0428同步年報-2021-全

Environmental and Earth Sciences 069 Fig. 2 : (a) Normalised Fe K-edge XANES spectra of Fe ore tailings from various treatments and Fe standard compounds ( e.g ., FeO, biotite and Fe 2 O 3 ) show changes of Fe speciation in tailings with varied treatments, (b) normalised Fe K-edge XANES spectra of tailing samples and Fe standards, and (c,d) LCF results indicates the Fe phase composition in tailings of various treatments. [Reproduced from Ref. 1] Fig. 1 : A diagram showing the critical role of sulfur-oxidizing bacteriom (SOB)- A. ferrooxidans in driving Fe-bearing mineral weathering and secondary mineral formation in Fe-ore tailings. [Reproduced from Ref. 1] Based on the above questions, Longbin Huang’s team (including Songlin Wu and Qing Yi) in University of Queensland, Australia, has investigated the colonization capacity of A. ferrooxidans and its biogeochemical functionality in alkaline Fe ore tailings, including biological oxidation of S 0 , neutralization of the alkaline pH conditions of tailings and the microbe-mediated weathering of Fe-bearing minerals. Collaborating with Ting-Shan Chan (NSRRC), Huang’s team was able to acquire Fe K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra at TLS 17C1 to verify the changes of Fe phase and Fe speciation after SOB and S 0 treatments. Figure 2 displays normalised Fe K-edge XANES spectra of Fe ore tailings from various treatments and Fe standard compounds, and the LCF analysis. The edge maxima shift of fresh tailings and samples from TB5S treatment ( Fig. 2(a) ) revealed the occurrence of both Fe(II) and Fe(III) in tailing minerals. Both biotite and the control tailings exhibited signals at 7126 and 7130.2 eV indicating the presence of biotite-like minerals in the tailings. In addition, the absence of a signal at 7126 eV and increased absorption at 7134 eV in the TB5S sample indicated that the S 0 amendment and A. ferrooxidans inoculation induced the transformation of biotite-like phyllosilicates and the oxidation of Fe(II) to Fe(III) in the tailings. The oxidation of solid-phase Fe(II) into Fe(III) was supported by the observed absence of Fe(II) and the increase/appearance of secondary Fe(III) oxyhydroxides ( e.g. , ferrihydrite, jarosite, or Fe(III)-oxalate-like minerals) in tailings from treatment TB5S (qXRD analysis and LCF fitting in Figs. 2(d) and 3(c) ). The structural ( e.g. , within silicate and Fe-oxide minerals) Fe(II) oxidation mediated by this SOB might involve direct bacterial enzymatic