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Synthesized siderite was used to remove As(III) and As(V) from water solutions under anoxic conditions and oxic conditions. Results showed that As adsorption on synthetic siderite under anoxic conditions was around 10 mg/g calculated with Langmuir isotherm. However, the calculated As adsorption on synthetic siderite under oxic conditions ranged between 115 and 121 mg/g, which was around 11 times higher than that under anoxic conditions. It was found that 75% siderite was transformed into goethite during oxic adsorption. However, synthetic goethite had lower As adsorption capacity than siderite under oxic conditions, although its adsorption capacity was a little higher than siderite under anoxic conditions. It suggested that the coexistence of goethite and siderite bimineral during mineral transformation probably contributed to the robust adsorption capacity of siderite under oxic conditions. Results of extended X-ray absorption fine structure (EXAF) spectroscopy indicated both As(III) and As(V) formed inner-sphere complexes on the surface of As-treated solid regardless of substrates, including the bidentate binuclear corner-sharing ((2)C) complexes and the monodentate mononuclear corner-sharing ((1)V) complexes. Monodenate ((1)V) and bidentate ((2)C) complexes would be related to high As adsorption capacity of siderite under oxic conditions. It showed that more Fe atoms were coordinated with As atom in the monodentate complexes and the bidentate complexes of As(V)/As(III)-treated siderite under oxic conditions, in comparison with As(V)/As(III)-treated siderite under anoxic conditions and As(V)/As(III)-treated goethite. Calcinations of natural siderite resulting in the coexistence of goethite and siderite greatly increased As adsorption on the solid, which confirmed that the coexistence of bimineral during mineral transformation from siderite to goethite greatly enhanced As adsorption capacity of siderite adsorbent. The observation can be applied for modification of natural siderite for As removal from high As waters.

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Due to the rapid development of the nuclear power industry, and consequently, the nuclear accident in Fukushima, much attention has been paid to novel materials for the efficient and rapid separation, removal and recovery of nuclear fuel associated radionuclides from aqueous solutions. Herein, a novel mesoporous material, dihydroimidazole functionalized SBA-15 (DIMS), was synthesized via a postgrafting method and used as an efficient sorbent for the extraction of U(VI) from aqueous solution. The synthesized material was found to possess highly ordered mesoporous structures with a large surface area and a uniform pore diameter. The sorption tests under various conditions demonstrated that the sorption of U(VI) by DIMS was fast, with an equilibrium time of less than 10 min. Additionally, the maximum sorption capacity reached 268 mg g À1 at pH 5.0 AE 0.1. Changes in the solid-to-liquid ratio (m sorbent /V solution ) did not have any remarkable effect on the U(VI) sorption. Besides, the sorbed U(VI) can be easily desorbed by 0.01 mol L À1 or more concentrated HNO 3 solution, resulting in a U(VI) solution with a concentration factor of 300 at a solid-liquid ratio as low as 0.013 g L À1 . The reclaimed sorbent can be reused with no obvious decrease in the sorption capacity. The selectivity of the DIMS sorbent for U(VI) ions was found to be fairly desirable by the sorption tests with the solutions containing a range of competing metal ions.

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The effect of Mn on the catalytic performance of V2O5/TiO2 catalyst for the selective catalytic reduction of NO x by NH3 (NH3-SCR) has been investigated in this study. It was found that the added Mn significantly enhanced the activity of V2O5/TiO2 catalyst for NH3-SCR below 400 °C. The redox cycle (V4+ + Mn4+ ↔ V5+ + Mn3+) over Mn-promoted V2O5/TiO2 catalyst plays a key role for the high catalytic deNO x performance. The redox cycle promotes the adsorption and activation of NH3 and NO, forming more reactive intermediates (NH4 +, coordinated NH3, NO2, and monodentate nitrate species), thus promoting the NH3-SCR to proceed.

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