Experimental and theoretical study of malachite green adsorption on CaSiO3/CuO nano-ceramic adsorbent: Molecular and physicochemical insights

Copper oxide–modified wollastonite (CaSiO ₃) was synthesized via a controlled coprecipitation route and assessed as a nano-ceramic adsorbent for malachite green (MG) removal from aqueous media. Adsorption behavior was evaluated using conventional kinetic and isotherm models coupled with statistical physics analysis to elucidate molecular-scale mechanisms. The adsorption process followed pseudo-first-order kinetics, while the Liu isotherm best described equilibrium data, yielding maximum capacities of 103.75–117.11 mg/g. Statistical physics modeling indicated a multi-docking adsorption mechanism, with steric parameter values (n = 0.39–0.78) suggesting predominantly horizontal alignment of MG molecules on the adsorbent surface. Increasing temperature enhanced both active site density and saturation capacity, confirming the endothermic nature of adsorption. Low adsorption energies (1.26–3.42 kJ/mol) demonstrated that physisorption dominated, driven mainly by electrostatic and van der Waals interactions. Thermodynamic parameters confirmed the spontaneous nature of MG uptake. The developed ceramic adsorbent exhibited excellent stability and reusability over five adsorption-desorption cycles.