Synthesis and Characterization of KOH-modified Alhagi biomass for Efficient Biosorption of Cadmium (Cd2+) and Lead (Pb2+) from Aqueous Solutions

Abstract

Water systems are polluted by heavy metals and need cheap, effective biosorbents. A major knowledge gap is that raw lignocellulosic materials have low intrinsic capacities and are not directly applicable without specific modifications. In this work, a new highly porous biosorbent (KMAB) has been prepared by chemical activation of Alhagi biomass with potassium hydroxide (KOH) for removal of cadmium (Cd2+) and lead (Pb2+) from aqueous solutions. Characterization showed high BET surface area of 285.4 m2/g and mesoporous network (pore diameter: 2.61 nm). Batch experiments (200 mg/L initial concentration) gave maximum removal efficiencies and adsorption capacities (qe) of 79% (21.07 mg/g) for Pb2+(0.75 g dose, pH 7.0, 100rpm, 60 min) and 66% (10.56 mg/g) for Cd2+ (1.25 g dose, pH 5.0, 200 rpm, 30 min). Lead showed a higher uptake due to its higher chemical affinity to oxygenated functional groups (verified by FTIR) and lower hydrated radius. Biosorption was predominantly governed by a physical adsorption mechanism (physisorption), supported by intraparticle diffusion through the mesoporous channels and physical electrostatic attraction. KOH- modified Alhagi biomass is a sustainable and highly efficient material for industrial heavy metal remediation.