- 學位論文
以氣舉式反應槽形成冰晶石結合羥磷灰石吸附剩餘含氟廢水之研究
Treatment of fluoride-containing wastewater by air-lift reactor for cryolite crystallization and adsorption of residual fluoride by hydroxyapatite
摘要
氫氟酸（HF）用於IC，TFT-LCD和太陽能電池製造工藝中，以蝕刻玻璃面板和矽晶片。在台灣每月氫氟酸之用量達到2000 噸（〜49％）。化學沉澱法通常用於通過添加含鈣化學物質(例如CaCl2,Ca(OH)2和CaCO3形成CaF2(S）來去除氟化物。CaF2(S）可用來作冶金工業的材料達到循環再利用。但是，由於氟化鈣顆粒粒徑極小（約0.16 µm）而難以沉澱。而在沉澱過程中需添加聚合物和PAC，使微小的顆粒變重，以增進沉降速率。因此，由於CaF2(S）之高水分含量和低純度，CaF2(S）污泥的再利用受到了限制。 此研究中設計氣升式結晶反應槽並添加了顆粒作為擔體，利用形成冰晶石（Na3AlF6）達到除去氟的目的。該系統的pH控制在5至6之間，並且通過將Al / F摩爾比的值保持在0.8/6 至1.1/6 的範圍內來添加適量的鈉和氫氧化鋁。結果表明，氣舉式反應槽可去除70％以上的氟，而且形成的冰晶石尺寸在運行5天後，從反應器中取出的固體顆粒的平均尺寸超過1公釐。
並列摘要
Hydrofluoric acid (HF) is used in IC, TFT-LCD, and solar cell manufacturing processes for etching glass panel and silicon wafer. In Taiwan, 2000 m3 of HF (~49%) is used each month. Chemical precipitation method is usually used to remove fluoride by forming CaF2(S) via adding calcium sources, such as CaCl2, Ca(OH)2, and CaCO3. CaF2(S) can be used as material in metallurgical industry. However, the particle of calcium fluoride is hard to precipitate due to the small particle size (ca., 0.16 µm). Polymer and PAC are added in the precipitate process to make tiny particle became heavy and then settle down quickly. So, the CaF2(S) sludge reuse was limited because of high moisture content and low concentration of CaF2(S). An air-lift crystallization reactor with pellet added was designed and operated for the removal of fluoride by forming cryolite (Na3AlF6). The system was operated with pH controlled between 5 and 6, and a suitable amount of sodium and aluminum hydroxide were added by maintaining the values of Al/F molar ratio in the range of 0.8/6 to 1.1/6. The result shows that the twin-pipe air-lift circulation reactor could remove more than 70% of fluoride, and the size of cryolite formed is quite big. The average size reaches more than 1 mm for the sample taken from the reactor after a 5-day of operation.