Mechanistic and performance evaluation of SnO2-AcCS composite in the adsorptive remediation of hg (II) ions from aqueous systems

Mercury (Hg) pollution has severe consequences for both environmental and human health with extraordinary toxicity and ability to persist in aquatic environment. Present study investigates the potential of tin (IV) oxide-coconut shell activated carbon composite (SnO2-AcCS) as eco-friendly and cost-effective material for eradicating Hg (II) ions in polluted water. The SnO2-AcCS composite was synthesized by a low-cost method and characterized using XRD, SEM, and FTIR spectroscopy. Adsorption batch experiments evaluated the influence of pH, time, dose of adsorbent, adsorbate initial concentration, and temperature on adsorption performance. Evaluation of adsorption isotherms on the experimental data obtained revealed a strong fit with the Freundlich and Langmuir models indicating that Hg (II) ions adsorption onto SnO2-AcCS composite is beyond single-layer with theoretical maximum adsorption of 333.33 mgg− 1 and the separation factors calculated for all initial concentrations fell below 1. Thermodynamic evaluation illustrated the viability, spontaneity and endothermic characteristics of the adsorption process with temperature between of 20–65 °C. Adsorption kinetic of Hg(II) ions onto SnO2-AcCS composite is well presented by the pseudo-second-order model, with k2 values decreasing from 0.006 to 0.002 g mg− 1 min− 1 as initial concentration of mercury ions increases. SnO2-AcCS composite demonstrated excellent reusability over five cycles, maintaining over 70% efficiency. These findings highlight the composite’s potential as a practical solution for mercury remediation in water treatment.