UV/peroxysulfate/ozone (UV/PS/O3) oxidation system for efficient degradation of organic matters in nanofilter membrane concentrates

The dissolved organic matters in the membrane concentrates often cause scaling/blockage problems and significantly deteriorate the quality of the recovered salts when the evaporation crystallization process is used to treat membrane concentrates. It is important to find a cost-effective method to decrease the dissolved organic matters in concentrates. This study explores the feasibility of using an ultraviolet/peroxysulfate/ozone (UV/PS/O 3 ) process for the degradation of organic matters in nanofiltration membrane concentrates (NMCs). The UV/PS/O 3 process outperformed other processes, including UV photolysis alone, PS oxidation alone, UV/PS, and UV/O 3 , and achieved a complete oxidative degradation of 200 mg/L quinoline (QL) within 40 min in concentrated Na 2 SO 4 solutions. The experiments also revealed that OH and SO 4 − were the primary reactive radicals for QL oxidation in the UV/PS/O 3 process. QL removal efficiency increased along with the amount of aerated O 3 , the PS dosage, and was especially enhanced under a weakly alkaline condition. The response surface analysis showed that the optimal condition for QL removal was 4.68 mM PS, 3.43 mg/L O 3 gas, and pH ini 8.43. The presence of chloride ions (5–15 mM) inhibited the removal of QL. When the combination of UV/PS/O 3 process and evaporation crystallization was examined for the treatment of real NMC from a coking plant, it was found that the heating process could thermally activate the residual PS for the removal of organic impurity, and the whole process allowed to recycle sulfate salts with better brightness from the NMC. This study provides a prospective technology for the efficient treatment of NMC wastewater.