【作者】 李萌；

【导师】 邹东雷；

【作者基本信息】 吉林大学 ， 环境工程， 2011， 硕士

【摘要】 近年来,随着生产的发展和科学技术的进步,大量的化学品被合成出来以满足人类生活、工业、农业等不同领域的需要。有机物的大量生产和使用必然导致大量有机物质进入环境中,使环境水体中有机物污染日益严重。有机污染物在水体中即使是微量的,对人体和其它生物体的危害也是不可估量的。苯、甲苯、乙苯、二甲苯(简称为BTEX),氯苯和硝基苯在石油工业和有机化工的很多领域有着广泛的应用,是非常重要的化工原料和有机溶剂,是典型的具有代表性的有机物。本文以这几种有机物为研究对象,初步研究其治理方法。微电解法是利用金属腐蚀原理,形成原电池对废水进行处理的一种电化学处理技术,又称内电解法、零价铁法、铁屑过滤法等。微电解法是一种重要的污水预处理方法。此法具有适用范围广,处理效果好,成本低廉及操作维护方便等特点,由于不需要消耗电力资源,具有“以废治废”的意义。该法从某种程度上改变了传统废水处理系统的投资大、运行费用高等缺点。本文以规整化微电解填料作为有机废水的预处理方法,可有效预防传统微电解的板结问题。本文以铁屑、活性炭粉和粘土为主要原料,采用加热焙烧法制备规整化微电解填料。以含苯模拟废水为研究对象,考察粘土、铁碳比、填料粒径、粘土比例、添加剂和焙烧温度等因素对填料处理效果的影响,得到制备微电解填料的最佳条件。结果表明：粘土经造粒焙烧后,对苯的吸附作用很小,微电解填料中粘土对苯的吸附作用可以忽略,主要是铁碳的微电解作用。在3mm-8mm范围内,填料粒径对苯的去除率影响不大。在填料中加入碳酸铵,氯化铵,硝酸铜和硫酸锰四种添加剂,都没有明显提高填料对苯的处理效果。制备填料的最佳条件为：铁屑与活性炭质量比为6：1,粘土的质量分数为25%,焙烧温度为300℃。填料在焙烧过程中有一定的质量损失,焙烧温度越高质量,填料越容易氧化,质量损失越大。填料的硬度与粘土的比例有关,粘土比例越高,制备填料时越容易成型,填料的硬度越大。以代表性有机物BTEX,氯苯和硝基苯为研究对象,通过一系列的试验对微电解填料去除模拟废水中有机污染物的性能进行了系统的研究,得出以下结论：对于浓度范围在25mg/L-100mg/L的BTEX混合水样,可以用一级动力学方程进行拟合。其中乙苯和二甲苯的反应速率常数大于苯和甲苯的速率常数。对于浓度范围分别在25mg/L-500mg/L的苯水样、25mg/L-250mg/L的甲苯水样、25mg/L-100mg/L的乙苯水样和25mg/L-100mg/L的二甲苯水样,可以用一级动力学方程进行拟合。除乙苯外,各个浓度下的速率常数相差不大。pH对填料去除苯水样的影响不大；温度是影响微电解反应的重要因素,在5℃-30℃范围内,温度越高,填料对苯的去除率越大；填料用量也是影响微电解反应的重要因素,在填料用量5g/200m -40g/200ml范围内,填料用量越多,单位时间内去除率越高。60天的动态连续运行实验表明,对于浓度分别为200mg/L, 100mg/L, 50mg/L,50mg/L的BTEX混合水样,停留时间约60min的条件下,填料对有机物的去除率可以达到80%-90%左右,且具有较好的稳定性,运行期间需要定期用盐酸进行反冲洗,以去除填料表面附着的絮凝物。在整个运行期间内,没有明显的板结现象,因此微电解填料在一定程度上解决了传统铁碳微电解的板结问题。对于浓度范围在50mg/L-200mg/L的氯苯水样可以用一级动力学方程进行拟合。pH对填料去除氯苯水样的影响不大。温度是影响氯苯去除率的重要因素,在5℃-30℃范围内,温度越高,填料对有机物的去除率越大；填料用量也是影响氯苯去除率的重要因素,在填料用量10g-50g/200ml范围内,填料用量越多,单位时间内去除率越高。通过70天氯苯连续实验表明,对于200mg/L的氯苯水样,在停留时间约100min的条件下,填料对氯苯的去除率可以达到90%以上,具有较好的稳定性,同样,运行期间需要定期进行反冲洗以去除填料表面的絮凝物。对于浓度为200mg/L、500mg/L的硝基苯水样,可以用一级动力学方程进行拟合,硝基苯在转化过程中生成苯胺,苯胺的生成近似符合零级反应动力学。pH是影响硝基苯去除率和苯胺生成率的重要因素,酸性条件有利于硝基苯的去除和苯胺的生成,中性和弱碱性条件下硝基苯的去除率和苯胺的生成率相差不大。温度是影响硝基苯去除率和苯胺生成率的重要因素,在5℃-30℃范围内,温度越高,填料对硝基苯的去除率越大；填料用量也是影响硝基苯去除率的重要因素,在填料用量10g-50g/200ml范围内,填料用量越多,单位时间内去除率越高。通过68天硝基苯连续运行实验表明,对于500mg/L的硝基苯水样,在停留时间约2h的条件下,填料对硝基苯的去除率可以达到90%以上,随着时间的延长,铁表面的絮凝物越来越多,去除率逐渐下降,酸洗可以提高填料的活性,使填料得到再生。在整个过程中,苯胺浓度及苯胺生成率随硝基苯去除率减小而减小,成正相关。通过对填料在不同时期的SEM-EDS扫描分析,结果表明：高温焙烧能使填料中粘土含有的有机质挥发,提高填料中铁的含量；利用盐酸对填料进行再生反冲洗可以去除填料表明的絮凝物,使填料恢复活性；经过长期运行,填料中的铁含量有不同程度的损失,铁的损失量与进水浓度、反冲洗次数等有关。更多还原

【Abstract】 In recent years, with the development of production and progress of science and technology, a large number of chemicals have been synthesized to meet the need of human live, industry, agriculture and other areas. The large amounts production and use of organic compounds led to massive organic substances into environment inevitably, resulting in the organic pollution of water body more and more seriously. Organic pollutants have immeasurable effect on human as well as other organisms even at trace levels. Benzene, toluene, ethylbenzene, xylene (referred to as BTEX), chlorobenzene and nitrobenzene are typical organic matters that are widely used in many sectors of petroleum and chemical industry as important industrial raw materials and organic solvents. In this paper, the treatment method of these organic matters was studied preliminarily.Iron-carbon micro-electrolysis, also called interior micro-electrolysis, zero-valent iron or iron chips filtration, has been used to pre-treat industrial wastewater or contaminative groundwater due to extensive adaptability to wide variations of compositions of wastewater. It is based on the electrochemical reaction on the surface of electrodes. Iron-carbon micro-electrolysis pretreatment is low cost, high efficiency, no selection for pollutants and operational simplicity because it does not require chemical coagulant and external power as in the cases of coagulation and electrolysis. In this study, to resolve passivation and clogging problems