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题名: 多孔炭材料上挥发性有机物吸附过程的研究
作者: 王刚
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 郝郑平
关键词: 挥发性有机物,多孔炭,孔径调变,疏水改性,吸附动力学,Volatile organic compounds, porous carbon material, tunable pore size, hydrophobization, adsorption kinetics
其他题名: Adsorption property of volatile organic compounds (VOCs) on porous carbon materials
学位专业: 环境工程
中文摘要:     进入二十一世纪,伴随着我国石油化工、制造业等的快速增长,环境污染问题日益严峻。其中空气污染由于污染程度深、影响范围大引起了政府与公众的极大关注。挥发性有机物(Volatile Organic Compounds, VOCs)是造成空气污染的主要因素之一。吸附法可浓缩回收大部分的有机气体,是一种有效的控制VOCs的技术。本文针对工业源排放的VOCs,采用多孔炭为吸附剂,研究了多孔炭材料上VOCs的吸附过程,阐明VOCs分子在多孔炭材料上的吸附机理及影响吸附剂吸附性能的主要影响因素。研究的主要内容及取得的成果和结论如下:
    1,不同尺寸的VOCs分子在有序介孔炭上的吸附性能
    采用溶剂挥发自组装的方法合成了有序介孔炭,其具有二维六方的直形孔道和较大的比表面积、孔体积。采用具有相同碳原子数、不同分子结构的苯、环己烷和正己烷作为吸附质,研究了三种吸附质在介孔炭上的吸附性能。 研究结果表明,由于具有较大的孔体积,介孔炭对三种吸附质的饱和吸附量均较高;但由于介孔炭微孔含量较低,因而动态吸附量远低于静态饱和吸附量。吸附动力学研究表明,由于具有较宽的孔径,吸附质在介孔炭上的扩散速率高于活性炭;且分子尺寸不同的吸附质,扩散速率相差不大。
    2,吸附质在孔径调变介孔炭上的吸附性能
     通过硬模板添加扩孔剂的方法合成了小介孔(3-8纳米)范围内孔径调变的有序介孔炭,所得到的介孔炭系列材料,其总孔容和微孔孔容均保持基本不变,孔径随着扩孔剂用量的增加依次增大。选择苯作为典型污染物,研究了苯在不同孔径介孔炭上的静态及动态吸附性能。 研究结果表明,在相同的吸附质浓度下,吸附质在介孔炭上的静态和动态吸附量均会随着孔径的增大而下降,等量吸附热也具有相同的变化规律,主要原因是由于孔道内势能叠加作用随着孔径的增加而降低。
    3,活性炭疏水改性及对VOCs的吸附性能
    为了提高传统吸附剂活性炭的疏水性能,增加高湿度条件下活性炭对VOCs的吸附量,采用三甲基氯硅烷、六甲基二硅胺烷和四氯化硅三种有机硅烷作为改性剂对活性炭进行疏水改性。采用各种表征手段考察了改性前后活性炭的结构、性质变化,并以苯为吸附质研究了改性前后活性炭在不同湿度情况下对VOCs的吸附性能。
     研究结果表明,通过改性,有机官能团成功嫁接于活性炭表面,但同时会造成活性炭比表面积和孔体积的下降。吸附试验结果表明,在改性后单位比表面积上VOCs的吸附量有所增加,同时由于有机改性后活性炭总孔容和比表面积降低,在高湿度条件下,改性后的活性炭对VOCs的总吸附量有一定程度的下降。
英文摘要:     In the 21st century, with the rapid increase of petrochemical and manufacturing industry in China, the environmental pollution problem is growing serious. Among these problems, the air pollution causes great concern to the government and public for its high degree of pollution level and wide scope of influence. Volatile organic compounds (VOCs) are one of the main factors resulting in the air pollution. Adsorption method can be used to concentrate and recycle most of organic compounds and is an effective technology for VOCs control. In this work, porous carbon materials were used as adsorbents for the removal of VOCs. Adsorption procedure of VOCs onto porous carbon materials were studied, the adsorption mechanism and factors influencing adsorption property were clarified. Main contents and conclusions are summarized as follows:
    1, Adsorption property of VOCs with different molecular sizes onto ordered mesoporous carbon (OMC)
    Evaporation induced self-assembly method was used to synthesize ordered mesoporous carbon, the OMC possesses high specific surface area and large pore volume. Benzene, cyclohexane and hexane were selected as typical adsorbates as they have different molecular structures based on six carbon atoms. Adsorption property of three kinds of adsorbates onto OMC were studied. The results show that because of the large pore volume, the saturation adsorption amounts of adsorbates onto OMC are large. However, as the micropore volume of OMC is small, dynamic adsorption amounts are relative smaller. Research on adsorption kinetics reveal that benefit from the wide pore size, diffusion rate of adsorbates onto OMC is faster than activated carbon, and molecules with different sizes own similar diffusion rates.
    2, Adsorption of benzene onto OMCs with tunable pore size
    Hard-template method and pore-expanding agent were adopted to synthesize OMCs with tunable pore size in the small mesopore range 3-8 nanometer. The pore sizes of OMCs increased with the dosage of pore-expanding agent, but the total and micropore volumes were almost the same with each other. Benzene was selected as adsorbate and adsorption property of benzene onto tunable OMCs was studied. Results show that with the same concentration of adsorbate, the adsorbed amount of benzene onto OMCs under static and dynamic conditions decreased with the pore size increased, and the isosteric heats of adsorption follow the same tendency. The main reason is that the overlap of potential energy originated from pore wall decreased as the pore size increased.
    3, Hydrophobization of activated carbon and the adsorption property
    In order to enhance the hydrophobicity of activated carbon and increase the adsorption amount of VOCs onto activated carbon under high relative humidity, trimethylchlorosilane (TMCS), hexamethyl disilazane (HMDZ) and silicon(IV) chloride (SiCl4) were used for the hydrophobization of activated carbon. Various methods were used to investigate the structure change after hydrophobization, adsorption property of benzene onto activated carbon under different humidity conditions before and after hydrophobization were studied.        
     Results show that through hydrophobization, organic functional groups were successfully grafted onto activated carbon. Meanwhile, the BET specific surface area and pore volume decreased. Adsorption test results indicated that after hydrophobization, the adsorbed amount per specific surface area of benzene on modified activated carbon increased a certain degree, the total adsorbed amount of benzene decreased under high relative humidity condition as the surface area, pore volume decreased.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34382
Appears in Collections:环境纳米技术与健康效应重点实验室_学位论文

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Recommended Citation:
王刚. 多孔炭材料上挥发性有机物吸附过程的研究[D]. 北京. 中国科学院研究生院. 2015.
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