MXene-based composites as emerging adsorbents for removal of environmental pollutants

The presence of water pollutants poses a significant threat to both human health and aquatic ecosystems, highlighting the necessity of their removal. Among various removal technologies, adsorption is an effective and reliable method for removing harmful substances from water and wastewater, and its performance is closely related to the structural characteristics of the adsorbent. MXene is a new class of two-dimensional (2D) inorganic materials, consisting of atomically thin layers, mainly including transition metal carbides, nitrides, or carbon–nitrogen compounds. With a unique 2D structure, large specific surface area, and abundant functional groups, MXene shows good removal effects on various pollutants. This review focused on MXene-based composites as emerging adsorbents for the removal of environmental pollutants. First, recent research progress on the structure and properties of MXene-based composites, as well as their synthesis and modification methods, was studied. Additionally, the adsorption performance and mechanisms of different pollutants, including metal cations, radionuclides, and organic pollutants onto MXene-based composites, were systematically reviewed. Our research indicates that the number of layers and surface functional groups of MXene, as well as the initial concentration, pH, and temperature of the solution, significantly influence adsorption performance. Additionally, MXene-based composites (e.g., hydroxyl groups, oxygen, fluorine, etc.) are able to strongly interact with pollutants through electrostatic interactions, ion-exchange interactions, and surface complexation. These adsorbents also exhibit good regeneration ability and recycling performance. Finally, we summarized the challenges faced by MXene-based adsorbents, such as the need to focus more on the efficient modification of MXene materials, improving their performance in actual water bodies, considering their biocompatibility, developing new MXene materials, and promoting sustainable development, among others. We also outlined future research directions for MXene-based materials. This review deepens our understanding of MXene-based composite materials and lays the foundation for their application in pollutant removal.