Treatment of reverse osmosis concentrate from industrial coal wastewater using an electro-peroxone process with a natural air diffusion electrode

Abstract

• Electro-peroxone (EP) treated reverse osmosis concentrate (ROC) for the first time. • The use of natural air diffusion electrode in EP was studied for the first time. • EP could remove refractory substances in ROC within 2 h. • The EP process had high tolerance to wastewater quality. • The combination of peroxi-coagulation (PC) and EP outperformed EP. Reverse osmosis concentrate (ROC) produced in the RO treatment of coal chemical wastewater is highly toxic and difficult to degrade. In this study, an electro-peroxone (EP) process was applied to treat ROC with a natural air diffusion electrode (NADE), which was used as the cathode to efficiently generate H 2 O 2 . The treatment efficiency of EP, electro-Fenton, electro-oxidation (EO), peroxi-coagulation (PC) and ozonation for the removal of total organic carbon, colour and UV 254 in ROC were studied and compared, confirming that EP was the most efficient process. The EP process as well as electric energy consumption (EEC) were optimized, and an optimum reaction conditions (current of 200 mA, pH of 4 and O 3 dose of 6 mg/min) were selected. The production of ⋅ OH in EP was much higher than that in ozonation and EO, as indicated by the EPR measurement. Excitation-emission matrix spectra of ROC after EP treatment verified that all the fluorescent contaminants in ROC was removed within 2 h. Further, the combination of PC and EP processes (2 h + 3 h) significantly reduced EEC by 58% as compared with EP (6 h), realizing complete decolouration. This study declared the potential of using EP and the combined PC-EP process to effectively treat the real ROC wastewater.