| Abstract: | 本論文成功的將結合電化學及薄膜微胞法(MEUF)之結合程序運用於去除低濃度銅廢液，其方法為利用MEUF將自由銅離子累積於結合程序中，再利用電化學法還原銅及界面活性劑，在不斷的吸附(MEUF)及脫附(電化學)，可經濟有效的處理低濃度金屬銅廢液。根據實驗結果發現，去除效率隨SDS進流濃度、電流密度、pH值及水力停留時間增加而增加，最佳操作條件為當水力停留時間15分鐘、SDS進流濃度5.67mM、pH=6及電流密度66A/m2時，銅去除效率及電流效率可分別達到90.3%及30.5%以上，若以最佳操作條件操作24小時，並不會造成薄膜嚴重的阻塞。添加非離子型界面活性劑 Triton X-100於其臨界微胞濃度以上時，可以有效降低SDS的臨界微胞濃度而且SDS滲出濃度亦可以有效的降低；根據實驗結果發現，去除效率會隨著Triton X-100添加量增加而增加，而且不會影響SDS吸附銅離子的能力，其吸附能力為0.21 mole-Cu/mole-SDS，換句話說，5莫耳SDS可以吸附1莫耳的銅離子，但添加Triton X-100後則會造成薄膜阻塞趨於嚴重。而在混合金屬競爭研究中發現，競爭現象與電負度及金屬原子半徑有密切關係，就本研究而言去除效率依序為 鉛>銅~鎳>鋅，以金屬濃度、SDS濃度及Triton X-100濃度分別為136mg/L、8.5mM及3.01mM為例，鉛、銅、鎳及鋅的去除效率分別為63.8%、18.0%、14.0%及5.2%。另外，薄膜阻塞係數Rc可藉由達西定理求得，由原先起始濃度為13.6mg/L時的0.82 (m-1)上升至136mg/L時的11.28 (m-1) ，造成此現象的原因目前尚未了解，可以於之後再更深入的研究探討。
A novel hybrid process combining electrolysis process and micellar enhanced ultrafiltration process (MEUF) for treatment low-concentration-copper wastewater was developed. While MEUF process is employed to retain copper ions inside the reactor, the electrolysis process liberates copper ions from the micellar-copper complexes and continuously reduces copper ions by electroplating them onto the cathode. Thus the proposed hybrid process is operated as a continuous adsorption (MEUF) and regeneration (electrolysis) process. Experimental results show the removal efficiency of copper increases with increasing feed SDS concentration, current density, initial pH value, and hydraulic retention time (HRT). Under the optimum operation condition which has current density of 66A/m2, SDS influent concentration of 5.67mM, pH value of 6, and HRT of 15min, the system was able to obtain copper removal and electrolytic current efficiencies of above 90.3% and 30.5%, respectively, and membrane was not significant with transmembrane pressure (TMP) increasing only around 10% after 24-hour operation.
Addition of a nonionic surfactant, polyoxyethylene Octyl phenyl ether (Triton X-100), with concentration higher than its critical micellar concentration (CMC), to a MEUF process can decrease the CMC value and permeate concentration of sodium dodecyl sulfate (SDS). Results show that the removal efficiency of copper increases with increasing Triton X-100 concentration. The adsorption density (q) of SDS micelles for copper was not affected by Triton X-100 addition with q of around 0.21 mole-Cu per mole-SDS, indicating that each mole copper would need five moles of SDS. However, the membrane fouling was worsening by addition of Triton X-100.
Competitive binding of mixed metals onto SDS micelles was studied, and both atomic electronegative and radius of metals affect their removal efficiencies which are in the order of Pb>Cu≒Ni>Zn. For example, with metals, SDS and Triton X-100 concentration fixed at 136 mg/L of each metals, 8.5mM and 3.01mM, respectively, the metal removal efficiency of Pb, Cu, Ni and Zn are 63.8%, 18.0%, 14.0% and 5.2%, respectively. Membrane fouling is calculation by Darcy’s law, and the membrane fouling resistance (RC) increases from 0.8 to 11.28 (m-1) when metal concentration increasing from 13.6 to 136mg/L. The reason for the increases of membrane fouling with increasing metals concentration is not clear at this point, deserving further investigation in the future. |
