Mechanochemical removal and recovery of fluorine from hazardous fluorine-containing solid waste: Experiments and mechanisms

• Published in: Journal of environmental chemical engineering 2024-12, Vol.12 (6), p.114280, Article 114280
• Main Authors: Zhao, Hang, Zhang, Xiaoguang, Zhang, Qijun, Pan, De’an, Tan, Zhe, Jiang, Guosai, Yang, Feihua
• Format: Article
• Language: English
• Subjects: Density functional theory; Fluorine removal and recovery; Fluorine-containing solid waste; Mechanochemical; Reaction mechanism
• ISSN: 2213-3437
• DOI: 10.1016/j.jece.2024.114280

Large amounts of hazardous fluorine-containing solid waste (HFSW) are produced globally each year. Recycling HFSW not only conserves valuable F resources but also serves as a crucial step towards environmental sustainability. This work proposed an efficient and green approach for F removal and recovery from the HFSW using a mechanochemical method. The results showed that MgF2 component in the HFSW can be almost completely converted to NaF and Mg(OH)2 by the mechanochemical force with NaOH as co-grinding agent. A possible NaOH mechanochemical decomposition and conversion mechanism of MgF2 is also proposed based on thermodynamics, XRD, TEM and DFT calculations. By optimizing the mechanochemical conditions, such as NaOH concentration of 35 mol/L, ball-to-material ratio of 10:1 g/g, liquid-solid-ratio of 1.8 mL/g, mechanical activation speed of 600 rpm, and mechanical activation time of 150 min, 99.51 % of F in the HFSW can be leached. Finally, 98.69 % purity of NaF product was recovered from the as-obtained F-containing leachate through N235 extraction and evaporative crystallization. The results of this work are expected to provide a promising solution for F removal and recovery from HFSW. [Display omitted] •NaOH was selected as the co-grinding reagent for mechanochemical.•Over 99 % of F removal from hazardous fluorine-containing solid waste.•The mechanochemical conditions were optimized with the response surface analysis.•Possible mechanochemical conversion mechanism of fluorinated components is proposed.