【作者】 刘金泉；

【导师】 黄君礼；

【作者基本信息】 哈尔滨工业大学 ， 环境工程， 2007， 博士

【摘要】 多环芳烃类化合物是环境中广泛存在的一类持久性有机污染物,具有水溶性低、稳定性强、生物降解能力差、致癌性强等特性,对环境和人类健康构成极大的威胁,引起环境科学家的极大关注,也一直是各国严格控制的污染物。目前,国内外对多环芳烃类污染物的处理技术主要有生物修复法、光解法、吸附法、氧化法和超声降解法等,但均处于研究的起步阶段,且这些技术尚不能应用到实际工程中。ClO₂是一种具有良好应用前景的优良消毒剂和强氧化剂,对水中的许多有机和无机污染物均具有较好的去除效果,而且几乎不与水中的有机物形成THMs等有机卤代物,在水处理中具有广阔的应用前景。本论文以ClO₂为氧化剂,系统地研究了其对多环芳烃类化合物的去除效果及二者之间的反应动力学,探讨了ClO₂氧化处理多环芳烃类污染物的可行性,为ClO₂处理实际污染水体中多环芳烃类污染物的应用奠定了理论基础。本文以萘、二氢苊、芴、菲、蒽、荧蒽、芘、苯并[a]蒽及苯并[a]芘等9种典型多环芳烃为模拟污染物,对ClO₂处理多环芳烃类污染物的效果进行了系统研究。结果表明,在同等反应条件下,ClO₂对9种多环芳烃的去除率有很大区别,处理效果最好的为二氢苊、蒽、苯并[a]蒽及苯并[a]芘等4种,去除率在90%以上;其次为芴、菲及芘,去除率在30⁷0%之间;处理效果最差的为萘和荧蒽,120min内的去除率不超过20%。以去除效果较好的二氢苊、蒽、芘、苯并[a]蒽和苯并[a]芘为代表,研究了影响多环芳烃去除效果的因素如ClO₂投量、反应时间和溶液pH等,结果表明ClO₂投量和反应时间对多环芳烃去除率的影响明显,而pH在3.2⁹.7的范围内对其没有太大影响。确定出ClO₂氧化这5种多环芳烃的最佳工艺条件为:ClO₂投量分别为30、5、40、35和5mg/L,反应时间分别为90、30、120、120和30min,pH为7.2。最佳条件下这5种多环芳烃的最大去除率分别为96.0%、99.0%、62.8%、90.0%和99.5%。论文对ClO₂与模拟水体中二氢苊、蒽、芘、苯并[a]蒽和苯并[a]芘等5种多环芳烃类化合物的反应动力学进行了研究。结果表明,ClO₂和多环芳烃类化合物的反应级数对二者均为一级,总反应级数为二级。在pH6.8、反应温度20℃的条件下,ClO₂与芘、苯并[a]蒽、二氢苊、蒽和苯并[a]芘的反应速率常数分别为0.141、0.605、0.722、6.780和7.795 L/（mol·s）,这与它们去除率的大小顺序一致。考察了溶液pH、ClO₂浓度和温度对ClO₂与蒽反应速率常数k的影响,结果表明k值受溶液pH和ClO₂浓度的影响不显著,但却随温度的增加而增大。论文对ClO₂氧化蒽的反应机理进行了研究。结果表明,在pH6.8、温度293K条件下,ClO₂与蒽的反应活化能为44.235 kJ / mol,表明ClO₂与蒽的反应为一吸热过程且在常规水处理条件下即可发生。通过GC-MS技术和红外光谱技术对ClO₂与蒽的反应产物进行了鉴定,结果表明反应的主要产物为9, 10-蒽醌。通过分析蒽与ClO₂的反应特性,在单电子转移理论的基础上,对ClO₂与蒽的反应机理进行了讨论,并提出了二者可能的反应途径。采用MOPAC软件中的AM1和PM3方法计算了9种多环芳烃的分子轨道能量和原子净电荷,通过比较各多环芳烃分子的最高占据分子轨道能量及其分子结构特点,阐述了它们与ClO₂之间反应活性的差别。并通过鉴定二氢苊、蒽、苯并[a]蒽和苯并[a]芘等4种多环芳烃与ClO₂反应生成的醌类产物,比较了各分子中形成羰基的位置与其所带原子净电荷之间的关系,结果表明这几种多环芳烃分子中反应活性最强的碳位均位于带负电荷较多的碳原子上。本研究将量子化学参数用于评价多环芳烃的反应活性并对其分子中的反应活性碳位进行了预测,是量子化学在描述多环芳烃性质方面的一个新的尝试。论文讨论了ClO₂处理实际生产废水中多环芳烃的影响因素。以某石化厂炼油废水的二沉池出水为研究对象,采用正交试验方法,对ClO₂处理其中残留多环芳烃污染物及COD的影响因素包括ClO₂投量、反应时间、温度、pH等进行了深入探讨。结果表明,经ClO₂处理后,二沉池出水中所含的多环芳烃及联苯类化合物得到有效去除,且COD值得到进一步的降低。试验所考察的各影响因素的主次顺序为:ClO₂投量→反应时间→温度→pH。最佳工艺参数为:ClO₂投量10mg/L,反应时间60min,pH6.9,温度20℃,此时多环芳烃及COD去除率分别达到64.55%和75.62%。本论文为ClO₂应用于处理水中的多环芳烃类化合物提供了科学依据,具有重要的理论意义和实际应用价值。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons （PAHs） represent an important group of persistent organic pollutants, which are known to be poor water-soluble, recalcitrant, microbial resistent and carcinogenic. PAHs have received considerable attention and been strictly controlled for its potential threat to environment and people’s health. Nowadays, removal technologies for PAHs mainly include bioremediation, photolysis, adsorption, oxidation and sonolysis et al., however these techniques could not be applied to practice because researches in this field were just underway. As a sort of excellent disinfectant and oxidant, chlorine dioxide （ClO2） has promising future for its excellent ability in removing both organic and inorganic contaminants without forming halo-substituted organics such as trihalogenmethane （THMs）. The reactivity and mechanism of PAHs with ClO2 and the feasibility of ClO2 in oxidizing PAHs were studied systematically in this dissertation, which established the theoretical basis for the application of ClO2 in removing PAHs in practical wastewater.The effects of chlorine dioxide （ClO2） on the degradation of nine typical PAHs including naphthalene （NPH）, acenaphthene （ACE）, fluorene （FLR）, phenanthrene （PHN）, anthracene （ANTH）, fluoranthene （FLN）, pyrene （PYR）, benzo[a]anthracene （BaA） and benzo[a]pyrene （BaP） in aqueous solution were investigated systematically and the results showed that ClO2 has different removal ratio to these nine PAHs under identical conditions, with the best value above 90% for ACE, ANTH, BaA and BaP, and 30% to 70% for FLU, PHN and PYR, and less than 20% for NPH and FLN within 120min. Several factors included ClO2 