In situ growth of ZIF-8 on carboxymethyl chitosan beads for improved adsorption of lead ion from aqueous solutions

In this study, a method for the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on carboxymethyl chitosan beads (BCMC) to produce a composite adsorbent (BCMC@ZIF-8) for the removal of Pb2+ from water is proposed. The results revealed that the utilization of the BCMC as a framework enhanced the stability of ZIF-8, and the presence of the latter in the composite improved the removal efficiency of Pb2+ from water. Data from X-ray photoelectron spectroscopy analysis and adsorption kinetics revealed that the adsorption mechanism included diffusion and the sharing/transfer of electrons between BCMC@ZIF-8 and Pb2+. The maximum adsorption capacity of BCMC@ZIF-8 fitted using the Langmuir model was 566.09 mg/g. Results of the experiments on the regeneration of the adsorbent and its stability in water further indicated that BCMC improved the stability of ZIF-8. This study demonstrated that the stability of metal-organic framework (MOF) materials, which exhibited high efficiencies for the removal of heavy metals in water can be improved through fixation of the polymer skeleton. Thus, the present study offers practical and theoretical guidance for the application of MOF materials in water treatment.