Abstract: A process is provided for the removal of fluoride from a metal sulphate solution, such as a zinc sulphate solution, which presents an option for the disposal of waste treatment sludge from the aluminum anodizing industry. The fluoride is removed from metal sulphate solution by mixing the sludge with the solution for a predetermined period of time and then performing a solid/liquid separation.

Abstract: A process is disclosed for the production of free-flowing, non-caking, stable granular ammonium sulphate containing micronutrients comprising granulating ammonium sulphate in the presence of a granulating aid which is stripped zinc electrolyte derived from an electrolytic zinc operation. An effective amount of stripped zinc electrolyte is used to yield a final ammonium sulphate product containing about 0.4% to 1.3% by weight zinc, up to about 0.16% by weight magnesium and up to about 0.09% by weight manganese. The stripped zinc electrolyte, typically containing 20-25 g/L zinc, 2-4 g/L magnesium, 1-2 g/L manganese and sulphuric acid, may be added during reaction of ammonia and sulphuric acid prior to granulation. A free-flowing, non-caking, hard, ammonium sulphate granular fertilizer having a pH of about 2 to 7.5 as 10% solution, containing by weight 0.4% to 1.3% by weight zinc, up to about 0.16% by weight magnesium and up to about 0.09% by weight manganese is produced.