Microstructure and surface control of MXene films for water purification

Heavy metal ions (HMIs), such as those containing chromate and arsenic, are toxic and need to be removed from drinking water to protect public health. Films based on two-dimensional materials are promising regarding the removal of HMIs from water, but they typically use pressure-driven filtration. This study reports the application of two-dimensional titanium carbide (Ti3C2Tx MXene)-based films for pressure-free removal of multiple negatively and positively charged HMIs from water. The Ti3C2Tx MXene-based film's microstructure was optimized by insertion of reduced graphene oxide between the layers, and the film's surface was progressively hydroxylated to increase the accessibility of Ti3C2Tx, improve the film's wettability and enhance the adsorption and reduction of HMIs. These steps synergistically improved the film's HMI removal efficiency. This study provides a straightforward paradigm to manipulate the pivotal solid-liquid interactions for water purification under pressure-free conditions using two-dimensional materials-based films. Moreover, it could open a new vista of rationally designed, versatile, Ti3C2Tx-based films for target applications.