Arsenical concentrates, cobalt extraction

The extraction of cobalt from arsenical concentrates consisting of autooxidation acid leaching under pressure, separation, purification, hydrogen reduction of ammoniacal leach solution, and removal of sulfur and granulation of the metal was described by Mitchell (M37). The final product contained 95.6% cobalt, 3.90% nickel, and 0.03% arsenic compared to the feed concentrate with an assay of 17.5% cobalt, 1% nickel, and 24% arsenic. 

Concentrated hydrochloric acid also dissolves the trichloride, about 100 g. of the latter dissolving in 1 litre of acid at 100° C.7 Dissolution in hydriodic acid is accompanied by evolution of heat and the triiodide is formed.8 Ethyl iodide reacts similarly.9 Double decomposition reactions occur w hen arsenic trichloride is heated with phosphorus triiodide, stannic iodide or germanium iodide, the reactions being complete.10 Similarly, potassium iodide heated with arsenic trichloride in a sealed tube at 210° C., and potassium bromide at 180° to 200° C., form respectively arsenic triiodide and tribromide.11 Stannous chloride, added to the solution in hydrochloric acid, causes reduction to arsenic (see p. 29). Arsenic trichloride may be completely separated from germanium chloride by extraction with concentrated hydrochloric acid.12 Ammonium, sodium and cobaltic chlorides react with arsenic trichloride to form additive compounds with magnesium, zinc and chromic chlorides there is no reaction.13... 

The properties of anion-exchange resins of several types have been described in detail by Kraus and Nelson 351-356) and others (557, 358). Selenium(IV), tellurium(IV), and arsenic(III) and (V) can be extracted from a variety of media 359-361). Thallium(III) and antimony(V) can be separated using the iodide and chloride forms of Dowex-1 (5(52, 363). Beryllium(II) was efficiently extracted by the carbonate form 364, 365) and chromium(III) and lead(II) by the phosphate form of AV-17 resin 366). Zinc(II) can be removed from a solution containing several metals (5(57, 368) and silver in concentrations at the 0.04-ppb level can be extracted from seawater (5(59). Cobalt(II), zinc(II), antimony(III), silver(I), and iron(III) ions have also been extracted from spiked seawater samples by anion exchange even though the actual form of the ions in the aged solution was uncertain (570). Anion resins have been modified with Trilon B (577) and with a-hydroxyisobutyronitrile (572) to increase the extraction of several trace-metal pollutants. Amberlite IRA 400 treated with the sulfonic acid derivative of dithizone can be used to concentrate heavy metals (575). 

Arsenic-containing concentrates (from cobaltite ores) are roasted in a fluidized bed at 700°C to remove most of the arsenic as As Oj. After leaching with hydrochloric or sulfuric acid the purified leach solution can be used for electro-extraction of cobalt or for precipitation of cobalt as carbonate. 

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