Abstract: A process is provided for the removal of fluoride from a metal sulphate solution, such as a zinc sulphate solution, which presents an option for the disposal of waste treatment sludge from the aluminum anodizing industry. The fluoride is removed from metal sulphate solution by mixing the sludge with the solution for a predetermined period of time and then performing a solid/liquid separation.

Abstract: Cyanide-containing solution is subjected to two-stage membrane electrolysis in units each comprising a cathode, an anode and one or more bipolar electrodes interspaced with cationic membranes defining alternating anode and cathode compartments containing anolyte and catholyte, respectively. Electrolysis causes generation of hydrogen cyanide in the recirculating first stage anolyte, and alkali metal hydroxide is formed in the recirculating first-stage catholyte. The hydrogen cyanide is stripped from the first stage anolyte and is subsequently absorbed in catholyte in an absorption unit for the recovery of alkali metal cyanide-containing solution.

Abstract: Zinc is selectively extracted from zinc sulfate solutions that may also contain sulfuric acid and amounts of other metals with an organic extractant mixture containing both organic substituted phosphoric acid and organic substituted thiophosphinic acid. The phosphoric acids are preferably chosen from mono- and di-2-ethylhexylphosphoric acids and mixtures thereof, and the phosphinic acids are preferably chosen from bis- 2, 4, 4-trimethylpentyl mono- and dithiophosphinic acids. The use of an extractant mixture of the dithiophosphinic acid with mono- and di-2-ethylhexyl phosphoric acids or an extractant mixture of the dithiophosphinic acid with di-2-ethylhexylphosphoric acid is preferred. The pH during zinc extraction is controlled at a value in the range of about 1.3 to 5. Control of pH is carried out either by neutralization or by acid extraction with an organic amine-type extractant. The acid content of the feed solution may be reduced by neutralization or acid removal by dialysis.

Abstract: Electrodialysis is used to separate at least one species of a first group of elements present in ionized form from at least one species of a second group of elements present in nonionized form in water-containing solutions, provided that the pH of the solutions and the oxidation state of species of the second group have the appropriate values. If necessary, either the pH, the oxidation state or both are adjusted in the solution fed to the electrodialysis unit such that species of the first group are present in ionized form and species of the second group are present in a nonionized form. The method is applicable to a large number of solutions from metallurgical and chemical processes. Species of the first group include at least one element of groups IA, except Fr, IB, IIA, IIB, IIIA except B, IIIB, IVB, VIIB and VIII except Os of the periodic table; the elements V, Cr, Sn, Pb and Bi; and acids of N, S, F, Cl, Br and I.

Abstract: There is provided a method for treating zinc-containing sulfate solutions which comprises an acid removal for the recovery of a substantially pure sulfuric acid solution and a solution low in acid and containing the zinc and metal impurities from the sulfate solution. The acid removal is carried out by a membrane process that consists of dialysis, electrodialysis or dialysis integrated with electrodialysis. The dialyzate or diluate is subjected to a dual-circuit, side-by-side, simultaneous solvent extraction of zinc and sulfuric acid. In one circuit sulfuric acid is extracted from the dialyzate or diluate and the raffinate from the zinc extraction with an amine-containing extractant. Acid is stripped from the loaded organic with water or an alkaline substance, and is recovered as sulfuric acid or as a sulfate, preferably as ammonium sulfate.

Abstract: Insoluble mercury salts and any mercury in mercury-containing material are converted into a soluble form by controlled chlorination. The soluble forms of mercury in the chlorination solution are reduced with iron, preferably iron powder, to elemental mercury. After separation from the reduced solution, the solids from the reduction containing entrained mercury, are subjected to a separation for the separation and substantially quantitative recovery of substantially pure mercury. Separation by elutriation through a body of mercury is preferred. Prior to separation, the reduction solids may be kneaded for coalescence of fine mercury particles, followed by slurrying of the kneaded material. Any selenium in the reduced solution may be recovered in a reduction with a suitable reductant, preferably by adding strong sulfuric acid in the presence of the ferrous chloride formed in the preceding reduction, and excess sulfur dioxide.