dosage, reaction time and pH of solution influencing the removal ratio of ACE, ANTH, PYR, BaA and BaP have been studied by batch experiments. The results showed that the removal ratios of these PAHs were affected by the ClO2 dosage and reaction time instead of pH. The removal ratios of ACE, ANTH, PYR, BaA and BaP could reach to their maximum as approximately 96.0%、99.0%、62.8%、90.0% and 99.5% respectively under the conditions as follows: the ClO2 dosage 30, 5, 40, 35 and 5 mg/L, reaction time 90, 30, 120, 120 and 30 min, and pH 7.2. Kinetics about ACE, ANTH, PYR, BaA and BaP in simulated aqueous solution with ClO₂ were studied and the results showed that the reaction was pseudo-first order with respect to both PAHs and ClO₂, and the general reaction could be described as second order. Under the condition with pH and temperature of solution was 6.8 and 20℃, the reaction rate constants （k） was 0.141, 0.605, 0.722, 6.780 and 7.795L/（mol·s） for PYR, BaA, ACE, ANTH and BaP respectively, which has the same sequence with their removal ratios. The value of pH and concentration of ClO₂ have slight effects on the value of k, which however increased with the enhancement of temperature.ANTH was selected as the representative to study the reaction mechanism with ClO₂. The reaction activation energy was calculated as 44.235 kJ/mol, which revealed that the ANTH-ClO₂ reaction is an endothermic process and can occur under conventional water treatment conditions. The oxidation products formed in the ANTH-ClO₂ reaction were tentatively identified by gas chromatography-mass spectrometry （GC-MS） and Fourier transform infrared spectrum （FTIR） and the results showed that the main product was 9,10-anthraquinone. Through analyzing the reaction properties of ClO₂ and ANTH, the mechanism of ANTH-ClO₂ reaction was discussed and the possible pathway was proposed based on the theory of single electron transfer （SET）.AM1 （Austin model 1） and PM3 （parametrisation 3 of modified neglect of diatomic overlap） methods in MOPAC computation application were used to calculate the molecular orbital energy and net charges on each atom of these nine PAHs. Their different reactivity with ClO₂ was expatiated by comparing the HOMO （highest occupied molecular orbit） energy and structural proterties of each PAHs. Respective quinonoid compounds of ACE, ANTH, BaA and BaP oxidized by ClO₂ were identified and the relationship between the oxidation positions and atom net charge of PAHs were examined, the results revealed that the most reactive positions were in accord with carbons with highest neglect charges. Parameters of quantum chemistry were induced to evaluate the reactivity and predicting the oxidation positions of PAHs in this study, which is a new tempt for parameters of quantum chemistry in describing properties of PAHs.Orthogonal experiment was used to discuss detailedly the influence factors as ClO₂ dosage, reaction time, temperature and pH in removing the residual PAHs and COD in secondary effluent from petroleum refinery by ClO₂ in this chapter. Results showed that after treated by ClO₂, the PAHs and biphenyl in secondary effluent were removed effectively and COD value was reduced further. Sequence of the influence factors investigated in the experiment is: ClO₂ dosage > reaction time > temperature > pH. The optimal parameters were as follows: ClO₂ dosage 10mg/L, reaction time 60min, pH 6.9 and temperature 20℃, under which the removal ratios of PAHs and COD were 64.55% and 75.62%, respectively. Work of this dissertation has great theoretical and practical value as it provided enough scientific basis for the application of ClO₂ in removing PAHs from aqueous solution.更多还原