The development of low-cost, efficient, and environmentally friendly adsorbents capable of simultaneously removing both heavy metals and synthetic dyes from wastewater remains a critical challenge in environmental remediation. In this study, a novel chitosan/pumice (CS/PM) composite was synthesized and evaluated for its multifunctional adsorption performance toward four common and toxic pollutants: lead (Pb(II)), cadmium (Cd(II)), methylene blue (MB), and Congo red (CR). Characterization confirmed the successful integration of chitosan with pumice, resulting in reduced crystallinity, enhanced thermal stability, and active functional groups involved in adsorption. Adsorption experiments demonstrated optimal pollutant removal at a pH value of 6, with the composite exhibiting high affinity for all tested contaminants. The adsorption kinetics followed a pseudo-second-order model, indicating that chemical interactions predominantly govern the adsorption process. Furthermore, the adsorption isotherms closely fit the Langmuir model, followed by the Sips model, suggesting monolayer adsorption on a homogeneous surface with potential heterogeneous interactions. The maximum adsorption capacities of CS/PM, calculated from the Langmuir model, were 150.60 mg/g, 123.14 mg/g, 135.20 mg/g, and 120.33 mg/g for Pb(II), Cd(II), MB, and CR, respectively. This study introduces a straightforward approach for designing porous composite materials with high adsorption capacities, offering promising applications in environmental remediation.
