REPRODUCING AND REUTILIZING METHOD FOR SULFURIC ACID

PURPOSE:To reduce a quantity of sulfuric acid to be disposed by utilizing in circulation in the producing process of a semiconductor device or the like. CONSTITUTION:A waste sulfuric acid discharged from a sulfuric acid using process is supplied to an anode chamber 6 of a sulfuric acid concentration electrolysis vessel 4 partitioned with at least one piece of cation exchange membrane 5 to concentrate sulfuric acid and to form an oxidizing material. The sulfuric acid is reused for the sulfuric acid using process and in the case the conc. of impurities accumulated in the system reaches above a fixed level, a part of sulfuric acid in the system is supplied to a sulfuric acid purifying device to purify and the purified sulfuric acid is supplied to the system to circulate sulfuric acid. As a result, sulfuric acid is reused and sulfuric acid having large oxidizing ability is obtained without adding the oxidizing material such as hydrogen peroxide into the sulfuric acid.