(中南大学 冶金科学与工程学院，长沙 410083)
摘 要: 通过CaF2溶解实验对Ca2+-F−-H+-H2O体系的热力学性质进行研究，考察CaF2粒径、pH等因素对CaF2沉淀溶解−平衡的影响，结合热力学计算得到影响CaF2沉淀效果的因素。结果表明：CaF2粒径对溶液平衡总氟浓度有重要影响，CaF2粒径越大，其溶解度越小，溶液平衡总氟浓度越低；当CaF2粒径大于16.97 μm时，平衡总氟浓度低于8 mg/L，而细颗粒CaF2在溶液中的平衡总氟浓度高于25 mg/L；化学沉淀法处理含氟废水时，应尽可能增大CaF2沉淀粒径，并将反应终点pH控制在4.0~10.0之间，达到降低CaF2溶解度、强化CaF2沉淀效果的目的。
关键字: CaF2；沉淀；热力学；粒径
precipitation-dissolution equilibrium of CaF2
（School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The thermodynamic properties were studied by dissolution experiment. The effects of pH and particle size of CaF2 on the precipitation dissolution equilibrium of Ca2+-F−-H+-H2O system were investigated, and then the factors influencing the precipitation effect were determined combined with the thermodynamic analysis. The results show that the particle size of CaF2 is a critical factor that influences the equilibrium concentration of F. The solubility of CaF2 and equilibrium concentration of F decreases with increasing the particle size of CaF2. The equilibrium concentration of F is less than 8 mg/L with coarse particles larger than 16.97 μm, while it is more than 25 mg/L with fine particles. In order to decrease the solubility of CaF2 and improve the F removal efficiency in the precipitation process, the terminal pH value of the reaction should be controlled between 4.0 and 10.0, while the particle size of the precipitate should be increased as much as possible.
Key words: CaF2; precipitation; thermodynamics; particle size
