METHOD FOR CONTROLLING ELECTROLYSIS IN ELECTROLYTIC DEVICE FOR REDUCING COD VALUE OF CHEMICAL COPPER PLATING WASTE LIQUID

摘要

PURPOSE:To recognize conveniently the end point and to control the electrolysis rapidly and inexpensively by detecting the pH of a liq. to be treated while electrolyzing the liq., and finishing the electrolysis when the pH value increases to a specified value after the pH decreases. CONSTITUTION:When a chemical copper plating liq. is continuously used, a chelating agent increases, Na formate formed by the oxidation of 37% formalin and Na sulfate formed by an increase of sulfate radicals deposit in the soln., the quality of a copper plating deteriorates as the electrical conductivity of the soln. decreases, and the liq. is disused. The waste liq. is electrolyzed, the pH value is measured, and the electrolysis is finished when the pH value increases to a specified value (e.g., 9.3-9.4) after the pH value decreases. Consequently, the end point can be recognized conveniently unlike the process wherein the COD value is directly detected to detect the end point of the electrolysis and the electrolysis can be controlled rapidly and inexpensively.