching is performed in a manner to prevent carbon dioxide gas (CO2) discharge thereby plugging host rock permeability avenues to preclude further leaching. This requires controlling the rate of acetic acid leaching to be in step with availability of solution to dissolve the resulting discharged CO2. Sulphide leaching is subsequently conducted on the carbonate-depleted host.

Abstract: A hydrometallurgical process for a nickel oxide ore comprising obtaining an aqueous solution of crude nickel sulfate by high pressure acid leaching of a nickel oxide ore; obtaining a zinc free final solution by sulfurization of the solution; obtaining a waste solution; and scrubbing hydrogen sulfide gas from an exhaust gas. The process is characterized by at least one of the following operations: Adjusting the total volume (m3) of a sulfurization reactor to a ratio of 0.2-0.9 (m3/kg/h) relative to the input mass (kg/h) of the nickel to be introduced to the reactor; and/or subjecting the waste solution and the exhaust gas to countercurrent contact, then introducing the exhaust gas back to the scrubber and charging the waste solution from the scrubber into the sulfurization reactor.

Abstract: The present invention relates to methods for recovering precious metals including silver and gold, rare metals including indium and gallium, base metals including copper, lead and zinc or a combination of precious, rare and base metals from complex oxide ores, sulfide ores or oxide and sulphide ores using an acid chloride oxidizing leach.

Abstract: A method of sequestering carbon dioxide emissions during recovery of hydrocarbons from hydrocarbonaceous materials can include forming a constructed permeability control infrastructure. This constructed infrastructure defines a substantially encapsulated volume. A comminuted hydrocarbonaceous material can be introduced into the control infrastructure to form a permeable body of hydrocarbonaceous material. The permeable body can be heated sufficient to remove hydrocarbons therefrom. During heating, the hydrocarbonaceous material is substantially stationary as the constructed infrastructure is a fixed structure. Additionally, during heating, any carbon dioxide that is produced can be sequestered. Removed hydrocarbons can be collected for further processing, use in the process, and/or use as recovered.

Abstract: Objects of the invention are to further enhance crystallinity and crystallinity uniformity of a semiconductor crystal produced through the flux method, and to effectively enhance the production yield of the semiconductor crystal. The c-axis of a seed crystal including a GaN single-crystal layer is aligned in a horizontal direction (y-axis direction), one a-axis of the seed crystal is aligned in the vertical direction, and one m-axis is aligned in the x-axis direction. Thus, three contact points at which a supporting tool contacts the seed crystal are present on m-plane. The supporting tool has two supporting members, which extend in the vertical direction. One supporting member has an end part, which is inclined at 30° with respect to the horizontal plane ?. The reasons for supporting a seed crystal at m-plane thereof are that m-plane exhibits a crystal growth rate, which is lower than that of a-plane, and that desired crystal growth on c-plane is not inhibited.

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 for metal leaching/solvent extraction are described which comprise: (a) providing a first aqueous leach pulp which comprises a mixture of leached solids and an aqueous leach solution comprising a metal, a leaching agent and water; (b) subjecting the first aqueous leach pulp to a first solid-liquid separation to provide a first clarified aqueous leach solution and a second aqueous leach pulp, wherein the second aqueous leach pulp comprises the leached solids at a % solids level greater than the first pulp; (c) subjecting the first clarified aqueous leach solution to a first solvent extraction prior to any significant dilution, whereby a first aqueous raffinate is obtained; (d) subjecting the second aqueous leach pulp to a second solid-liquid separation with dilution via an aqueous stream to obtain a second clarified aqueous leach solution; and (e) subjecting the second clarified aqueous leach solution to a second solvent extraction whereby a second is aqueous raffinate is obtained.

Abstract: A system and method are disclosed for improving component extraction from heap leach operations. Following heap leaching for some time, portions of the heap deficient in component extraction are identified, and treatment wells are drilled and remedial treatments are selectively performed on the identified portions of the heap. The remedial treatment can include hydraulically fracturing the identified portions of the heap followed by selective treatment with leach solution of the area impacted by the fracturing.

