Production CNT/TiO2 Nanocomposite Using Modified CVD Method for VOCs Removal from Air Sterams

According to our previous study, carbon nanotubes/nanophotocatalyst composites havebeen shown to be efficient in removing VOCs from an air stream. Their efficiency lies in theadvantage of combining the VOCs adsorption and degradation processes without the need fora further regeneration process. The 10%CNTs/TiO2 nanocomposites show a better acetone(ACE) conversion and a higher rate constant of photo-catalytic reaction as compared to thepure TiO2 photocatalysts. This indicates that the presence of CNTs in the photo-catalystcomposites not only offer a good framework and support for the TiO2 particles, but alsoenhance the photo-catalytic activity of TiO2 by efficient removal of electrons from the surfaceof TiO2 nanoparticles. The sol-gel method was employed to produce nano-composites. Thiswas a simple way to control the weight ratio of CNTs/TiO2 and reduce potential errors in thelab work procedure. However, this method suffers from the interference of light interferenceand a further modified procedure is needed. Practically, the preparation method must bemodified to produce nanophotocatalyst composites directly onto the surface of the support andcombine all the preparation procedure into a singular process. This will have the advantage ofsaving time and reducing the cost of the overall process.This is a two-year project. In the first year, different modified chemical vapor deposition(CVD) procedures will be employed to fabricate nanocomposites. Samples from this will becompared through a batch test taking isopropyl alcohol (IPA) and ACE as target pollutants.The aim is to obtain the optimum nanophotocatalyst composite preparation procedure whichcan combine CNTs growth with TiO2 photocatalyst synthesis. The adsorption andphotodegration characteristics will be determined by the batch experiments.In the second year, the best modified CVD process will be further improved with anitrogen doping process. The aim is to enhance the ability of the nanophotocatalystcomposites to interact with visible light, and strengthen their possible applications.Furthermore, a continuous experiment setup will be applied to test the IPA and ACE removalperformance of nanophotocatalyst composites. The mathematical modeling analysis will bealso concluded during the study, to describe the total reaction process and help in defining theexperimental parameters. This will be helpful in the design of a full-scale reactor, properlyestimating the expected VOCs removal efficiency.根據先前研究成果，發現奈米碳管(CNTs)與二氧化鈦(TiO2)光觸媒複合材料較純TiO2其吸附量明顯提升，且CNTs 的存在可以有效移除光催化反應時所產生之電子，阻擾電子、電洞對再結合，進而提升光催化分解丙酮之效率，顯示CNTs-TiO2 光觸媒複合材料具有相當高的開發與應用潛力。但由於sol-gel 製備程序較為複雜，且有光遮蔽效應降低光催化分解速率問題產生，因此針對CNTs-TiO2 複合材料的製備及應用程序仍需進一步研究及探討，以期找出更簡單及快速的製備方法，增加實際應用的可行性。本計畫延續先前研究，針對奈米碳管-光觸媒複合材料的製備程序做更深入的探討，比較不同製備程序下製備材料之差異性，並針對實場應用可行性進行測試評估。第一年目的在建立一高效率CNTs-TiO2 光觸媒複合材料之製備技術，選用3 種不同化學氣相沈積法(CVD)製備程序，調整各項製備參數，並利用批次反應系統進行光催化降解揮發性有機物質效能測試，以求取等溫吸附常數、吸附動力常數及光觸媒催化降解數率常數等特性參數進行比較。第二年則進行連續式反應器設計及試驗，將所得最佳製備程序及製備條件進行若干修正，配合連續式反應器直接製備光觸媒複合材料樣本，以模擬實際應用時，連續式的操作條件下，測試各環境因子對吸附及光觸媒催化降解速率之影響。研究內容並持續改良CVD 製備程序，試圖加入可見光光觸媒改質程序，建立一完整應用性製備程序。研究最後建立一數值理論模式及進行驗證，期望模擬結果與應用性測試實驗結果具有良好之一致性，進而進行模式相關靈敏度分析，並建立實用性設計之方程式，以提供全尺寸反應器設計之參考依據

