Regeneration of spent ammonium persulfate etching solutions

摘要

1,176,892. Etching. FMC CORP. 17 Jan., 1968 [17 Feb., 1967], No. 2458/68. Heading B6J. An etching solution containing hydrogen peroxide and sulphuric acid, which has been used to dissolve copper and which contains residual hydrogen peroxide values is reactivated by cooling to crystallize copper sulphate values therefrom without substantially reducing the amount of residual hydrogen peroxide and separating the crystallized material from the remaining solution. Cooling may be to temperatures from - 8‹ to +20‹ C. The etching solution may contain ammonium sulphate in which case cooling may be to temperatures from - 2‹ to + 20‹ C. The solution remaining after separation may be refortified by the addition of more H 2 O 2 and H 2 SO 4 thereto. Alternatively, more H 2 SO 4 may be added prior to cooling. The reactivated solution may be recycled to an etching station.