Two-Dimensional Titanium Carbides (Ti ₃C ₂T _x) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium

Abstract

Titanium carbides (MXenes) are promising multifunctional materials. However, the negative surface charge and layer-by-layer restacking of MXenes severely restrict their application in the field of anionic pollutants, including in hexavalent chromium (Cr(VI)). Herein, Ti ₃C ₂T _x MXenes was functionalized through in situ polymerization and intercalation of poly(m-phenylenediamine) (PmPD), then Ti ₃C ₂T _x/PmPD composites were obtained. Delightedly, Ti ₃C ₂T _x/PmPD composites exhibited positive surface charge, expanded interlayer spacing, and enhanced hydrophobicity. Furthermore, the specific surface area of Ti ₃C ₂T _x/PmPD composite was five and 23 times that of Ti ₃C ₂T _x and PmPD, respectively. These advantages endowed Ti ₃C ₂T _x/PmPD composite with an excellent adsorption capacity of Cr(VI) (540.47 mg g ⁻¹), which was superior to PmPD (384.73 mg g ⁻¹), Ti ₃C ₂T _x MXene (137.45 mg g ⁻¹), and the reported MXene-based adsorbents. The Cr(VI) removal mechanism mainly involved electrostatic adsorption, reduction, and chelation interaction. This study developed a simple functionalization strategy, which would greatly explore the potential of MXenes in the field of anionic pollutants.