GB1141407A - Electrolytic regeneration of ammonium persulphate - Google Patents

Abstract

1,141,407. Electrolytic regeneration of ammonium persulphate solutions. F.M. C. CORP. Sept. 27, 1966 [Oct. 1, 1965], No. 42967/66. Heading C7B. In a process for the regeneration of an ammonium persulphate etching solution which contains therefrom dissolved copper, cobalt, iron, nickel and/or zinc, a persulphate-free mixture containing sulphate values of ammonium and the dissolved metal is separated from said solution and passed to the cathode compartment of an electrolytic cell, the remaining solution containing the persulphate from the original solution and other sulphate values being passed to the anode compartment of said cell, the dissolved metal in the catholyte being deposited upon the cathode and persulphate ions being formed at the anode during electrolysis, the resulting anolyte forming the regenerated etchant. Additional sulphate, e. g. the catholyte produced in a previous operation, may be added to the anolyte or to the original solution prior to separation therefrom of the persulphate-free portion of the exhausted etchant. Urea and ammonium thiocyanate may also be added to the anolyte. The persulphatefree catholyte may be obtained from the original etchant solution by condensing said etchant and crystalizing out therefrom metal sulphate and ammonium sulphate which is then redissolved in the water given off by condensing the original solution, the mother liquor forming the anolyte. The examples given use a platinum wire anode and a cathode of copper tubing, and the diaphragm cell formed by a porous porcelain cup within a glass beaker, the copper tube being wound as a helix about the porous cup and having water passed therethrough for better temperature control.