利用沉澱法及逆滲透薄膜過濾法降低TFT-LCD廢水中硼及碘之濃度

Abstract

TFT-LCD近幾年來成為台灣不可或缺之重要產業，但在製造TFT-LCD面板過程中，偏光板之製程往往會使其排放廢水中含有硼與碘。因此本研究主要目的為開發有效除硼之方法且找尋此方法之最佳參數，並探討以逆滲透薄膜過濾法去除及回收廢水中碘之可行性。 本研究在除硼方面以氫氧化鈣為礦化劑，使其與水中之硼酸根離子結合形成偏硼酸鈣後沉澱。由於本實驗合成廢水為較低濃度之50 ppm，當只加入氫氧化鈣於合成廢水時，去除效率並不理想。當同時添加氫氧化鈣及磷酸時，磷酸會與氫氧化鈣合成氫氧基磷灰石覆蓋在偏硼酸鈣上，以防止偏硼酸鈣再溶解而提高去除廢水中硼之效果。本實驗之最佳操作參數為在pH=9之情況下以130℃加熱30分鐘，除硼效率可高達99%。 除碘方面，分別測試GE、DOW以及Hydranautics三家公司所生產之RO膜，實驗結果以Hydranautics公司的SWC5-LD-4040膜除碘效果最好，當進留碘濃度為500 ppm之情況下可達到95%碘去除效率; 而當進流濃度小於15 ppm時，碘去除效率僅剩下10%左右。

Manufacturing of TFT-LCD has become one of the most important industries in Taiwan in recent years. But due to polarizer process, the wastewater generally contains boron and iodine. The main objectives of this study were (1) to develop an effective method to remove boron and to find its optimal operating conditions, and (2) to investigate the feasibility of using reverse osmosis to remove and recover iodine in wastewater. In this study, Ca(OH)2 was used as the mineralizer to precipitate B(OH)4－ to form Ca2B2O5•H2O. Due to the low concentration of boron (50 ppm), use of Ca(OH)2 alone was not effective, with the combined addition of Ca(OH)2 and H3PO4, the boron removal efficiency could be raised to 99% under pH=9 at 130℃ after 30mins. Three reverse osmosis membranes produced from GE, Dow and Hydranautics were tested for removal and recover of iodine. The results showed that the membrane from Hydranautics (SWC5-LD-4040) was the most effective one. When influent concentration of iodine was 500 ppm, the removal efficiency could reach up to 95%; however, when influent concentration was less than 15 ppm, the removal efficiency was only 10%.