诱导结晶法去除地下水中氟离子

针对现行高氟地下水处理工艺中存在的工艺复杂、运行管理困难等问题，提出采用诱导结晶法除氟。其技术核心是在高氟水中投加氟磷灰石作为晶种，并投加磷酸盐和钙盐使水中氟离子在晶种表面生成氟磷酸钙（Ca10（PO4） 6F2）结晶。通过单因素实验得出最佳工艺条件：投加8g/L氟磷灰石，并投加NaH2PO4和CaCl2，使钙离子、磷酸根离子和氟离子的摩尔比为10：5：1，搅拌速度为100 r/min，反应时间1 h。反应中磷酸根离子和钙离子的利用率分别达到98%和25%以上。电子扫描显微镜（SEM）表征晶种在参与反应后，表面有结晶生成。研究表明，采用诱导结晶法可将水中氟离子浓度从5~10 mg/L降至1 mg/L以下，达到饮用水水质标准。

Removal of fluoride from groundwater by induced crystallization

Aimed to solve the problem of complex process and difficult operation management in the present high fluoride groundwater treatment process, a method was proposed to remove fluoride by induced crystallization. Fluorapatite as seed crystal as well as phosphate and calium salt were added into the high fluoride water, which could induce calcium fluophosphate (Ca10(PO4)6F2) crystallized on the surface of the seed crystal. The best operation conditions for fluoride removal were confirmed through the single factor experiments: adding fluorapatite of 8 g/L with NaH2PO4 and CaCl2 to make molar ratio of the calcium ion, phosphate ion and fluorinion be 10:5:1, the reaction time was 1 h, and the stirring rate was 100 r/min. The results showed that this method could remove the fluoride from water effectively.High utilization rates of phosphate ion and calcium ion were also achieved during the reaction (higher than 98% and 25%, respectively). Scanning electron microscope (SEM) showed that crystal was formed on the surface of seed crystal after the reaction. This research proved that the induced crystallization method could reduce the concentration of fluoride in water from 5~10 mg/L to less than 1 mg/L which meets the standard of drinking water quality.