Sunlight-mediated efficient remediation of organic pollutants from water by chitosan co-decorated nanocomposites of NiO loaded with WO3: Green synthesis, kinetics, and photoactivity.

[Display omitted] • Feasible, cost-effective and green approach for synthesis of NiO@WO 3 -Chitosan nanocomposite. • High photodegradation of Tropaeolin OOO (96%) and Eriochrome black T (92%) by NiO@WO 3 -Chitosan. • Degradation of pollutants followed first order kinetics under daylight. • Smaller non-toxic by-products and high reusability (8th cycle) confirm high efficiency. Azo dyes such as Tropaeolin OOO (TOOO) and Eriochrome black T (EBT) are used in various industrial and laboratory applications. However, their recalcitrant properties make them toxic chemicals and require efficient removal-strategy based on polymer decorated semiconductor nanocomposite. Herein, photodegradation of TOOO and EBT in water was investigated at different reaction parameters through NiO@WO 3 -chitosan synthesized by green procedure using A. indica. PXRD spectra peaks show semi-crystalline behaviour with spherical morphology and chitosan around metal oxide. In FT-IR, New spectral peaks observed at 1023 cm−1, 870 cm−1, and 540 cm−1 vibration indicated between Ni-O-W, Ni-N, and W-N confirmed effecting coupling. Both dyes (10 mg/L) were found completely colourless within 3 h under sunlight with pH of 7 at 20 mg of catalyst load. Difference in max degradation of 96 % and 92 %, respectively to TOOO and EBT dye credit to structure difference. 1st-order reaction kinetics following early Langmuir adsorption and degradation at optimum condition rate constant k (0.26–0.19-min−1) and half time t 1/2 (2.68––3.64 min−1). Efficiency of NiO@WO 3 -chitosan was maintained due to its fine morphology with elevated surface-area (75 m2g−1), large negative zeta potential (−29.5 mV), and lesser value of band distance (2.1 eV). Involvement of •OH, O 2 –• and holes in photocatalysis mechanism to break complex molecules of TOOO and EBT was revealed in Scavenger analysis. After degradation, small-safer metabolites were confirmed by LC-MS. Reusability up to 8th cycle of NiO@WO 3 -chitosan without photoactivity reduction makes it a cost-effective cum sustainable composite for industries and wastewater pollutants removal with good surface properties. [ABSTRACT FROM AUTHOR]