Separation of oil–water emulsions by electrocoagulation and electro-persulfate with sonication pretreatment: Determination of economical electrode configuration, optimization, and comparison

Abstract

This study aimed to separate oil–water emulsions by electrocoagulation (EC), which is considered an effective and promising method for sustainable water management, and the electro-persulfate method (EPS) as an advanced EC process. Firstly, oil–water emulsions were treated with EC using three different electrode configurations and the most economical electrode pair (perforated and plate electrodes) was determined. Secondly, the Box-Behnken design (BBD) was applied to explore the influence of operational variables (pH, current density, and electrolysis time for EC; pH, current density, PS/COD, and electrolysis time for EPS) on the removal of COD (5800 mg/L) as a response with the identified electrodes. As a result, at neutral pH, the optimal operating conditions determined for maximum COD removal were 27 mA/cm2 and 37 min for EC and 27 mA/cm2, 25 min, and PS/COD = 0.5 for EPS. At the predicted optimal conditions, the predicted and tested COD removal was respectively 100 % and 97.15 % for EC, 88.18 % and 87.94 % for EPS. Moreover, the total cost was 2.39 $/m3 and 1.27 $/m3 for EC and EPS, respectively. Consequently, it was determined that perforated electrodes were more economical, and EC achieved higher wastewater treatment performance than EPS, however, from an economic point of view, the EPS process enabled the more efficient treatment of oil–water emulsions.