【作者】 魏金枝；

【导师】 冯玉杰；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2011， 博士

【摘要】 农药废水因具有化学需氧量高、可生化性差、毒性大等特点,采用传统的生化处理难以高效去除、达标排放。电催化氧化技术作为一种高级氧化技术已被证明对有毒有机物可高效降解并去除其毒性。而三维电极氧化技术因能更好地解决电催化氧化技术应用中存在的电流效率低、能耗高等瓶颈问题,成为近些年电化学领域的研究热点。本论文以电催化氧化技术为核心,建立电絮凝-三维电催化氧化-生物接触氧化组合工艺,并对除草剂废水的处理开展了试验研究,具体研究内容及成果如下。以Sb掺杂Ti/SnO₂电极为阳极,采用电催化氧化技术对含丙草胺、异噁草酮、2,4-D等除草剂的模拟废水分别进行电催化氧化预处理的可行性研究。以除草剂的去除率、TOC去除率、能耗等为考察指标,优化了电催化氧化反应条件;借助于HPLC、GC-MS等分析检测技术推测了丙草胺电催化氧化降解机理;采用微生物呼吸曲线法以及藻类生长抑制试验对预处理后废水的可生化性及毒性的变化进行了研究。结果表明,电催化氧化技术可有效去除废水中的异噁草酮、丙草胺、2,4-D及部分中间体,当电流密度为20 mA/cm2,电解质投加量为0.1 mol/L,分别处理100 mL的50 mg/L丙草胺、100 mg/L异噁草酮、100 mg/L 2,4-D废水,电解60 min后,除草剂的去除率分别为丙草胺98.8%、异噁草酮73%、2,4-D 98.7%;丙草胺、异噁草酮、2,4-D废水中TOC的去除率分别为43.1%、34.3%和52.3%;能耗分别为12.4 kWh/m3、12.48 kWh/m3和14.88 kWh/m3。此时废水不可生物降解,且对藻类的生长具有抑制作用。当电解时间延长到120 min后可去除废水中全部的除草剂,丙草胺、异噁草酮、2,4-D废水中TOC的去除率也分别增加到70.2%、57.9%和75.4%,此时废水的可生化性能明显提高,对藻类生长的抑制作用明显降低。为了能高效低耗处理除草剂废水,需建立新型三维电催化氧化体系。以价廉易得的石英微孔瓷环为载体,采用浸渍-焙烧法制备了新型的负载Sb掺杂SnO₂的石英微孔瓷环粒子电极,借助扫描电子显微镜（SEM）、能量色散X射线能谱（EDS）和X射线衍射（XRD）等分析检测技术对所制备的粒子电极的形貌及晶相组成进行了表征。以Sb掺杂Ti/SnO₂涂层电极为阳极,钛板为阴极,填充所制备的瓷环粒子电极,建立三维电极体系,以COD去除率、能耗为考察指标对二维电极体系与三维电极体系的降解效果进行对比;采用极化曲线、循环伏安曲线、羟基自由基的荧光光谱检测技术对三维电极体系的电催化氧化机理进行研究。结果表明,本论文所建立的三维电极体系因羟基自由基的产生量多于二维电极体系,因此对除草剂废水COD的去除率明显高于二维电极体系,而能耗反而低于二维电极体系,当电解120 min时,两体系COD去除率差值为28.7%,能耗差值为20.2 kWh/ kgCOD。通过对三维电极反应体系内粒子电极的电位分布进行测定表明,所建立的三维电极体系内电位分布是均匀的。采用Fluent软件对所设计反应器内流场分布进行模拟,表明反应器内流场分布也是均匀的。由此优化设计了新型的复极性三维固定床反应器。通过可行性研究,构建了电絮凝-三维电催化氧化-生物接触氧化组合工艺,并对电絮凝、三维电催化氧化以及生物接触氧化的运行工艺进行优化,结果表明,采用电絮凝预处理COD为3000 mg/L左右的除草剂废水,在电流密度为15 mA/cm2、进水流速为4 L/h的条件下,电絮凝30 min后,出水COD为1700 mg/L左右,浊度为25 NTU,此时能耗为0.78 kWh/m3。采用三维电极反应器继续处理电絮凝出水,当槽电压调节为30 V,曝气量控制在50 mL/min、粒子电极填充量为反应器体积的2/3、水力停留时间达到120 min,出水COD为400 mg/L左右,可生化性明显提高,B/C达到0.38以上,能耗为6.9 kWh/m3。继续采用生物接触氧化工艺对废水进行生化处理,通过对生物接触氧化反应器的启动、驯化、运行,保证出水COD﹤150 mg/L。然后建立连续运行的电絮凝-三维电催化氧化-生物接触氧化组合工艺处理除草剂实际废水,整个工艺对废水的COD去除率达95%以上,实现废水达标排放。本研究可为农药厂废水的实际处理提高基础研究数据。更多还原

