Application of titanium dioxide based photocatalytic membrane system on removal of morpholine and its N-nitrosomorpholine formation potential

N-nitrosomorpholine (NMOR), its important precursor (morpholine, MOR) and formation potential (NMOR FP) were detected in effluents with concentrations of up to 15 ng/L, 1.62 mu g/L, and 24.1 ng/L, respectively. The photodegradation of NMOR can produce the non-photodegradable MOR, regenerating NMOR by chloramine, and different concentrations of NMOR (50, 100, 200, 500 mu g/L) can be completely photodegraded within 60 min with generation of MOR with range from 2 to 14 mu g/L. In this study, a TiO2 based photocatalytic ceramic membrane system was designed and developed for removing MOR and NMOR FP in water environment. Microfiltration membrane with pore size of 100 nm can control the loss of TiO2 by the flat membrane pores, while TiO2 of 4-40 g/m2 accumulated to form a TiO2 layer generating hydroxyl radicals (& sdot;OH) sufficiently under 8.93 mW/cm2 of ultraviolet irradiation. Moreover, MOR (10, 100, and 1000 mu g/L) and NMOR FP showed effective removal by TiO2 based photocatalytic membrane system with removal efficiency up to 60 %. In addition, although NMOR had different precursors, the near removal efficiency between MOR and NMOR FP indicated that MOR was the main precursor of NMOR. Furthermore, the designed system achieved recycling of the catalyst to avoid the risk on release of the catalyst into water environment.