Abstract: An arsenate solution is treated by electrolysis with membranes for at least partial conversion into arsenic acid and hydroxide. Electrolysis is carried out in an electrolytic unit containing an arrangement of electrodes and membranes. Depending on the electrode and membrane type and configuration, arsenic acid having a reduced content of alkali metal or ammonium cations and impurities is recovered. Arsenic acid-containing solution and hydroxide solution are removed. An electrolysis unit comprises, preferably, a stack of 2- or 3-compartment cells, comprising at least one electrode/membrane group arranged between terminal electrodes with or without terminal membranes. Each group may comprise a bipolar or a monopolar electrode in combination with either cationic or cationic and anionic membranes. Hydroxide and acid compartments are defined between electrodes and membranes, and diluate compartments may be defined between membranes.

Abstract: In a process for the manufacture of copper arsenate, an arsenic-containing material is subjected to an oxidative pressure leach with sodium hydroxide forming a leach solution containing sodium arsenate. Sodium arsenate solution is mixed with a solution of copper sulfate for the formation of a copper and arsenic-containing solution without the precipitation of copper arsenate. The copper and arsenic-containing solution is treated for the precipitation of copper arsenate with formation of sodium sulfate solution. At least one of the sodium arsenate-containing solution and the sodium sulfate solution is subjected to electrolysis with membrances for at least partial conversion to arsenic acid and sulfuric acid, respectively, and sodium hydroxide.

Abstract: An improved method for selectively rcovering Ge from acidic solution containing Ge and typically Zn, As, Cd, Sb, In, Cu and Fe (II) by multistage, countercurrent liquid-liquid extraction is described. The extractant used in the organic phase is an oxime, for example, 5,8-diethyl-7-hydroxy-6-dodecanone oxime, mixed with at least one alkylphosphoric acid, for example either di-2-ethylhexyl phosphate alone or admixed with mono-2-ethylhexyl phosphate, dissolved in a hydrocarbon diluent. This mixed system shows better efficiency and selectivity for germanium than known systems using either oximes or alkylphosphoric acids separately.

Abstract: Monovalent ions, especially chloride and fluoride, but also thallium, sodium and potassium are efficiently removed from ZnSO.sub.4 electrolyte by electrodialysis. Monovalent anions are removed using alternating monovalent anion permselective membranes and cation exchange membranes. Monovalent anions and cations are removed using alternating monovalent anion and monovalent cation permselective membranes. Electrodialysis is carried out under turbulent conditions, at up to 60.degree. C., a differential membrane pressure of less than 150 kPa, a current density of 10 to 500 A/m.sup.2, and a pH of less than 5.5. Where both chloride and fluoride are removed a pH of 3.5 to 5.5 is maintained.

Abstract: Lithium-containing brines containing mono and multivalent cations, especially magnesium, and anions are treated by electrodialysis to effect separation of a lithium concentrate low in multivalent cations from which lithium can be recovered as chloride, sulfate, or carbonate. Brine containing 0.03 to 15 g/L Li and a ratio of Mg:Li as high as 60:1 is subjected to one or more electrodialysis steps. The preferred cationic and anionic membranes are those that are strongly acidic and have sulphonic acid radical and trimethylamine derivatives, respectively, as active groups at 3 to 4 milligram equivalent per gram of dry resin and have a matrix of styrene divinyl benzene copolymer on a pvc base. Electrodialysis is carried out at a pH below 7 under turbulent conditions. The number of electrodialysis steps depends on the permselectivity of the membranes, the Mg:Li ratio in the feed and that in the concentrate, the latter being maintained at 5:1 or less.

Abstract: Germanium is recovered from aqueous solutions containing germanium, zinc, and antimony by sorption with an ion exchange resin which has as its matrix a backbone polymer to which are attached amine active groups chosen from secondary and tertiary amines and quaternary ammonium groups. The resin exhibits a high selectivity ratio of germanium relative to antimony. The method is particularly useful for the recovery of germanium from materials or electrolytes encountered in the recovery of zinc from ores and complex concentrates.