Abstract: A method for reclaiming a semiconductor material from a glass substrate is disclosed, the method comprises the steps of providing at least one glass substrate having the semiconductor material disposed thereon, reducing the glass substrate having a semiconductor material disposed thereon to a plurality of glass particles having the semiconductor material disposed thereon by introducing a source of energy thereto, separating the semiconductor material from the plurality of glass particles to obtain semiconductor particles, and pyrometall?rgicaHy refining the semiconductor particles and the fine glass particles.

Abstract: A mineral processing facility is provided that includes a cogen plant to provide electrical energy and waste heat to the facility and an electrochemical acid generation plant to generate, from a salt, a mineral acid for use in recovering valuable metals.

Abstract: The separation method for zinc sulfide, in the hydrometallurgical process by a High Pressure Acid Leach for nickel oxide ore comprising leaching and solid/liquid separation step, neutralization step, zinc removal step, and nickel recovery step, which can inhibit clogging of a filter cloth and reduce a frequency of washing operation and replacement operation of a filter cloth by improving filtration performance of zinc sulfide, and inhibit decrease of nickel recovery ratio, in the zinc removal step in which zinc sulfide is formed by adding a sulfurizing agent to the neutralization final liquid containing zinc as well as nickel and cobalt and zinc sulfide is separated to obtain a mother liquid for nickel recovery containing nickel and cobalt. The separation method for zinc sulfide of the present invention is characterized in that in the above-described neutralization step, the leach residue is added to the leach liquor, and pH of the neutralization final liquid is adjusted so as to fall to the range from 3.

Abstract: Method for producing hydrometallurgical zinc oxide powder having characteristics equivalent to that derived from a French process, comprising formation of an aqueous pulp from a starting zinc oxide having particles of nodular structure, wet milling of this aqueous pulp, separation in this milled pulp between a liquid phase and a solid phase containing the zinc oxide, and drying of said solid phase, coupled with a mechanical deagglomeration of the particles during drying, to obtain a dry zinc oxide powder with particles of nodular structure having a particle size distribution where the particles have an average size (d50) between 0.02 and 20 ?m.

Abstract: A process for separation of no-carrier-added thallium radionuclide from no-carrier-added lead and mercury comprising providing a solution of no-carrier-added thallium radionuclide and no-carrier-added lead and mercury to dialysis. By this method separation of 199Tl radionuclides has also been achieved in presence of macro quantity of inactive thallium, which is as high as 10 mM. The method is capable of being used in Medical industry, diagnosis of cardiac diseases by 201Tl or 199Tl and all other industries where trace amount of thallium separation is required from mercury and lead.

Abstract: A process for producing metal compounds directly from underground mineral deposits including the steps of forming a borehole at a site into a mineral deposit containing metal compounds, inserting a slurry-forming device having a nozzle into the borehole adapted to direct pressurized water through the nozzle into the mineral deposit, supplying pressured water through the nozzle into the mineral deposit forming a mineral slurry containing metal compounds, extracting the mineral slurry containing metal compounds through the borehole, leaching the mineral slurry to convert the metal compounds to a soluble form in a leach solution, and removing metals and metal compounds by treating the leach solution with an extraction treatment adapted to remove the metal products. Steps of leaching the mineral slurry and removing metal products are performed at a location remote from the borehole site. Alternatively, the step of removing metal products from mineral slurry may be accomplished by pyrometallurgical processes.

Abstract: The invention relates to a method, by means of which the valuable metals contained in a sulphidic, multicomponent concentrate are recovered using hydrometallurgical treatment. One constituent of the concentrate is copper sulphide, which is leached using an alkali chloride-copper (II) chloride solution. The sulphides of other valuable metals, such as zinc, nickel, cobalt and lead are leached before copper leaching and each is recovered as a separate product before copper recovery.

