【作者】 李大伟；

【导师】 全燮；

【作者基本信息】 大连理工大学 ， 环境工程， 2008， 博士

【摘要】 本论文针对石油污染土壤,采用碳材料增强的微波热修复方法,利用微波加热技术的加热速度快、内外同时加热以及选择性加热等特点,将石油污染物从土壤中快速去除,同时将其绝大部分回收;通过对不同类型石油污染土壤的修复研究,考察该修复方法的实用可行性。研究工作主要包括以下几个方面:1.以颗粒活性碳增强的微波热修复方法处理柴油污染土壤。首先研究了土壤的微波加热行为,并向土壤中加入颗粒活性碳考察其对土壤微波加热的增强效果;在此基础上,以污染浓度为10.20 wt%的柴油污染土壤为研究对象,采用惰性气体（N₂）保护、微波辐照加热、气态产物冷凝回收等工艺过程对污染土壤进行修复,考察了土壤修复效果的影响因素以及修复过程的污染油回收和颗粒活性碳重复使用情况等。研究结果显示,颗粒活性碳加入土壤中能够有效提高土壤的微波加热能力,可以用于增强微波热修复污染土壤;当柴油污染土壤中加入5.0 wt%颗粒活性碳时,800 W微波辐照10 min即可将土壤加热到500℃左右,土壤中的污染油可去除99%以上;同时约有96.2%的污染油可以得到回收,回收油与初始污染油比较,化学组成及物理性质没有明显改变;颗粒活性碳可以重复用于增强污染土壤的微波热修复,修复过程中颗粒活性碳约有1-3%的质量损失,但其增强土壤微波加热的能力没有明显改变;修复过程对土壤组成破坏较小。2.分别以颗粒活性碳和碳纤维增强的微波热修复方法处理污染浓度约为8 wt%的实际原油污染土壤。在原油污染土壤的颗粒活性碳增强微波热修复中,向污染土壤中加入一定量的颗粒活性碳,采用惰性气体保护、微波辐照加热、适当真空减压、气态产物冷凝回收等工艺过程对污染土壤进行修复,对修复过程相关参数及污染油的回收等进行了考察。结果显示,当颗粒活性碳添加剂量为10.0 wt%时,该方法在15 min内可将土壤中污染油去除99%以上;修复过程在快速去除土壤中污染油的同时也可以将其有效回收,回收率约为91%。在原油污染土壤的碳纤维增强微波热修复中,将不同吸波材料加入到土壤中,考察其对土壤微波加热的增强效果;并根据此实验结果,以碳纤维增强的微波热修复方法处理原油污染土壤,考察了土壤中污染油的去除、回收以及碳纤维的重复使用等情况。研究表明,碳纤维可以通过电导损耗和界面损耗联合的方式显著提高土壤体系的有效介电损耗因子,从而更加有效地提高土壤在微波场中的加热升温能力;在一定条件下,当碳纤维添加剂量为0.10 wt%时对原油污染土壤进行微波热修复,即可将土壤加热到700℃左右、污染油去除99%以上,污染油回收率可达94%以上,且污染油在去除及回收过程中同样没有发生明显的化学组成变化。3.探讨了污染土壤的碳材料增强微波热修复过程中污染物的去除机制。以C₁₀、C₁₆、C₂₈为模拟污染物,分别对其污染土壤进行碳材料增强的微波热修复,通过分析修复过程中土壤的加热升温、污染物的去除、回收以及修复产物等情况,探讨了修复过程中不同类型污染物在不同浓度下的去除机制。实验结果表明:污染物的去除机制与污染物的类型及其在土壤中的浓度有关;挥发性、半挥发性污染物,无论浓度高低,污染物主要以微波诱导蒸汽蒸馏、蒸发及热解吸等方式从土壤中去除,基本不发生热解;难挥发或不挥发性污染物,浓度较低时（如1 wt%左右）,主要以热解吸、高温热解的方式从土壤中去除,热解比例大,浓度较高（如10 wt%左右）时,主要以蒸发和热解吸的方式从土壤中去除,热解比例小。4.比较了碳材料增强的微波热修复与微波诱导蒸汽蒸馏及传统电加热修复方法对原油污染土壤的修复效果。分别以微波诱导蒸汽蒸馏及传统电加热技术对同一原油土壤样品进行热修复,并将其修复效果与碳材料增强的微波热修复效果进行比较。结果显示,与微波诱导蒸汽蒸馏相比,碳材料增强的微波热修复方法适用范围更广;与传统的电加热修复相比,碳材料增强的微波热修复方法对污染油的破坏较小,更有利于在修复污染土壤的同时将污染油回收。更多还原

