Abstract: To address the environmental hazards caused by the industrial discharge of fluoride-containing wastewater, the effects of calcium-fluoride ratio, pH value, reaction temperature, and reaction time on fluoride removal efficiency were investigated by simulating the calcium salt precipitation reaction process of fluorine-containing wastewater. The relationship between the particle number density and the growth rate of calcium fluoride nuclei under various factors was analyzed by using the particle number balance model. The relative growth kinetic equation of calcium fluoride nucleation and its corresponding sensitivity coefficient under each condition were obtained, and the characteristics of crystallization products were characterized by XRD and SEM-EDS. The crystallization behavior of calcium fluoride in the chemical precipitation reaction of NaF and CaCl2 was clarified. The results showed that when the calcium-fluorine ratio was 2, the pH value was 7, the reaction temperature was 60℃, and the reaction time was 60 min, the fluoride ion concentration in the treated wastewater was decreased from the initial fluoride ion concentration of 5000.00 mg/L to 8.82 mg/L using CaCl2 as a calcium salt precipitant. The fluoride removal rate was 99.82%. Under these conditions, the nucleation rate of calcium fluoride precipitation was 0.19470 */(mL?min) and the growth rate was 2.952×10-3 μm/min. The relationship between the sensitivity coefficients of each factor was ipH<iT<0<it<iCa/F. The calcium-fluorine ratio and time were conducive to the nucleation of calcium fluoride crystals, and moderate pH and temperature were conducive to the growth of calcium fluoride crystals. The final precipitation product is calcium fluoride, and its surface microstructure consisted of an agglomerate structure composed of spherical calcium fluoride clusters.

Key words: fluoride wastewater, calcium fluoride, crystallization kinetics, defluorination

摘要： 为解决工业排放含氟废水所带来的环境危害问题，通过模拟含氟废水钙盐沉淀反应过程，考察钙氟比、pH值、反应温度和反应时间对除氟效果的影响，运用粒数衡算模型分析各因素下氟化钙晶核粒数密度与生长速率的关系，得出各条件下氟化钙成核相对生长动力学方程及其对应敏感系数，并利用X射线衍射(XRD)和扫描电镜-能谱(SEM-EDS)表征结晶产物特征，明确NaF与CaCl2化学沉淀反应生成氟化钙的结晶行为。研究结果表明，初始F-浓度5000.00 mg/L含氟废水，以CaCl2为钙盐沉淀剂，当钙氟比为2、pH值为7、反应温度为60℃、反应时间为60 min时，沉淀除氟效果较好，处理后废水中F-浓度降至8.82 mg/L，除氟率达99.82%，该条件下，氟化钙沉淀结晶成核速率为0.19470 */(mL?min)、生长速率为2.952×10-3 μm/min。各因素敏感系数大小关系为：ipH<iT<0<it<iCa/F，适当增大钙氟比和时间有利于氟化钙晶体成核，适中的pH和温度有利于氟化钙晶体生长。最终沉淀产物为氟化钙，其表面微观形貌为球状团聚体组成的堆积结构。

关键词: 含氟废水, 氟化钙, 结晶动力学, 除氟效果