農業廢棄物製備活性碳吸附劑去除揮發性有機物-以甲苯為例

Adsorbent from agricultural wastes for removal of volatile organic compounds (toluene)

10.6841/NTUT.2012.00464

劉思成

農業廢棄物 ； 吸附 ； 活性碳 ； 揮發性有機物 ； agricultural wastes ； adsorption ； activated carbon ； VOCs

臺北科技大學環境工程與管理研究所學位論文

2012年

碩士

席行正

繁體中文

由於大氣中揮發性有機物(volatile organic compounds, VOCs)濃度及工業排放量不斷上升，影響環境及人體健康，因此VOCs之污染問題已引起世界各國的高度重視，許多國家都已嚴格規範VOCs之排放標準，積極尋找減量技術，而活性碳吸附法除了可有效去除低濃度之VOCs外，尚可針對具有回收價值之高濃度有機溶劑蒸氣以吸附方式回收，以減少有機溶劑之使用，而許多研究指出利用農業廢棄物製備活性碳吸附劑吸附VOCs為可行性技術之一。有鑑於此，本研究以不同農業廢棄物(如廢麥粕、銀合歡及竹材)所製備之高比表面積活性碳，作為本實驗之碳吸附劑，以甲苯蒸氣進行活性碳吸附實驗，並透過BET比表面積、孔洞體積、孔洞大小之量測進一步瞭解活性碳吸附特性與物化特性關係，探討其吸附行為及其吸附特性。結果顯示，溫度在25–90℃，濃度在2500–20000 ppm之間，廢麥粕活性碳甲苯吸附量範圍分別介於285–665 mg g-1；銀合歡活性碳甲苯吸附量範圍分別介於253–916 mg g-1；球狀活性碳甲苯吸附量範圍分別介於135–183 mg g-1，其中球狀活性碳吸附量為三種活性碳中最低，原因為球狀活性碳之比表面積僅446 m2 g-1，因此可吸附位址有限，導致吸附量不高。而各活性碳之甲苯吸附量都將隨甲苯濃度增加而增加，但隨溫度升高而降低，而利用吸附實驗數據可求得Langmuir、Freundlich、與Temkin方程式之參數，藉由此參數能獲得不同溫度時之等溫吸附曲線，由等溫吸附曲線可發現，分壓越大其甲苯吸附量也跟著上升，而分壓持續上升時，飽和吸附量曲線逐漸趨於水平。由模擬結果顯示利用Langmuir、Freundlich、與Temkin方程式皆可描述廢麥粕、銀合歡及球狀活性碳之甲苯等溫吸附曲線，其中以Langmuir等溫吸附曲線可獲得較佳之模擬結果(R2＞0.999)。

The concentration of VOCs and the amount of industrial emissions are rising in the atmosphere, and that would be greatly impacting the environment and human health. Therefore, the pollution of VOCs has been concerned around the world. Many countries have strict regulations on VOCs emission standards and are actively seeking reduction technology. Activated carbon adsorption process no only effectively removes the low concentrations of VOCs, but also has capability to recover organic solvent vapor with a high concentration. In order to reduce the use of organic solvents, many studies have pointed out that adsorbing VOCs using activated carbon recovered from agricultural waste material would be a feasible technology. This research aims to use different agricultural wastes (such as waste barley meal, Leucaena leucocephala and bamboo scrap) derived activated carbon with high surface area as the carbon adsorbents. The physical properties included BET and micropore surface area/pore volume and pore size distribution were first investigated. The activated carbon adsorption experiments using toluene vapor as adsorbate was performed to understand the relationships between physico-chemical properties and adsorption capacity. The results revealed that when the temperatures were within a range from 25 to 90℃ and with a concentration between 2,500 and 20,000 ppm, the range of the toluene adsorption capacities for waste barley meal activated carbon, Leucaena leucocephala activated carbon, and spherical bamboo activated carbon were 285–665 mg g-1, 253–916 mg g-1, and 135–183 mg g-1, respectively. The spherical bamboo activated carbon had the smallest adsorption capacity, mainly due to its small surface area of about 446 m2 g-1, which limited its equilibrium toluene adsorption. The toluene adsorption capacity increased with an increase in toluene concentration and a decrease in temperature. The adsorption isotherm was successfully fitted with Langmuir, Freundlich, and Temkin models for all tested sampled and corresponding parameters were determined. Langmuir models showed best fit to the experimental results (R2＞0.999).