Synergistic removal of organic pollutant and metal ions in photocatalysis-membrane distillation system

The removal of pollutants including aqueous organics and metal ions in the wastewater has been widely concerned. The coupled photocatalysis-membrane separation system can simultaneously realize the photoreaction of pollutants and their separation from wastewater to achieve the complete purification of wastewater. Herein, a photocatalysis-membrane distillation reactor (PMR) was designed to simultaneously remove the aqueous organics and metal ions for the wastewater treatment. The simultaneous removal of the probe pollutants, 4-chlorophenol (4-CP) and Ag+ ion, was successfully achieved via the synergistic effect of photocatalysis and direct contact membrane distillation (MD). Following the systematic investigation, it had been found that the rapid photo-reduction of Ag+ ions into Ag nanoparticles on BiOBr films was promoted by the coupling effect of the photo-degradation of 4-CP and the concentration effect of the membrane separation process. Meanwhile, the photo-degradation process of 4-CP was improved via the surface plasma effect and the promotion effect to photo-induced electron transfer of Ag nanoparticles. Furthermore, the photo-induced holes converted to act as the main active species for the oxidation of 4-CP in the synergistic PMR system, unlike the process in bare BiOBr system with the main active species of center dot O-2(-) radical. This synergistic photocatalysis-membrane separation system provided a valuable sight into the simultaneous removal of aqueous organics and metal ions for the practical applications.