Highly Efficient and Selective Hg(II) Removal from Water Using Multilayered TiCO MXene via Adsorption Coupled with Catalytic Reduction Mechanism.

Mercury (Hg) removal is crucial to the safety of water resources, yet it lacks an effective removal technology, especially for emergency on-site remediation. Herein, multilayered oxygen-functionalized TiC (TiCO) (abbreviated as M-TiC) nanosheets were prepared to remove Hg(II) from water. The M-TiC has demonstrated ultrafast adsorption kinetics (the concentration decreased from 10 400 to 33 μg L in 10 s), impressively high capacity (4806 mg g), high selectivity, and broad working pH range (3-12). The density functional theory (DFT) calculations and experimental characterizations unveil that this exceptional Hg(II) removal is owing to the distinct interaction (., adsorption coupled with catalytic reduction). Specifically, Ti atoms on the {001} facets of M-TiC prefer to adsorb Hg(II) in the form of HgClOH, which subsequently undergoes homolytic cleavage to form radical species (., OH and HgCl). Immediately, the HgCl radicals dimerize and form crystalline HgCl on the edges of M-TiC. Up to ∼95% of dimeric HgCl can be efficiently recovered via facile thermal treatment. Notably, owing to the adsorbed OH and energy released during the distinct interaction, M-TiC has been oxidized to TiO/C nanocomposites. And the TiO/C nanocomposites have shown to have better performance on the photocatalytic degradation of organic pollutants than Degussa P25. These exceptional features coupled with mercuric recyclable nature make M-TiC an outstanding candidate for rapid/urgent Hg(II) removal and recovery.