Electrochemical degradation of the sodium diclofenac

Author(s)

Robson da Silva Rocha

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica
• Defense date: 2007-02-15

Examining board members

Marcos Roberto de Vasconcelos Lanza; Christianne de Arruda Rodrigues; Cláudia Longo

• Advisor: Marcos Roberto de Vasconcelos Lanza

Abstract

This work proposes the development and the optimization of the electrochemical treatment of a synthetic effluent with sodium diclofenac. In this work two stages were executed the study of the redox reactions of the sodium diclofenac and, the process of this organic compound. Hydrodynamic voltammetry experiments were recorded to identity sodium diclofenaco redox reaction in a non-aqueous medium (DMF with 0,1 mol L-1 of NaClO4) and in aqueous medium (0.1 M of K2SO4). These experiments were performed using glassy carbon as working electrodes, at different rotations (0 up to 3000 rpm). The glassy carbon electrode in non aqueous medium presented the best answers, where observed two peaks of oxidation, at 0.33 V vs. Ag/AgCl and 0.57 V vs. Ag/AgCl, and a peak of reduction at 0.73 V vs. Ag/AgCl. The hydrodynamic voltammetry it experiments showed that the redox reactions of the sodium diclofenac are influenced by the rotation of the glassy carbon electrode. A flow electrochemical reactor was used for the sodium diclofenac degradation. It was used a gas diffusion electrode as cathode and DSA-Cl2 ® as anode. The electrolyte used was 1.0 L of 0.1 M K2SO4 with 200 mg L-1 of sodium diclofenac (flow rate: 200 L.h-1, pressure (O2): 0,2 Bar), with and without 10 mM of FeSO4. The performance was evaluated considering concentration decay of sodium diclofenac concentration (HPLC) and chemical oxygen demand (COD) as a function of the applied current and addiction of Fe(II) ions. The results showed that the electrochemical reactor was efficient in the generation of 350 mg L-1 of H2O2 after two hours of electrolysis without the addition of the organic compound. The sodium diclofenac degradation occurred by indirect chemical oxidation, for the hydroxyl radicals formation from H2O2 electrogenerated, and by direct electrochemical oxidation on anode. This process showed the efficiency in the degradation of sodium diclofenaco: 99,2 % of reduction of the initial concentration and 27,4 % of reduction of the chemical oxygen demand (COD). When electro-Fenton was used by addition of FeSO4 as catalyst hydroxyl radicals formation, the degradation efficiency increased. The of the drug degradation was 99,4 % of the initial concentration and the COD reduction was 63,2 %. The results showned that the degradation process using electrochemical reactor was efficient in the sodium diclofenac degradation and COD reduction (AU)