Multifunctional nanocomposite for sustainable Yamuna water treatment: Insight into adsorption, statistical...

This study addresses the treatment of polluted Yamuna river water in Delhi using a green-synthesized ZnO@MoS₂/Rheum emodi (ZMR) nanocomposite as adsorbent. The ZMR was comprehensively characterized by FT-IR, XRD, BET, SEM, TEM, SAED, EDS, XPS, and TGA techniques. Yamuna water was collected and analysed for various pollutants using ICP-OES technique. It was found to contain 0.52 mg L^-1 of Cr(VI), which exceeds the permissible limits. For removal, the adsorption conditions were optimized via central composite design (CCD) of the response surface methodologies (RSM) which yielded optimal performance at 80 min contact time, pH 9.0, and 0.15 g L^-1 ZMR dose, achieving 98.84 % Cr(VI) removal. The adsorption followed pseudo-second order kinetics and Langmuir isotherm (Q_m = 684 mg g^-1). Thermodynamic analysis confirmed the process to be spontaneous, endothermic, and governed by electrostatic forces, hydrogen bonding, and complexation. The ZMR nanocomposite exhibited structural integrity, excellent regeneration (three cycles), and negligible Zn/Mo leaching across acidic, neutral, and basic media which was supported by UV-Vis. and post-treatment XRD analysis. Also, antibacterial efficacy against Serratia marcescens demonstrated colony reduction and inhibition zone formation. Additionally, physiochemical analysis of Yamuna river water revealed improvements in water quality parameters, such as DO, BOD, COD, pH, and salinity. Furthermore, a toxicity evaluation was conducted using the toxicity estimation software tool (TEST), which confirmed low ecological risk from major Rheum emodi phytoconstituents and a phytotoxicity assay with Trigonella foenum-graecum seeds showed high germination and healthy growth in ZMR-treated water. Overall, ZMR nanocomposite offered a cost-effective, eco-friendly, and multifunctional approach for Cr(VI) remediation and holistic improvement of river water quality.