Efficient zinc ion biosorption on the biomass of Ericaria selaginoides algae following response surface methodology optimization: uptake behaviors and mechanisms

Background Biosorption using marine algae biosorbents is a sustainable and effective method for removing of heavy metals from aquatic environments. Methods This study explored the biosorption of zinc ions from aqueous solutions using the biomass of the brown alga Ericaria selaginoides . The impacts of biosorbent dose, pH, and biosorbate concentration were optimized using the Response Surface Methodology (RSM) and 3-D surface plots generated via Design-Expert software. Results Under optimized conditions, RSM predicted a maximum zinc removal efficiency of 89.79% which matches the experimental value of 87.72% ± 7.3%. These conditions included biosorbent dosage of 0.28 g/100 mL, zinc concentration of 33.62 mg/L, and pH of 6.97. The Langmuir model showed a maximum biosorption capacity of 114.94 mg/g, while the kinetic data were best described by the pseudo-second order model. The combined adsorption equilibrium, kinetic, thermodynamic, and surface characterization data show that Zn(II) biosorption by E. selaginoides involves a heterogeneous physicochemical process that includes surface complexation, ion exchange and auxiliary co-ordination with hydroxyl, amine, and phosphate groups. Overall, E. selaginoides exhibits promising potential as a low-cost and environmentally friendly biosorbent for zinc remediation from contaminated water, and additional process optimization could increase its efficacy in wastewater treatment. This research uniquely combines the optimization of zinc uptake by E. selaginoides using RSM with experimental evidence of the underlying biosorption behavior and mechanism.