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US 5,470,444 AGranted
Process for preparing low iron ammonium alum
AssigneeMetallgesellschaft Aktiengesellschaft
InventorsIngo F. Litzenberger, Gunter Roller, Dieter Stein
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Abstract
An aqueous ammonium alum solution which contains Fe.sup.3+ ions and has a pH not in excess of 5 is passed through at least one half of the Fe.sup.3+ ions in the solution to Fe.sup.2+ ions. The solution is cooled and ammonium alum is crystallized whereas the Fe.sup.2+ ions remain in the liquid phase.
Claims7
A process for preparing ammonium alum with reduced iron content from an aqueous ammonium alum solution which contains Fe.sup.3+ ions, which comprises the steps of:
- (a) passing the aqueous ammonium alum solution containing Fe.sup.3+ and having a pH not in excess of 5 through at least one electrolytic cell containing an anode and a cathode, and an external power source to generate a current and conducting the current through the electrolytic cell to electrolytically reduce at least half of the Fe.sup.3+ ions to Fe.sup.2+ ions;
- (b) subjecting the aqueous ammonium alum solution electrolytically reduced during step (a) to cooling and crystallization to form a liquid phase suspension containing crystalline ammonium alum and containing Fe.sup.2+ ions in the liquid phase;
- and
- (c) separating the liquid phase from the crystallized ammonium alum.
1 more element
Dependencies are inferred from the claim text.