Abstract: A process for leaching a value metal from a base metal sulfide ore, comprising the step of leaching the ore with a lixiviant comprising a chloride, an oxidant and hydrochloric acid is disclosed. The leaching is controlled, by use of low concentrations of hydrochloric acid and a redox potential, to effect formation of hydrogen sulfide from the base metal sulfide ore. The hydrogen sulfide is stripped from the leach solution, thereby reducing the amount of sulfate generated in the leach to very low levels. The leaching may also be conducted to limit the co-dissolution of platinum group metals and gold with the base value metals. The leach forms a value metal-rich leachate and a solids residue. The solids residue may be subsequently leached to recover the platinum group metals and gold. The value metal-rich leachate can be is oxidized and neutralized to recover the value base metals. In an embodiment, the chloride is magnesium chloride and lixiviant solution is regenerated.

Abstract: The present invention relates to a method and system for recovery of waste.

Abstract: Method for producing hydrometallurgical zinc oxide powder having characteristics equivalent to that derived from a French process, comprising formation of an aqueous pulp from a starting zinc oxide having particles of nodular structure, wet milling of this aqueous pulp, separation in this milled pulp between a liquid phase and a solid phase containing the zinc oxide, and drying of said solid phase, coupled with a mechanical deagglomeration of the particles during drying, to obtain a dry zinc oxide powder with particles of nodular structure having a particle size distribution where the particles have an average size (d50) between 0.02 and 20 ?m.

Abstract: The invention relates to a method for reversing the dispersion formed in the mixing section of liquid-liquid extraction and kept condensed in the separation section and the separated solutions form the rear end of the separation section to flow back towards the feed end of the separation section. The invention also refers to the extraction equipment for implementing the reversed flow.

Abstract: The separation method for zinc sulfide, in the hydrometallurgical process by a High Pressure Acid Leach for nickel oxide ore comprising leaching and solid/liquid separation step, neutralization step, zinc removal step, and nickel recovery step, which can inhibit clogging of a filter cloth and reduce a frequency of washing operation and replacement operation of a filter cloth by improving filtration performance of zinc sulfide, and inhibit decrease of nickel recovery ratio, in the zinc removal step in which zinc sulfide is formed by adding a sulfurizing agent to the neutralization final liquid containing zinc as well as nickel and cobalt and zinc sulfide is separated to obtain a mother liquid for nickel recovery containing nickel and cobalt. The separation method for zinc sulfide of the present invention is characterized in that in the above-described neutralization step, the leach residue is added to the leach liquor, and pH of the neutralization final liquid is adjusted so as to fall to the range from 3.

Abstract: A process for reclaiming spent selenium filter mass containing an inert material. The spent mass is treated with a hydrogen peroxide solution for leaching out selenium content from unspent active substance present in the filter mass to form selenious acid. The filter mass is treated with aqua regia solution to dissolve mercury selenide present in the mass. The aqua regia solution is separated from the mass and isolated. Suitably, the filter mass, which now contains inert carrier material, is transferred with the isolated selenious acid, to production of new selenium filter mass. After partial neutralization of the aqua regia solution, mercury is precipitated out for disposal. Before this, elemental selenium can be separated from the aqua regia solution by adjusting the pH level and used advantageously for production of new filter mass. Thusly, reclaimed selenium content and inert carrier material can be advantageously used for production of new selenium filters.

Abstract: It is an object to provide a method for producing stable alkaline metal oxide sols having a uniform particle size distribution. The method comprises the steps of: heating a metal compound at a temperature of 60° C. to 110° C. in an aqueous medium that contains a carbonate of quaternary ammonium; and carrying out hydrothermal processing at a temperature of 110° C. to 250° C. The carbonate of quaternary ammonium is (NR4)2CO3 or NR4HCO3 in which R represents a hydrocarbon group, or a mixture thereof. The metal compound is one, or two or more metal compounds selected from a group of compounds based on a metal having a valence that is bivalent, trivalent, or tetravalent.

Abstract: A method for treating a polymetallic sulfide ore containing gold and/or silver, and further containing base metals selected from the group consisting of iron, aluminum, chromium, titanium, copper, zinc, lead, nickel, cobalt, mercury, tin, and mixtures thereof, is disclosed. The method comprises the steps of grinding the polymetallic sulfide ore to produce granules, oxidizing the granules to produce oxidized granules, and chloride leaching the granules using a brine solution including dissolved halogens, as well as chloride and bromide salts.