【Abstract】 Microwave thermal remediation enhanced by carbon materials（MTREC） was explored for decontamination of petroleum-contaminated soil.The advantage of rapid,selective and simultaneous heating of microwave heating technology was taken to clear up the soil rapidly and to recover the oil contaminant efficiently.The process was applied to the remediation of soils contaminated with different petroleum contaminants,such as diesel oil and crude oil,to investigate the possibility of its practical application.The following works were carried out in this dissertation:1.Microwave thermal remediation of the soil contaminated with 10.20 wt%diesel oil enhanced by granular activated carbon（GAC） was explored.The study on the microwave heaitng of soil and its enhancement of GAC were performmed,and the results revealed that soil could be heated to an appropriate temperature in microwave field when GAC was added. Some process parameters and oil recovery of the remediation were investigated.It was shown that,using the technics of protecting by inert gas（N₂）,heating with microwave irradiation and condensation of gas products,when 5.0 wt%GAC mixed in,the soil could be heat to about 500℃within 10 min and that the contaminated soil could be remediated by this microwave thermal process such that more than 99%contaminant removal could be achieved.The analysis performed on the recovered oil indicated that up to 96.2%of diesel oil contaminant could be recovered during the remediation without changing obviously in chemical composition and physical properties,compared with the original oil.In addition,the experimental results showed that GAC could be reused in enhancing the microwave heating of soil with a little mass loss and that the remediation process did not destruct the soil significantly.2.Thermal remediation of the practical soil contaminated with about 8 wt%crude oil using microwave heating enhanced by GAC and carbon fiber（CF） was explored respectively. The results of GAC-enhanced microwave thermal remediation revealed that,using the technics of protecting by inert gas,heating with microwave irradiation,proper decompressing with vacuum and condensation of gas products,when 10.0 wt%GAC was mixed into the soil, more than 99%of the oil contaminant could be removed within 15 min,at the same time, about 91%crude oil in soil could be recovered. The experiment results of CF-enhanced microwave thermal remediation indicated that, when mixed into soil,CF,for its fiber shape and electric condutivity,could strongly increase the effective dielectric loss factor of the soil sample as terms of electrical conduction loss and Maxwell-Wagner loss,thereby,strongly enhancing microwave heating of soil more efficiently than other accepted microwave absorbers.When 0.10 wt%CF mixed in,the soil could be heated to approximately 700℃within 4 min using 800 W of microwave irradiation. And correspondingly,more than 99%removal efficiency of the oil contaminant could be obtained under some conditions.Investigation on the recovered oil of the process showed that the crude oil in the contaminated soil could also be removed and recovered without significant changes in chemical composition during the remediation and that the recovery efficiency could be more than 94%.3.Removal mechanisms of the contaminants during microwave thermal remediation of the contaminated soil enhanced by carbon materials were explored with different model contamiants of volatile,semi-volatile and non-volatile compounds.The experiment results showed that the removal mechanisms of the contaminant were relevant with its volatility and concentration in soil.For volatile and semi-volatile contaminant,no matter whether the concentration was low or high,the main removal mechanisms were the physical removal such as microwave-induced steam distillation（MISD）,evaporation and thermal desoption without pyrolysis happenning.For non-volatile contaminant,when the concentration was low（e.g. about 1 wt%）,pyrolysis played an important role in contaminant removal with some thermal desorption and a little MISD;when the concentration was reletivly high（e.g.about 10 wt%）, however,evaporation and thermal desorption played an important role in contaminant removal with a little MISD and pyrolysis.4.MTREC was compared with other thermal remediation process on the decontamination of crude oil-contaminated soil.Comparing with MISD,MTREC could be used in a wider range.It could remove non-volatile contaminant in soil besides volatile and semi-volatile contaminant.Comparing with conventional thermal remediation of electric heating,MTREC could remediate the contaminated soil successfully with less energy comsuption and minor destruction of the contaminant,which may be good for the recovery of the oil contaminant.更多还原