PROCESS FOR EXTRACTING AN ALUMINIUM SULPHATE FROM AN IMPURE SOLUTION CONTAINING SAID SULPHATE

摘要

High-purity well crystd. and readily filterable Al2(SO4)3 0.5H2SO411-12H2O can be obtained from impure Al2(SO4)3-contg. soln. obtained in the H2SO4 digestion of aluminous materials. The crystals, which form a compact filter cake, are pptd. by controlling the temp. and Al2O3 concn. in each vessel according to a phase diagram. The temp. in the lst vessel is kept at the supersatn. temp under agitation. In each successive vessel the temp. is reduced corresponding to the temperature required to maintain a supersatd. soln. of grdually decreasing Al2O3 concentration.