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Probing the sorption reactivity of the edge surfaces in birnessite nanoparticles using nickel(II)
Simanova, A.A.,Kwon, K.D.,Bone, S.E.,Bargar, J.R.,Refson, K.,Sposito, G.,Pena, J. Pergamon Press ; Elsevier Science Ltd 2015 Geochimica et cosmochimica acta Vol.164 No.-
Birnessite minerals are layer-type manganese oxides characterized by large surface areas, the presence of cation vacancy sites and varying amounts of structural and adsorbed Mn(III). In this study, we identify the conditions that favor trace metal adsorption on the edge surfaces of birnessite nanoparticles by using Ni as a probe ion for Ni K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and geometry optimizations based on density function theory (DFT). In δ-MnO<SUB>2</SUB> nanoparticles free of Mn(II,III) at pH 6.6, Ni was adsorbed primarily at vacancy sites, with a minor fraction of Ni present as a double-edge sharing (DES) or a double-corner sharing (DCS) complex at surface loadings exceeding the vacancy content. In Mn(III)-rich δ-MnO<SUB>2</SUB> nanoparticles, about 80% of the adsorbed Ni formed a mixture of DES and DCS complexes at particle edges in samples with loadings ranging from 0.01 to 0.08molNimol<SUP>-1</SUP>Mn, with only a small fraction of vacancy sites available to adsorb Ni. The presence of Mn(III) at the nanoparticle edges also changed the architecture of the DES complex, causing the Ni octahedra to adsorb onto the cavity formed between two Mn(III) octahedra at the particle edges. The EXAFS-derived Ni-Mn interatomic distances of 3.01-3.05A for this ''flipped'' Ni-DES complex were in excellent agreement with those obtained by DFT geometry optimization. Edge surfaces on birnessite nanoparticles have a lower affinity for trace metals than vacancy sites, but have a moderate sorption capacity (ca. 0.14molNimol<SUP>-1</SUP>Mn at vacancies vs. 0.06molNimol<SUP>-1</SUP>Mn at edge surfaces). Finally, although Mn(III) increases the relative proportion of Ni adsorbed at particle edges by blocking sorption sites on the basal surface, the overall sorption capacity of the mineral diminishes significantly.
이창수 ( Lee Chane-soo ),정봉조 ( Chung Bone-jo ),최원일 ( Choi One-il ) 한국구조물진단유지관리공학회 2004 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.8 No.1
Citizen demand the application of safe, economic, and environment-friendly demolition methods as society has been developed. This study investigates problems of existing demolition methods, develops new demolition method which can be minimized cooling water and sludge for the main cause of the environmental pollution, and certifies validity of new method by finite element methods. For many cases it chooses parameters as a number, depth and size of boring, and according to self weight, calculates appropriate those of boring by comparison and analysis.