Preparation of a redox mediator membrane and its application to catalyzing biodegradation of azo dyes

Abstract

Anthraquinone redox mediators can promote the bacterial degradation of azo dyes. In the present work, a redox mediator membrane was prepared by the phase inversion via immersion precipitation method using poly(vinylidene fluoride) (PVDF) as the polymer membrane material and 1, 8-dichloroanthraquinon (1, 8-AQ) as the redox mediator and its application to promoting the bacterial degradation of azo dyes was demonstrated. The Redox mediator/PVDF membrane was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), atomic force microscope (AFM) and water contact angle. It exhibits extremely high permeability with the maximum pure water flux of 140 L/m2·h, 2.3 times higher than that of the PVDF membrane. Yet, the introduction of 1, 8-AQ reduces the BSA rejection rate. The Redox mediator/PVDF (RM/PVDF) membrane prepared under optimal conditions is able to shorten the complete degradation time of azo dye from more than 120 h to 48 h and improve the degradation efficiency by 2.5 times. The cyclic test suggests that the RM/PVDF membrane remains high catalytic efficiency for the bacterial degradation of azo dyes for 5 cycles with slight increases in the promoting effect. These results demonstrate great application potentials of the Redox mediator membrane.