Purification of zinc containing Waelz oxides from chlorine and fluorine
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2017-01-01
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Abstract
The Waelz oxides (WO) obtained upon processing of zinc containing semi products in Waelz kilns are rich in impurities such as alkalines, chlorides and fluorides. After acid leaching of the WO chlorine and fluorine ions dissolve into the zinc electrolyte, causing corrosion of aluminum cathode and lead anode and sticking of the deposited zinc on the cathode. For normal production operation the WO must contain up to 1000 ppm chlorine and 100 ppm fluorine. In the present study the laboratory tests on alkaline scrubbing of zinc containing WO in sodium carbonate solutions are presented. The effect of sodium carbonate concentration, pulp density and test duration on the degree of fluorine and chlorine purification is investigated. Based on the conducted research it was established that at temperature 363 K, pulp density 300 g l-1, concentration of sodium carbonate 100 g l-1 and test duration 180 min, the final concentration of fluorine and chlorine in the treated WO is 90 and 220 ppm, respectively. WO with such concentration of impurities are appropriate for further processing for cathode zinc production.