Hybrid electro-Fenton and peroxi-coagulation process for high removal of 2,4-dichlorophenoxiacetic acid with low iron sludge generation

Abstract

2,4-D is one of the most predominant herbicides around the world, though many advanced oxidation processes (AOPs) including peroxi-coagulation (PC) have been applied for its removal, the traditional PC still has restricted application due to disadvantages of huge sludge generation for a high pollutant removal and increased subsequent disposal costs. Herein, we developed a hybrid EF and PC process, using iron and dimensionally stable anode (DSA) electrodes as anodes, and a natural air diffusion electrode (NADE) without external aeration as the cathode. The optimal conditions for the hybrid process were optimized (initial pH 3, initial 2,4-D concentration 100 mgL−1, and total current of 100 mA with the ratio of DSA anode and iron anode of 7:3). Under these optimal conditions, 2,4-D could be almost completely removed within 30 min, and the TOC removal reached 71.9% within 2 h with a low electric energy consumption (EEC) of 19.59 kWh kg−1 TOC. The performance was comparable with traditional PC process but the iron sludge generation significantly reduced by ~73%. Therefore this hybrid process would have more potential to replace traditional PC process with cost-effective pollutants removal, low iron sludge generation and low EEC.