Theoretical and Practical Basis of the Regeneration and Disposal of Sulfuric Copper Etching Solutions Used in the Production of Printed Circuit Boards by Membrane and Membraneless Electrolysis

Abstract

An electrochemical method for the neutralization, disposal, and regeneration of sulfuric acid solutions of copper etching used in the production of printed circuit boards has been proposed. The possibility of the electrochemical regeneration of sulfuric acid solutions of a copper etching containing H2O2 or $${{{\text{S}}}_{{\text{2}}}}{\text{O}}_{{\text{8}}}^{{{\text{2}} - }}$$ oxidizer is investigated. Membraneless electrolysis is suitable exclusively for the disposal of spent solutions by removing residues of the H2O2 or $${{{\text{S}}}_{{\text{2}}}}{\text{O}}_{{\text{8}}}^{{{\text{2}} - }}$$ oxidizing agents and toxic Cu2+ from spent solutions with a minimum power consumption of 3.88 (kW h)/(kg Cu). The possibilities of membrane electrolysis in a two-chamber cell are limited by the removal of Cu2+ and with the possibility of creating conditions for the synthesis of $${{{\text{S}}}_{{\text{2}}}}{\text{O}}_{{\text{8}}}^{{{\text{2}} - }},$$ while the regeneration of the H2O2 oxidant is impossible. Electrolysis in a three-chamber cell with two ion-exchange membranes has great functionality, as it allows one to simultaneously remove Cu2+ with a fraction of the current carried by Cu2+ up to 9.7%, preserve the H2O2 oxidizer, or synthesize a $${{{\text{S}}}_{{\text{2}}}}{\text{O}}_{{\text{8}}}^{{{\text{2}} - }}$$ oxidizer with a current efficiency of up to 42.6% (in the absence of special additives).