Abstract: In one aspect the present invention provides a method of recovering gold from each of at least two different refractory gold-bearing sulfidic mineral materials. A first mineral material is subjected to biooxidation pretreatment to release gold locked within sulfide minerals. The biooxidation produces an acidic biooxidation liquor effluent that contains significant dissolved iron in the ferric form. All or a portion of the biooxidation liquor effluent is used as an acidic treatment liquid to treat the second mineral material, which contains acid-consuming minerals. During the treatment, acid-consuming minerals react with the acidic solution, raising solution pH and resulting in reduced solubility and precipitation of dissolved iron and other metals. Also during the treating, sulfides in the second mineral material or oxidized, thereby releasing gold for subsequent recovery.

Abstract: A process for the recovery of zinc metal from a zinc mineral includes the steps of leaching the zinc mineral in a solution including a halide species formed from two or more different halides, to leach the zinc into the solution. The zinc-bearing solution is then electrolyzed to yield zinc metal and to generate the halide species. The electrolyzed solution including the halide species is then returned to the leaching step. A portion of the electrolyzed solution can be removed as a bleed stream from a cathode compartment of an electrolytic cell of the electrolysis process and processed to remove manganese as manganese dioxide precipitate by adding thereto limestone, and the halide species from an anode compartment of the electrolysis process. In this regard, the pH and Eh of the solution can regulated in a manner that favors the formation of the manganese dioxide precipitate over the formation of a precipitate of zinc.

Abstract: A process for the extraction of a base metal such as Ni, Co or Zn, from suiphide ore or concentrate containing copper and the base metal comprises the step of subjecting the ore or concentrate to pressure oxidation in the presence of oxygen and an acidic solution containing halide and sulphate ions to produce a product solution containing copper and the base metal. The product solution is subjected to a copper extraction process for recovering copper from the solution and the product solution containing the base metal after copper recovery is recirculated for recycled to the pressure oxidation to effect build-up of the base metal in the product solution. Preferably, a stream which is split from the product solution is treated for the recovery of the base metal.

Abstract: Methods and apparatus utilizing chlorine dioxide and hydrogen peroxide are useful to reduce emissions of NOx, SOx, and heavy metals, e.g., mercury, emissions from combustion flue gas streams.

Abstract: The present invention relates generally to a process for recovering copper and other metal values from metal-containing materials using controlled, super-fine grinding and medium temperature pressure leaching. Processes embodying aspects of the present invention may be beneficial for recovering a variety of metals such as copper, gold, silver, nickel, cobalt, molybdenum, rhenium, zinc, uranium, and platinum group metals, from metal-bearing materials, and find particular utility in connection with the extraction of copper from copper sulfide ores and concentrates.

Abstract: A process for the separation of cobalt and/or manganese from impurity elements selected from one or more of calcium and magnesium contained in a leach solution, the process comprising the step of subjecting the leach solution to solvent extraction using an organic solution of a carboxylic acid such as Versatic 10 and a hydroxyoxime such as LIX 63, optionally together with a stabilzer.

Abstract: A concentration process of zinc silicated minerals, particularly willemite and calamine concentration, by single operations, or conventional steps of ore treatment, some of which include the following: Preparation of stockpiles of different mineralogical and contents compositions, crushing, screening, storage, dense separation, washing, homogenization, magnetic separation, grinding, classification, rubbing, conditioning, flotation, thickening, filtering, calcination, storage and waste deposition.

Abstract: The invention relates to a method for the hydrolytic precipitation of iron as jarosite from a sulphate-containing solution in connection with zinc recovery from zinc calcine. The recovey contains neutral leach, ferrite leach, zinc electrolysis and iron precipitation stages. The ferrite included in the calcine is leached with return acid of the electrolysis after which the iron present in ferrous form is neutralized and routed to an iron precipitation stage, where the iron is oxidised to the trivalent form using an oxygen-containing gas. Also present in the precipitation stage arc Na, K or NH4 ions and jarosite nuclei.

