Abstract: The invention relates to a method for the hydrolytic precipitation of iron from a sulphate solution as jarosite. A sulphate-containing solution, with iron present in divalent form, is 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 are Na, K or NH4 ions and jarosite nuclei.

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 sulfurous compound such as a sulfur-rich “float” (concentrate) obtained by flotation of the residue from the leaching of a zinc concentrate is heated at a temperature not lower than the melting point of sulfur but below its boiling point, preferably not higher than 200° C., more preferably not higher than 140° C., and the evolving gas containing sulfur vapor is cooled at a temperature less than the melting point of sulfur, preferably at ordinary temperature, to condense sulfur.

Abstract: Liquor compositions for the extraction of metallic elements from a metal-contaminated starting material such as mineral ores, recyclable wastes, contaminated soils, toxic wastes such as dusts producing through steelmaking processes by effectuating preferably prolonged contacting of such starting material with the liquor 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. Once the plurality of metallic elements contained in the starting material have been solubilized, they tend to remain in solution, and then may be routinely extracted and removed using conventional extraction methodologies such as precipitation of insoluble salts, electrowinning, or electrodeposition.

Abstract: A method for producing small spherical particles that are especially useful as catalysts and catalyst supports employed in chemical processes is disclosed. According to some embodiments, the method includes impregnating a porous support with a metal or metal oxide and dissolving the support to release spherical particles. In certain embodiments the support that is employed in the method comprises a number of spherical voids which determine the size of the spherical particles, and preferably have micrometer range diameters. One embodiment of an attrition resistant Fischer-Tropsch catalyst comprises a plurality of micrometer size spherical metal and/or metal oxide particles that are prepared according to the above-described method.

Abstract: An industrial waste stream recycling method for recovery of high purity zinc oxide products and other chemical and metal values from industrial waste streams containing zinc compounds by leaching the waste stream with a solution of 30% or greater by weight ammonium chloride, resulting in a first product solution and undissolved materials; adding zinc metal to the first product solution, whereby zinc-displaceable metal ions contained in the first product solution are displaced by the zinc metal and precipitate out of the first product solution as metals, leaving a second product solution; and diluting the second product solution with water, resulting in the precipitation of zinc oxide.

Abstract: A method for the treatment of air pollution control (APC) residues comprising the steps of washing the residues at least one time in an alkaline solution maintained at a pH not lower than about 11.5, separating the alkaline washed residues from the alkaline solution. The present method further comprises an optional step of verifying whether the alkaline washed residues are substantially devoid of metal components. When the alkaline washed residues are not substantially devoid of metal components, the alkaline washed residues are washed at least one time in an acid solution maintained at a pH between about 2 and about 4.5 and the acid washed residues are separated from the acid solution so as to produce residues substantially devoid of metal components. The APC residues obtained in application of the methods according to the present invention constitute non-hazardous material/waste.

Abstract: A method for directly leaching a zinc concentrate in one of the stages contained in the hydrometallurgical process for the production of electrolytic zinc. The method comprises: a neutral leach step, a zinc concentrate leach step, and an iron oxidation step. In the zinc concentrate leach step, a neutral leach residue and an iron sediment returned from the iron oxidation step are repulped by the spent electrolyte followed by adding thereto zinc concentrate to extract zinc from the zinc concentrate by carrying out a leaching under atmospheric pressure and at a temperature of not lower than 90° C., but not higher than the boiling point of the solution. According to this method, the concentration of Fe(III) ions in the zinc concentrate leach solution is significantly increased. Due to this Fe(III) ion concentration, the leaching rate of the zinc concentrate is enhanced.

Abstract: A processs for the recovery of zinc from a zinc sulphide ore or concentrate comprises the steps of subjecting the concentrate to pressure leaching with an acidic solution containing at least about 15 g/L iron in solution to produce a zinc solution and a solid leach residue containing iron. The zinc solution is subjected to zinc solvent extraction to produce a raffinate and a pregnant zinc solution. A method of removing ion from an iron bearing raffinate is also provided which comprises pressure leaching a zinc sulphide ore with the iron bearing raffinate to produce a solid leach residue containing iron and a zinc solution.

