Evaluation of sodium thiosulfate activated carbon for high-performance mercury removal from aqueous solutions

The current study presents a novel approach for the synthesis of activated carbon that is both environmentally benign and efficient in removing mercury from aqueous solutions. Activated carbon was produced by utilizing walnut shells as a renewable precursor and sodium thiosulfate as a benign activating agent. This approach effectively addressed environmental concerns traditionally associated with activated carbon fabrication. The resulting product exhibited a BET surface area of 451.1 m2/g and a total pore volume of 0.303 cm3/g. Comprehensive kinetic and equilibrium studies illustrated the underlying mechanisms governing mercury adsorption. Advanced characterization techniques, including SEM, EDX, XPS, and N2 adsorption/desorption isotherms, were employed to provide detailed insights into the adsorption process. The maximum adsorption capacity demonstrated by the synthesized AC is 164.4 mg/g under the following experimental conditions: 35 °C temperature, pH solution of ≈ 2, 0.02 g mass, and 180 RPM of mechanical shaking. The process was effectively described by the Freundlich isotherm and pseudo-second-order kinetics, which emphasized the significance of both chemical and physical adsorption.