in traditional micro-electrolysis, a new preparation method of iron-carbon micro-electrolysis packing was proposed to pre-treat organic wastewater.Using iron filings, activated carbon power and clay as raw materials, the granular iron-carbon micro-electrolysis packing was made by the method of calcination. The influences of clay, Fe/C mass ratio, packing diameter, clay proportion, additives and calcination temperature on the removal rate of benzene in simulated wastewater were investigated and the optimum conditions of preparation were obtained. The results showed that the adsorption effect of clay on benzene can be neglected, and iron-carbon micro-electrolysis contributed to mostly of the benzene removal. Packing diameter had no obvious effect on the removal rate in the ranges of 3mm～8mm. Adding ammonium carbonate, ammonium chloride, copper nitrate and manganese sulfate into packing didn’t improve the removal rate significantly. The optimum condition of preparation was obtained when the Fe/C mass ratio was set at 6:1, clay proportion was set at 25% and calcination temperature was 300℃. The packing had some mass loss in the calcination process, the higher the calcination temperature, the more easily oxidized of the packing, the greater the mass loss. There was a relationship between the packing hardness and clay proportion. A high proportion of clay in the packing could increase the hardness and the packing were made easily.Typical organic compounds, such as benzene, toluene, ethylbenzene, xylene (referred to as BTEX), chlorobenzene and nitrobenzene were selected as model compounds. Through a series of experiments, the performance of micro-electrolysis packing on removal of organic pollutants in simulated wastewater was studied systematically. The conclusions showed that:The reaction of BTEX samples with iron-carbon micro-electrolysis packing can be described by pseudo-first-order kinetics in the ranges of 25mg/L-100mg/L and the rate constants of ethylbenzene and xylene were bigger than that of benzene and toluene. The reactions of benzene in the ranges of 25mg/L-500mg/L, toluene in the ranges of 25mg/L-250mg/L, ethylbenzene in the ranges of 25mg/L-100mg/L, and xylene in the ranges of 25mg/L-100mg/L can be described by pseudo-first-order kinetics. The effect of initial concentrations on rate constants wasn’t significant except ethylbenzene. Initial pH had no obvious effect on the removal rate when the pH raged from 3 to 9. Temperature was an important parameter influencing the performance of the packing. It was observed that an increase in temperature could significantly raise the reaction rates in the ranges of 5℃-30℃. The removal rate was strongly packing amount dependent and an increase in the packing amount could significantly raise the removal rate as the packing amount increased from 5g/200ml to 40g/200ml. The flow-through column packed with packing was designed to remove BTEX solution of 200mg/L, 100mg/L,50mg/L and 50mg/L from simulated wastewater running for approximately 60d with approximately 60 min residence time. The packing had good performance and the removal rate could reach 80%-90% after running steadily. The accumulation of precipitates (corrosion products) on the packing surface may necessitate periodic backwash or cleanup steps using hydrochloric acid in the continuous column operation. There were no obvious agglomeration and clogging phenomena after running for 60 days. The passivation and clogging problems in traditional micro-electrolysis were resolved in some extent.The reaction of chlorobenzene solution with iron-carbon micro-electrolysis packing can be described by pseudo-first-order kinetics in the ranges of 50mg/L-200mg/L. Initial pH had no obvious effect on the removal