Comparative removal of commercial diclofenac sodium by electro-oxidation on platinum anode and combined electro-oxidation and electrocoagulation on stainless steel anode

Abstract

Aqueous solution of diclofenac sodium (DCFNa) from commercial analgesic pill was electro-oxidized on platinum and stainless steel (SS) anodes. On platinum anode, 66% degradation of the parent drug was achieved at pH 4.5 with a corresponding COD reduction of 49% for a specific charge of 4200 Coulombs/L. Degradation and COD reduction were less at higher pHs of 8.5 and 10.9. A number of intermediates were detected with some of them persisting at the end of the treatment. On SS anode, 84% drug removal and 80% COD decline were achieved for a specific charge of 4200 Coulombs/L at pH 10.9, owing to combined electro-oxidation and electrocoagulation. Contrary to platinum anode, here the drug removal and COD reduction were lesser at lower pHs of 8.5 and 4.5. Electrocoagulation was found to proceed with the organics directly forming complex with iron in the matrix of the SS anode with the iron oxidizing to Fe(III) at pH 10.9 and Fe(II) at pHs 8.5 and 4.5. Intermediates detected in residual liquid were much less in number and abundance.