Improved oil removal ability by the integrated electrocoagulation (EC)-carbon membrane coupling with electrochemical anodic oxidation (CM/EAO) system

A novel electrocoagulation (EC)-carbon membrane coupling with electrochemical anodic oxidation (CM/EAO) integrated system was designed and constructed for oily wastewater treatment. Electrocoagulation was adopted as a primary unit, and the effects of many parameters, including current density, electrolyte concentration, initial pH, feed oil concentration, and operating time on pretreatment performance were investigated and optimized. Subsequently, CM/EAO was set as a secondary unit for further deep purification of the EC effluent. The results showed the integrated system had great potential for oil removal from wastewater. The EC unit could remove nearly half of COD and TOC in the feed, and the following CM/EAO unit further degraded the EC effluent, and the COD, and TOC were reduced to 13 mg/L and 22 mg/L, respectively. The mechanisms involved in each stage were proposed. A large proportion of oil droplets in oily wastewater were firstly removed by electrocoagulation process, and the remaining oil droplets were further decomposed into small molecules or even into CO2 and H2O by hydroxyl radicals generated from electrochemical anode oxidation reactions. The degraded intermediate products including various n-alkanes and polycyclic aromatic hydrocarbons were identified by GC-MS.