Two-Dimensional Materials for Heavy Metal Removal

Two-dimensional materials are referring to the materials which are confined in one dimension and growing in another two dimensions. Based on the chemical composition, two-dimensional materials can be further classified into single element layered two-dimensional material, such as graphene and phosphorene, and mixed elements two-dimensional materials, such as transition metal dichalcogenides, MXenes, clay minerals, layered double hydroxides and so on.

This chapter highlights the applications of two-dimensional materials on removing heavy metal ions from aquatic environment. The heavy metal ions removal mechanisms, including surface complexation, van der Waals force, and ion exchange were illustrated combining with typical examples of heavy metal ions removal by two-dimensional materials. Six recently extensively studied types of two-dimensional materials, graphene-based materials, dichalcogenides, MXenes, clay minerals, layered double hydroxides, and layered zeolites, have been discussed in details. Reference to the classification of two-dimensional materials, the most recent researches on developing two-dimensional materials for heavy metal removal, together with a perspective that could be instructive for future research in this topic has been addressed.

By employing different functionalities and techniques, the two-dimensional materials can be fabricated as adsorbents, membranes or electro-device to remove heavy metal from aqueous environment. In this chapter, most of the heavy metal removal by two-dimensional materials mentioned were based on adsorption techniques, because adsorption is one of the most intensive studied techniques for removing heavy metals, especially for novel two-dimensional materials. Besides, the heavy metal removal techniques other than adsorption were also introduced briefly in this chapter.