以電容去離子技術回收銦離子之可行性研究

Abstract

The consumption of indium has increased over the past decades due to the development of high-tech industry. It is essential to explore a clean and efficient process for indium ions (In3+) separation from aqueous solutions. Capacitive deionization (CDI) with highly porous carbon electrodes is an energy-efficient and environmentally-friendly process to remove ions via electrical double layer formation. More recently, membrane capacitive deionization (MCDI) has been developed by placing ion-exchange membranes (IEMs) in the front of electrodes to reduce the co-ion effect. Therefore, MCDI has improved salt adsorption capacity and charge efficiency in comparison with CDI. The objective of this study is to evaluate the feasibility of using CDI to recover In3+. As demonstrated by surface and electrochemical measurements, the activated carbon electrodes with a high specific area and high ratio of mesopores volume and total volume show good capacitive performance for the storage of In3+. The effects of voltage, pH, and In3+ concentration on CDI performance were further investigated to optimize operation parameters for In3+ removal. When increasing potential, pH value, and concentration, the removal capacity of activated carbon electrodes was enhanced. The experimental results show that a high recovery of 90% to recover In3+ can be achieved in CDI, which was conducted at a concentration of 50 mg L−1, pH=3.5 and potential of 1.2 V. Note that the precipitation happened in CDI process at pH=4. Additionally, In3+ selectivity in MCDI process was lower than that in CDI process due to the relatively low mobility of In3+ in the membrane matrix. Overall, CDI can be considered as a promising technology for recovery of In3+.