Removal of As and Se Oxoanions from Solution Using Calcination Products of Ca(OH)2–Al(OH)3 and CaCO3–Al(OH)3 Mixtures
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概要
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The present study investigates the removal of As and Se oxoanions from solution by calcination products of Ca(OH)2–Al(OH)3 and CaCO3–Al(OH)3 mixtures with various Ca/(Ca+Al) molar ratios at 1273 K. In the calcination products obtained from the mixtures with Ca/(Ca+Al)=0.833, lime (CaO) and Ca–Al oxides were detected as the predominant and minor crystalline compounds, respectively. The calcination products were then immersed in solutions contained As and Se oxoanions to examine their removal efficiency at rather high pH (>11). The highest arsenite removal efficiencies were observed when the calcination product with Ca/(Ca+Al) molar ratio >0.7 was employed, while the arsenate removal efficiency was independent of the Ca/(Ca+Al) ratio. The selenate removal efficiency attained the peak value when the Ca/(Ca+Al) ratio was 0.7–0.8. The maximum removal amount per unit weight of the calcination products for arsenite, arsenate, selenite, and selenate were 6–9, 4, 6–8 and 1.4–1.9 mmol/g, respectively, which were considerably higher than previously reported values. Upon reaction with the calcination product, arsenite, arsenate and selenite formed hard-soluble Ca salts, Ca(HAsO3), Ca3(AsO4)2 with Ca5(AsO4)3(OH) and CaSeO3, respectively, where the quick lime (CaO) in the calcination product is an active component for removing these oxoanions. On the other hand, selenate was removed by forming ettringite substituted by selenate, Ca6Al2(SeO4)3(OH)12·26H2O, where the synergistic effect of Ca and Al compounds in the calcination product should be exhibited.
著者
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SHIGEMOTO Naoya
Chemical Technology Department, Shikoku Research Institute, Inc.
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Shigemoto Naoya
Chemical Technol. Dep. Shikoku Res. Inst. Inc.
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Hiraga Yuki
Chemical Technol. Dep. Shikoku Res. Inst. Inc.
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