【Abstract】 The pesticide wastewater can not be treated in a conventional biological way due to the characteristics （high chemical oxygen demand, unbiodegradability and toxicity） of the wastewater. Electro-catalytic oxidation which is one method of Advanced Oxidation Processes was confirmed to treat the bio-refractory toxic organic pollutants effectively. Three-dimensional electrode reactor which solved problem of high consumption and low efficiency in the electro-catalytic oxidation process particularly becomes a research hotspot in the field of electrochemistry in recent years. In this paper, the electro-coagulation-electrocatalytic oxidization- biologicalcontact oxidation combined process system was founded with the core technology of electro-catalytic oxidation, and the herbicides wastewater treatment research was conducted.The feasibility study of electro-catalytic oxidation degradation of lab-synthetic pretilachlor, clomazone and 2,4-D wastewater was carried out with Sb doped Ti/ SnO₂ electrode as anode in this paper. The herbicide removal, TOC removal and energy consumption were investigated in order to determine the reaction conditions of the electro-catalytic. Degradation mechanism of pretilachlor was analyzed with the help of HPLC and GC-MS. The biodegradability and toxicity of processed wastewater were investigated by means of microbial respiration curve and algal growth inhibition test. The results showed that electro-catalytic oxidation technology can effectively remove clomazone, pretilachlor, 2,4-D and some intermediate in wastewater. Under the conditions of current density of 20 mA/cm2, Na2SO4 dosage of 0.1 mol/L,initial pretilachlor concentration of 50 mg/L, clomazone concentration of 100 mg/L, 2,4-D concentration of 100 mg/L, treatment time of 60 min, the removal of pretilachlor, clomazone and 2,4-D were 98.8%,73% and 98.7,and the TOC removal were 43.1%, 34.3% and 52.3%; and the energy consumption were 12.4 kWh/m3,12.48 kWh/m3 and 14.88 kWh/m3,respectively. The wastewater was bio-refractory and inhibiting the growth of algae. After electrolysis 120min, all herbicides （pretilachlor, clomazone, 2,4-D） were removed, TOC removal increased to 70.2%, 57.9% and 75.4%, respectively. And the biodegradability of wastewater was improved significantly, algal growth inhibition was significantly reduced. Accordingly it is necessary to establish the new three-dimensional electrode system in order to achieve high efficiency low consumption treatment herbicide wastewater.Quartz ceramic ring particle electrodes loaded with Sb doped SnO₂ were prepared by dip coating method. The micrograph, crystal phase structure of the particle electrodes were characterized by means of scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques.The three-dimensional electrode system was established with Sb doped Ti/SnO₂ electrode as anode and stainless steel as cathode. The COD removal and energy consumption were investigated in order to compare with the efficiency of electrochemical degradation of herbicide wastewater between the three-dimensional electrode and the two-dimensional electrode. The electro-catalytic oxidation degradation mechanism of three-dimensional electrode was investigated be the means of anodic polarization curve, cyclic voltammetry and fluorescence spectroscopy. The results showed that the amount of hydroxyl radicals generated in three-dimensional electrode was much more than in the two-dimensional electrode. Therefore, the COD removal of herbicide wastewater was higher than the two-dimensional electrode. But the energy consumption was less than the two-dimensional electrode. After electrolysis 120 min, the difference of the COD removal and energy consumption between the two systems was 28.7% and 20.2 kWh/ kgCOD, respectively. Determination the potential distribution was measured in the three-dimensional electrode reactor. The results showed that the potential distribution was uniform in the reactor. Fluent software to simulate the flow field distribution was used in the reactor. And the results show that the flow field was uniform in the reactor. Thus a new type of bipolar three-dimensional fixed-bed reactor was designed.The electrocoagulation-electrocatalytic oxidization-biological contact oxidation combined process was constructed and the process parameters were optimized. The results showed that effluent COD and turbidity were 1700 mg/L and 25 NTU, under the conditions of initial COD concentration of 3000 mg/L, current density of 15 mA/cm2 and upstream speed of 4 L/h after electrocoagulation 30 min, meanwhile the energy consumption was 0.78 kWh/m3.The three-dimensional electrode reactor was used to treat the herbicide wastewater in the next step. When the cell voltage was 30 V, the amount of aeration was 50 mL/min, the volume of particle electrodes was 2/3 of the packed bed,the hydraulic retention time was 120 min, the effluent COD was 400 mg/L and the biodegradability of the wastewater was significantly improved and the ratio of B/C was larger than 0.38, meanwhile the energy consumption was 6.9 kWh/m3.Through startup, domestication, operation of bio-contact oxidation reactor, the effluent COD﹤150 mg/L in the biological oxidation process of wastewater biological treatment. On this basis, the establishment of continuous operation of the electrocoagulation- electro-catalytic oxidation - biological contact oxidation process for actual herbicide wastewater. The results showed that the COD removal rate was 95%, wastewater discharge standards to achieve. All of this will provide the basic research data for the practical treatment of the herbicide wastewater.更多还原