Highly efficient and ultra-fast Pb(II) adsorption by a chitosan-modified Fe3O4@UiO-66-COOH core–shell structure

In this study, an effective and magnetically separable nano-adsorbent of Fe 3 O 4 @UiO-66-COOH@chitosan was developed by coating chitosan on Fe 3 O 4 @UiO-66-COOH core–shell using a novel solvothermal method. In this innovative approach, the efficacy of amine and hydroxyl functional groups present in chitosan was utilized in conjunction with carboxylic acid functional groups, the extensive surface area, metal nodes, and pores of the metal–organic framework (MOF) are for efficient and rapid adsorption of lead (Pb(II)) ions from water. The nano composites were characterized utilizing a variety of analytical techniques, including XRD, FTIR, TGA, BET, SEM, TEM, and VSM. The comparative analysis of the kinetic and isotherm parameters for both Fe 3 O 4 @UiO-66-COOH and Fe 3 O 4 @UiO-66-COOH@chitosan confirmed the beneficial effects of the chitosan coating. The Fe 3 O 4 @UiO-66-COOH @chitosan conformed to the Langmuir isotherm model, with the predicted maximum adsorption capacity for Fe 3 O 4 @UiO-66-COOH@chitosan being established at 526.31 mg/g, notably exceeding the 208.33 mg/g capacity observed for Fe 3 O 4 @UiO-66-COOH. Furthermore, the Fe 3 O 4 @UiO-66-COOH@chitosan achieved a remarkable 92% adsorption efficiency within 5 min, reaching equilibrium within 60 min, while Fe 3 O 4 @UiO-66-COOH required 300 min to reach equilibrium. The adherence of Fe 3 O 4 @UiO-66-COOH@chitosan to the pseudo-second-order kinetic model and the isotherm parameters indicated a strong chemical affinity of Pb(II) ions to the adsorbent. The optimal pH and dosage for adsorption were found to be pH = 7 and 0.5 g/L. Based on the thermodynamic parameters, the adsorption process was endothermic and spontaneous, exhibiting a rise in entropy. Moreover, Fe 3 O 4 @UiO-66-COOH@chitosan maintained high adsorption efficiency even after five consecutive cycles and across various real water samples, exhibited reasonable selectivity toward Pb 2+ in the presence of common coexisting cations, demonstrating its potential for industrial applications.