Abstract: A method for reducing the formation of Zn(NH4)4Cl2 from ZnO/NH4Cl solutions formed during an industrial waste stream recycling method useful for the recovery of high purity zinc oxide products and other chemical and metal values from industrial waste streams.

Abstract: The present invention relates to an apparatus and a process for producing zinc oxide from a zinc-bearing material. The process according to the present invention comprises the steps of leaching the complex sulfide material with hydrochloric acid and oxygen; precipitating iron from the leach solution using magnesium oxide and oxygen; removing copper, silver, cadmium, cobalt and lead from the leach solution by cementation with zinc dust; precipitating zinc oxide from the leach solution using magnesium oxide; and spray roasting the remaining magnesium chloride leach solution to regenerate hydrochloric acid and magnesium oxide. The present invention further relates to processes for recovering copper, silver, lead, and iron from complex sulfide materials.

Abstract: Thiobacillus ferrooxidans and Thiobacillus thiooxidans play major roles in bacterial leaching of metals from ores and tailings through their oxidative action on ferrous iron (Fe2+) and sulfide or sulfur (S0). We have studied the effects of various inhibitors such as cyanide, azide and anions (phosphate, nitrate, chloride) on Fe2+ or S0 oxidation by resting cells, on Fe2+ or S0 as an energy source for growth and finally on leaching of Fe or Zn from a sample containing pyrite (FeS2) and sphalerite (ZnS). All of these inhibitors inhibited Fe2+ oxidation more strongly than S0 oxidation and generally stopped the growth on Fe2+ at lower concentrations than on S0. All three anions inhibited the leaching of Fe more strongly than Zn leaching, but potassium phosphate was the most selective. In the leaching experiments with T. ferrooxidans and T.

Abstract: The invention relates to a method for leaching zinc concentrate in atmospheric conditions in the presence of trivalent iron. It is essential that the zinc concentrate is fed into conditions where in addition to trivalent iron, there are also jarosite nuclei. The sulfuric acid content of the leaching step is maintained within the region 10-40 g/l, and the temperature within the region 80° C.—the solution boiling point, and into the leaching step there is fed oxygen, so that the zinc concentrate is dissolved and the iron is precipitated as jarosite.

Abstract: The process uses hydrochloric acid solutions to extract zinc from electric arc furnace dusts containing zinc oxide and zinc ferrite. To selectively leach zinc and minimize iron dissolution by precipitating as FeO.OH and Fe2O3, hot acid leaching with the aqueous solution containing 37 g/l-74 g/l HCl and 104 g/l-270 g/l ZnCl2 is used. New dust is introduced to remove iron from the filtrate of the hot acid leaching. The zinc chloride solutions purified by activated carbon and metallic zinc powder is electrolysed in electrowinning cells which had cation exchange membrane to produce high purity zinc metal and to regenerate hydrochloric acid. Electrolysing an aqueous solution of zinc chloride with Zn concentration of 50-130 g/litre below 40° C. in a cell divided by cation exchange membrane, whereby coherent zinc is yielded at the cathode with high current efficiency of exceeding 90%. HCl is directly regenerated with a very small loss below 2% and low energy consumption below 5.

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

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

Abstract: An industrial waste stream recycling method for recovery of high purity zinc oxide products and other chemical and metal values from industrial waste streams containing zinc compounds by leaching the waste stream with a solution of 30% or greater by weight ammonium chloride, resulting in a first product solution and undissolved materials; adding zinc metal to the first product solution, whereby zinc-displaceable metal ions contained in the first product solution are displaced by the zinc metal and precipitate out of the first product solution as metals, leaving a second product solution; and diluting the second product solution with water, resulting in the precipitation of zinc oxide.

Abstract: The process of the present invention is directed to the use of sulfuric acid and/or an organic acid to regenerate spent sorbent from a metal recovery process. The sorbent can be activated carbon.

