Abstract: A process is provided for reducing the concentration of water soluble ionic selenium species in aqueous waste solutions containing the same. The process comprises passing said waste solution through a treatment zone containing a porous matrix on which are retained populations of at least one bacteria of the genus Clostridium. The passing of said aqueous solution through said treatment zone is carried out at predetermined rates of flow, and contact between said solution and said bacteria is conducted under anaerobic conditions and at predetermined pH and temperature levels. The process provides for the conversion of the water soluble ionic selenium species to water insoluble selenium metal, which metal is retained on the porous matrix and can be recovered therefrom.

Abstract: A process for reducing the concentration of selenium ions in the Se(VI) oxidation state in an aqueous solution. The aqueous solution is admixed with a quantity of metallic iron. The iron reduces the selenium ions from the Se(VI) oxidation state to a lower oxidation state and then dissolves in the aqueous solution. If the pH level of the aqueous solution is above about 2.3, the selenium ions are reduced to at least the Se(IV) oxidation state and the dissolved metallic iron hydrolyses to form an iron hydroxide that precipitates. The precipitated material is separated from the aqueous solution to provide a solution having a lower concentration of selenium ions. If the pH level of the aqueous solution is below about 2.3, no iron hydrolysis is observed to occur. At least a portion of the selenium in the Se(VI) oxidation state is believed to be reduced to the elemental state. The elemental selenium then is separated from the aqueous solution to provide a solution having a lower concentration of selenium ions.

Abstract: A process for removing, by absorption, sulfur dioxide from a gaseous mixture such as a flue gas by scrubbing said mixture with an aqueous scrubbing liquor to which a solution of an alkaline reagent such as sodium carbonate is added to maintain alkalinity of the scrubbing liquor. The solution also has dissolved in it a quantity of silica which tends to precipitate when solution is added to the scrubbing liquor. The silica precipitated in this manner tends to form extremely hard solid deposits in the scrubbing device and associated equipment. If a water soluble acid salt such as ferrous or ferric sulfate is added to the alkaline reagent solution prior to its use in the process, the precipitate formed has a minimum deleterious effect.

Abstract: The present process involves an improvement in the hydrometallurgical recovery of metal values from metal bearing sources such as ores and the like. When subjecting a metal bearing source to a reductive roast in a reducing atmosphere followed by cooling the reduced metal bearing source, extracting the cooled source and recovering the resultant nickel value, it is possible to utilize a smaller amount of an additive which assists in the recovery of metal values by scrubbing the off-gases from the reductive roast utilizing a fresh metal bearing source feed as the scrubbing material.

Abstract: Titanium metal values may be recovered from iron and titanium bearing sources such as an ilmenite ore by subjecting the source to a reductive roast after having crushed the source to a desired particle size. The reduced source is then leached by treatment with a halogen-containing compound to form soluble titanium halides and iron halides. Thereafter, the soluble titanium halide is precipitated as titanium dioxide by treatment with an iron oxide such as ferric oxide. The desired titanium dioxide or rutile may be recovered without an appreciable loss by effecting the leach step of the process in such a manner so that the solution potential is not greater than about +150 millivolts.

Abstract: Metal values may be recovered from metal bearing sources in a hydrometallurgical process in which a metal bearing source such as an ore and the like is reduced with a reductive roast only or with the presence of at least one additive at temperatures ranging from about 500.degree. to about 900.degree. C. Thereafter the reduced source is subjected to a leach in the presence of a basic leaching agent to extract the desired metals from the source. In the present invention, the basic leaching agent which is employed comprises an ammoniacal ammonium chloride solution.

Abstract: Metallic lead may be obtained from lead bearing sources such as lead sulfide ores or concentrates by halogenating the lead source, brine leaching the lead halide to separate the soluble lead halide from solid material such as gangue and recrystallizing the lead halide at a reduced temperature. Following this the lead halide is then converted to lead carbonate by treatment with carbon dioxide followed by solubilizing the lead carbonate in hydrofluosilicic acid and electrowinning the product to produce a purer lead sheet on the cathodes.

Abstract: The production of metallic lead from lead bearing sources may be facilitated by a process in which a lead bearing source such as lead sulfide ores or concentrates are halogenated and the halogenated source is then brine leached in the presence of a sodium chloride solution to separate the soluble lead halide from solid material such as gangue and elemental sulfur. The soluble lead halide is recrystallized at a reduced temperature and thereafter converted to lead carbonate by treatment with sodium carbonate. Metallic lead in the form of sheets is recovered by solubilizing the lead carbonate in hydrofluosilicic acid and electrowinning lead from the solution.

Abstract: Metallic lead may be obtained from lead bearing sources such as lead sulfide ores or concentrates by halogenating the lead source, brine leaching the lead halide to separate the soluble lead halide from solid material such as gangue and recrystallizing the lead halide at a reduced temperature. Following this the lead halide is then converted to lead carbonate by treating the lead chloride with sodium bicarbonate. Thereafter the lead compounds are solubilized in hydrofluosilicic acid and subjected to electrowinning to produce lead sheet on the cathode.

Abstract: Metallic lead is obtained from lead sulfide ores or concentrates by subjecting the concentrate to a drying step followed by halogenating the dried concentrate in a dry atmosphere at a temperature in the range of 90.degree. to about 120.degree. C. Thereafter the halogenated mixture is subjected to a water wash and leached with a brine solution. The brine solution is then filtered to separate elemental sulfur and residue from the solubilized lead halide, the latter being then crystallized and subjected to fused salt electrolysis to recover metallic lead.

Abstract: The production of metallic lead from lead bearing sources such as lead sulfide concentrates may be improved by subjecting the lead sulfide concentrates to a prehalogenation activation treatment at a temperature in the range of from about 300.degree. to about 600.degree. C. before subjecting said concentrate to the halogenation step which is effected at a temperature in the range of from about 80.degree. to about 120.degree. C. followed by leaching, filtering, crystallization and electrolysis.

Abstract: Chromium values may be recovered from the chromium bearing ores or sources by subjecting the chromium bearing source to a roast in the presence of sulfuric acid and an oxidant which contains manganese compounds at temperatures ranging from about 200.degree. to about 500.degree. C. followed by leaching, separation and solvent or ion exchange extraction whereby chromium is selectively extracted and recovered.

Abstract: Manganese values may be recovered from manganese bearing sources by subjecting said source to a roast in the presence of sulfuric acid and a reductant which comprises a chromium-containing compound at temperatures ranging from about 200.degree. to about 500.degree. C. followed by leaching, separation, solvent extraction or ion exchange whereby manganese is extracted, followed by separation and recovery of the manganese.

Abstract: Copper ore is leached by static leaching methods, and the effluent pregnant leach liquor is divided into portions forming a high-concentration pregnant leach liquor and a recycleable leach liquor.

Abstract: An improved process and apparatus for electrolyzing ions in a liquid electrolyte wherein the electrolyte is covered by an immiscible liquid of low conductivity and whereby the entrainment of said immiscible liquid in said electrolyte is prevented.

Abstract: Metallic lead may be obtained from lead sulfide feed stocks or concentrates by fluorinating the lead sulfide, dissolving the resultant lead fluoride in hydrofluosilicic acid, separating the solid residue from the liquid and subjecting the liquid to electrolysis.

Abstract: An improved process and apparatus for electrolysis of a high purity metal from an aqueous pregnant liquor acid electrolyte at high efficiency and high current density in the presence of impurities. In one embodiment the electrolysis cell employed in such process is provided with a fluid cover.