Abstract: The invention relates to a process involving the following steps: a) performing leaching of the raw material with an acid aqueous solution to dissolve the zinc if said raw material is a solid; b) optionally performing solid-liquid separation; c) neutralizing the aqueous solution once the zinc-containing raw material is in liquid form; d) performing solid-liquid separation of the solution rich in zinc from the solids precipitated during the neutralization step; e) extracting the zinc using an acid organic solvent; f) purifying the organic solvent from the extraction step; g) re-extracting zinc from the organic solvent using an acid aqueous solution; h) recovering the zinc by electrolysis and/or crystallization and/or precipitation.

Abstract: Methodology for the extraction of metallic elements from solid and liquid metal-contaminated starting material such as mineral ores, recyclable wastes, contaminated soils, engraving solutions, metal finishing solutions, battery manufacturing solutions, toxic wastes such as dusts producing through steelmaking processes by effectuating preferably prolonged contacting of such starting material with liquor compositions to cause the underlying structure of the starting material to be broken down. The contaminated starting materials are more susceptible to metal separation because the released metallic element are readily solubilized in the contacting liquor. Compositions of the contacting liquor comprise caustic silicate solutions containing essentially saturating levels of silica.

Abstract: A method for the recovery of high purity zinc oxide products, and optionally iron-carbon feedstocks, from industrial waste streams containing zinc oxide and/or iron. The waste streams preliminary can be treated by adding carbon and an ammonium chloride solution, separating any undissolved components from the solution, displacing undesired metal ions from the solution using zinc metal, treating the solution to remove therefrom zinc compounds, and further treating the zinc compounds and the undissolved components, as necessary, resulting in the zinc products and the optional iron-carbon feedbacks. Once the zinc oxide has been recovered, the purification process is used to further purify the zinc oxide to obtain zinc oxide which is at least 99.8% pure and which has predeterminable purity and particle characteristics. Various zinc compounds may then be quickly, easily, and economically produced from this recovered zinc oxide.

Abstract: A hydrometallurgical process utilizing an atmospheric calcium chloride leach to selectively recover from various metal feed stocks (consisting of elemental metals, metal oxides, metal ferrite, metal hydroxide, metal carbonates, metal sulfate/sulfur compounds, and their hydrates, specifically including but not limited to EAF Dust KO61) zinc, lead, cadmium, silver, copper and other valuable metals to the exclusion of iron, magnesium, halogen salts and other unwanted elements. The process solves the problem of iron and magnesium leach solution contamination because iron is unexpectedly converted to magnetite. The heavy metals are cemented out of solution using zinc or other selected dust at a pH of 6 or greater under unique and unexpected conditions, which do not require acid.

Abstract: The present invention relates to an apparatus and a process for producing zinc oxide from an acid soluble zinc-bearing material. The process according to the present invention comprises the steps of leaching the zinc oxide material with sulphuric acid; precipitating iron and silica from the leach solution using calcium oxide; removing copper, cadmium and cobalt from the leach solution by cementation with zinc dust; precipitating zinc oxide from the leach solution using calcium oxide; and upgrading zinc content in zinc oxide precipitates by separating zinc oxide from gypsum using a flotation or granulometric sizing technique.

Abstract: A method for the recovery of high purity zinc oxide products, and optionally iron-carbon feedstocks, from industrial waste streams containing zinc oxide and/or iron. The waste streams preliminary can be treated by adding carbon and an ammonium chloride solution, separating any undissolved components from the solution, displacing undesired metal ions from the solution using zinc metal, treating the solution to remove therefrom zinc compounds, and further treating the zinc compounds and the undissolved components, as necessary, resulting in the zinc products and the optional iron-carbon feedbacks. Once the zinc oxide has been recovered, the purification process is used to further purify the zinc oxide to obtain zinc oxide which is at least 99.8% pure and which has predeterminable purity and particle characteristics. Various zinc compounds may then be quickly, easily, and economically produced from this recovered zinc oxide.