Metallic 1T/1T' phase TMD nanosheets with enhanced chemisorption sites for ultrahigh-efficiency lead removal.

Abstract

Two-dimensional (2D) materials, as adsorbents, have garnered great attention in removing heavy metal ions (HMIs) from drinking water due to their extensive exposed adsorption sites. Nevertheless, there remains a paucity of experimental research to remarkably unlock their adsorption capabilities and fully elucidate their adsorption mechanisms. In this work, exceptional lead ion (Pb²⁺) (a common HMI) removal capacity (up to 758 mg g^-1) is achieved using our synthesized metallic 1T/1T' phase 2D transition metal dichalcogenide (TMD, including MoS₂, WS₂, TaS₂, and TiS₂) nanosheets, which hold tremendous activated S chemisorption sites. The residual Pb²⁺ concentration can be reduced from 2 mg L^-1 to 2 μg L^-1 within 0.5 min, meeting the drinking water standards following World Health Organization guideline (Pb²⁺ concentrations <10 μg L^-1). Atomic-scale characterizations and calculations based on density functional theory unveil that Pb²⁺ bond to the top positions of transition metal atoms in a single-atom form through the formation of S-Pb bonds. Point-of-use (POU) devices fabricated by our reported metallic phase MoS₂ nanosheets exhibit treatment capacity of 55 L-water g^-1-adsorbent for feed Pb²⁺ concentration of 1 mg L^-1, which is 1-3 orders of magnitude higher than other 2D materials and commercial activated carbon.