Application of the electro-Fenton process for cutting fluid mineralization.

Organic compound is the main pollutant in industrial effluent. Conventional wastewater treatment processes are inefficient for the removal of toxic or non-biodegradable organic pollutants. Advanced electrochemical depollution is a very efficient and economic method, suitable when the wastewater contains toxic and recalcitrant organic pollutants. The aim of the present study was to investigate the application of the electro-Fenton (EF) process for the degradation and mineralization of a stable oil-in-water emulsion (0.01% in v/v). The effects of operating parameters such as cathode material (graphite, Ti/Pt and steel), nature (Na2SO4, NaNO3 and NaCl) and dose of electrolyte (25-75 mM), initial ferrous ions concentration (1-75 mM), current intensity (0.1-0.2 A) and operating time, on chemical oxygen demand (COD) removal efficiency, were studied. Results showed that the EF method can be used efficiently for the degradation of stable cutting oil emulsion. For considered initial conditions (bubbling compressed air at 1 L/min, 0.15 A, pH 3, [Na2SO4]=0.05 M, [FeSO4]=0.015 M, COD0=400 mg O2/L), the best removal efficiencies were obtained under the following conditions: graphite as cathode material, 180 min for treatment duration and 0.05 M [Na2SO4]. For these conditions, treatment of 250 mL of emulsion led to 93.6% of cutting fluid mineralization, which correspond to 25 mg O2/L of final COD, 19 kWh/m3 of treated wastewater and 24.039 kWh/kg of COD removal.