A hybrid ZA@ZnO1−X nanocomposite-based tubular membrane process for enhanced degradation of organics: A bench scale study for Bismarck brown R effluent

Abstract

Nanocomposite-based ceramic membrane with microbubble is an emerging hybrid technology for treating recalcitrant organics in wastewater. The current work is based on the synergistic effect of photocatalyst, microbubble, and membrane separation for enhanced degradation of Bismarck brown R, which is otherwise very low in the standalone process. In this study, we have fabricated a bench-scale membrane set up of submerged type, modified tubular membrane with the novel Zeolite A@ZnO1−X nanocomposite, and detailed analytical characteristics are investigated. The thin layer coating (average thickness 24.6 µm) of oxygen-deficient ZA@ZnO1−X photocatalyst gives a high photocatalytic efficiency under visible light without hampering the rejection rate. Here, we have treated Bismarck brown R contaminated wastewater in our prototype setup with simulated and natural wastewater collected from a local dying factory. The operational parameters such as Bismarck brown R concentration, solution pH, temperature, and flux are varied and analyzed optimized reaction conditions favorable for actual wastewater treatment. The hybrid ZA@ZnO1−X nanocomposite-based tubular membrane improved the degradation of natural wastewater to 95.4 % decolorization and 94 % COD removal in 90 mins at pH 8.15, solution flux 120 ml/min and temperature 30 °C. The scavenging experiment resolved responsible reactive species for organic dye degradation: holes and HO•. The tentative mechanistic degradation pathway involved homolytic cleavage of the azo bond followed by phenyl radical generation to a small intermediate of hydroxyquinol. This work represents an efficient alternative to conventional membrane technology with lesser membrane fouling tendency and enhanced catalytic efficiency in assistance with microbubbles simultaneously.