Sustainable sequestration of Pb²⁺ ions from electroplating wastewater using OSB@ZnO nanocomposites: Statistical modelling and phytotoxicity evaluation

The electroplating industry uses heavy metal ions on a large scale, resulting in disruption of human health and aquatic ecosystems. The main goal of this research article was to synthesize an efficient adsorbent for Pb²⁺ ions adsorption using Oryza sativa biochar after post-impregnation with zinc sulfate, resulting in OSB@ZnO Nanocomposites (NCs). The synthesized adsorbent was characterized using SEM-EDX-EM, FTIR, XRD, BET, Zeta potential, and sizer. The BET study revealed that the synthesized NCs had a total surface area of 90.3 m 2 /g, compared to pristine biochar (23.1 m 2 /g). The adsorption effectiveness was examined through isotherm, kinetic, and thermodynamic studies. Two distinct modelling approaches were used in this study: response surface methodology (RSM) and artificial neural networks (ANN) for optimization effectiveness, facilitating improved decision-making and process enhancement in wastewater treatment. ANN model outperformed the RSM model, with R 2 = 0.9502 vs. 0.932 and MSE = 0.177 vs. 0.40. The quadratic terms (A, B, C, AC, BC, A2, B2, and C2) and F-value (237.46) were significant, while the lack of fit was not significant, suggesting the ANOVA model was well fitted to experimental data. The q max was 166.6 mg/g for Pb²⁺ ions adsorption, representing a good adsorption potential of OSB@ZnO NCs. The OSB@ZnO NCs were regenerated using HCl reagent with good regeneration power over five cycles. The physicochemical parameters (pH, nitrate, phosphate, grease, BOD, COD, EC) and heavy metal concentrations (Pb, Cr, Cd, Ni, and Cu) in untreated electroplating wastewater (UTEW) were beyond the permissible limits, and toxicological studies showed that the UTEW had a high degree of phytotoxicity, as it inhibited seed germination in Vigna radiata. Treated electroplating wastewater (TEW) showed excellent seed germination performance.