Theoretical and Experimental Analysis of Pb (II) Ion Adsorption Using Surface Modified Macroalgal Biosorbents: Modelling and Desorption Study

Abstract

The critical issue of lead pollution in wastewater, which, even in low quantities, presents serious health risks, is the focus of this investigation. The study investigates the adsorption capacities of Physically Modified Seaweed Biosorbent (PMSB) and Chemically Modified Seaweed Biosorbent (CMSB) for Pb (II) ion removal. SEM, EDX, FTIR, and XRD techniques were used to analyze surface morphology, elemental composition, functional groups, and crystallographic structure. Furthermore, it assesses the effect of pH, biosorbent dosage, temperature, initial Pb (II) ion concentration, and contact time on adsorption efficiency. The results indicated that the optimal parameters were 303 K in temperature, 5.0 in pH, and 1 g/L and 2.5 g/L of biosorbent for CMSB and PMSB, respectively, with contact durations of 40 and 80 min. The Freundlich isotherm model indicated adsorption on heterogeneous surfaces, with maximum adsorption capacities of 149.8 mg/g for PMSB and 175.5 mg/g for CMSB, demonstrating efficient Pb (II) ion removal. Higher R² values from kinetic investigations indicate that the pseudo-first-order model fits PMSB and CMSB better for the adsorption of Pb (II) ions. The thermodynamic analysis found negative ΔH° and ΔG° values, indicating an exothermic and spontaneous adsorption mechanism, respectively. Desorption tests showed that CMSB retains greater efficiency across several cycles, demonstrating its durability and adaptability for long-term use. According to the studies, chemical modifications significantly enhance CMSB’s adsorption stability and effectiveness, which makes it a viable option for eliminating Pb (II) ions from wastewater and improving water quality.