硼摻雜還原氧化石墨烯應用於電容去離子之研究

Abstract

水資源缺乏與污染為當前人類所面臨的環境危機之一。電容去離子技術為一種電化學水處理技術，利用電吸附程序去除水中無機離子，操作及維護簡便，無二次性汙染、低能量消耗以及電極可再生之優勢。本研究利用硼摻雜還原氧化石墨烯作為電極，應用於電容去離子技術移除水中帶電荷離子，評估此電極對於帶電荷離子之去除效率及電吸附效能之研究。研究中利用微波輔助水熱法合成不同含硼比例之硼摻雜還原氧化石墨烯，以電化學循環伏安法及批次式電吸附實驗，探討硼摻雜還原氧化石墨烯在不同離子濃度與操作電壓下，離子電吸附行為，並探討不同陽離子(Na+、Ca2+、Fe3+與Cu2+)於單一與競爭環境下之吸附能力。研究發現，合成反應溫度為170 oC且含硼量為30 wt%的硼摻雜還原氧化石墨烯，在掃描速率5 mV/s之下，比電容值可達356 F/g，另在1.2 V電壓其對於初始濃度100 mg/L之鈉離子有最佳去除率45.9 %，其比電吸附能力(Specific electrosorption capacity, SEC) 2695 µmol/g是還原氧化石墨烯的12.5倍。再將30 wt%之含硼量之硼摻雜還原氧化石墨電極材料烯於電吸附程序中欲去除陽離子(Ca2+、Fe3+與Cu2+)，測試初始濃度為50 mg/L，在1.2電壓下其電吸附效能分別為785 µmol/g、871 µmol/g與940 µmol/g。本研究結果顯示，硼摻雜還原氧化石墨烯作為電容去離子法之電極，可藉由化學摻入硼原子提升其石墨烯之導電性及電子快速地傳遞達成離子的電吸附，增加其移除帶電荷離子的效能。

In present, the shortage of clean freshwater and pollution had poses a critical issue to human habitat on this planet. Here in, capacitive deionization (CDI), an electrochemical water treatment technology has been implemented with the purpose to remove the inorganic ions from the water. CDI holds the promise not only available for ion removal but also consuming low energy consumption, easy operation and act as renewable electrodes. In this study, boron-doped reduced graphene oxide (B-rGO) was synthesized from microwave-assisted hydrothermal method and been selected as an electrode in removing the charge ions from the water through CDI technology. The amount of boron used during the doping process was studied together with the electrochemical cyclic voltammetry and batch type electro-adsorption experiments. The adsorption behavior of B-rGO under different ion concentrations, operating voltages and adsorption capacity of different cations (Na+、Ca2+、Fe3+ and Cu2+) in a single and competitive environment was examined. The results indicated that 30 wt% of B-rGO that synthesized at 170 ºC provide the highest capacitance value up to 356 F/g at 5 mV/s scanning rate. Besides, sodium ion removal has been optimized for 45.9 % when the applied voltage is 1.2 V at concentration of 100 mg/L. The specific electrosorption capacity (SEC) of the B-rGO is 2695 µmol/g, which is 12.5 times higher than reduced graphene oxide. In addition, the electro-adsorption efficiency of the cation removal for Ca2+、Fe3+ and Cu2+ at fixed concentration 50 mg/L and voltage 1.2 V is 785 µmol/g, 871 µmol/g and 940 µmol/g, respectively. With all of the reported results, it is proven that the boron atom that doped onto the graphene sheets not only enhance the conductivity of the materials, but also improve the rate of the electron transfer and in directly enhance the efficiency of charge ions removal.