Abstract

In the leaching process for the residue in zinc hydrometallurgy, most of gallium is concentrated into the solution together with zinc and sulfuric acid. Such solution is then neutralized with calcium carbonate till pH 4.0, thus forming the precipitates of gallic hydroxide and gypsum. In order to recover and utilize gallium from the precipitates, selective flotation of gallic hydroxide from gypsum has been investigated.The floatability of gallic hydroxide was first examined using dodecylammonium acetate (DAA) and sodium dodecylsulfate (SDS) as a collector. Gallic hydroxide floated completely with SDS in the pH range of 4-7. On the contrary, it didn't float entirely with DAA in the same conditions. When the flotation was made in saturated solution of gypsum, both gallic hydroxide and gypsum floated to some extent with either of these collectors. As gypsum was quite floatable in these conditions, it was necessary to use some depressant for the selective flotation of gallic hydroxide from gypsum. Then, selective flotation was made for the mixture of gallic hydroxide and gypsum. It was shown that soluble starch and gum arabic were effective depressant for gallic hydroxide in DAA flotation.Synthetic metallurgical process with water containing 100mg/l of gallium ions, 3700mg/l of sulfate ions and 621mg/l of calcium ions was neutralized with calcium carbonate from its pH 1.5 till pH 4.0. Flotation tests were conducted for the precipitates thus formed. Gallic hydroxide was effectively separated from gypsum with DAA collector when soluble starch or gum arabic was added as a depressant, and some 91% of gallic hydroxide was recovered in the tailing. Also, gallium was up graded from 1.65% to 14.73%.

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