Abstract: A method is disclosed for recovering a metal from a metal containing material by autoclaving with an autoclave which includes an agitator that includes a first inlet for a recycled oxygen-containing gas, a second inlet for a fresh oxygen-containing gas, an impeller having a plurality of outlets to recirculate or introduce the oxygen-containing gases into the slurry and a set of mixing blades located below the outlets to radially disperse gas bubbles substantially uniformly throughout the slurry. The outlets for the gas can be located in an intermediate set of blades for thorough dispersion of the gas bubbles in the slurry.

Abstract: A process for the extraction of metal from an ore or concentrate which contains nickel and/or cobalt values and other metals, comprises subjecting the ore or concentrate to acid leaching under pressure at pH≦2 to obtain a liquor containing nickel and/or cobalt values, subjecting the liquor to a first precipitation stage at pH of about 5 to 6 to produce a solid containing non nickel and non cobalt metals and a resultant solution containing the nickel and/or cobalt values and subjecting the resultant solution to a second precipitation stage at a pH of about 7 to 8 to produce a solid containing nickel and/or cobalt.

Abstract: A process for recovery of zinc from sphalerite containing ores or concentrates, whereby, in a first step, these ores or concentrates are submitted to a thermal treatment consisting essentially of a heating cycle performed under non-oxidizing conditions above 900.degree. C. thereby at least partly transforming the sphalerite to wurtzite, and subsequently the wurtzite is quenched in such conditions as to retain at least partly the wurtzite after quenching. In a second step zinc is leached out of the converted ore or concentrate, and in a third step zinc is recovered from the leaching solution by electrolysis.

Abstract: The invention relates to a process for recovering the transition metal component of catalysts used in the hydroconversion of heavy hydrocarbonaceous materials. In accordance with the invention, a slurry of a transition metal catalyst and hydrocarbon is catalytically desulfurized resulting in a desulfurized product and a solid residue containing the transition metal. The transition metal may be recovered by coking the residue and then dividing the coker residue into two portions are combusted with the flue dust from the first combustion zone being conducted to the second combustion zone. The flue dust from the second combustion zone is treated with ammonia and ammonium carbonate in order to obtain ammonium molybdate.

Abstract: A method for reclaiming a metallic material from a article including a non-metallic friable substrate. The method comprising crushing the article into a plurality of pieces. An acidic solution capable of dissolving the metallic material is provided dissolving the metallic material in the acidic material to form an etchant effluent. The etchant effluent is separated from the friable substrate. A precipitation agent, capable of precipitating the metallic material, is added to the etchant effluent to precipitate out the metallic material from the etchant effluent. The metallic material is then recovered.

Abstract: A device is provided for removing and concentrating neutral mercury species from air and water. The device includes a nonporous polymeric membrane, preferably in the form of a flattened tube, for capturing and removing the neutral mercury species from the environment and a sequestration medium contained within the tube for transforming the neutral mercury species captured by the tube into a stabilized mercury species. The sequestration medium can comprise an acidic oxidant for transforming the neutral mercury species into a ionic soluble mercury species or a complexing agent for transforming the mercury species into a complexed soluble mercury species. The nonporous membrane can be made of a number of different synthetic polymers including polyethylene. The device is ideally suited for the passive integrative sequestration of neutral mercury species from a wide variety of environments.

Abstract: The present invention relates to a process for cleaning mercury-contaminated soils that is simple, efficient and safe to use. This process can also be used to clean soils contaminated with additional metals, such as zinc, copper and lead, at a lower pH. The invention involves treating contaminated soils with solid hypochlorite in a continuous counter-current process.

Abstract: A process for preparing compounds of the formulae I and II ##STR1## where R.sup.1 and R have the meanings indicated in the specification by an addition reaction of a compound of the formula IIIR.sup.1 OH IIIwith an acetylene or allene of the formula IV or V ##STR2## in the gas phase at elevated temperatures in the presence of a heterogeneous catalyst. The catalyst is obtained by impregnating silica with a zinc salt, by a process in which the reaction is carried out at below 200.degree. C. and the catalyst contains, as an active component, an X-ray amorphous zinc silicate or cadmium silicate containing from 1 to 40% by weight, calculated as oxide, of zinc or cadmium, obtainable by applying a salt of zinc or cadmium and an inorganic oxo acid, which salt is decomposable at below 400.degree. C., to amorphous silica and forming the catalyst before the reaction at from 50 to 500.degree. C. or during the reaction in situ at from 50 to 200.degree. C.

