Local structure and chemical durability of FeOOH-fixed sodium silicate glass prepared from water glass |
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Authors: | T Nishida H Oku |
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Institution: | (1) Department of Biological and Environmental Chemistry, Kyushu School of Engineering, Kinki University, Kayanomori 11-6, Iizuka, 820-8555, Japan;(2) Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashiku, Fukuoka, 812-8555, Japan |
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Abstract: | A 12M HCl solution of iron oxyhydroxide (a-FeOOH: goethite) was mixed with water glass (18Na2O.36SiO2
.46H2O) at room temperature. The mixture (sol) changed into a dry gel when dried at 25 °C for 120 hours in air. Glass-ceramic and glass samples were prepared when the dry gel was heated for 1-3 hours in an electric furnace at 800 and 900 °C, respectively. The 57Fe Mössbauer spectrum of the dry gel is composed of a magnetic hyperfine structure owing to the formation of g-FeOOH (lepidocrocite). By contrast, the 57Fe Mössbauer spectrum of glass-ceramic and glasses is composed of paramagnetic Fe(III) with distorted tetrahedral symmetry. This proves that Fe(III) atoms occupy network-forming Si(IV) sites in the FeOOH-fixed sodium silicate glass. A leaching test of the silicate glass in the acid rain simulant composed of HNO3 (pH 3.5) and H2SO4 (pH 3.5) revealed high chemical durability, indicating that Fe(III) is firmly fixed in the glass matrix. |
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