【作者】 王松林；

【导师】 陆晓华； 廖利；

【作者基本信息】 华中科技大学 ， 环境工程， 2006， 博士

【摘要】 本论文综述了垃圾渗沥液处理技术、超声化学以及持久性有机污染物处理技术的研究现状,分析鉴定了垃圾渗沥液中有机污染物的种类和含量,系统研究了超声对垃圾渗沥液中COD和氨氮的去除效果和作用机理,并以难降解有机物邻二氯苯和持久性有机污染物五氯苯酚为处理对象,研究超声降解水溶液中邻二氯苯的作用机理,探讨了双频超声降解水溶液中五氯苯酚的频率效应和协同效应。本论文的主要结论如下:1)垃圾渗沥液中有机物的分析结论如下:采用气相色谱质谱联用技术鉴定垃圾渗沥液中有机物。共鉴定出的39种有机物,其中被列入我国水环境优先污染物“黑名单”的有2种,被确认为促癌物、辅致癌物的有1种。2)超声去除垃圾渗沥液中COD和氨氮的研究主要结论如下:①垃圾渗沥液中COD的超声去除随着输入功率密度的增大,COD去除率上升。降低初始浓度有利于提高COD的超声去除率,但是去除总量仍是初始浓度高时的比较高。提高初始pH,COD的去除率上升,但是初始pH的影响不很明显。曝气能够一定程度地促进COD的超声去除。投加适量的NaCl能够提高COD的超声去除率,然而过量的NaCl反而阻碍COD的超声去除。投加TiO2能够提高COD的超声去除率。垃圾渗沥液中有机物的超声去除主要是通过羟自由基的氧化反应,高温热解反应虽然存在,但贡献相对较小。超声去除垃圾渗沥液中COD的动力学模式的关系曲线的线性关系不好,一方面是由于超声降解有机物反应的复杂性和垃圾渗沥液中有机物种类的多样性,另一方面是由于基于K2Cr2O7氧化法测定出的COD指标不能完全表征超声去除垃圾渗沥液中有机污染物的程度。②垃圾渗沥液中氨氮的超声去除随着初始pH值的升高,氨氮去除率迅速上升。氨氮去除率随着超声时间的延长而逐渐提高,但在180min后提高不大。提高输入功率密度,氨氮的去除率升高。初始氨氮浓度对氨氮去除率的影响不大,去除率都在80%以上。超声和空气曝气联用对氨氮去除效果明显高于单独超声或者单独空气曝气。单独超声时去除的氨氮是由于游离氨在空化泡内高温热解生成氮气和氢气而后排出;而在曝气条件下部分去除的氨氮被吹脱出来,以氨气气体的形式去除。垃圾渗沥液中氨氮的超声去除反应符合一级反应动力学。3)超声去除水溶液中邻二氯苯的研究主要结论如下:随着输入控制电流的增大,邻二氯苯去除率相应提高,但去除效果差别不大。随着初始浓度的降低,相应的邻二氯苯去除率升高,但去除总量仍是初始浓度高时比较高。溶液pH值对其超声去除的影响不大。空气曝气促进了邻二氯苯的超声去除。邻二氯苯的超声去除不是自由基的氧化反应所致,在空化泡内绝大多数邻二氯苯将热解成小分子物质,进一步氧化成CO2和H2O。水溶液中邻二氯苯的超声降解反应符合一级反应动力学。4)双频超声降解水溶液中五氯酚的研究主要结论如下:对于声功率指标,不同频率的超声设备在和20kHz超声反应器联用时表现出一定的频率效应。不同单频超声在相同的声功率条件下,降解水溶液中五氯酚的速度不同,表现出一定的频率效应。双频超声能够大大促进五氯酚的降解,证明双频超声能够显著提高声化学效应。各个频率的超声都对20kHz超声降解五氯酚具有一定的协同效应;在双频超声降解水溶液中五氯酚的过程中协同效应表现出明显的频率敏感性,对20kHz超声降解水溶液中五氯酚的协同效应顺序为:530kHz >800 kHz>40 kHz>1040kHz。更多还原

