Flexible cotton fabrics/PDA/BiOBr composite photocatalyst using bioinspired polydopamine as electron transfer mediators for dye degradation and Cr(VI) reduction under visible light

Efficient visible-light driven photocatalytic degradation of co-existing organic and inorganic pollutants in wastewater is important for practical application in eliminating multiple contaminants. We report herein the preparation and application of a new recyclable photocatalyst of cotton fabrics/PDA/BiOBr (CFPB), which was prepared by immobilization of BiOBr component on the polydopamine (PDA) modified cotton fabrics via a solvothermal reaction. Characterization of structural composition, morphology, optical and photoelectrochemical features of CFPB were conducted. The activity of CFPB was evaluated on the photo-oxidation of rhodamine B (RhB) and photo-reduction of Cr(VI) under visible light. Simultaneous removal of RhB and Cr(VI) from their mixture solution under CFPB was further investigated. 98 % of RhB could be degraded in 40 min within the pH range of 2.5-6.6, while Cr(VI) could be nearly completely reduced to non-toxic Cr(III) in 130 min at pH 2.5. The simultaneous removal of mixed RhB and Cr(VI) at pH 2.5 indicated that the efficiencies of both RhB degradation and Cr(VI) reduction were higher than that in their single component solutions. Wherein RhB could be nearly completely degraded in 20 min while 96 % of Cr(VI) could be reduced in 110 min. The enhanced activity of CFPB was attributed to the incorporation of PDA networking which promoted light harvest and charge carriers separation. The mechanism of photocatalytic degradation of individual RhB or Cr(VI) and their mixture by CFPB was proposed according to optical and photoelectrochemical properties, radicals trapping and electron spin resonance (ESR) analyses. This work provides a clean and economic way for simultaneously removing organic and inorganic pollutants in real wastewater.