Dissolution Behavior of Fe from CaO-SiO2-FeOx Glassy Phase

To recover the degraded paddy field, the efficient supply of Fe, Ca, and Si to the soil water is important. Steelmaking slag was confirmed as a useful fertilizer for paddy growth to supply Ca and Si. In addition, to suppress the H2S generation in paddy soil, supplement of Fe from fertilizer made of slag has been expected. By our previous research, it was found that Fe was supplied mainly from the CaO-SiO2-FeO glassy phase in slag. However, to design the fertilizer made of slag, the optimum composition of the glassy phase has to be clarified. In this research, the glassy phases with difference iron valence, basicity, and FeO content were synthesized to investigate the dissolution behavior of Fe in paddy water. The experiment was conducted by the addition of grounded power of the synthesized phase into water which kept pH at 5 by adding HNO3 to simulate the initial stage after irrigation of paddy fields. The dissolved amount of each element in water was analyzed by ICP-AES. The result showed that the dissolution ratio of Fe increased by increasing the ratio of Fe2+/T-Fe and the FeO content in the glassy oxides, and showed local maximum by the increase in CaO/SiO2 ratio at 0.67.