【Abstract】 In this dissertation, the recent research on the treatment of landfill leachate and persistent organic pollutants and ultrasound technology were reviewed at first. The research on the determination of organic pollutants in landfill leachate by gas chromatography-mass spectrometry was carried out. Then the research on the removal mechanism and kinetics of COD and ammonia nitrogen in landfill leachate by ultrasound irradiation was studied, and the sonolysis mechanism of o-DCB in solution was also studied. Meanwhile, the comparison of enhancement effect of pentachlorophenol sonolysis at 20 kHz by different dual-frequency ultrasonic irradiations was investigated.1)Results of the determination of organic pollutants in landfill leachate are summarized as follows:39 kinds of main organic pollutants in landfill leachate by GC-MS were identified. In the detected organic matters, 4-methyl-phenol has been confirmed to be cancer-boosting substance or assisting, and another two, dichloromethane and methylbenzene belong to the blacklist of environmental priority control pollutants in China.2)Results of the removal mechanism and kinetics of COD and ammonia nitrogen in landfill leachate by ultrasound irradiation are summarized as follows:①The removal mechanism and kinetics of COD in landfill leachate by ultrasound irradiationCOD removal efficiency increases with increased ultrasound power input. Decreased initial COD concentration makes for COD removal efficiency, but the COD removal gross is smaller than that of higher initial COD concentration. The effect of initial pH on COD removal is not obvious. Air aeration and the dosage of TiO2 can enhance COD removal efficiency. COD removal efficiency increases with dosage of NaCl, but overdoses may cause efficiency retardation.The main sonolysis of landfill leachate proceeds via reaction with·OH radicals, a thermal reaction also occurs, although its contribution is small. The kinetics mode of removal of COD from landfill leachate could be explained by the complexity of organic pollutant sonolysis and organic pollutants in landfill leachate and COD measurement based on K2Cr2O7 methods.②The removal mechanism and kinetics of ammonia nitrogen in landfill leachate by ultrasound irradiationAmmonia nitrogen removal efficiency increases with increased initial pH. Ammonia nitrogen removal efficiency increases gradually with extended reaction time, but increases little after 180min reaction. Increased ultrasound power input makes for ammonia nitrogen removal efficiency. Air aeration can enhance ammonia nitrogen removal efficiency.The mechanism of ammonia-nitrogen removal by ultrasound irradiation may mainly be that the ammonia molecules in leachate enter into the cavitation bubbles and transform into nitrogen molecules and hydrogen molecules via pyrolysis under instant high temperature and high pressure in the cavitation bubbles. The pseudo-first-order removal kinetics of ammonia nitrogen in landfill leachate by ultrasound irradiation was observed.3)Results of the removal of o-DCB in solution by ultrasound irradiation are summarized as follows:Removal efficiency of o-DCB increases little with increased ultrasound power input. Decreased initial o-DCB concentration makes for o-DCB removal efficiency, but the o-DCB removal gross is smaller than that of higher initial o-DCB concentration. The effect of initial pH on o-DCB removal is not obvious. Air aeration can enhance o-DCB removal efficiency. The o-DCB removal by ultrasound irradiation mainly dissociates by pyrolysis to CO2 and H2O under instant high temperature and high pressure in the cavitation bubbles. The pseudo-first-order removal kinetics of o-DCB by ultrasound irradiation was observed.4)Results of the degradation of pentachlorophenol in solution by dual-frequency ultrasound irradiation are summarized as follows:As to the actual power dissipated in the solution, different frequency ultrasound combined with 20kHz appears to be frequency sensitive. Pentachlorophenol degradation rates were different at mono-frequency ultrasound irradiation with the same actual dissipated power.Pentachlorophenol degradation rate at dual-frequency ultrasonic irradiation is the highest compared to mono-frequency ultrasonic systems. The combination of dual-frequency systems has synergistic effect and the enhancement effect of sonochemical degradation of pentachlorophenol at 20 kHz by dual-frequency systems appears to be remarkable frequency sensitive. The order of contribution to the enhancement effect of sonochemical degradation of pentachlorophenol at 20 kHz is as follows: 530kHz >800kHz>40 kHz >1040kHz.更多还原