以具分散反萃取相支撐式液膜回收螯合銅離子

Abstract

現今螯合劑的使用非常廣泛，常應用於印刷電路板、造紙業及半導體製程等，經過上述製程後往往會產生許多含螯合劑之金屬廢液，若能將其中具經濟價值之金屬離子進行回收，不但能節省製程成本，更能降低對環境之汙染。因此本研究以Lix984N為萃取劑，使用具分散反萃取相支撐式液膜搭配過氧化氫/UV光法、三價鐵離子置換法，回收及濃縮螯合系統中的銅離子，並於純銅系統中利用電解法將具分散反萃取相支撐式液膜後所得的高濃度銅離子還原成零價金屬銅。 本研究之螯合銅系統選用三種不同的螯合劑，分別為IDA、HIDA及EDTA。IDA與HIDA系統使用具分散反萃取相支撐式液膜單一程序即可回收進料相中之銅離子，前者可於15分鐘的操作下，將進料相溶液中300 mg/L之銅離子完全回收，透過係數達1.3×10-4 (m/min)；後者於600分鐘的操作下可移除進料相中270 mg/L之銅離子，透過係數為1.7×10-6 (m/min)。EDTA系統於相同條件下透過係數僅為1.3×10-7 (m/min)，因EDTA與銅離子之螯合性遠大於前述兩種螯合劑，因此本研究於具分散反萃取相支撐式液膜前先進行前處理，以提高回收效率。前處理方法分為過氧化氫/UV光法及三價鐵離子置換法兩種。過氧化氫/UV光法於EDTA/Cu2+/H2O2莫爾數比為1:1:100時，可降解進料相溶液中的EDTA，接著使用具分散反萃取相支撐式液膜回收銅離子，透過係數達1.4×10-4 (m/min)，回收率達92%。三價鐵離子置換法於EDTA/Cu2+/Fe3+莫爾數比為1:1:3之前處理條件下，鐵離子可與大部分的銅離子進行置換，接續利用具分散反萃取相支撐式液膜進行回收，透過係數達7.8×10-5 (m/min)，回收率達95%。 除了回收螯合系統中之銅離子，本研究亦利用具分散反萃取相支撐式液膜回收純銅離子，並接續進行電解程序，將銅離子還原成金屬銅，依序進行四次批次循環實驗後，發現反萃取相經電解後可以再次使用於具分散反萃取相支撐式液膜中，並不會影響銅離子之透過係數。此外因批次實驗將花費較多時間與成本，故本研究將具分散反萃取相支撐式液膜程序與電解程序串聯，同時進行以提高操作效率，結果顯示在具分散反萃取相支撐式液膜操作的同時，反萃取相中的銅離子可藉由電解還原成金屬銅，而經電解後的反萃取相可再回流至具分散反萃取相支撐式液膜中使用。由此可見此串聯程序確實可提操作效率，後續若參數調整得宜，可於實驗室規模下進行連續式操作，同時亦可作為日後製程放大的參考依據。

The wide application of chelating agents in printed circuit board industry, paper-making industry and semiconductor process results in wastewater which contains various metal ions and chelating agents. Recovery and purification of the metal ions, not only can reuse of them, but have great merits for cost reduction and pollution control. The present work reports on the technique of supported liquid membranes with strip dispersion (SLMSD) using Lix984N as extractant, H2O2/UV method, Fe3+ substitution method to recover copper ion from chelating agent systems. Additionally, electrolysis was operated after SLMSD in pure copper system to recover copper at metal state. The chelating agents in this study were chosen as IDA, HIDA and EDTA. Almost 300 mg/L Cu2+ could be removed from feed phase by SLMSD in Cu-IDA system and Cu-HIDA system. In Cu-IDA system, it took 15 minutes to remove 300 mg/L Cu2+, and the permeability was 1.3×10-4 m/min. In Cu-HIDA system, 270 mg/L Cu2+ was removed in 600 minutes and the permeability was 1.7×10-6 m/min. In Cu-EDTA system, the permeability was 1.3×10-7 m/min at the same condition. Because of high stability constant between Cu2+ and EDTA, there were two pretreatment methods (H2O2/UV method and Fe3+ substitution method) could be chosen before starting SLMSD to enhance copper recovery efficiency. H2O2/UV method could degrade EDTA efficiently at molar ratio EDTA : Cu2+: H2O2 = 1:1:100, and the permeability of Cu2+ was 1.4×10-4 m/min by SLMSD. With Fe3+ substitution method, most chelated copper ion could be substituted by Fe3+at molar ratio EDTA : Cu2+: Fe3+ = 1:1:3. Then recover copper ion by SLMSD after substitution, the permeability was 7.8×10-5 m/min at pH2. In addition to recover copper ion from chelating agent system, the present work also recovered copper ion from pure copper system by SLMSD, and electrolysis was operated after SLMSD. After four cycles of SLMSD and electrolysis batch experiments, it was found that stripping solution could reuse in SLMSD after electrolysis, and would not affect the permeability of copper ion. Due to long operation time and high cost of batch process, this study also connected SLMSD and electrolysis in series. The result showed that copper ion in stripping solution could be reduced to metal state simultaneously when SLMSD was operating, and stripping solution could return and reuse in SLMSD after electrolysis, too. Thus it can be seen the SLMSD and electrolysis in series process could indeed enhance copper recovery efficiency.