Tian Q, Bai Y, Pan Y, Yao S, Chen C, Zhang H, Sasaki K. Influence of aluminate and silicate on selenate immobilization using alkaline-earth metal oxides and ferrous salt.
THE SCIENCE OF THE TOTAL ENVIRONMENT 2022;
851:158126. [PMID:
35987217 DOI:
10.1016/j.scitotenv.2022.158126]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/29/2022] [Accepted: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Effects of aluminate and silicate species on the SeO42- immobilization using alkali-earth metal oxides and ferrous species have not been clearly elucidated. In the present study, Al and Si species were separately added into MgO/Fe(II) and CaO/Fe(II) reactions containing SeO42-, studied by toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray absorption fine structure (XAFS), and PHREEQC simulation. Approximately 42 % of SeO42- was reduced to SeO32- for MgO/Fe(II) reaction in the presence of Al species, being consistent with the case without Al species. The Al species only showed slight inhibition of Se leaching for the MgO/Fe(II) reaction. Most of Se oxyanions were adsorbed onto Mg(OH)2 through outer-sphere complexation. For CaO/Fe(II) reaction, all of SeO42- was reduced to SeO32- with or without Al species. However, the Se leaching amount (3 %) of sample added with Al species (CE3) is much lower than that (12 %) of sample without Al species (CE2). This is mainly because SeO32- can be sorbed onto the iron-based minerals through binuclear bidentate corner-sharing (2C) complexation instead of monodentate mononuclear corner-sharing (1V) complexation of the case without Al species. On the other hand, SeO42- was not reduced to SeO32- in the presence of silicate, and almost all of Se was leached out for silicate-contained samples except CaO/Fe(II) reaction with the addition of Al species. This is due to the polymerization of Al and Si species under a high-alkalinity environment, thereby stabilizing SeO42- in the amorphous silicon-aluminum structure and contributing to the decrease of Se leaching.
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