PREPARATION METHOD OF β-GYPSUM HEMIHYDRATE USING SLUDGE GENERATED IN REFINING STAINLESS STEEL AND WASTE SULFURIC ACID

摘要

PURPOSE: Provided is a preparation method of β-gypsum hemihydrate by using sludge generated by a refining process of stainless steel and waste sulfuric acid generated by a plating process. The method recycles waste resources and decreases environmental problems. CONSTITUTION: The preparation method of β-gypsum hemihydrate(CaSO4·1/2H2O) comprises the steps of: preparing Ca(OH)2 suspension by preprocessing sludge generated by refining processes of stainless steel through sieving, gravity separating, magnetic separating, filtering and drying; removing impurities such as iron ions from waste sulfuric acid; reacting Ca(OH)2 suspension with sulfuric acid in a molar ratio of 1:0.4 - 1:1.2 at 20-100deg.C; adding 1-20wt.% of NaCl; drying it at 50deg.C for 24hrs to stabilize gypsum hemihydrate.