Dissolution Mechanism of Various Elements into Seawater for Recycling of Steelmaking Slag

Abstract

For the efficient supply of nutrition for phytoplankton multiplication in marine environment, the dissolution behaviors and the dissolution mechanisms of Ca, Si, P and Fe elements from steelmaking slag into seawater were investigated. The shaking experiment with synthesized CaO–SiO₂–P₂O₅–FeO slag was conducted at room temperature. The variations of shaking time, the CaO/SiO₂ ratio of slag and the slag/seawater ratio were taken into consideration.
The dissolution behavior of elements especially Si and P, pH of solution and the effect of slag/seawater ratio on dissolution are classified into two types by the CaO/SiO₂ ratio of slag. The dissolved concentration of Ca of slag with large CaO/SiO₂ ratio is much larger than that with small ratio. Mg²⁺ ion originally contained in seawater provides an obvious buffering action on pH increasing process which is caused by the dissolution of Ca. Moreover, the solubility diagrams are applied to elucidate the dissolution mechanisms. Additionally the dissolution of Fe is also analyzed with potential - pH diagram.