Abstract
With their natural abundance and minimal processing requirements, clays hold the potential to serve as economical adsorbents for various heavy metals. In this research, the adsorption capacity of hydrochloric acid (HCl) modified clay to adsorb mercury(II) (Hg2+) ions from aqueous solutions was investigated. The parameters affecting the adsorption capacity were determined by studying the initial metal ion concentration, contact time, and temperature effects. For natural clay, an optimal initial concentration of 400 mg/L and a contact time of 50 minutes were identified. Meanwhile, modified clay showed best results with an initial concentration of 400 mg/L and a contact time of 60 minutes for Hg2+ ions. The analysis of isotherm data revealed that the Langmuir isotherm model exhibited the best fit for both materials in Hg2+ ion adsorption. At temperatures of 298 K, 308 K, and 318 K, the adsorption capacity for natural clay and Hg2+ ions were found to be 4.56, 5.01, and 5.08 mg/g, respectively. Meanwhile, the modified clay displayed adsorption capacities of 11.12, 11.37, and 12.30 mg/g for Hg2+ ions at the same temperatures. Additionally, the kinetic analysis determined that the pseudo-second-order kinetic model was the best fit for both materials in Hg2+ ion adsorption. The adsorption experiments investigated the adsorption mechanisms of Hg2+ metal ions on both natural clay and modified clay, with results indicating that the modified clay had a higher adsorption capacity for metal ions compared to the raw clay.