Leaching kinetics and dissolution model of steel slag in NaOH solution

As a typical silica-aluminum solid waste, the leaching activity of Si, Al, and Ca ions in steel slag in alkaline solution determines its potential application in alkali-activated slag cement. This study investigates the reactivity and leaching kinetics of Si and Al in steel slag in an NaOH solution. The results indicate that the coupled factors of NaOH concentration and leaching temperature have the most significant influence on the dissolution rate of Si and Al ions in steel slag. The dissolved Si and Al in steel slag mainly participate in the formation of N-(C)-A-S-H. A dissolution model for steel slag has been established, where the concentration of NaOH and the dissolution temperature are coupled, resulting in the most significant dissolution of Si and Al ions in the steel slag. The leaching process of steel slag in NaOH solution is controlled by chemical reactions on the surface of unreacted particles. The activation energies for Si and Al leaching were 14.7549 kJ/mol and 29.6498 kJ/mol, respectively. •The leaching rate of Si in steel slag was consistently higher than that of Al.•The mutual reactions between the ions generated N-(C)-A-S-H and Ca(OH)2.•Effect of single factor on dissolution rate: concentration > temperature > time.•NaOH concentration and temperature were the most significant at both factors.•Dissolution is controlled by chemical reactions on the particle surface.