Thermally air oxidation of activated carbon for enhanced lead(II) removal with preliminary insights into CO2 and 222radon adsorption.

This study evaluates a simple thermal air oxidation strategy to enhance commercial steam-activated carbon from coconut shells (SAC) for multifunctional environmental remediation. SAC samples oxidized at different durations showed that SAC-90 (90 min at 350 °C) achieved the highest Pb2+ adsorption capacity (87.96 mg g⁻1), nearly twice that of SAC (44.50 mg g⁻1), due to increased surface oxygen-containing functional groups and specific surface area. Adsorption isotherm analysis indicated that the Langmuir and Redlich-Peterson models best described Pb2+ uptake on SAC-90, reflecting predominantly monolayer adsorption on a heterogeneous surface. Thermodynamic parameters confirmed that Pb2+ adsorption on SAC-90 is endothermic and spontaneous. In addition, SAC-90 displayed enhanced CO₂ adsorption (1.61 mmol g⁻1) and substantially improved 222Rn uptake (0.2933 cps g⁻1) while maintaining good performance over five adsorption-desorption cycles. Overall, thermal air oxidation provides an efficient and environmentally benign route to upgrade commercial activated carbon for simultaneous treatment of aqueous Pb2+ and gaseous CO₂ and 222Rn.