Mechanism of Cation–Oxygen Bond Activation and K⁺/Na⁺ Synergistic Promotion of Silicate Phase Dissociation in Smelting Slag

Abstract

Silicate phase was identified as the key phase of smelting slag and also the main constraint for its resource utilization. Therefore, unraveling the dissociation mechanism of silicate phase was crucial for enhancing the resource utilization of smelting slag. In this study, the activation of synthesized pure olivine was utilized as a research template to investigate the silicate phase activation mechanism. The optimal conditions for olivine activation were established as olivine:NaOH:KOH = 1:5:0.5 (molar ratio), roasting temperature of 700 °C, and roasting time of 3 h. Response surface methodology (RSM) was employed to verify the correlation of the main influencing factors on the activation effect in the order of mineral alkali molar ratio > temperature > time. The lattice site substitution mechanism and the transformation law of the physical phase of the activation process were elucidated by DFT calculations. The activation mechanism of silicate phase was revealed to involve: 1) OH– adsorption on cation sites, leading to the activation of cation–oxygen bonds and the formation of the hydroxyl compounds. 2) K+/Na+ created a synergistic effect to fill the cation vacancies, facilitating the gradual release of cations. This research aims to offer theoretical guidance for smelting slag treatment by providing a deeper understanding of the activation mechanism of silicate-type minerals.