Efficacy of Alkaline-Treated Soy Waste Biomass for the Removal of Heavy-Metal Ions and Opportunities for Their Recovery

In this study, soy waste biomass (SW) resulting from oil extraction was treated with alkaline solution, and the obtained material (Na-SW) was used as biosorbent for the removal of Pb(II), Cd(II), and Zn(II) ions from aqueous media. The performance of this biosorbent was examined in batch systems, at different initial metal ion concentrations and contact times (pH 3.4; 5 g of biosorbent/L). Isotherm and kinetic modeling was used to calculate the equilibrium and kinetics of the biosorption processes. The maximum biosorption capacity, calculated from the Langmuir isotherm model, followed the order Zn(II) (0.49 mmol/g) > Cd(II) (0.41 mmol/g) ≈ Pb(II) (0.40 mmol/g), while the kinetics of biosorption processes fit the pseudo-second-order model. Three cycles of biosorption/desorption were performed to estimate the reusability of Na-SW biosorbent, and the regeneration efficiency was higher than 97% in all cases. The practical applicability of Na-SW biosorbent in treating of wastewater contaminated with Pb(II), Cd(II), and Zn(II) ions was examined using simulated wastewater samples, and the main quality characteristics of the effluents obtained after treatment were evaluated. All these aspects highlight the potential applicability of Na-SW for large-scale wastewater treatment.