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Recovery of Arsenic from Ores and Concentrates.
Flynn-CM Jr.; Carnahan-TG
U S Pat 4 888 207 1989 Dec; :
Arsenic, in the form of as2o3 is recovered from arsenical ores or concentrates by leaching with a hot acidic ferric salt solution to extract arsenic, followed by cooling the pregnant leach solution to crystallize as2o3. Leaching of some ores or concentrates is facilitated by addition of silver sulfate or mercuric sulfate to catalyze the leaching reaction. Thus, 20.0 G of cobaltite concentrate, containing 8.6 G as and 1.9 G fe was leached with a boiling solution composed of 80 g anhydrous fe2(so4)3 and 318 g of 30.8-Pct aqueous h2so4 for 6 h. During the leaching period the volume of the solution, originally about 280 ml, was allowed to decrease to about 220 ml, corresponding to a solvent concentration of about 37 pct h2so4, by evaporation of water. Water lost beyond that point was replaced. The slurries were filtered hot to separate leach residues and precipitated sulfate salts from the pregnant solution. The filter cake was washed with 10 to 20 ml of water, which was added to the filtrate. The filtrate was cooled to crystallize as2o3, which was then filtered off, washed with water, and air dried. The water washing removed soluble cocrystallized sulfate salts, except gypsum. The leach residue from hot filtration, after washing with dilute h2so4 to remove soluble salts, weighed 4.8 G and contained 0.4 G as2o3 and 0.1 G fe. The as2o3 product contained <0.1 pct fe and <0.01 pct cu or carbon monoxide
U.S. Pat. 4,888,207, Dec. 19, 1989
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