Synthesis of ZIF-8/chitosan composites for Cu removal from water.

In this work, a kind of novel Chitosan (Cs)-doped zeolite imidazole framework (ZIF-8@Cs) with a larger surface area and a smaller pore size was synthesised via a facial solvothermal approach and applied to remove Cu from mine wastewater. Compared to nondoped ZIF-8, ZIF-8@Cs exhibited a stronger adsorption performance and removal efficiency. The reason was that ZIF-8@Cs doped by the Cs could suppress the aggregation and increase the monodispersity of ZIF-8. Using the high-performance ZIF-8@Cs, as a novel adsorbent, was successfully developed for the efficient removal of Cu from mine wastewater. Various parameters, such as contact time, initial Cu concentration, adsorbent dosage, and pH, were investigated. The results showed that a removal efficiency of 85% was obtained at 4 h contact time for a Cu concentration of 30 mg/L at the optimum pH of 6.0. Equilibrium data were analysed using different isothermal models and kinetic models, analytic results indicated that the capture of Cu by ZIF-8@Cs could favourably comply with the pseudo-first-order kinetic model and Langmuir isotherm model. The single-layer adsorption of Cu on ZIF-8@Cs was dominated by diffusional mass transfer. Additionally, the results of the thermodynamic analysis indicated that the adsorption of Cu by ZIF-8/Cs was a spontaneous, exothermic, and ordered process. Overall, the results reported herein indicated that ZIF-8/Cs with high adsorption efficiency are very attractive and imply a potential practical application for the removal of potentially toxic elements in wastewater.