1T-MoS2 Removes Toxic Metals in Aquatic Systems

1T phase MoS₂ (1T-MoS₂) could remove toxic metals in aquatic systems according to recent research. The research team of the Environmental and Energy Nanomaterials Center of the Nanomaterials and Device Technology Research Department of the Chinese Academy of Sciences Hefei Research Institute used a two-step solvothermal synthesis method to prepare a high-purity 1T- MoS₂, which is chemically stable high, and it can be placed in the air for a year, and maintain a stable wide-spaced structure in the water environment, thereby ensuring the transport of ions, and efficiently removing toxic metals ions in the water, such as hexavalent chromium.

Synthesized MoS₂ nanosheets have disadvantages such as low purity (phase conversion), low stability (charge density), limited active sites and complex preparation procedures, severely hindering their applications, such as in aquatic systems. Herein, a facile method was designed to synthesize high-phase-purity and high-negative-charge-density solar-induced atomic-defect-rich 1T-MoS2 (S-ADR- MoS₂) nanosheets.

The metallic 1T phase structure of MoS₂ is often used as a permeable channel for ion transmission and adsorption and to remove heavy metal ions from water treatment. However, the researchers found that the stability of MoS₂ after adsorption is poor, and the 1T phase will completely transform into the 2H phase or the wide-spaced structure will collapse, which will reduce its cycle durability.

In addition, the high-purity 1T phase molybdenum dioxide prepared by the vapor deposition method is also difficult to apply to aquatic systems in batches. Therefore, to improve the removal ability of toxic metals ions in water, it is urgent to synthesize high-purity 1T phase MoS₂ and ensure that the interlayer structure is stable during the adsorption process and will not collapse.

In response to the above problems, the researchers of the Institute of Solid State, based on the one-step hydrothermal reaction to obtain the mixed phase MoS₂, used ethanol for phase modulation, and successfully synthesized a high-purity 1T-MoS₂ with a wide interlayer structure and rich sulfur vacancies.

Experiments have shown that the percentage content of the 1T phase in the 1T-MoS₂ is close to 100%, and it can maintain a high degree of stability even in the 360-day exposure to the air, so it can well remove chromium ions in the water. In addition, under certain conditions, 1T-MoS₂ nanosheets exhibit excellent Cr(VI) adsorption capacity (200.3mg/g at p H=6), which is more than twice that of mixed phase MoS₂ and 2H phase MoS₂, and It can maintain a stable phase structure even during multiple adsorption cycles.

The study on the adsorption mechanism of Cr(VI) shows that the adsorption of chromium is due to insufficient coordination of Mo(IV) as an active site, and is related to the oxidation-reduction reaction in the removal process.

This research work is of great significance to the batch preparation of 1T-MoS2 and the application of new molybdenum dioxide-based adsorbents in aquatic systems. Relevant research results are titled "Ethanol introduced synthesis of ultrastable 1T-MoS₂ for removal of Cr(VI)" and published in the Journal of Hazardous Materials.

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