Abstract: A method for producing zinc bromide from zinc hydroxide contaminated with iron and manganese compounds. The method comprises the step of mixing zinc hydroxide feedstock containing metal impurities with a hydrobromic acid comprising elemental bromine in the presence of a reducing agent to produce an impure zinc bromide solution. The metal impurities are removed from the zinc bromide solution in a two-stage process: the first stage comprises the steps of precipitating iron by maintaining the pH within a range of from about 3.6 to 4.15 and filtering out the insoluble iron compounds. The second stage comprises the steps of acidifying the zinc hydroxide solution and adjusting the pH to a range of 3.8 to 4.3 with a alkalinity source from metal oxide, hydroxide or carbonate to precipitate the manganese compounds. The resulting mixture is filtered and concentrated to form a solution comprising zinc bromide essentially free of iron and manganese compounds.

Abstract: The invention relates to a process for recovering metals from used nickel/hydride storage batteries, in which storage battery scrap has been mechanically comminuted and divided into at least a coarse fraction and a fine fraction capable of being treated separately from one another. The process comprises the steps of digesting and dissolving the fine fraction with a mixture of sulfuric acid and hydrogen peroxide, performing a double sulfate precipitation of the rare earths by raising the pH, performing a precipitation of the iron and of the aluminum by further raising the pH, performing a solvent extraction of other metals to separate nickel and cobalt which remain in the aqueous phase from the other metals which are extracted into the organic phase. Optionally, the nickel and the cobalt can be separated from each other and, if desired, the mixed-metal rare earth component which has been recovered can be melted together with cobalt and nickel alloy for the fabrication of new batteries.

Abstract: A method of selectively leaching zinc from a source material containing zinc in sulphide form and iron, comprises the steps of subjecting the source material to bioleaching with a strict sulphur oxidizing micro organism or a mixed culture of sulphur oxidizing and iron oxidizing micro organisms, in the presence of a nutrient solution containing less than about 15 mg/L phosphate ions. In another embodiment, the source material is in the form of a slurry having a solids concentration of at least about 25% on a weight per volume basis and a nutrient solution containing from about 1 mg/L to less than about 100 mg/L ammonium ions, from about 0.5 mg/L to less than about 40 mg/L magnesium ions and from about 2 mg/L to less than about 60 mg/L phosphate ions.

Abstract: A method for removing a heavy metal from sludge, including the step of putting the sludge into contact with a treating liquid to dissolve the heavy metal contained in the sludge into the treating liquid. The treating liquid is formed of either A or B, where (A) is an aqueous solution of phosphoric acid, and (B) is an aqueous solution of phosphoric acid containing at least one of B1 and B2, where (B1) is at least one acid other than phosphoric acid, and (B2) is at least one oxidant. The concentration of the phosphoric acid in the treating liquid is 3% by weight or more. Alternatively, the sludge is put into contact with the treating liquid at a temperature of 40.degree. C. or higher.

Abstract: A method for preparing inorganic pigments from steel mill dust, particularly electric steel mill dust, wherein (a) the dust is separated into a magnetic fraction and a non-magnetic fraction; (b) the non-magnetic fraction is subjected to a basic leaching reaction; (c) the resulting solid batch is rinsed until neutralized and then separated; (d) the resulting batch is calcined at 450-650.degree. C.; (e) the calcined batch is treated with sulfuric acid in the presence of a catalyst; (f) the inorganic pigments are recovered; and (g) the solutions from (c) and (e) are used to precipitate other pigments.

Abstract: The present invention relates to a process for cleaning mercury-contaminated soils that is simple, efficient and safe to use. This process can also be used to clean soils contaminated with additional metals, such as zinc, copper and lead, at a lower pH. The present invention involves screening the contaminated soil to remove unwanted materials, leaching the contaminated soils with hypochlorite in a screw reactor, thickening, leaching with hypochlorite and sodium chloride, thickening again and then separating the mercury-containing liquids from the clean soil. This invention also relates to a process which uses sulfide to treat the mercury-containing liquids.

