Biological degradation coupled to photocatalysis by ZnO/polypyrrole composite for the treatment of real textile wastewater

The novelty of this work lies in the use of a real textile wastewater (RTW), without a pretreatment, without additional carbon sources and undiluted, with coupling a photocatalysis by using an unprecedented composite for this application. The collected RTW containing the azo dye Direct Black 22 (205.15 mg L-1 TOC: 672.7 mg L-1), was treated with a bacterial consortium and after 96 h the sequential photocatalysis process was employed using ZnO/Polypyrrole during 60 min. The coupling of both treatment processes resulted in a total decolorization efficiency of 95.7 % and 99.8 % of TOC degradation (8.76 mg L-1 TOC: 1.33 mg L-1). Degradation product analysis was carried out by LC-MS/MS and a degradation pathway is proposed. The textile wastewater treatment proposed in this work is an attractive alternative and it is highly recommended to apply this system before the disposal of textile effluents in water bodies.