探討電對流式電透析處理含銅廢水及不同物化因子對陽離子交換膜的傳輸影響

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Title:	探討電對流式電透析處理含銅廢水及不同物化因子對陽離子交換膜的傳輸影響 Studies on electroconvection control of electrodialysis to treat copper wastewater and transfer characteristics of cation exchange membrane by different physico-chemical factors
Authors:	蔡明偉 Tsai, Ming-wei
Contributors:	環境工程與管理系碩士班章日行 Jih-hsing Chang
Keywords:	電化學;電對流;廢水;離子交換膜;電透析;電流電壓曲線 electroconvection;electrochemistry;electrodialysis;ionic exchange membrane;current voltage curve;wastewater
Date:	2008-12-31
Issue Date:	2016-01-11 16:13:52 (UTC+8)
Abstract:	本研究利用電化學分析儀對陽離子交換膜進行特性分析及評估電對流式電透析系統處理含銅廢水的可能性。經結果顯示，在不同含銅濃度下，形成極限電流密度的時間與銅離子濃度無關，且極限電流密度與銅離子濃度成正比，其意旨濃度擴散效應為歐姆區間內，離子傳輸的主要限制因子；在電對流區間方面，當銅離子濃度增加，電對流區間的初始電壓就減少，與能士特方程式一致。在pH值試驗中發現，當系統為酸性條件下，不論是歐姆區間或電對流區間時，皆能有助於提升離子的傳輸速率，其意謂著氫離子將會影響銅離子的傳輸速率。在不同陰離子試驗中發現，控制在歐姆區間內的極限電流密度大小依序為硝酸鹽、氯化物及硫酸鹽，其離子的傳輸特性可能與陰離子種類有關，還需更進一步的研究；在電對流區間時，電流電壓曲線呈現不穩定狀態，此線性關係亦不存在。以電對流式電透析技術處理含銅廢水試驗後發現，電透析系統在處理60分鐘後，濃極室及淡極室的pH值皆趨近於2，其酸化的情形為水解產生所導致，而薄膜表面也觀察到有氫氧化物的結垢產生，可能是薄膜表面產生的氫氧根離子所致；另外，陽離子交換膜於吸附飽和的狀態下，銅離子仍可穿透離子交膜，其意謂著去除效率的減少為其他原因所導致。最後，將使用前後之離子交換膜經由能量散射光譜儀(EDS)及X光射線繞射光譜儀(XRD)分析後發現，使用後的陰離子交換膜靠濃極室表面，有氫氧化銅的結晶物產生；經由傅立葉轉換紅外線光譜儀(FTIR)分析後發現，在使用前後之離子交換膜無明顯變化產生。 This research works on utilizing an electrochemical analyzer to determine ionic transport characteristics of the cationic exchange membrane and evaluating the feasibility of treating copper wastewater by the electrodialysis system under electroconvection control. Results based on different copper concentration exhibit that the occurrence time of limiting current density is irrelevant to the copper concentration and there is a proportional relationship between limiting current density and the copper concentration. This illustrates that the concentration diffusion effect is the major limiting factor of the ionic transport under the ohmic application. For the electroconvection region, the initial voltage of electroconvection region will decrease with increasing the copper concentration, which is consistent with Nernst equation. For testing pH effect, the acid condition aids to enhance the ionic transport rate under both ohmic and electroconvection control. That means the H+ ions will influence the transport rate of copper ions significantly. For testing the effect of different anions, the magnitude order of the limiting current density is nitrate, chloride, and sulfate under ohmic control. There may have certain correlation between the ionic transport characteristics and the anionic species, which needs more investigations. However, the above order can not be followed under the electroconvection control. After treating copper wastewater for 60 minutes by the electrodialysis system under electroconvection control, the pH value of dense compartment and dilute compartment is around 2. This acidification results form the water hydrolysis reactions. It is also observed that some hydroxide scaling attach on the surface membrane, which may be caused by the occurrence of OH- on the membrane surface. In addition, copper ions still can penetrate through the cationic exchange membrane under the saturated condition, which implies the decreasing removal efficiency induced by other reasons. In comparison with the new and used membranes by energy diffused spectrometer (EDS) and X-Ray diffract meter (XRD), we can find that the crystal of copper hydroxide produced on the used anionic exchange membrane in the dense compartment. By Fourier transform infrared spectroscopy (FTIR), there are no significant changes between new and used membranes.
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