Superior adsorption of Re(VII) by anionic imprinted chitosan-silica composite: Adsorption performance, selectivity and mechanism study

In this study, a three-dimensional chitosan/mesoporous silica composite material (I-CTS-KIT-6) was successfully synthesized by one-step method using ion imprinting technology. To overcome the enormous cost problem, MoO 4 2− with similar radius to ReO 4 − was selected as template ion. In addition, the adsorbent was prepared by using glutaraldehyde and chitosan as crosslinking agents and monomers and TEOS as silicon source in the process of imprinting. The effects of pH values, mass of chitosan and template ion, contact time, temperature and concentration on Re(VII) adsorption were studied. The results revealed that the I-CTS-KIT-6 has the saturated adsorption capacity of 368.8 mg g −1 at pH 3.0 for Re(VII), and the adsorption process corresponded to Langmuir isotherm and pseudo-second-order kinetics. Especially, the I-CTS-KIT-6 has higher selectivity for rhenium ions compared with the non-imprinted adsorbent. To verify the adsorption mechanism, density functional theory (DFT) was adopted to analyze the binding patterns of Re(VII) with the I-CTS-KIT-6. The test analysis and calculation results further mentioned that the adsorption mechanism is mainly three N atoms of I-CTS-KIT-6 coordinated with three oxygen atoms of ReO 4 −, which provides the theoretical foundations and explanations for adsorption process.