Efficient removal of Cu(Ⅱ) and Pb(Ⅱ) from water by in situ synthesis of CS-ZIF-8 composite beads

Water pollution caused by heavy metals is still a serious problem, consequently; Developing an efficient adsorbent for easy recovery and separation is an essential issue. In this work, Chitosan-ZIF-8 (CS-ZIF-8) composite beads were prepared by in situ synthesis of a zeolitic imidazolium-based MOF (ZIF-8) on low-cost chitosan (CS) to adsorb Cu(Ⅱ) and Pb(Ⅱ) from water, which were characterized by FT-IR, PXRD and TGA, etc. The optimal adsorption conditions were obtained through a series of the condition optimization. The adsorption of Cu(Ⅱ) and Pb(Ⅱ) by CS-ZIF-8-1:2 was in accordance with both the Langmuir adsorption mode and the pseudo-secondary kinetic model, and the theoretical maximum adsorption amounts were 165.7 mg/g and 131.4 mg/g, respectively. The adsorption thermodynamics demonstrated that the adsorption process of CS-ZIF-8-1:2 on Cu(Ⅱ) and Pb(Ⅱ) was spontaneous and endothermic. The cycling test confirmed the good cycling stability of the adsorbent. In summary, this strategy provides a new idea for designing efficient and easily recyclable Chitosan-MOFs composites for the removal of heavy metals from water.