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標題: | 使用活性碳纖維布結合電熱再生系統吸附與回收汞蒸氣研究 Elemental Mercury Adsorption and Recovery by Electrothermal Swing System with Activated Carbon Fiber Cloth |
作者: | Bing-Ci Chen 陳秉圻 |
指導教授: | 席行正(Hsing-Cheng Hsi) |
關鍵字: | 汞,日光燈管,電熱再生,含氧官能基,活性碳纖維布, Electrothermal swing system,mercury adsorption,mercury recovery,activated carbon fiber cloth,fluorescent lamps recycling, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 汞(Hg)與其化合物是一種危害性很高的氣相汙染物,在過去的數十年科學家投注了許多努力發展替代Hg的科技減少人類對Hg的需求進而減少排放,但現今還是有許多產品是無法避免使用Hg進行製造,其中包括日光燈管、冷陰極燈管和其他醫療設備,日光燈管在日本有很穩定的需求,而液晶螢幕的需求近年有上升的趨勢,同時在台灣每年都有4,500,000公斤的廢含Hg燈管被回收,由此可知含Hg產品的汞回收和逸散防治對於環境生態的保護與人類健康的維護相當重要。本研究想改善的現今日光燈管的Hg回收程序,現今在台灣含Hg的廢日光燈管回收程序依序為: 產品的零件拆解、螢光粉的收集、元素汞(Hg0)蒸氣冷凝程序和最後的低濃度Hg0蒸氣之活性碳床吸附,在燈管回收中所採用之活性碳為含硫活性碳(SAC),利用SAC表面的硫元素取捕捉尾氣中的Hg0提高材料的吸附效率,然而SAC的再生卻極困難,被捕捉的Hg0蒸氣會在SAC表面形成硫化汞(HgS)穩定的吸附在SAC表面,HgS非常穩定因此SAC的再生需要花費較多的能源與金錢,使用過的SAC通常會因為再生不易而被視為有害事業廢棄物進行固化和掩埋的處理。
本研究的目的是提出一個有效且易再生的材料去吸附和回收汞且提出一個較便宜和環保的方式去再生所使用的材料,因此本研究採用活性碳纖維布(ACFC)吸附汞並且使用不同功率的電(20 W、40 W和60 W)以電熱的方式再生ACFC。實驗結果顯示,採用ACFC為Hg0吸附材料以吸附260~300 μg/m3的Hg0吸附效率為80%,經過電熱再生的程序後吸附效率不但沒下降反上升,同時Hg0的回收效率也很好,根據材料表面物化性分析本研究推估吸附效率上升的原因跟ACFC表面之含氧官能基有很大的關係,所以本研究嘗試利用酸洗的方式增加ACFC表面含氧官能基的數量,檢驗含氧官能基是否確實可以增進ACFC的吸附效率,結果顯示酸洗過後ACFC的吸附效率從80%增加至90%以上,但是Hg0的回收率有下降的趨勢,為了檢測ACFC電熱系統的持續運作能力,本研究對ACFC進行九次吸脫附試驗以檢測ACFC的可再生性,結果顯示ACFC經九次吸脫附之後還擁有89%的去除效率(去除效率隨者吸脫附次數持續上升),種種結果都顯示ACFC是一個具高度潛力可再生的Hg0吸附材,本研究也提出了可能的表面反應機制解釋 Hg0的吸脫附現象,並同時以脫附動力學模型式了解Hg0在ACFC和酸洗過後的ACFC表面鍵結關係。 Mercury (Hg) is one of the most hazardous air pollutants. It has a wide range of effects on humans and natural organisms. In the past decades, efforts have been devoted to Hg usage reduction. However, with the huge amount of abandoned fluorescent lamps, it is important to carefully capture and recover the Hg0 in the products in order to both cut down humans’ Hg demand from the environment and avoid the hazardous effect of Hg on the environment and human health. The work presented aims to develop a novel and sustainable approach to adsorb and recover the low-concentration Hg0 in the tail gas of recycling processes for fluorescent lamps. Activated carbon fiber cloth (ACFC) is a material used for high-efficiency adsorption due to its high surface area and fiber structure. In this study, a series of experiments were carried out to determine ACFC and nitric acid treated ACFC (HNO3-ACFC) Hg0 adsorption efficiency and regeneration efficiency. The purpose of nitric acid treatment is to examine the effect of different amount of oxygen functional groups on Hg0 adsorption efficiency. The regeneration was done by an electrothermal process. The electrothermal regeneration was conducted with 20 W, 40 W and 60 W of regenerating electricity. Through excessive heat, adsorbed Hg0 would be released rapidly from ACFC surface, resulting in high Hg0 concentration in the effluent, nearly three times of the amount of initial concentration that could make condensation easier for the recycling plant to recover Hg0. The effectiveness of regenerated ACFC and HNO3-ACFC for Hg0 adsorption was also examined in this study. The experimental results showed that, with an initial Hg0 concentration in a range of 260~300 µg/m3, ACFC had about 80% of Hg0 adsorption efficiency. After electrothermal regeneration ACFC Hg0 adsorption efficiency generally rose up to nearly 90% after 60 W electrothermal regeneration. After acid treatment, the content of oxygen functional groups on HNO3-ACFC increased and enhanced the adsorption kinetics, resulting in over 90% of adsorption efficiency before and after electrothermal regeneration. Both ACFC and HNO3-ACFC still had great adsorption efficiency after nine cycles of adsorption and regeneration. These results indicated that ACFC and HNO3-ACFC can be an effective and renewable adsorbent for low concentration Hg0 adsorption and recovery. A mechanism was proposed in this thesis to explain the increasing adsorption efficiency after electrthermal regeneration and the higher adsorption efficiency for HNO3-ACFC. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69299 |
DOI: | 10.6342/NTU201801540 |
全文授權: | 有償授權 |
顯示於系所單位: | 環境工程學研究所 |
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