Water cleaning ability and local structure of iron-containing soda-lime silicate glass

Abstract

A relationship between waste-water cleaning ability and local structure of iron-containing soda-lime silicate glass, 15Na₂O·15CaO·xFe₂O₃·(70-x)SiO₂ (x = 10–50 in mass%), abbreviated as NCFSx glass, was investigated by means of ⁵⁷Fe-Mössbauer spectroscopy, redox titration with KMnO₄ for the determination of chemical oxygen demand (COD) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Mössbauer spectra of NCFSx glass with “x” of 10 and 30 were composed of two doublets: one due to Fe^IIIO₄ tetrahedra (T _d) with isomer shift (δ) of 0.23–0.26 mm s^− 1 and quadrupole splitting (Δ) 1.01–1.04 mm s^− 1, and the other due to Fe^IIO₆ octahedra (O _h) with δ of 1.00–1.03 mm s^− 1 and Δ of 2.03–2.05 mm s^− 1. Absorption area for Fe^II(T _d) was decreased from 9.7 to 6.5 and 0.0 % when “x” was increased from 10 to 30 and 50. A leaching test performed with 500 mL of artificial waste water and 2.0 g of NCFS50 revealed waste-water cleaning ability of soda-lime glass, e.g., COD was reduced from 280 to 55.2 mg L^− 1 after 10 day-leaching. After 10 day-leaching, it proved that iron was dissolved into waste water to a level of 5.3$_{7} \times 10^{-1}$ mg L^− 1. These results prove that organic matter could be effectively decomposed with iron-containing soda-lime silicate glass.