BiOCl0.875Br0.125/polydopamine functionalized PVDF membrane for highly efficient visible-light-driven photocatalytic degradation of roxarsone and simultaneous arsenic immobilization

A bifunctional membrane modified by BiOCl0.875Br0.125 and polydopamine (PDA) was developed in the current study and employed for the photocatalytic degradation of roxarsone (ROX) under visible-light and simultaneous immobilization of the released inorganic arsenic by sorption. Characterization techniques, such as FESEM, XRD, FTIR-ATR, DRS and XPS were used to characterize as-prepared membranes so as to analyze their structural and functional attributes. Dynamic cyclic experiments indicated that a satisfactory degradation efficiency of ROX ( similar to 100%) could be achieved by the photocatalytic process within 5 h. Simultaneously, the released inorganic arsenic could be completely converted to As(V) and eventually immobilized onto the surface of membrane. The critical reactive oxidation species (ROS) including center dot O-2(-), h(+) and center dot OH contributed to the photodegradation of ROX, and the PDA coating played multiple roles as an adhesive interface, an electron transfer layer, and an active adsorptive layer. Additionally, based on the HPLC-AFS and GC-MS analysis, the major degradation products were detected and the mechanism of ROX degradation and simultaneous arsenic immobilization by BiOCl0.875Br0.125/PDA functionalized PVDF membranes (BPMs) was given, and the reaction pathway of ROX during the photocatalytic/filtration process was also taken into consideration. Combined with the exceptional photocatalytic property and high adsorption capacity of arsenic, the fabricated BPMs may open new opportunities for the control of ROX in water treatment.