| 摘要: | 奈米科技為目前國家發展重點之一，不僅只是對其製造方法與理論加以研究，更積極的運用於各產業，可想而知，在不久的未來，廢棄物中勢必會有更多奈米級的污染物。半導體產業的化學機械研磨製程廢水為例，由於其中含有粒徑小且帶高電荷的奈米顆粒，因此造成其去除效率不佳。本研究是利用磁種凝聚作用將廢水中的奈米顆粒(SiO2)與磁性顆粒(Fe3O4)碰撞凝聚，再加以沉澱去除。 由於市售的磁性顆粒粒徑較大，單位重量所含的顆粒數較少，因此對於氧化膜CMP廢水的濁度去除效率較差，基於成本及處理效率的考量，本研究採用化學共沈法以FeCl2．4H2O和 FeCl3逐滴滴入NaOH鹼性溶夜中，製備成飽和磁化率為55.6 emu/g，粒徑小於300 nm的Fe3O4磁性奈米顆粒。再利用合成的Fe3O4磁性奈米顆粒處理實廠的CMP廢水，探討各操作條件(包括pH、電解質濃度、G及靜置於外加磁場…等)對處理效率的影響。由實驗結果發現，在操作條件控制上以pH?6，NaCl ＝ 0 M，並且G值在30?60 (1/sec)間時，濁度去除效率為最佳，可達到95 ％甚或更高，並且Fe3O4也可以重複再利用。同時，凝聚物沈降時，若加入磁場時，由於Fe3O4為磁性顆粒，所以Fe3O4-SiO2相互碰撞附著的顆粒不僅只受到重力的沈降，也受到磁力的作用使得去除率提高且沈降也更快速。因此對於CMP廢水的處理，可說是發展了一個操作簡單又快速的處理程序。根據所提出的理論基礎，相信此方法不僅能使用於CMP廢水的處理，同時也可適用於其他產業所產生的奈米顆粒廢水加以處理。 Nano materials have drawn great attractions from scientists and engineers for their phenomena, syntheses, and applications all over our country. It can be foreseen that, within near future, there would be more nano-scale waste in our environment. For example, nanoparticles (e.g., SiO2) from chemical-mechanical polishing (CMP) process of the semiconductor industry are very small and highly charged; hence, they are very difficult to be separated from wastewaters. The purpose of this study is to use magnetic seeding aggregation to enhance the aggregation of silica nanoparticles, and as the consequence, to improve the removal efficiency of silica nanoparticles. The collision frequency between commercial magnetite and silica nanoparticles might not be sufficient since the number of particles per unit weight of the commercial magnetite is very small due to its large size; therefore, magnetite nanoparticles are required to have efficient removal efficiency of the turbidity. Magnetite nanoparticles, whose saturated magnetic susceptibility and size were 55.6 emu/g and less than 300 nm, respectively, were synthesized by chemical co-precipitation of FeCl2•4H2O and FeCl3 in NaOH solution in this study. Synthesized magnetite nanoparticles were then used in the magnetic seeding aggregation of CMP wastewater. Influences of solution pH, salt concentration, G value, and application of an external magnetic field during sedimentation on the removal efficiency of nano silica were examined. It was found that when the solution pH is about 6, NaCl = 0 M, and G = 30 ~ 60 (1/sec), the removal efficiency of the turbidity is the highest, which is about 95% or even higher. When magnetite-silica aggregates settled down in an external magnetic field, besides gravity, they also experienced magnetic forces, which enhance the settling velocity. Hence, high removal efficiency could be achieved in a much shorter time. |
