Preparation and characterization of the eco-friendly chitosan/vermiculite biocomposite with excellent removal capacity for cadmium and lead

The chitosan/vermiculite biocomposite (CTS-VMT) was synthesized successfully with epichlorohydrin (ECH) cross-linking agent and used to remove cadmium and lead from the aqueous solution. CTS-VMT was characterized by FTIR, SEM, BET, TG-DTG, zeta potential and XPS. The effects of critical parameters including solution pH, contact time, initial heavy-metal concentration and adsorbent regeneration were investigated. Besides, adsorption mechanisms were also researched. The results indicated that chitosan molecule cannot intercalate into the interlayer space but cross link on the external surface of VMT. The maximum adsorption capacities for Cd(II) and Pb(II) were 58.48 mg g− 1 and 166.67 mg g− 1 at pH 4, respectively. The adsorption process fitted well the pseudo-second-order model and the adsorption isotherms could be correctly simulated by the Langmuir isotherm model. The zeta potential analyses put forward that electrostatic attraction existed in the adsorption process between the metal cations and CTS-VMT. However, the principal mechanism for adsorption on CTS-VMT was chelation according to the kinetic study and XPS analyses. Moreover, the desorption experiments revealed the prepared adsorbent tended to be regenerated by using HCl and the removal rations for four cycles were all > 90%. Therefore, the synthesized CTS-VMT in this study has the potential to be utilized as an eco-friendly adsorbent for removing Cd(II) and Pb(II).