不同炭质吸附剂对多氯联苯的长时间吸附特性研究及应用

发布时间：2018-03-17 15:09

本文选题：炭质吸附剂　切入点：理化性质　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：沉积物是持久性有机污染物的大储库,虽然在1974年禁止生产,但沉积物中的污染物仍然会通过释放作用进入到水环境中,威胁着人类的健康,所以治理沉积物污染已经成为一个热点话题。本论文应用5种炭质吸附剂(椰壳活性炭、木炭活性炭、原炭(未活化炭)、东海电厂灰、煤基活性炭),以多氯联苯(PCBs)为吸附质,利用仿生被动采样提取及测定吸附质,研究各炭质吸附剂的吸附动力学及等温曲线,探究炭质吸附剂的吸附原理,进而应用其中的煤基活性炭、椰壳活性炭、果壳、原碳为修复剂,进行实际污染沉积物(蒲河支流某河段)的治理与修复研究,为炭质吸附剂的应用提供理论基础。研究所得结论如下:(1)煤基活性炭、木质活性炭具有较高的比表面积,且以中孔及微孔为主,椰壳活性炭、原炭、东海电厂灰的比表面积较小,东海电厂灰以大孔为主,几乎没有微孔结构。本研究中使用5种炭质吸附剂都含有苯环及羟基基团,且所含有的官能团类似。三维荧光图谱显示,研究中使用的天然有机质(NOM)主要成分是富里酸,结合排阻色谱可以看出,其平均分子量在5000Da附近。(2)吸附动力学研究表明：准二级动力学能够很好的拟合5种炭质吸附剂对PCBs的吸附动力学过程(相关系数R20.99),说明吸附过程是一个多重而复杂的过程;研究发现以大孔为主的炭质吸附剂(如:东海电厂灰、椰壳活性炭、原炭)颗粒内扩散方程参数k值较大,Elovich方程参数b值较大,说明表观吸附速率快,达到平衡所需要的时间较短,快吸附到慢吸附转换过程不明显,其主要以表面吸附为主;以微孔和中孔为主的炭质吸附剂(煤基活性炭、木炭)孔隙较为发达,表观吸附速率小,快吸附到慢吸附转换显著,说明以内部吸附为主;NOM对炭质吸附剂吸附性能的影响实验表明,NOM的存在使得孔径不发达的炭质吸附剂(如:东海电厂灰、椰壳活性炭、原炭)表观吸附速率下降,快-慢吸附速率差距增大,而NOM对孔径较发达的炭质吸附剂(如:煤基活性炭、木炭)具有相反的作用。(3)吸附等温曲线研究结果表明,Freundlich吸附模型能较好的模拟实验数据(R20.6);吸附时间为1个月及12个月,孔隙结构较为发达的煤基活性炭和木炭活性炭的吸附量均大于其他炭质吸附剂,但吸附1个月时,这种差距不显著,而吸附12个月时差距较大,原因是,吸附1个月时,吸附并未达到平衡(吸附动力学研究得到同样的结论),分配系数(Kd)并不能体现吸附剂的实际吸附能力,吸附12个月时,吸附达到平衡,此时的Kd值能够体现吸附剂的实际吸附能力。短时吸附,NOM降低了 5种炭质吸附剂对PCBs的吸附容量,尤其是对椰壳活性炭、原炭、东海电厂灰的降低幅度较大;当吸附时间为12个月时,NOM对5种炭质吸附剂的影响均小,究其原因,短时吸附,NOM附着在炭质吸附剂表面(尤其是以中孔和大孔为主的吸附剂),竞争和堵塞作用阻碍了其对PCBs的吸附,随着时间的延长,PCBs分子能够穿越NOM,进而进入炭质吸附剂的内部孔道,NOM的影响大大降低。(4)现场试验表明,煤基活性炭对PCBs的治理效果最佳,治理效果顺序为:煤基活性炭果壳活性炭椰壳活性炭原炭,此结果与实验室研究结果完全匹配。
[Abstract]:The sediments are large reservoirs of persistent organic pollutants, while banning the production in 1974, but the pollutant in sediment will still be through release into the aquatic environment, pose a threat to human health, so the control of sediment pollution has become a hot topic. This paper used 5 kinds of carbon adsorbent (coconut shell activated carbon charcoal, activated carbon, raw carbon (non activated carbon), the East China Sea power plant ash, coal based activated carbon), with polychlorinated biphenyls (PCBs) as adsorbent, using the bionic passive sampling, extraction and determination of adsorption, adsorption kinetics and isotherm of the carbonaceous adsorbent, the adsorption principle of carbon adsorbent. Then the application of coal based activated carbon, coconut shell activated carbon, shell, raw carbon as repair agent, the actual contaminated sediments (Po River tributary of a river) governance and repair research, provide a theoretical basis for the application of carbon adsorbent. The research The conclusions are as follows: (1) coal based activated carbon and wood activated carbon with high specific surface area, and the mesopores and micropores of coconut shell activated carbon, the carbon, the East China Sea power plant ash surface area is smaller, the East China Sea power plant ash to larger pores, almost no pore structure. This study used 5 kinds of carbon adsorbent containing phenyl and hydroxyl groups, and contains similar functional groups. Show the three-dimensional fluorescence spectra, used in the study of natural organic matter (NOM) is the main component of fulvic acid, combined exclusion chromatography can be seen, the average molecular weight in the vicinity of 5000Da. (2) the results showed that