以薄膜過濾及離子交換處理含錯合劑及金屬離子之廢水

Treatment of Water Containing Complexing Agents and Metal Ions by Membrane Filtration and Ion Exchange

王宗源(Tsung-Yuan Wang)

指導教授 ： 莊瑞鑫

元智大學/工程學院/化學工程與材料科學學系/碩士(2002年)

摘要

中文摘要
離子交換與化學濃縮技術廣用於廢水中重金屬離子交換之移除，而形成錯合物之移除效能受錯合劑與金屬離子形成反應的影響。本論文主要在探討工業廢水及核能廢水中，錯合劑存在時對陽離子交換樹脂與薄膜分離篩濾對金屬離子吸附效能之影響。然而離子交換樹脂與薄膜分離法為水污染防治極具發展潛能之廢水處理技術，在配合環境保護之原則下，朝向低成本、高效率、無二次公害及資源回收之目標努力。
本研究以不同金屬離子（Mn2+、Co2+、Ni2+、Sr2+）及不同之錯合劑（EDTA、NTA、檸檬酸）進行陽離子樹脂交換，再配合薄膜篩濾試驗及現場放射性廢水模擬測試，藉由改變pH值，錯合劑種類及莫耳濃度來對整個去除的效能做探討，在單成分金屬離子且pH 大於9時，Mn2+、Co2+、Ni2+、Sr2+與EDTA、NTA、檸檬酸錯合，其去除率皆大於99﹪，唯獨Sr2+與檸檬酸錯合去除率小於92﹪。而於多成分金屬離子混合在兩價離子競爭效應下，其去除率EDTA＞NTA＞檸檬酸。
由實驗結果得知，當水溶液pH值上升時，金屬與錯合劑作用增強，所以大部份金屬離子被錯合劑捉住，以致離子交換樹脂對金屬離子之去除率下降。當pH 低於2 時，大部分金屬離子不與錯合劑形成錯合反應，陽離子吸附性最大。故pH 大於9 時，錯合能力最大，但離子交換效果差。pH 低於2時，金屬離子吸附性最大，錯合能力卻最小。在此，我們將這些變數分別討論之。

關鍵字

錯合劑 ； 離子交換 ； 薄膜分離

並列摘要

Abstract
Ion exchange and chemical precipitation processes are well-established methods for removal of heavy metal ions from aqueous solutions and widely used in industry and nuclear wastewater treatment. While in the presence of complexing agents the treatment performance is severely affected due to the complex formation of the complexing agents and metal ions. This study aims at investigating the effects of complexing agents on the removal efficiency of metal ions from aqueous solutions by ion exchange method and exploring feasible strategies for solving the treatment problems caused by complexing agents contained in the aqueous wastewaters.
Experiments were performed using sodium salt of ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and citric acid as the model complexing agents and using Mn2+, Co2+, Ni2+, Sr2+ as the model metal ions to be removed from the aqueous solutions. Methods of membrane separation and ion exchange were employed to investigate the separation efficiencies of metal ions by changing various parameters including pH, kinds and molar concentrations of the complexing agents.
Results show that in single component systems almost all of the metal ions in solutions conjugate with complexing agents at pH above 9 and can be separated from the solutions by nanofiltration. Separation efficiencies for all metal ions conjugated with EDTA and NTA are greater than 99 percent. While for Sr2+ ions conjugated with citric acid only 92 percent efficiency is obtained. The tendency for mental ions to form complexes with complexing agents follows the sequence: EDTA > NTA > citric acid.
It also reveals that removal efficiencies of metal ions by ion exchange decrease as the pH rises due to enhanced conjugation between metal ions and complexing agents. While at pH below 2, removal efficiencies are grater than 95 percent because most of the metal ions doesn’t form complexes with the complexing agents and can be removed by ion exchange.

並列關鍵字

Complexing Agents ； Ion exchange ； Membrane separation

參考文獻

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