去除半导体废水中氟化物以合成冰晶石之研究

Removal of Fluoride from Semiconductor Wastewater to Synthesize Cryolite

摘要: 氟污染的议题近年来备受关注，再加上3C产品的普及使得半导体业所产生之高浓度含氟废水的处理成为一值得研究探讨之议题，因此本研究以冰晶石结晶法处理含氟溶液，藉由铝盐与氢氧化钠的添加去除水中氟化物，并合成出具经济价值之产物。实验中以批次式实验方式探讨氟/铝莫耳比、pH值、不同初始氟浓度对冰晶石的合成与氟去除率的影响，接着于仿半导体废水中进行不同铝盐对除氟效率之比较，最后利用X光绕射光谱仪(XRD)、扫描式电子显微镜(SEM)了解材料之特性。结果显示：调整氟/铝莫耳比为冰晶石的理论化学计量、pH在一定范围内，可在室温环境中有效去除水中氟离子并合成出冰晶石，接着由不同初始氟浓度实验得知初始氟浓度渐增，除氟效率随之提升，而过量钠盐的添加对除氟效率亦有正向影响。于仿半导体废水中比较不同铝盐，结果可得知硝酸铝之除氟效率略优于其他铝盐。

Abstract: The issue of fluoride pollution recently has attracted much attention. Beside that the popularity of 3C products, the treatment of fluoride wastewater from semiconductor industry is worthy to be studied and discussed. In this study, the fluoride-containing solution was treated with cryolite crystallization method. The fluoride was removed by the addition of aluminum salts and sodium hydroxide to produce valuable cryolite by-product. Several parameters of process such as fluorine and aluminum molar ratio, pH, and different initial concentrations of fluoride might affected the composite of cryolite and fluoride removal efficiency, which was investigated in batch experiments. Then, different aluminum salts to removal efficiency were investigated with imitative sem-iconductor wastewater. Finally, the properties of material were analyzed by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The results showed that adjusting fluorine and aluminum molar ratio in theoretical stoichiometry of cryolite and controlling pH could recycle fluoride ion validly and produce cryolite successfully at room temperature. The initial fluoride concentration experiments demonstrated that the fluoride removal efficiency was improved as the initial fluorine concentration was increased, and the addition of excessive amounts of sodium salt had a positive effect as well. From the result of different aluminums in the imitative semiconductor wastewater, we could know that aluminum nitrate had a better removal efficiency than other aluminum salts.