Removal of Sulfonated Humic Acid through a Hybrid Electrocoagulation–Ultrafiltration Process

This study investigated the removal of sulfonated humic acid (SHA) from water through a hybrid electrocoagulation–ultrafiltration treatment process. The effects of major operating parameters including electrocoagulation time, current density, and initial pH on the electrocoagulation performance were evaluated. The increase in current density and operating time as well as decrease of pH improved the SHA removal efficiency. The operating conditions of electrocoagulation process were optimized through Box–Behnken design to maximize SHA removal. The optimum conditions for electrocoagulation included time of 7 min, current density of 10 mA/cm2, and pH of 5. Effective SHA removal was further achieved in the hybrid electrocoagulation–ultrafiltration treatment process. The performances of three molecular weight cutoff membranes were examined. The results showed that the SHA removal efficiency increased with the increasing initial concentration of SHA and decreased with the increasing transmembrane pressure. The SHA removal efficiency was more than 95% by 5 kDa membrane. The SHA removal efficiency by different membranes from high to low in turn was: 5 kDa > 8 kDa > 10 kDa. The results will have significant implications for the treatment of complex drilling and hydraulic fracturing wastewater through electrocoagulation–ultrafiltration process.