O3/H2O2-NF Coupling for treating coal chemical reverse osmosis Concentrate: Organic matter removal and membrane fouling control

In the coal chemical industry, direct evaporation of reverse osmosis (RO) concentrate generates numerous hazardous solid wastes containing mixed salts and organic matters. Nanofiltration (NF) membrane can selectively separate these contents and reduce the disposal of solid waste. However, the high concentration of organics in the RO concentrate exacerbates NF membrane fouling. We applied O 3 and O 3 /H 2 O 2 as pretreatment methods to mitigate the membrane fouling. The excitation-emission matrix (EEM) fluorescence spectroscopy demonstrated that O 3 /H 2 O 2 was more effective at removing organic matter in RO concentrate. Organic molecular weight distribution specifically showed that O 3 /H 2 O 2 was more efficient at degrading large organic molecules, making it more effective in reducing membrane fouling. The strong oxidative ability of the O 3 /H 2 O 2 system allowed the potential mineralization of smaller organics. In contrast, the O 3 oxidation increased the concentration of organic matter with small molecular weights ( M w  < 1,000 Da). The thorough degradation of organics using O 3 /H 2 O 2 reduced the organic content in the produced mixed salts.