Study on Optimization of Extracting Magnesium Sulfate from Acid-leaching Eluent of Serpentine by Solventing-out Crystallization

In order to make full use of China's non-metallic mineral resources containing magnesium, and improve the comprehensive recovery rate of magnesium in serpentine, a new process of enriching magnesium from serpentine leaching solution at normal temperature and pressure was proposed. In this process, the solution crystallization method was used to recover the magnesium from the acid leaching solution of serpentine. The test conditions were optimized by response surface methodology to determine the optimal crystallization process conditions. In this study, response surface method was employed to optimize test conditions and select the best crystallization process conditions. In addition, the effect and interaction of crystallization time, temperature, and absolute ethanol consumption on magnesium sulfate crystallization efficiency were study. The results showed that the magnesium sulfate crystallization efficiency reached 93.52% under the optimum condition (crystallization time: 97 min, crystallization temperature: 18°C and absolute ethanol consumption: 68 mL). Moreover, the absolute ethanol consumption exhibited significant influence on magnesium sulfate crystallization, while temperature had the least effect, and the interaction between absolute ethanol consumption and crystallization temperature or time was significant. The crystalline product was rod-shaped magnesium sulfate hexahydrate, which met the production requirements of domestic class IV MgSO₄·nH₂O products.