- 學位論文
以模擬移動床吸附與脫附技術分離海水中銫離子之研究
Separation of Cesium Ions from Seawater by Simulated Moving Bed Adsorption-Desorption Process
摘要
本研究針對遭輻射污染的高鹽分廢水，提出一種以模擬移動床搭載離子交換樹脂進行處理的方法技術，並成功證實遭受銫污染的模擬海水經處理後可將其中的銫離子與海水中的鈉離子分離。研究所使用之模擬移動床係由8支填充管柱所組成的設備，其配管設計可順利讓填充的離子交換樹脂與污染海水進行逆向流動接觸。8支管柱則進一步被區分為吸附段、精餾段、再生段、脫附段，而每一個區段則各有2支管柱。污染海水進入吸附段以及精餾段後，將鈉與銫離子予以吸附，經過脫附段時則只選擇性地脫附鈉離子，經再生段時再將銫離子予以完全脫附分離。其中由精餾段所流出的萃餘液將不含銫離子，而從再生段所流出的萃出液則含高比例的銫離子。 一旦完成離子交換樹脂的吸附與脫附行為調查後，本研究利用一套設定準則，進行模擬移動床實驗的操作條件設定。在所設定的操作條件下，本研究進一步完成調查再生段與脫附段的流速與鹽酸濃度對模擬移動床之影響。研究結果發現再生段的鹽酸濃度與流速必須確保能將離子交換樹脂上的離子予以完全清除，否則容易導致銫離子污染了精餾段出口的萃餘液。脫附段的鹽酸濃度與流速，則主要影響了再生段出口的萃出液之銫離子與鈉離子的含量比例。本研究進一步將每公升含有2000 mg銫離子以及10700 mg鈉離子的海水，成功予以分離成不含銫(低於0.01 mg/L)的廢水以及含銫與鈉離子含量比例高(4.65)的廢水。本研究證實了利用模擬移動床技術進行海水中鈉與銫離子分離的可行性，進一步篩選更適當的離子交換樹脂，則可提升鈉與銫的分離成效以及降低污染廢水被嚴重稀釋的問題。
並列摘要
By a simulated moving bed (SMB) with strong acidic ion exchange resin (SA-IEX), this study has successfully separated sodium and cesium ions from the simulated contaminated seawater. The SMB contains eight packed columns in series, and the piping design of the SMB allows the countercurrent flow of SA-IEX and seawater. The eight columns are partitioned as four sections, the adsorption, the fractionation, the desorption, and the regeneration, and there are two columns in each section. The contaminated seawater flows into the adsorption and fractionation sections to adsorb sodium and cesium ions. The function of desorption section allows selectively to desorb sodium ion, and that of regeneration section allows totally to desorb cesium ions. The raffinate effluent from the fractionation section will mainly contain sodium, and extract effluent from the regeneration section will rich in cesium ions. By examining the behaviors of the adsorption and desorption for the selected IEX, this study also established a criterion to set up the operation conditions for the SMB. With the set up operation conditions, this study also investigated the influences of flow rate and concentration of the hydrogen chloride on both the regeneration and the desorption sections. It is found that the regeneration section should promise total removal of the ions from IEX to avoid the contamination of cesium in the effluent of raffinate. The concentration and the flow rate of hydrogen chloride for the desorption section mainly affects the ratio of cesium to sodium in the effluent of extract. A contaminated seawater with 2000 mg-Cs/L and 10700 mg-Na/L was successfully separated into a wasted stream with 0.01 mg/L of cesium and a wasted stream with a ratio of cesium to sodium as 4.65. This study demonstrates that the separation of sodium and cesium by SMB is feasible. Further investigation on the screening of IEX could promote the effectiveness of the separation and reduce the product dilution by the SMB.