Cobalt-polydopamine nanocomposite for efficient removal of Pb(II) and Cd(II) from water: Synthesis, characterization, and adsorption mechanisms

This study investigates the enhanced adsorptive removal of lead (Pb (II)) and cadmium (Cd (II)) ions from drinking water using a cobalt-doped polydopamine (Co/PDA) composite. The Co/PDA was synthesized through a co-precipitation method and characterized by various techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Under optimized conditions, the composite achieved removal efficiencies of 91.8% for Pb (II) and 89.9% for Cd (II) at an adsorbent dosage of 1.25 mg/L, a contact time of 75 minutes, and an agitation speed of 180 rpm. The optimal pH values for maximum adsorption were found to be 8 for Pb (II) and 7 for Cd (II) ions. The adsorption process was well-described by the Langmuir isotherm model, with high R² values (0.9999 for Pb (II) and 0.9998 for Cd (II)), indicating a monolayer adsorption on a homogeneous surface. Kinetic studies revealed that the adsorption followed a pseudo-second-order model, with rate constants of 24.272 g/mg·min for Pb (II) and 30.303 g/mg·min for Cd (II). These findings highlight the Co/PDA composite as a promising, cost-effective solution for effectively removing heavy metal ions from aqueous solutions, emphasizing its potential application in water treatment technologies.