Treatment of Emerging Pollutants from Effluent Wastewater by Nanocomposites

在高科技產業放流水中，常出現苯乙烯、正丁基苯、三氯甲烷、雙酚A及鉬離子等新興污染物，此類污染物大多具有高生物毒性或為會造成內分泌干擾的環境荷爾蒙物質。有鑑於此，我國環保署已針對光電產業之放流水增訂銦、鎵、鉬與30項毒性有機物管制項目，但傳統的廢水處理單元對於此類污染物的去除能力明顯不足，無法有效的將廢水處理至合乎標準。吸附法與光降解還原法是較具成本效益的新興污染物處理技術。奈米碳管(CNTs)為一有效的新型吸附劑，能有效的吸附水中的污染物質；而二氧化鈦(TiO2)已被證實是相當優良的光觸媒，常應用在有機物的降解與礦化。本研究之期程為三年，針對高科技產業放流水中的新興污染物去除技術進行開發。第一年度將進行CNTs的製備與改質，並以改質之CNTs進行水中環境荷爾蒙、毒性有機污染物與鉬離子的批次吸附試驗，來評估CNTs對水中新興污染物之吸附效果及建立相關操作參數等。第二年度將製備CNT/TiO2複合材料，針對毒性有機污染物做吸附及光分解及操作參數之研究。第三年度是製備CNT/TiO2複合薄膜，同時進行過濾與光降解有害污染物質，將堆積於薄膜上之有害有機物質降解，達到薄膜的自淨功能，此技術將可使薄膜系統達到有效的連續操作，解決薄膜積垢(fouling)之問題，並進一步評估CNT/TiO2複合薄膜應用於實場的可行性。本計畫所開發之CNT/TiO2複合奈米材料及複合薄膜將可以應用於水中環境荷爾蒙、毒性有機物與重金屬離子的去除，改善高科技產業廢水處理系統之效率，藉以達到法規要求之放流水排放標準。There are many kinds of emerging contaminants in the effluent wastewater from high-technology industries, such as styrene, n-butylbenzene, trichloromethane, bisphenol A and molybdenum. These contaminants are toxic and cause hormonal imbalance to organisms. As a result of this, the new stringent effluent standards for the optoelectronics industries announced by the Environmental Protection Agency (EPA) require the removal of indium, gallium, molybdenum and 30 kinds of toxic organics. However, traditional waste water treatment units are either unable or inadequate in providing sufficient removal efficiency of these contaminants. Adsorption and reduction by photodegradation are possible cost effective means for removing them.Carbon nanotubes (CNTs) are superior adsorbents for removing pollutants from aqueous solutions and titanium dioxide (TiO2) has been proven to be an excellent photocatalyst for degradation and mineralization of organics.This is a three-year project, aiming to remove these emerging environmental contaminants from high-technology industries effluent. In the first year CNTs will be prepared and functioned for adsorption of environmental hormones, toxic organics and molybdenum ions from aqueous solutions. Adsorption performance and some operation parameters of CNTs will be evaluated by batch experiments. In the second year, TiO2 will be combined with CNTs to form composite materials, which are used in the photodegradation of toxic organics. The removal efficiency and operational parameters of adsorption/ photodegradation will also be evaluated. In the third year, TiO2-coated CNT membranes (CNTM) will be prepared to provide filtration with photodegradation simultaneously remove toxic organic contaminants from the effluent whilst reducing them and self cleaning the membrane in the process. This solution seeks to treat waste water with a continuously usable system, avoiding fouling problems associated with membrane technology. An evaluation of this system applied in the field will be made following this project.The TiO2-coated CNTM nanomaterial developed in this project will be able to be applied in the filtration and removal of environmental hormones, toxic organics and metal ions improving wastewater treatment systems in the optoelectronics and other industries allowing them to meet effluent standards

