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First-Principles Insights into the Selective Separation of MoS 4 2- and WO 4 2- : Crucial Role of Hydration Structures.

Mingjun HanDong FanChenyang ZhangHengzhi LiuYong PeiJie LiJianhua ChenWei SunZhongwei Zhao
Published in: Inorganic chemistry (2024)
The selective separation of MoS 4 2- and WO 4 2- using quaternary ammonium salt through solvent extraction or ion exchange methods has been well-established in the metallurgical industry. However, the conventional electrostatic adsorption theory falls short in explaining the separation mechanism. Through first-principles density functional theory (DFT) calculations and newly self-developed deep potential molecular dynamics (DPMD) simulation method, our work first reveals that the disparity in hydration structures of MoS 4 2- and WO 4 2- plays a crucial role in their selective separation. It is proposed that MoS 4 2- and WO 4 2- anions undergo hydration to form [MoS 4 (H 2 O) n ] 2- and [WO 4 (H 2 O) n ] 2- , respectively, facilitated by hydrogen bond (H-bond) interactions. Emphasis is placed on the discrepancy between MoS 4 2- and WO 4 2- in hydration structures by the hydration energy, Hirshfeld charge, evaluation of weak interactions, hydration radius, hydration coordination number, and H-bonds distribution. MoS 4 2- presents a larger first hydration radius and a lower first hydration coordination number due to weaker interactions with H 2 O, while WO 4 2- is subjected to enhanced hydration shielding, resulting in MoS 4 2- anions being more susceptible to be selectively separated by a quaternary ammonium salt. This insight paves the way for the selective separation of MoS 4 2- and WO 4 2- , further bridging the gap between theory and industry applications.
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