(173aa) Molecular Dynamics Predicted Selenium Extraction to Reduce Selenate Toxicity in Wastewater

Selenium (Se) is an essential micronutrient for animals and humans at low concentrations, but it becomes extremely toxic at higher levels. Its presence in the environment arises from both natural sources (such as volatilization of water bodies, terrestrial weathering, and volcanic activities) and anthropogenic activities (including fossil fuels, mining, and oil refining). In water systems, selenate (SeO₄²⁻) and selenite (SeO₃²⁻) are the predominant Se species. Selenate, being highly soluble and poorly adsorbed by sediments and soil, poses a significant challenge due to its mobility and potential bioaccumulation. Selenite, though less soluble, can also accumulate in aquatic ecosystems. The consequences of selenium toxicity are far-reaching. Acute exposure to Se compounds can lead to neurological issues, respiratory problems, and other health complications. Chronic exposure has been linked to cancer development, decreased sperm movement, and disruptions in insulin signaling. Therefore, understanding the occurrence and effective management of selenate and selenite in water is critical for safeguarding human health and the environment.

In our computational study predicting selenate breakdown to selenium at different pH using AIMD involves initializing the system with selenate ions, introducing excess electrons, and allowing the dynamics to evolve. By analyzing trajectories and electronic properties, we have gained the insights into the reduction process of selenite/selenate and the formation of selenium species in steps like Se2 à Se4 à Se8. We have adjusted H+ concentration and convergence criteria appropriately to accurately predict reaction conditions to precipitate Se8 from water. Based on the simulation guided pH, experiments were performed and we were able to precipitate Se8 from selenate containing water at room temperature.