Cominco, Ltd.

Donald L Ball

Daniel A Boateng

Godefridus M Swinkels

Richard S Varley

This invention is directed to a novel method for purifying calomel (Hg.sub.2 Cl.sub.2). More particularly, this invention pertains to a novel process for treating impure calomel (Hg.sub.2 Cl.sub.2) to produce a highly purified calomel product that passes American Chemical Society requirements for calomel assay and mercuric chloride contamination. A process for treating impure calomel to produce purified calomel comprising: (a) incorporating impure calomel into an aqueous slurry; (b) oxidizing the aqueous slurry with an oxidizing agent to form soluble mercuric chloride; (c) filtering the aqueous slurry containing soluble mercuric chloride into liquid and solid components; (d) heating the liquid component to greater than 70.degree. C; (e) treating the liquid component with a reducing agent to precipitate purified calomel; and (f) separating the precipitated purified calomel from the filtrate.

Calomel (Hg.sub.2 Cl.sub.2) purification process

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. The process is carried out at ambient conditions, and the amount of liquid in the process is controlled. Substantially no mercury is discharged from the process in residues, or residual liquid.

Method for the recovery of mercury from mercury-containing material

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. Deposition of manganese and zinc on the electrodes is minimized by at least one of a number of means including arranging the membranes such that the end membranes are monovalent anion permselective; selecting a large electrode rinse flow; adding a small amount of soluble antimony and/or cobalt; and using a cathode made of a material that promotes hydrogen evolution over zinc deposition. The electrode compartments are preferably rinsed with a 0.1 to 1.0 M Na.sub.2 SO.sub.4 solution at pH 0 to 4.

Method for removal of monovalent ions from ZnSO.sub.4 electrolyte by

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. The chloride concentration in the electrode compartments is maintained at less than 3 g/L. In multi-step electrodialysis, a portion of the magnesium may be removed in an intermediate stage by the addition of lime, the lithium in the resulting solution being further concentrated by electrodialysis.

Method for the recovery of lithium from solutions by electrodialysis

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.

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Castlegar, Canada

Donald L Ball