Green and Sustainable Strategy for Separation and Recovery of High-Value Fluorine and Magnesium from Fluorine Slag by Alkaline Roasting-Hydrometallurgy

Abstract

As the fluorine chemical industry continues to expand rapidly, fluorite has been classified as a strategic resource with restricted mining, raising concerns about the stability of the fluorine supply chain. Recycling fluorine slag has emerged as a promising solution to alleviate supply chain constraints and reduce environmental pollution, drawing considerable attention. However, fluorine slag is generally disregarded due to limited research and low recovery efficiency. This study developed a roasting-leaching technology to convert key components F and Mg in fluorine slag into high-value-added products. The results are promising, with 97.60% of the F and 96.70% of Mg in the fluorine slag recovered, and the purity of the recovered NaF and MgSO4 reached 98.73% and 99.03%, respectively. Furthermore, the mechanisms of fluoride conversion during the roasting process and the hydrometallurgical separation and purification of NaF were investigated. The advantages of the as-proposed technology include: (1) no toxic HF flue gas release, (2) higher leaching efficiency and benefit, (3) more eco-friendly with avoids the use of strong acids and alkali, (4) obtaining NaF product, in contrast to previous process for recovering F from fluorine slag. This research can provide a valuable reference for the environmentally friendly, efficient conversion and recovery of F and Mg from fluorine slag and the purification of fluorides, further promoting the sustainable development of the fluoride chemical industry.

Keywords: Fluorine slag, High-efficiency recovery, Roasting, Mechanism exploration, High purity NaF