MXene@MOF for synergetic removal of Cr(VI) by adsorption and reduction

MOF-based nanomaterials have shown great potential for absorbing Cr(VI) contamination, however, reducing Cr(VI) to Cr(III) with low solubility and toxicity has been challenging. In this work, MXene@MIL-53-NH2 nanocomposite was fabricated and supreme to pristine MOF and MXene in Cr(VI) removal. The hybridization of MOF and MXene increased the distribution coefficient (LgKd=4.8), demonstrating the large binding affinity to Cr(VI) oxyanions and enhanced Cr(VI) adsorption of MXene@MIL-53-NH2. According to batch experiment analysis, 0.6MXene@MIL-53-NH2 showed a high Cr(VI) removal at pH 3. The adsorption kinetics fitted to pseudo-second-order model, and adsorption isotherms followed Langmuir and Temkin models well. The calculated theoretical adsorption capacity was up to 224.46 mg·g−1. The thermodynamics revealed that the reaction process was spontaneous and endothermic. Notably, the adsorption and reduction processes simultaneously determine the Cr(VI) sequestration on MXene@MIL-53-NH2. Spectroscopic and electrochemical analysis showed that MXene@MIL-53-NH2 boosted the conversion of adsorbed Cr(VI) to Cr(III) by promoting electron conversion and elevating the electron-donating potential. The prepared MXene@MIL-53-NH2 showed superior ionic interference resistance and recyclability under experimental conditions, which provided information for better evaluation and design of nanomaterials for Cr(VI) remediation.