Abstract: A method for utilization of zinc byproducts in the manufacture of clear brine fluids comprising the step of mixing zinc feedstock containing metal impurities with a halogenic acid to produce an impure zinc halide solution. The metal impurities are removed from the zinc halide solution in a two-stage process: the first stage comprises the steps of precipitating and filtering out manganese and iron and the second stage comprises the steps of contacting the zinc halide solution with elemental zinc to cement out the remaining metals comprising nickel, lead, cadmium, copper, mercury and cobalt. Preferably, the zinc halide solution is contacted with zinc shot in multiple passes through zinc-filled column systems. The pH is adjusted between each step, if necessary, to maintain the pH in the first stage within a range of from about 3.5 to 4.5 and the alkalinity during the second stage at less than 1.0% zinc oxide.

Abstract: The present invention relates to methods for digesting diphosphonic acid substituted cation exchange resins that have become loaded with actinides, rare earth metals, or heavy metals, in a way that allows for downstream chromatographic analysis of the adsorbed species without damage to or inadequate elution from the downstream chromatographic resins. The methods of the present invention involve contacting the loaded diphosphonic acid resin with concentrated oxidizing acid in a closed vessel, and irradiating this mixture with microwave radiation. This efficiently increases the temperature of the mixture to a level suitable for digestion of the resin without the use of dehydrating acids that can damage downstream analytical resins. In order to ensure more complete digestion, the irradiated mixture can be mixed with hydrogen peroxide or other oxidant, and reirradiated with microwave radiation.

Abstract: The beneficiation of an electric arc furnace (EAF) dust waste stream comprising zinc compounds by collecting and combining dust from two or more EAF batches with coal fines to form briquettes, adding the briquettes to a final EAF batch with the charge, and collecting the dust from the final EAF batch, so that the zinc in the beneficiated dust is of a greater proportion than in a typical batch of EAF dust. Alternatively, the EAF dust can be split into two dust streams, one of which is returned to the EAF, while the other is treated in a hydrometallurgical process. Either waste stream 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 resulting in zinc products and an optional iron-carbon feedback.

Abstract: Process for removing mercury from a gas contaminated with mercury vapor, comprising the steps of cooling the contaminated gas, removing water vapor from the cooled gas and filtering the dehydrated gas through a medium comprised of pure elemental sulfur. The mercury bound to the medium may be removed by heating liquid carbon disulfide to form a carbon disulfide vapor, cooling the carbon disulfide vapor so that liquid carbon disulfide is formed, spraying the liquid carbon disulfide over the medium containing the bound mercury, so as to remove the mercury from the medium and allowing elemental sulfur to dissolve into the liquid carbon disulfide and allowing said elemental mercury to separate away from the elemental sulfur/carbon disulfide solution.

Abstract: A treatment of metallurgical dust and recovery of valuable chemical commodities, comprising the steps of: leaching salts from the dust with water to create a washed EAF dust; reacting the washed EAF dust in a nitric acid solution resulting in a nearly complete dissolution of the zinc, cadmium, copper, magnesium, calcium, manganese and lead from a filtrate; removing iron from the filtrate by raising pH in the system with basic zinc carbonate; removing cadmium, copper and lead in an electrolytic cell, where copper and cadmium are collected at the cathode, and lead is collected at the anode; evaporating and decomposing the filtrate to obtain metal oxides and anhydrous calcium nitrate; leaching the solid residue with water to separate calcium nitrate in a marketable form; removing the zinc from the magnesium and manganese by leaching the residue with an amine solution; stripping the filtrate of ammonium carbonate to yield zinc precipitated as a zinc oxycarbonate; dividing the zinc oxycarbonate into a first stream

Abstract: A process for the recovery of mercury from mercury-containing caustic sludge, generated from a mercury cell, chlor-alkali plant, wherein mercury is removed from the caustic sludge by treatment in a hydraulic mineral separator. The process provides a ready method for removal of mercury from caustic sludge which can allow recovery of the mercury for re-use. Alternatively, the process provides a smaller volume of mercury-contaminated material to be treated and/or land-filled.

