Patent ID: 9593424
Date: 2017-03-14
CPC Classifications: B08B,C02F,C25B,H01L

Claim:
1. A sulfuric acid recycling system for continuously regenerating persulfuric acid from a persulfuric acid solution comprising: an electrolytic reaction apparatus having electrodes that include at least one anode and at least one cathode arranged in the persulfuric acid solution connected to a source of electrical power with the persulfuric acid solution adapted to flow between the electrodes for electrolyzing the solution based on a predetermined sulfuric acid concentration, such that persulfuric acid is being continuously regenerated by an electrolytic reaction which produces persulfate ions at the at least one anode from sulfate ions; cleaning apparatus for removing contaminants from an object to be cleaned and dissolving the contaminants by said persulfuric acid solution; circulation apparatus including a circulation line connected between said electrolytic reaction apparatus and said cleaning apparatus for continuously recirculating the persulfuric acid solution in said circulation line between the cleaning apparatus and the electrolytic reaction apparatus while simultaneously regenerating persulfuric acid, with the circulation line being connected to an inlet of said cleaning apparatus; heating means, capable of heating the solution to 100 to 170° C., located in the circulation line so as to heat the solution upstream of the cleaning apparatus so that the heated solution enters the cleaning apparatus at the temperature of between 100 to 170° C.; cooling means, capable of cooling the solution to 10 to 90° C., located in the circulation line so as to cool the solution upstream of the electrolytic apparatus so that the cooled solution directly enters the electrolytic apparatus at the temperature of between 10 to 90° C.; a solution replenishment line of either ultrapure water or hydrogen peroxide for supplying ultrapure water or hydrogen peroxide directly to the persulfuric acid solution in said system to replenish the water content in the solution that otherwise gradually decreases as a result of electrolysis of the solution and/or evaporation; a sulfuric acid concentration measurement unit for monitoring the sulfuric acid concentration of the solution; and, a control unit programmed to control the supply of ultrapure water or the hydrogen peroxide directly to the persulfuric acid solution in said system from the solution replenishment line of ultrapure water or hydrogen peroxide in direct response to the concentration of sulfuric acid measured by the sulfuric acid concentration measurement unit so as to maintain the concentration of sulfuric acid at a prescribed sulfuric acid concentration during the continuous regeneration of persulfuric acid.