Synthesis of aluminum ammonium sulfate from waste aluminum processing solution by crystallization

Experimental tests were conducted in the present study to investigate synthesis of aluminum ammonium sulfate (aluminum alum) by crystallization from the waste acid solution of aluminum surface finishing industry. Effects of various operating conditions including the molar ratio of ammonia and aluminum ion, temperature, mixer speed, seed alum dosage, initial sulfuric acid and aluminum ion concentrations on the aluminum alum formation, crystal size distribution, acid remaining and aluminum ion removal were examined. The crystallization process was found to be quite effective in recovering resource materials (sulfuric acid and aluminum) in the form of aluminum alum from the waste acid solution. Based on the test results, optimum operating conditions were recommended for efficient operation of the crystallization process. (C) 1998 Elsevier Science B.V. All rights reserved.