以改質奈米碳管進行煙道氣二氧化碳捕獲與濃縮之研究

自2006 迄今，本團隊所發展出之3-aminopropyl-triethoxysilane(APTS)改質奈米碳管(carbon nanotubes, CNTs)為一具有高開發潛力新型奈米吸附材料，在吸附CO2 的研究上已經證明比傳統吸附材料（如活性碳、沸石）具有更高吸附容量與穩定循環吸附能力。CNT(APTS)於煙道除硫系統(Flue GasDesulfurization, FGD)後端條件下(溫度:50ºC、CO2≒15%)，吸附量達到82mg/g (1.9 mmol/g)，比一般碳素或矽素材吸附劑高出數倍，並接近聯合國之氣候變遷組織(Intergovernmental Panel on Climate Change, IPCC)所提出的固體吸附劑吸附量(2 mmol/g)。由研究中又發現CNT(APTS)可完全脫附CO2，20 次循環吸附後，吸附量能夠維持79 mg/g(回復率96%)以上，顯示吸附能力無明顯衰退，而活性碳及沸石則無法有此良好的穩定性。CNTs 優異的吸脫附速率、CO2 捕獲效率、低吸脫附熱值及反覆吸脫附能力，使CNT(APTS)吸附成本能夠降低，預期能夠達到US$40/ton-CO2 以下(歐洲碳排放交易價格)，未來在產業上捕獲煙道廢棄CO2 的應用極具潛力及商機。本計畫預以APTS 改質CNTs 進行煙道氣中CO2 捕獲及濃縮之研究，針對實場需求設計固定床及流體化床反應器，求取CO2 吸附及脫附/濃縮效率及實場操作參數，評估其應用於產業捕獲煙道氣CO2 之成本效益。本計畫為兩年期之研究，第一年度計畫將測試各種不同型式之商用CNTs 等吸附劑之CO2 吸脫附效率及成本分析，以及求取水蒸汽或變溫/變壓法等技術濃縮CO2 之操作參數。CNTs 藉由本研究團隊所開發的APTS 改質技術進行表面處理，以FGD 後端煙道氣條件和固定床吸附系統測試CNT 吸附CO2 能力，並求取水蒸汽或變溫/變壓法等技術濃縮CO2 之操作參數。因一般實場中煙道氣風量較大，固定床吸附系統體積必須增加，並容易發生壓降等問題，所以本研究規劃以流體化床系統來解決實場會面臨之問題。第二年度計畫將設計流體化床系統，進行CO2 吸脫附及濃縮之操作參數求取及成本分析，流體化床系統參數包括床壓與最小流體化速度、氣體流速、床體高度、粒徑尺寸與終端速度、溫濕度效應與熱傳導效率等操作參數，最後並利用水蒸汽或變溫/變壓法濃縮CO2 來評估流體化床應用於實場應用之可行性。本計畫完成後，預計可以提供未來模場或實場測試所需之吸附材改質技術及操作參數等，進行設計及操作，使國內碳捕獲技術更趨於商業化實廠應用。ABSTRACTThe 3-aminopropyl-triethoxysilane(APTS) modified CNTs have been proven to bepromising sorbents for CO2 capture in our previous studies from 2006 to 2009. The resultsindicated that CNTs showed the greatest CO2 adsorption as compared with conventionalsorbents such as activated carbon and zeolite. The CO2 adsorption capacity as high as 82 mg/g(1.9 mmol/g) was obtained with a 15$40/ton-CO2 and desorption of CO2 from CNTs requires lessdesorption heat making them promising sorbents for CO2 capture in the field.This research project will employ CNT(APTS) as sorbent for CO2 capture andconcentration by fixed and fluidized bed adsorption system to assess their feasibility in thefield. The aim of project in 1st year is to find the best commercially available CNTs for CO2adsorption and its operation parameters for steam and thermal/pressure swingdesorption. It includes the study of CO2 adsorption under a simulated environment (post-fluegas desulfurization (FGD)) to distinguish the adsorption and desorption properties foreach type of CNT. The fixed bed system could cause the large pressure drop due to amountof flow rate in the field, which makes the system needs huge volume of adosrber. Hence, thefluidized bed adsorption system will be tested in the 2nd year which is to determine theoperation parameters of fluidized bed CO2 adsorber for the field. It includes the minimumfluidization velocity, pressure of fluidized bed, velocity of CO2 gas, height of fluidized bed,particle size, terminal velocity of particle, effects of temperature and moisture, heatconduction efficiency and CO2 desorption/concentration parameters via steam andthermal/pressure swing desorption.This project expects to provide useful information with respect to the potentialcommercially available CNT and their best operating conditions as design criteria for afull-scale adsorber in the field