Efficient Schiff base ligand for selective Cd(ii) and Pb(ii) removal from water†

Abstract

This study reports the development and evaluation of a novel Schiff base ligand, 2-((E)-(4-aminophenylimino)methyl)benzoic acid, for the efficient removal of lead(II) and cadmium(II) from aqueous solutions. The ligand was synthesized via a simple condensation route and characterized to confirm its structural and functional properties. Batch adsorption experiments were performed to investigate the effects of pH, temperature, metal ion concentration, contact time, and competing ions. The ligand exhibited high sorption capacities—84.0 mg g⁻¹ for Pb(II) and 71.0 mg g⁻¹ for Cd(II)—with optimal performance at pH 6.0. Adsorption kinetics followed a pseudo-second-order model, while equilibrium data fit well with the Langmuir and Sips isotherms, indicating chemisorption and monolayer coverage. Thermodynamic analysis confirmed the spontaneous and exothermic nature of the process. The ligand demonstrated excellent reusability over multiple cycles and retained strong selectivity in the presence of competing ions and in real wastewater. These findings suggest that the synthesized ligand is a promising and sustainable candidate for heavy metal remediation in water treatment applications.