| 摘要: | 水資源匱乏問題日益受到世界各地關注，由於海水蘊藏量豐富，因此海水淡化技術的開發逐漸受到重視。電容去離子 (capacitive deionization, CDI)是新穎的海水淡化技術，CDI是一種利用電吸附程序去除水中離子的電化學水處理技術，具有操作及維護簡便、無二次性污染、低能耗以及可逆性等優勢。電極材料是影響CDI性能的最主要因素之一，因此本研究著重於電極材料特性之探討。
本研究所使用的電極材料為石墨烯(graphene, rGO)，石墨烯擁有極佳的電導率及電化學穩定性，故非常適合應用於電容去離子。但由於石墨烯屬於略為疏水的材質，較不利於水處理程序，因此本研究主要是利用強酸與強鹼改善石墨烯之親疏水性問題。
以混合酸HNO3:H2SO4= 2:1處理石墨烯電極後，其接觸角由78.09°下降至19.45°，親水性明顯提升；同時，其比電容亦從原本的39.06 F/g，提升至145.81 F/g，約為3.73倍。以強鹼改質部分，以KOH改質後之石墨烯，接觸角由78.09°下降至21.97°，由於親水性的提升，比電容亦從原本的39.06 F/g上升至56.83 F/g，約為1.46倍；兩種處理方法相較，以酸處理之整體效應優於鹼處理的方式，其中又以HNO3:H2SO4= 2:1比例處理的石墨烯，於電容去離子技術之應用深具潛力。
The shortage of potable water has become one of the major issues nowadays. In order to relieve this condition, desalination technologies has become more important. Capacitive deionization (CDI) is a novel technology for desalination, which is an electrosorption process. It works by attracting salt ions to the surface of electrodes where ions are held in electrical double layers (EDLs) when the electrodes are charged, then releases the ions when potential is removed. There are several advantages of CDI system, including easy to install and maintain, no secondary pollution, energy efficiency and easy to regenerate.
The electrode material is the most important factor to affect CDI performance, so this study focuses on the characteristics of electrode materials. In this study, we use graphene (rGO) for the electrode. Graphene is a carbon material with unique mechanic and electronic properties, which is very suitable for the electrode for CDI system. We use strong acid or strong base to improve the wettability of graphene to enhance the CDI performance.
When graphene was treated with mixed acid HNO3: H2SO4 = 2: 1 (volume ratio), the contact angle decreased from 78.09° to 19.45°, which indicating the wettability was improved. The specific capacitance was also increased around 3.73 times from 39.06 F/g to 145.81 F/g.
After graphene was modified by KOH, the contact angle of graphene decreased from 78.09° to 21.97°, and the specific capacitance increased around 1.46 times from 39.06 F/g to 56.83 F/g.
Comparison between these two treatment processes, acid modification is much better than strong base treatment. With acid treatment, the graphene treated by HNO3: H2SO4 = 2: 1 is the most suitable for CDI system. |
