Dissolution Behavior of Valuable Elements from the Glassy Phase of CaO-SiO2-FeOx System in Weakly Acidic Solution

Abstract

Dephosphorization slag consists of C₂S-C₂P phase, CaO-SiO₂-FeO_x glassy phase and RO phase. Compared with RO phase rich in a large amount of Fe element, CaO-SiO₂-FeO_x glassy phase, which also contains Fe, is more readily dissolved. Due to the low basicity of the dephosphorization slag, the proportion of CaO-SiO₂-FeO_x glassy phase is relatively high, and glassy phase contains more Ca, Fe and Si elements that are beneficial to the soil. The effect of composition and quenching temperature on the dissolution ratios of Ca, Si and Fe from glassy phases was investigated, and its silicate structure was analyzed. A lower Fe₂O₃ content facilitated the dissolution of the glassy phase, and the dissolution ratios of Ca, Si and Fe were approximately 35% at pH 5, far higher than those from other glassy phases. The leaching efficiency of the glassy phase containing 35% Fe₂O₃ decreased by 80%. The dissolution ratios of Ca and Si enhanced when the Fe₂O₃ content increased to 45%. It was attributed to the amphoteric properties of Fe₂O₃. As the CaO/SiO₂ ratio of the glassy phase increased, the dissolution ratio of each element from the glassy phase was promoted, causing CaO to introduce more non-bridging oxygens (NBOs), breaking the SiO₂ network structure.