Biosorption of Cd(II) from aqueous solutions using microalgae Chlorella sorokiniana dry biomass: A sustainable approach for water remediation

The occurrence of Cd(II) ions in water presents significant environmental and health hazards, necessitating cost-effective and sustainable removal methods. This study investigates the biosorptive capacity of dried biomass from Chlorella sorokiniana (C. sorokiniana) for the removal of Cd(II) ions from aqueous solutions. Batch studies were performed at 25 °C to investigate the effects of initial pH, biosorbent dosage, Cd(II) concentration, and contact time. Maximum experimental uptake was observed at pH 7, with a sorption capacity of 92 mg/g. The characterization using FTIR, SEM-EDX, and XRD validated the significant interaction between Cd(II) ions and the microalgal biomass. Kinetic modeling indicated that the biosorption process adhered to a pseudo-second-order model (R² = 0.9913), although the equilibrium data corresponded most closely with the Freundlich isotherm (R² = 0.9829), signifying heterogeneous multilayer adsorption. The biosorption process involves a combination of physisorption and chemisorption mechanisms, as evidenced by a ΔG° value close to − 20 kJ/mol, along with spectroscopic evidence and kinetic model fitting. The results indicate the potential of C. sorokiniana as an effective and environmentally sustainable biosorbent for the removal of Cd(II) from polluted water.