Delamination of multilayer Ti3C2Tx MXene alters its adsorpiton and reduction of heavy metals in water

MXenes are considered as an emerging class of two-dimensional (2D) adsorbent for various environmental applications. In this work, two different morphologies of Ti 3 C 2 T x MXene (multilayer (ML-Ti 3 C 2 T x ) and delaminated titanium carbide (DL-Ti 3 C 2 T x )) were prepared through mild in situ HF etching and further delamination . The structural differences between the two were explored with a focus on their effects on the performance and mechanism of removing heavy metals from water. In comparison to ML-Ti 3 C 2 T x , DL-Ti 3 C 2 T x had more oxygen-containing functional groups, higher specific surface area (19.713 vs. 8.243 m 2 /g), larger pore volume (0.135 vs. 0.040 cm 3 /g), higher maximum Pb(II) adsorption capacity (77.0 vs. 56.68 mg/g), but lower maximum Cu(II) adsorption capacity (23.08 vs. 55.46 mg/g). Further investigation revealed that the removal of Pb(II) by the MXenes was mainly controlled through electrostatic attraction and surface complexation mechanisms, while Cu(II) was removed mainly through surface reduction by Ti-related groups. Because delamination of ML-Ti 3 C 2 T x increased the surface area and surface functional groups, DL-Ti 3 C 2 T x became a better sorbent for Pb(II) in water. During sonication, however, delamination inevitably led to partial oxidation of Ti 3 C 2 T x nanosheets and thus weakened the reducing ability of DL-Ti 3 C 2 T x for Cu(II) in water. Nevertheless, both ML- and DL-Ti 3 C 2 T x not only exhibited excellent heavy metal adsorption capacity under different solution conditions, but also showed good reusability. Findings of this study indicate that Ti 3 C 2 T x MXenes are promising adsorbents for treating heavy metal pollutants in water.