Abstract: A process for the extraction of precious metals from a copper sulphide ore or concentrate, by treating a leach residue of the ore or concentrate, includes the steps of removing elemental sulphur from the leach residue to obtain a low sulphur residue and subjecting the low sulphur residue to an oxidative leach at elevated temperature and pressure to oxidize sulphur and precious metal compounds present in the low sulphur residue to produce a residue for the extraction of the precious metals therefrom.

Abstract: Ores containing copper, zinc, silver in the form of sulfides are treated by a solution of sulfurated sulfite ions and ammonium ions in order to remove most of the metals from the sulfide ores. This treatment renders the resulting gold bearing ores much more amenable to cyanide extraction. Dissolved metals are reclaimed by appropriate techniques, such as electrowinning or liquid-liquid extraction, and the solution of sulfurated sulfites and ammonia is recycled for further lixiviation of fresh ores.

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

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

Abstract: A portion of the concentrates is roasted and a portion of the resulting calcine is subjected to a neutral leaching step. Another portion of the concentrates is directly leached in an acidic medium in the presence of oxygen and under atmospheric conditions together with at least a portion of the neutral leaching residue. The zinc- and iron-rich solution resulting from acid leaching is neutralised with another portion of the calcine, the iron is removed and the solution is reused in the neutral leaching step. The method enables a gradual increase in the capacity of an existing zinc plant in accordance with demand, while capital costs may advantageously be spread out over time.

Abstract: An improved method for the recovery of metal and/or chemical values from an industrial waste stream containing zinc, cadmium, lead and/or iron compounds by heating the waste stream in a reducing atmosphere, treating the resultant fumes in an ammonium chloride solution, separating any undissolved components from the solution, adjusting the pH of the solution, if necessary, to less than about 6.3, displacing undesired metal ions from the solution using zinc metal, treating the solution to remove therefrom zinc compounds, adjusting the pH of the solution to about 6.5 to about 7.0, and further treating the zinc compounds and the undissolved components, as necessary, resulting in the zinc products and the optional iron-carbon feedstock.

Abstract: A method for producing direct reduced iron or/and pig iron from an industrial waste materials stream such as EAF and blast furnace dust generally comprising the steps of separating the materials contained in the waste materials stream by magnetic separation or flotation, briquetting the iron-containing materials separated during the separation process with carbon, and providing the briquettes to a reduction furnace or/and to a small scale blast furnace or cupola furnace to produce direct reduced iron or/and pig iron, respectively. The exhaust streams from the process are further treated to recover chemical values and to allow the recycle of the exhaust streams to the main process.

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: There is provided a novel class of additives, specifically coals, which are useful in zinc extraction processes involving one or more pressure leach stages carried out at temperatures above the melting point of sulphur. Such processes may include those incorporating a single stage pressure leach, a process involving two stage countercurrent or cocurrent pressure leaches or a multistage leach process for recovering zinc, lead and silver from zinc bearing sulphidic materials which also contain lead and silver.

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 preliminarily 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 hsa predeterminable purity and particle characteristics.

Abstract: Heavy metals are efficiently removed from contaminated soil by a process which comprises leaching or washing the soil with a mild leachant solution. The leachant solution is comprised of an aqueous solution of an acid and a salt. The anion of the acid forms a water-soluble salt with the heavy metals which contaminate the soil. The salt component is comprised of at least one alkali metal, alkaline earth metal, or an ammonium salt having one or more anions which also form a water-soluble salt with the heavy metals leached from the contaminated soil.

Abstract: There is provided a novel class of additives, specifically coals, which are useful in zinc extraction processes involving one or more pressure leach stages carried out at temperatures above the melting point of sulphur. Such processes may include those incorporating a single stage pressure leach, a process involving two stage countercurrent or cocurrent pressure leaches or a multistage leach process for recovering zinc, lead and silver from zinc bearing sulphidic materials which also contain lead and silver.