Understanding the artificial mineralized uranite for immobilizing uranium in wastewater.

Uranium (U(VI)) pollution comes from the development and utilization of natural minerals. Based on a new concept of ecological restoration of uranium pollution into natural minerals, a new artificial mineralized process was proposed to immobilize uranium (U(VI)) for wastewater decontamination. In this work, three systems of Mg 3 (PO 4) 2 + UO 2 2+, Mg2+ + PO 4 3− + UO 2 2+ and Mg2+ + PO 4 3− + Mg 3 (PO 4) 2 + UO 2 2+ were designed. Batch experiments and theoretical calculation were conducted to study the U(VI) immobilization effectiveness and artificial mineralization mechanisms. U(VI) removal efficiencies reached up to 96% in the pH value of 5.0 in the three systems. Both precipitation and surface adsorption contributed to favorable U(VI) removal in Mg 3 (PO 4) 2 + UO 2 2+, but resulting in U desorption. Precipitation of Mg2+, PO 4 3− and UO 2 2+ into saleeite (Mg(UO 2) 2 (PO 4) 2 ·10H 2 O) crystal contributed to UO 2 2+ immobilization in the Mg2+ + PO 4 3− + UO 2 2+ and Mg2+ + PO 4 3− + Mg 3 (PO 4) 2 + UO 2 2+ systems, resulting in the negligible U desorption. It is due to the crystallization of the Mg(UO 2) 2 (PO 4) 2 ·10H 2 O through precipitation of Mg2+ and PO 4 3− with UO 2 2+ in acidic medium. PHREEQC and Visual MINTEQ fitting confirmed the favorable precipitation of Mg2+ and PO 4 3− with UO 2 2+ into saleeite in acidic medium. Thus, the U(VI) immobilization effectiveness and artificial mineralization mechanism were understood, providing a promising strategy of artificial induced mineralization of Mg(UO 2) 2 (PO 4) 2 ·10H 2 O for U(VI) decontamination in wastewater. [Display omitted] • Artificially mineralization is proposed for immobilizing uranium. • Formation of Saleéite and chernikovite is the fate of uranium immobilization. • Theorical fitting confirmed the mineralization of dissolved Mg2+ and PO 4 3− with UO 2 2+. • The leaching rate of saleéite and chernikovites is negligible. • P/U and Mg/U molar ratios determined the artificially mineralization process. [ABSTRACT FROM AUTHOR]