Biomass‐Derived Photoactive Nano‐Adsorbent With Antibacterial Potentiality for Treatment of Tannery Wastewater: Mechanistic Insights, XDLVO, and BDST Model

This study aims to develop a photo‐induced nano‐adsorbent material derived from watermelon leaves (WML) by incorporating green‐synthesized titanium dioxide nanoparticles (TiO 2 NPs) using Pigeon Pea leaves extract. The prepared nano‐adsorbent will significantly reduce reliance on traditional chemical‐based methods for its synthesis. Morphological and structural studies confirm the successful formation of spherical TiO 2 NPs with an average size of 48 nm, whereas FESEM‐EDX studies further validate the incorporation of NPs within the bio‐adsorbent, and BET analysis demonstrates a substantial improvement in specific surface area from 31.6 to 96.99 m 2 /g after incorporating TiO 2 NPs in WML. The prepared nano‐adsorbent was used for removing Cr (VI) from industrial wastewater, and the results depict the highest Cr (VI) adsorption percentage, up to 90% compared to pristine WML at optimized conditions. Kinetics and isotherm findings predict the pseudo‐second‐order model (chemisorption‐controlled), and the Langmuir isotherm provides the best‐fitting model to the experimental data. Response surface methodology (RSM) using central composite design (CCD) reflects good agreement between actual and predicted value under optimized condition signify the reliability and adequacy of the predicted model. Moreover, the antibacterial efficacy of the prepared nano‐adsorbent was studied against Escherichia coli ( E.coli ) using extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory in terms of adsorbent surface charge and interfacial interactions between the foulant and the adsorbent surface. The result depicts a threefold reduction in interaction energy (less negative value of ∆GTOT) after incorporating TiO 2 NPs, depicting stronger antibacterial properties. Lastly, adsorption column design using Bed depth service time (BDST), the Adams–Bohart and Thomas model fitting concludes the mass‐transfer‐controlled adsorption process and deploy the scalability of the process in a packed bed application.