the adsorption kinetics the quasi two level dynamic can fit 5 kinds of carbon adsorption adsorption agent on PCBs (correlation coefficient R20.99), indicating that the adsorption process is a multiple and complicated process; the study found that the carbonaceous adsorbent to larger pores (such as: the East China Sea Power Plant Ash, coconut shell activated carbon, The original carbon particle diffusion equation) parameter K value is large, the parameter of Elovich equation b value is large, indicating the apparent adsorption rate, the time needed to reach equilibrium is short, fast to slow adsorption adsorption conversion process is not obvious, mainly by surface adsorption; carbon with microporous and mesoporous adsorbent (mainly coal based activated carbon, charcoal pore) is developed, the apparent adsorption rate of small, fast adsorption to slow adsorption conversion significantly, illustrated by the internal adsorption; experiments show the effect of agent NOM on adsorption performance of carbon adsorption, the presence of NOM carbonaceous adsorbent developed the aperture (such as the East China Sea power plant ash, coconut shell activated carbon, the carbon) apparent adsorption rate decreased fast slow adsorption rate gap increases, and the carbon NOM on the pore developed adsorbent (such as coal based activated carbon, charcoal) has the opposite effect. (3) adsorption isotherm results show that Freundlich adsorption model can To simulate the experimental data better (R20.6); the adsorption time was 1 months and 12 months, the adsorption amount of the more developed pore structure of coal based activated carbon and charcoal activated carbon are higher than that of other carbon adsorbent, but the adsorption at 1 months, the difference was not significant, while the adsorption of 12 month gap the reason is that, the adsorption at 1 months, the adsorption did not reach equilibrium (get the same conclusion adsorption kinetics), distribution coefficient (Kd) can not reflect the actual adsorption capacity, adsorption at 12 months, the adsorption equilibrium, the Kd value can reflect the actual adsorption capacity of absorbing agent. Short term adsorption, NOM reduced 5 carbon adsorption capacity of PCBs, especially for the coconut shell activated carbon, raw carbon, the East China Sea power plant ash is greatly reduced; when the adsorption time is 12 months, the effect of NOM on 5 kinds of carbon adsorbent are small, the reason for the short time of adsorption NOM, attached to The carbonaceous adsorbent surface (especially adsorbent to medium and large pore mainly), competition and blocking effects hindered the adsorption of PCBs, with the extension of time, PCBs molecules can pass through NOM and then enter the carbon adsorbent internal hole, the influence of NOM greatly reduced. (4) the field test show that the effect of coal based activated carbon treatment on PCBs best treatment effect order of coal based activated carbon coconut shell activated carbon raw carbon, with the result of laboratory results perfectly matched.

【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X52;O647.3

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