Enhanced Cadmium Removal by Raw Argan Shell Adsorbent: Experimental and Theoretical Investigations for Ecological Applications

Abstract

The removal of cadmium ions (Cd2+) using raw argan shells (ArS) was optimized through experimental and theoretical studies. Adsorption experiments revealed optimal conditions at an adsorbent dose of 3.5 g, an initial Cd2+ concentration of 20 mg·L−1, and a pH of 8, achieving a maximum sorption capacity of 3.92 mg·g−1. The kinetic analysis showed that the adsorption followed a pseudo-second-order model (R2 = 0.98), and the Langmuir isotherm model predicted a maximum adsorption capacity of 4 mg·g−1. Thermodynamic analysis indicated an endothermic adsorption process, with ΔG° shifting from positive to negative as temperature increased, confirming that adsorption is favored at higher temperatures. Desorption studies demonstrated that HCl was the most effective eluting agent, achieving a desorption efficiency of 90.02%, followed by HNO3 (76.65%) and CH3COOH (71.59%). The varying desorption efficiencies were attributed to differences in acid strength and ionic interactions with Cd2+. This study demonstrates the potential of raw argan shells as an efficient, reusable, and sustainable biosorbent for cadmium removal, offering a promising solution for water treatment and environmental remediation.