具有活性碳/碳黑複合網狀電極之垂直流電容去離子模組

Abstract

電容去離子技術利用外部電壓使電極產生電容，進而移除水中離子。常見的碳材有活性碳材、中孔性碳材及奈米碳管，均是以電雙層電容機制儲存電荷。而活性碳具有極高的比表面積，但導電度不佳，可在其中摻入碳黑來提高整體比電容值。故本研究活性碳之中摻入不同比例的碳黑進行比電容值與去離子效能的比較並且篩選出最佳碳黑比例之電極，再以上述優選之電極應用於垂直流(flow-through)模組評估其氯化鈉水溶液之去離子效能。 本研究分為兩部分，第一部分為探討比電容值與去離子效能之相關性，利用聚合黏著劑(polymer binder)將活性碳及碳黑混合起來，再以含浸法使其披覆於鈦網基材上，接著以不同的碳黑比例製備的電極分析其比電容值的變化，並進行電吸附試驗確認其電吸附能力；第二部分為以垂直流模組進行不同操作參數下(操作電壓、流速)之效能評估。 結果顯示，於10%PVdF時有最好的披覆效果，而不同碳黑比例製備電容去離子電極，隨著碳黑比例提升，比電容值有增加的趨勢，由於含有C=O鍵結的含氧官能基額外提供擬電容。結果也顯示出以水流流況為flow-through的模組進行電吸附評估，發現在碳黑比例為10%且於操作條件於1.2 V、20 ml/min時有最佳電容去離子效能。

Capacitive deionization (CDI) technology is the use of an external voltage for generation of electrode capacitance, thereby removing ions from the aqueous solution. Carbon material applied in the CDI technology include activated carbon, mesoporous carbon material and carbon nanotubes, which store charge with the mechanism of electrical double layer capacitance. Activated carbon processes a very high specific surface area, however, due to poor conductivity of activated carbon, carbon black can be then incorporated therein to improve the overall specific capacitance. Therefore, incorporate different proportions of carbon black in the activated carbon was conducted to prepare capacitive deionization electrode. With those electrodes, the specific capacitance and electrosorption capacity for the activated carbon with different proportions of carbon black could be compared, and screened out a best performance electrode. A Flow-through modular with this preferred electrode was then applied to evaluate its performance on the desalination of NaCl solution. This study can be divided into two parts, the first part is to realize the relationship between the specific capacitance and the desalting amount. Activated carbon (AC) were mixed with carbon black (CB) by using a polymer binder (PVdF), and then landed on the titanium mesh via dip coating method. The mesh AC electrodes with different the ratio of CB were prepared and their changes in the specific capacitance as well as electrically adsorption capacity were investigated. The second part is flow-through modules were operated at different voltages and flow rates for the evaluation of their performances. The results showed that 10% PVdF performed the best coating. With the increase of carbon black, the specific capacitance of CDI electrode has indeed improved due to pseudocapacitance contributed by oxygen-containg functional groups (C=O). The results also showed that flow-through type of CDI modules assembly with 10% of CB laden AC mesh electrode performs the best desalination capacity, especially at the operating voltage of 1.2 V and the flow rate of 20 ml/min.