以微胞輔助超過濾系統結合電透析程序純化/濃縮/回收含鉻電鍍廢水之研究

Purification, Concentration and Recovery of Chromate from Spent Plating Solution by Micellar-Enhanced Ultrafiltration and Membrane Electrodialysis

王家輝(Jia-Huei Wang)

指導教授 ： 陳孝行

國立臺北科技大學/工程學院/環境工程與管理研究所/碩士(2011年)

摘要

本研究以微胞輔助超過濾法 (Micellar-enhanced ultrafiltration, MEUF) 利用陽離子界面活性劑十六烷基三甲基溴化銨 (Cetyltrimethylammonium bromide, CTAB)結合電透析系統程序 (Membrane electrodialysis)，處理電鍍製程含鉻 (Cr(VI)) 重金屬廢水並達到場內水資源及物質循環再利用之可行性探討。
MEUF 系統研究結果顯示，利用導電法可以得知 CTAB 之臨界微胞濃度為 1 mM；本研究考量 Cr(VI) 截留率及系統流通量，故選定操作壓力為 30 psi；進流水 pH < 5 時，Cr(VI) 以 HCrO4- 存在，會有較佳的截留效率；不論進流水在任何 pH 值操作下，添加足夠的 CTAB 皆能獲得理想的截留效率；在相同的 [CTAB]/[Cr(VI)] 之操作下，進流水濃度越高，其 Cr(VI) 截留效率越好；當進流水 Cr(VI) 濃度為 50 mg/L，進流水 pH 值為 3，操作壓力為 30 psi，[CTAB]/[Cr(VI)] = 3 時，於系統體積迴流率達到 95 % 時，Cr(VI) 濃度可濃縮至原水的 26.6 倍。
於電透析系統試驗結果可知，未結合離子交換膜不能有效分離 Cr(VI) 及 CTAB，又由實驗結果顯示結合陰離子交換膜回收 Cr(VI) 效率較佳；提高進流水離子濃度可降低電力成本之浪費，因此本研究利用 MEUF 系統濃縮含鉻廢水；於電流密度試驗結果顯示，電流密度越大其驅動力越大 Cr(VI) 回收效率越好，但電流密度過大，會增加電解水之反應而造成電流效益下降；電流密度為 20 mA/cm2，於操作時間為 360 min，Cr(VI) 回收效率為 88.2 %。
本研究所採集之實廠廢水為電鍍廢水，其廢水中含有六價鉻、銅、鎳等重金屬離子；利用 MEUF 系統進行迴流濃縮試驗，於操作壓力為 30 psi，[CTAB]/[Cr(VI)] = 1，當系統體積回流率達到 95 % 時，Cr(VI)、銅離子、鎳離子質量截留率分別為 71.5 %、13.6 %、6.6 %；Cr(VI)、銅離子、鎳離子分別可濃縮至原水的 9.3、2.3、1.1 倍，確實可達到 Cr(VI) 純化濃縮之目的。濃縮後之廢液進行電透析系統結合陰離子交換膜回收 Cr(VI) 之程序；電流密度為 20 mA/cm2，操作時間為 360 min，Cr(VI) 回收效率為 85.3 %；確實可有效分離 Cr(VI) 與 CTAB 之結合。

關鍵字

微胞 ； 超過濾薄膜 ； 電透析程序 ； 六價鉻 ； 十六烷基三甲基溴化銨

並列摘要

The purpose of this study is to propose a process combining micellar-enhanced ultrafiltration by CTAB and membrane electrodialysis for the process of spent plating solution to purify, concentrate and recover chromate.
The result showed that CMC of CTAB calculated by conductivity method was 1 mM. The operating pressure of MEUF system was 30 psi, taking chromate rejection and system flux into account. When pH<5, the chromate existed as HCrO4- which caused rejection to increase. Adding enough CTAB in chromate wastewater at any pH value could cause chromate to achieve optimal rejection. In addition, at the same ratio of mole ([CTAB]/[Cr(VI)]) the rejection of chromate increased when feed concentration of chromate was higher. When pH was 3, chromate was 50 mg/L, operating pressure was 30 psi, [CTAB]/[Cr(VI)] was 3 and system volume ratio reached 95 %, the concentration of chromate increased to 26.6 times of raw wastewater concentration in the MEUF system.
The result showed that the recovery efficiency of chromate used anion-exchange membrane (AEM) in membrane electrodialysis system was higher than recovery efficiency of CATB used cation-exchange membrane (CEM). The cost of electricity could be reduced when feed concentration of chromate increased. Thus, this study used MEUF system to concentrate of chromate in wastewater. The result showed that recovery efficiency of chromate increased when current density elevated. However, current efficiency would reduce from reaction of electrolyzed water when current density was higher. When current density was 20 mA/cm2, operating time was 360 min, the recovery efficiency of chromate was 88.2 %.
The spent plating solution of industrial wastewater contained copper, nickel and chromate. Using the MEUF system when operating pressure was 30 psi, [CTAB]/[Cr(VI)] was 1 and system volume ratio reached 95 %, the concentration of chromate, copper and nickel increased to 9.3, 2.3 and 1.1 times of raw wastewater concentration, respectively. And the mass rejection efficiency of chromate, copper and nickel was 71.5 %, 13.6 %, and 6.6 %, respectively. The result could achieve purpose of purification and concentration for chromate. Using the membrane electrodialysis system when current density was 20 mA/cm2, operating time was 360 min, the recovery efficiency of chromate was 85.3 %. The result could achieve purpose of recovery for chromate.

並列關鍵字

micellar-enhanced ultrafiltration ； membrane electrodialysis ； chromate ； cetyltrimethylammonium bromide

參考文獻

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