rate when the pH raged from 3 to 9. Temperature was an important parameter influencing the performance of the packing. It was observed that an increase in temperature could significantly raise the reaction rates in the ranges of 5℃-30℃. The removal rate was strongly packing amount dependent and an increase in the packing amount could significantly raise the removal rate as the packing amount increased from 10g/200ml to 50g/200ml. The flow-through column packed with packing was designed to remove chlorobenzene solution of 200mg/L from simulated wastewater running for approximately 70d with approximately 120 min residence time. The packing had good performance and the removal rate was over 90% after running steadily. It could be seen that, the packing still had good performance and there were no obvious decrease on the removal efficiency of the packing after the long-time column experiment. The accumulation of precipitates (corrosion products) on the packing surface may necessitate periodic backwash or cleanup steps.The reaction of nitrobenzene solution with iron-carbon micro-electrolysis packing can be described by pseudo-first-order kinetics in the ranges of 50mg/L-200mg/L. The packing showed prominent activity to the reductive transformation of nitrobenzene to aniline. Furthermore, the aniline formation rate can be described by zero-order kinetics. The degradation performance was strongly pH dependent and a decrease of the initial pH values resulted in the increase of degradation efficiencies of nitrobenzene and formation rate of aniline. The optimum pH was 3.0 for the reductive degradation of NB in the tested pH ranges of 3-9. Temperature was an important parameter influencing the performance of the iron-carbon micro-electrolysis process. It was observed that an increase in temperature could significantly raise the removal rate of NB and formation rate of AN in the ranges of 5℃-30℃. The removal rate was strongly packing amount dependent and an increase in the packing amount could significantly raise the removal rate as the packing amount increased from 10g/200ml to 50g/200ml. The flow-through column packed with packing was designed to remove nitrobenzene solution of 500mg/L from simulated wastewater running for approximately 68d with approximately 120 min residence time. The packing had good performance and the removal rate was over 90% after running steadily. The degradation products of NB and the precipitates of iron oxides/hydroxides covered on the packing surface, which inhibited the contact between packing and NB, and thereby the activity of the packing surface was decreased and the further removal rate of NB was decreased accordingly. Throughout the operation, a decrease in the removal rate of NB resulted in the decrease of formation rate and concentration of aniline, showing positive correlation.The changes of the packing surfaces morphologies and matters before, during and after the. column experiment were analyzed by scanning electron microscopy (SEM) in conjunction with energy-dispersion spectroscopy (EDS). The results showed that carbon element decreasing after calcination indicated that some of the organic matters in the clay evaporated out of packing though high temperature calcinations. The content of iron element increased after calcination. Acid washing led to the cleaning of packing, and accordingly more reactant surface area was reactived for further surface reactions. Hydrochloric acid had effectively removed the absorbed precipitates, and thus the activity of packing was regenerated. After the long-term column experiment, there were mass losses of iron in the packing, and the extent of loss was dependent on the influent concentration, backwashing frequency and so on.更多还原