Fabrication of a novel magnetic carbon nanotube coated with polydopamine modified with EDTA for removing Cd2+ and Pb2+ ions from an aqueous solution

This work demonstrates the preparation of a new, effective, and reusable magnetic adsorbent by functionalizing dopamine with ethylenediaminetetraacetic dianhydride and polymerizing it on the surface of magnetic carbon nanotubes (EDTA@PD-CNT/Fe₃O₄). The adsorbent was analyzed using XRD, FT-IR, Zeta potential, FE-SEM, EDX, BET, TGA, DTA, and VSM. The synthesized adsorbent was used to remove lead and cadmium ions from aqueous solution. The adsorption process was improved by optimizing key parameters such as pH, adsorbent dosage, contact time, and ion concentration. For both ions, the thermodynamic data of the processes and adsorption kinetics were examined. Analyzing the experimental data revealed that the Langmuir isotherm was the most appropriate model, and the examination of adsorption kinetics showed a pseudo-second-order equation. The adsorption process by the EDTA@PD-CNT/Fe₃O₄ adsorbent was spontaneous and endothermic, according to the thermodynamic data, for Cd²⁺ and Pb²⁺, the highest adsorption capacities were found to be 204.54 mg g^-1 and 376.48 mg g^-1, respectively.