PRODUCTION OF GYPSUM FROM SULFURIC ACID WASTE LIQUID

摘要

PROBLEM TO BE SOLVED: To produce a gypsum having constantly stable water content from a high fluorine containing-sulfuric acid waste liquid. SOLUTION: In a method for recovering sulfuric acid portion in the sulfuric acid waste liquid as the gypsum by mixing at least one kind of lime stone, slaked lime and quick lime with the sulfuric acid waste liquid containing >1g/l fluorine while self-circulating a part of the produced gypsum as a seed crystal to react with each other, the gypsum is produced from the sulfuric acid waste liquid by keeping pH at 2.5±0.3. As a result, the gypsum increased in the particle diameter within the range of preventing the increase of fluorine content in the gypsum, is produced.