Browsing by Author "Chan, TS"

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    Bioaugmentation with Acidithiobacillus species accelerates mineral weathering and formation of secondary mineral cements for hardpan development in sulfidic Pb-Zn tailings
    (Elsevier, 2021-06) Liu, Y; Wu, S; Southam, G; Chan, TS; Lu, YR; Paterson, DJ; Huang, L
    The development of hardpan caps has great potential in rehabilitating sulfidic and metallic tailings, which may be accelerated by using exogenous Acidithiobacillus species. The present study aims to establish a bioaugmentation process with exogenous Acidithiobacillus species for accelerating the weathering of sulfidic minerals and formation of secondary mineral gels as precursors for hardpan structure development in a microcosm experiment. Exogenous Acidithiobacillus thiooxidans (ATCC 19377) and A. ferrooxidans (DSM 14882) were inoculated in a sulfidic Pb-Zn tailing containing negligible indigenous Acidithiobacillus species for accelerating the weathering of pyrite and metal sulfides. Microspectroscopic analysis revealed that the weathering of pyrite and biotite-like minerals was rapidly accelerated by exogenous Acidithiobacillus species, leading to the formation of secondary jarosite-like mineral gels and cemented profile in the tailings. Meanwhile, approximately 28% Zn liberated from Zn-rich minerals undergoing weathering was observed to be re-immobilized by Fe-rich secondary minerals such as jarosite-like mineral. Moreover, Pb-bearing minerals mostly remained undissolved, but approximately 30% Pb was immobilized by secondary Fe-rich minerals. The present findings revealed the critical role of exogenous Acidithiobacillus species in accelerating the precursory process of mineral weathering and secondary mineral formation for hardpan structure development in sulfidic Pb-Zn tailings. © 2020 Elsevier B.V.
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    Effects of oxygen deficiency on the magnetic ordering of Mn in Tb0.9Na0.1MnO2.9
    (Institute of Physics, 2008-03-12) Yang, CC; Wu, CM; Li, WH; Chan, TS; Liu, RS; Chen, YY; Avdeev, M
    Monovalent Na+ ions have been incorporated into a multiferroic TbMnO3 compound. Structural studies, using high-resolution neutron diffraction patterns, show that monovalent Na+-doping results in a noticeable oxygen deficiency in the compound. The alternations in crystalline and magnetic structures due to oxygen deficiency are investigated by neutron diffraction and magnetic susceptibility measurements. Na-doping turns the modulated incommensurate Mn spin structure, observed for the parent compound, into a simple commensurate one. The observed magnetic diffraction patterns agree very well with that calculated assuming a D-type arrangement for the Mn spins, with the moments pointing along the c-axis direction. No significant alternation in the ordering temperature of the Mn moments is found. © 2008, Institute of Physics