With the rapid development of nuclear power worldwide, the demand for uranium continues to increase. As a consequence, large quantities of uranium-containing wastewater are generated throughout the nuclear fuel cycle as well as during spent fuel reprocessing. Uranium (U) is highly chemical toxic and strongly carcinogenic to the living system. Therefore, it is important to develop materials that can capture U(VI) ions efficiently and selectively.
In a study published in Chem. Eng. J., Prof. FENG Meiling from Prof. HUANG Xiaoying's research group at the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported a layered manganese thiophosphate intercalated with NH4+, namely (NH4)0.48Mn0.76PS3·H2O (N-MPS), which could rapidly and selectively separate U(VI) from complex solutions. This is the first report of an intercalation compound of manganese thiophosphite (MnPS3) to enrich U(VI) efficiently.
The researchers prepared N-MPS by immersing a quantity of MnPS3 in 2 mol/L NH4Cl aqueous solution and stirring at room temperature for 24 hours. The prepared N-MPS shows good pH durability (2.8–12.2) and β/γ-ray irradiation resistance (100–200 KGy).
Moreover, they found that N-MPS exhibits an outstanding capacity (much higher than that of some reported superior sulfide adsorbents), fast kinetics, and superb selectivity towards U(VI).
In particular, the obtained distribution coefficient values in contaminated tap water and lake water are up to 2.23 × 104 mL/g.
Importantly, the adsorbed U(VI) could be eluted by a mild and eco-friendly method for the recovery of uranium and regeneration of adsorbent for at least five cycles.
Using various characterizations (Raman, XPS, Zeta potential and EXAFS) and batch adsorption experiments, the researchers revealed that the adsorption mechanism of N-MPS for U(VI) is the synergy of ion exchange and surface adsorption.
This study not only shows that intercalated metal sulfides have good application potential for highly efficient separation of U(VI) from wastewater, but also paves the way for developing new high-performance adsorbents by intercalation.
Schematic diagram of the layered MnPS3 intercalated with NH4+ (N-MPS) for the capture of U(VI). (Image by Prof. HUANG's group)
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