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標題: | 利用廢油砂焦碳透過微波化學活化法及傳統化學活化法合成活性碳應用於去除水溶液中的二價汞 Preparation of Activated Carbon from Waste Oil Sands Coke by Microwave and Conventional Chemical Activation for Removal of Mercury (II) from Aqueous Solution |
作者: | Tung-Fu Shih 施東甫 |
指導教授: | 席行正(Hsing-Cheng Hsi) |
關鍵字: | 汞,活性碳,吸附,油砂焦碳,微波,中央合成設計實驗,反應曲面法, mercury,activated carbon,adsorption,oil sands coke,microwave,central composite design,response surface methodology, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 汞為一重金屬,其毒性及生物累積性容易造成人類與其他哺乳類的健康危害。若汞經由人類活動排放至水體中若未經過控制,則會造成地區性的嚴重危害。活性碳吸附為目前控制水溶液中之汞的主要方法之一。同時,經過硫改質的活性碳含有硫官能基於其表面,在水溶液中吸附汞顯示了高效及高選擇性。
廢油砂焦碳(Waste oil sands coke)為從油砂提煉石油的過程中產生的副產物。2012年末之前已有7700萬噸的廢油砂焦碳因無法有效處置被儲存,已佔了大量土地。同時,由於其含有約90%的碳,可以不必經由碳化步驟,適合作為活性碳的前驅物。並且油砂焦碳含有約5-6%之硫,可以預測其製備之活性碳對汞的吸附效果佳。 本研究透過反應曲面法(Response surface methodology)結合中央合成設計實驗(Central composite design)作為觀察活性碳性質隨不同條件變化之工具。就產率、硫含量、及比表面積而言。發現微波化學活化的可預測性較差,而傳統化學活化法則相對穩定。 在吸附動力學方面,在初始濃度為100 mg-Hg2+/L測試條件下,不論透過微波化學活化法或傳統化學活化法,均以擬二階動力學模式適合模擬實驗結果。在等溫吸附的實驗中則以Freundlich equation較符合等溫吸附實驗結果。而在飽和吸附容量的實驗中,在初始濃度為100 mg-Hg2+/L測試條件下,油砂焦碳飽和吸附容量為12.58 mg-Hg2+/g-AC,去除率為14.44%;透過微波化學活化產生之活性碳飽和吸附容量達82.26 mg-Hg2+/g-AC,去除率可高達94.83%;而透過傳統化學活化產生之活性碳飽和吸附容量92.89 mg-Hg2+/g-AC,去除率可高達97.81%。研究結果顯示,不論透過微波化學活化或是傳統化學活化,均可有效將廢油砂焦炭轉化成有效的活性碳吸附劑應用於水相汞污染去除。透過X射線光電子能譜儀之分析可將去除效率之提升歸因於活化過程中COO及C-O-官能基的形成。 透過反應曲面法結合中央合成設計實驗優化微波活化的操作參數可以獲得,若欲達到94%以上之去除效率,則活化功率為750-1000瓦,活化時間為4-5分鐘。而傳統活化則是活化溫度為700-800℃,活化時間為45-80分鐘。 Mercury is a toxic element existing in nature. After mercury enters the aqueous system, it will be transformed into methylmercury and then go through a biomagnification process. If the release of mercury by human activities was not well controlled, it may result in the regional disaster. Activated carbon is the common sorbent used in removal of different kinds of substances in various phases. It has also been proven that activated carbon impregnated with different forms of sulfur is capable of improving the efficiency on adsorption of mercury in aqueous system. Oil sands coke is a byproduct in the process of upgrading the crude oil from oil sands. Moreover, it has high carbon content and sulfur content (approximately 5-6 wt%), which results into that oil sands coke is a good precursor of activated carbon used in removal of mercury from aqueous solution. In this study, activated carbons from oil sands coke were successfully prepared by microwave and conventional chemical activation under a series of activation conditions designed by response surface methodology in combination with central composite design (CCD-RSM). By doing so, the change of physical and chemical characteristics were able to be observed by the CCD-RSM analysis. Compared with conventional chemical activation, microwave chemical activation can develop the surface area and pore volume of activated carbon in shorter time and with a higher production yield and similar SBET. In contrast, the physical and chemical properties of activated carbon from conventional chemical activation is more predictable than activated carbon from microwave chemical activation, in terms of their variation on the activation parameters. The mercury (II) adsorption data for activated carbons from both microwave chemical activation and conventional chemical activation were best fitted with the pseudo-second order model in adsorption kinetics and Freundlich model in adsorption isotherm. The mercury (II) adsorption capacity and removal efficiency of original fluid coke were 12.58 mg-Hg2+/g-AC and 14.44% respectively. The mercury (II) adsorption capacity and removal efficiency of activated carbon from microwave activation were 82.26 mg-Hg2+/g-AC and 94.83% respectively. The mercury (II) adsorption capacity and removal efficiency of activated carbon from conventional activation were 92.89 mg-Hg2+/g-AC and 97.81% respectively. These results suggest that both conventional activation and microwave activation are able to transform the fluid coke into a suitable sorbent for mercury removal from aqueous phase. Pearson correlation analysis shows that the oxygen content and hydrogen content may be the main factors of determining mercury adsorption capacity of the resulting activated carbon. Through XPS analysis, the improvement of mercury (II) adsorption capacities can be attributed to that the formation of the phenolic, alcoholic, etheric functional groups (C-O-) and Carboxyl or ester functional groups (COO). The optimized operating condition of microwave chemical activation can be observed at the power level of 750-1000 W and time of 4-5 min and the removal efficiency would achieve 94%. The optimized operating condition of conventional chemical activation can be observed at the temperature of 700-800℃ and time of 45-85 min and the removal efficiency would achieve 94%. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/7676 |
DOI: | 10.6342/NTU201703567 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 環境工程學研究所 |
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