利用電容去離子系統處理氟系廢水之研究;Treatment of Fluoride-containing Wastewater By Capacitive Deionization

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Title:	利用電容去離子系統處理氟系廢水之研究;Treatment of Fluoride-containing Wastewater By Capacitive Deionization
Authors:	王新閎;Wang, Xing-Hong
Contributors:	環境工程研究所
Keywords:	電容去離子;氟化物;氫氧化鉀;濃縮;capacitive deionization;fluoride;potassium hydroxide;concentrated
Date:	2020-04-07
Issue Date:	2020-06-05 17:48:08 (UTC+8)
Publisher:	國立中央大學
Abstract:	電容去離子技術(capacitive deionization, CDI)為一種新興高級水處理技術，其利用帶電之電極吸附水中離子，優點甚多，為未來發展的趨勢之一。現今含氟廢水以半導體廠為大宗，包含廠內製程及其洗滌廢水，來源複雜，需加以處理始得排放，故本研究以預先加藥後，利用CDI去除氫氟酸及直接濃縮氟化銨之方式探討，以CDI技術降低水中氟離子濃度。研究中以氫氧化鉀為最佳之藥劑，並分別利用不同之K/F比進行。結果發現當K/F為1.5時，有最佳的吸附量0.090 mM F g 1-C，且也有最好的脫附效率，以及處理後之酸鹼值對環境水體的衝擊影響較小。而在濃縮的部分，以不同的操作條件進行濃縮。結果顯示充電至導電度為初始值時，所得到的濃縮率最佳為1.3倍。此外，本研究也擬合了動力學，結果顯示Elovich model最為符合，其R2均高於0.95。此動力模式表示了吸附氟化物的過程中牽涉化學鍵的變化。故本研究利用X射線光電子能譜(X-ray photoelectron spectroscopy, XPS)測定使用後的電極表面C1s化學態之組成變化，得知Semicovalent C-F的比例由6.37%提升至6.73%與Covalent C-F的比例由2.27%提升至4.86%。;Capacitive deionization (CDI) is an emerging advanced water treatment technology. It adsorbs ions in the water with charged electrodes. It has many advantages and is one of the future development trends. Fluoride-containing wastewater is one major problem semiconductor industry for its large amount and possible hazards. The source of fluoride is complex and must be treated and then disposed without causing environmental burden. The objectives of this work are two to remove the fluoride by choosing a proper chemical and to concentrate fluoride. According to the electrosorption amount and efficiency, potassium hydroxide was the best chemical and the optimal K/F ratios was 1.5. Also, at this condition, the pH value after treatment has the least impact to the environment. In terms of concentration, the best concentration ratio was obtained by charging the system until the conductivity rose to the initial value, at which the F- was concentrated 1.3 times. The kinetics results showed that the Elovich model fitted the experimental data best, with R2 above 0.95. This kinetic model suggested changes in chemical bonds involved in the electrosorption process. X-ray photoelectron spectroscopy (XPS) showed that the semicovalent C-F bonds increased from 6.37% to 6.73% and the covalent C F bonds increased from 2.27% to 4.86%.
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