Reaction mechanism of molten NaOH decomposing Zn₂SiO₄ in willemite

Abstract

Based on the existing form of Zn₂SiO₄ in willemite, the chemical precipitation method was used to synthesize Zn₂SiO₄. Through the orthogonal experimentation, the reaction conditions of melten NaOH decomposing Zn₂SiO₄ were optimized, and the optimal experimental conditions include reaction temperature of 400 °C, reaction time of 4 h, and alkaline-to-ore molar ratio of 20:1. Based on the optimized experiment, on-line detection for the alkali leaching was made by using Raman spectroscopy; XRD was used to analyze the structure of water leaching residue, to explore the reaction mechanism of NaOH decomposing Zn₂SiO₄. The results show that during the reaction process, the Si-O bond in SiO₄ is destroyed, and the NaOH inserts itself into the silicate lattice, producing an immediate Na₂ZnSiO₄ product. After the alkali leaching process, Zn²⁺ can be separated from the SiO₄ array, which can be released out of the silicate in the form of ZnO.

Keywords

Raman spectroscopy / Zn₂SiO₄ / alkali melting / reaction mechanism

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