臺灣博碩士論文加值系統

　　本研究之主要目的在於探討以沉澱－浮除程序處理半導體製造業含氟廢水之可行性，採樣自國內某半導體廠之製程含氟廢水，廢水中主要含有約700mg/l之氟離子、160 mg/l之硝酸根離子及少量的硫酸根離子約5mg/l，另含有極微量之金屬離子如鉛、鈉、鋁、鈣與砷等。
　　本研究中含氟廢水之處理係採用鈣鹽添加法產生氟化鈣固體沉澱，再以浮除法去除溶液中的氟化鈣。由分散空氣浮除系統之實驗結果顯示，當[Ca2+]/[F-]莫耳濃度比控制在１以上及酸鹼值大于3時，即可使殘餘氟離子濃度小於10 mg/l，浮除反應均在10分鐘內完成。氮氣流量、[Ca2+]/[F-]莫耳濃度比及酸鹼值對氟化鈣最終去除率並無明顯影響。十二烷基硫酸鈉(SDS)濃度是影響浮除效率的主要因素，其吸附機制是利用電性作用力，以帶負電的離子端吸附至的氟化鈣表面；添加不同類型之鈣鹽與界面活性劑，也會對於氟化鈣去除率造成影響。當離子強度增大，分散浮除系統之處理效率隨著降低，可利用增加界面活性劑(SDS)濃度的方式，提升氟化鈣去除率。
　　在溶解空氣浮除系統方面，殘餘氟離子濃度之最適操作條件如分散浮除系統所述，浮除反應約在10~15分鐘內可完成。由實驗結果證實油酸鈉(SO1)濃度是影響處理效率的主要因素，其可藉著不飽和雙鍵反應提升氟化鈣表面之疏水性，增加氣固間之吸附性。此外，控制操作壓力在3~5kg/cm2、迴流量在0.3~1.51/min、離子強度在0~0.5M及酸鹼值於5.5~10.0之範圍內，對去年率之影響並不明顯，氟化鈣之去除效率均可達到95%以上。
　　當含氟廢水存在硫酸根及磷酸根時，硫酸根及磷酸根會與氟離子競爭鈣離子，而致使溶液中殘餘氟離子濃度增加，並且降低浮除效率；可藉由增加鈣鹽量、提高界面活性劑濃度及SDS與SO1併用之方式加以改善。

　　The major objective of this study was to investigate the treatment of fluoride-containing wastewater of semiconductor industry through precipitate flotation processes.Fluoride-containing wastewater was obtained from semiconductor factory. There were about 700 mg/l of fluoride, 160 mg/l of nitrate, and 5 mg/l of sulfate in the wastewater sample.
　　The basic principle of the treatment processes is the addition of calcium chloride to generate the precipitate of calcium fluoride, and its subsequent removal. The results of despersed air flotation (DiAF) experiment indicated that through adjusting molar concentration ratio of calcium and fluoride and obtained. All flotation reactions were completed within 10 minutes. The concentration of sodium dodecy1 sulfate (SDS) has significant effect on the removal efficiency of calcium fluoride. Various types of calcium salts and surfactants were also investigated. It was found that nitrogen flowrate, molar concentration ratio of calcium and fluoride, and pH value have insignificant effects on the removal percentage of calcium fluoride. The removal efficiency decreases with increasing ionic strength, and can be overcome by increasing the concentration of SDS.
　　Results of dissolved air flotation (DAF) experiment showed that sodium oleate (SO1) concentration has critical effect on removal efficiency of calcium fluoride. Since adjacent oleate species were adsorbed at the calcium fluoride surface, the hydrophobicity of calcium fluoride surface was enhanced. Effects of pressure. recycle flowrate, pH value, and ionic strength were studied on the removal efficiency of calcium fluoried. In the presence of sulfate and of phosphate, the residual fluoride concentration became higher and the removal efficiency of calcium fluoride decreased significantly, due to the competition effect. It can be improved by increasing calcium concentration, surfactant concentrations (SDS or SO1), or the use of SDS in combination with SO1.