【作者】 孙艳；

【导师】 矫彩山；

【作者基本信息】 哈尔滨工程大学 ， 环境工程， 2007， 硕士

【摘要】 苯酚是优先被列入环境污染物“黑名单”的一种有机污染物，具有浓度高、排放量大、涉及面广等特点，未经处理而随意排放的苯酚废水将带来严重的环境污染。近年来，电催化氧化技术处理难降解有机废水成为研究的热点，其反应条件温和，通过有催化活性的电极反应在现场直接或间接产生羟基自由基，无需外加化学氧化剂，被公认为是一种绿色工艺。本论文主要是对气体扩散电极为阴极的电化学氧化技术进行研究，具体包括电极的制备、H₂O₂产生量及影响因素、降解苯酚废水的实际效果等。首先确定气体扩散电极最佳制备条件为活性碳：乙炔黑=9：1（质量比），以此制备气体扩散电极，着重研究电流密度、pH值、曝气量等因素对H₂O₂产生量的影响。结果表明：电流密度越大，产生的H₂O₂量越多，但当电流密度超过一定值后，H₂O₂产生量的变化不大，综合考虑能耗等因素，电流密度控制在50～75mA／cm²较好；pH值对系统的电流效率及H₂O₂产生量影响较小，综合考虑反应速度等因素，确定pH=3较好；曝气量对过氧化氢的产生量也有很大影响，综合能耗等因素，确定5L／min较好。利用上述气体扩散电极做阴极，石墨电极做阳极，以Na₂SO₄为电解质，研究了电解时间、电流密度、pH值、初始苯酚浓度、曝气量、加入不同浓度的Fe²⁺等因素对苯酚降解效果的影响。结果表明：在电流密度为75mA／cm²、曝气量为5L／min、初始pH=3的条件下，当苯酚的初始浓度为80mg／L时，1h后其去除率达77％；Fe²⁺的加入对苯酚降解率产生了很大影响，当溶液中加入0.2mmol／LFe²⁺时10min内苯酚降解率可达89％。同时，分别利用掺入锰、钴催化剂的气体扩散电极做阴极，在H₂O₂产生实验中，掺入锰、钴后的电极使得H₂O₂产生量迅速下降，验证了锰、钴等过渡金属对H₂O₂有催化分解作用；而在苯酚降解实验中，掺入锰、钴后的电极使苯酚降解率下降较少，因此可推测出锰、钴催化H₂O₂产生H₂O和·OH。最后，本实验还考察了不同时间时苯酚降解过程的全波扫描光谱图，分析苯酚降解过程；并对不同阴极条件下苯酚降解的过程进行比较。更多还原

【Abstract】 Phenol is a prior organic contamination in "blacklist" of environment contamination, with the characteristic of high concentration, large letting, and more involved. Environment contaminated is more severely if the wastewater is let without treated. In recent years, electrocatalysis-oxidation processes have attracted a lot of interest for degrading non-biodegradable wastewater. It is considered as a green technology because the reaction condition is mild and the hydroxyl radicals are produced through direct or indirect method by the reaction of a catalytic electrode without adding chemical reagents.In the text, electrochemical oxidation technology was studied using gas diffusion electrode as cathode, including preparation of electrode, H₂O₂ production and its influence factors, the degradation effect of phenol wastewater, and so on.Firstly, it was confirmed that the best proportion for preparing gas diffusion electrode was 9:1 with active carbon and acetylene black by weigh. The gas diffusion electrode was prepared with this proportion. The study was emphasized on the factors of influencing H₂O₂ production such as current consistency, pH values and blowing air volume. The result showed that the H₂O₂ production increased as the current density was raised. But the growth wasn’t notable while current efficiency beyond a certain value. The current density of 50mA/cm² and 75mA/cm² are both suitable with the consideration of energy consumption. The effect of current efficiency and H₂O₂ production by pH value was less. The pH value of 3 was chose to get accelerate reaction rate. H₂O₂ production was greatly influenced by blowing air volume. According to energy consumption, the tolerance at 5L/min was optimal.Furthermore, factors influencing phenol degradation, such as electrolysis time, current density, pH values, original phenol concentration, blowing air volume, and different concentrations of Fe²⁺, were investigated in the system with cathode of the gas diffusion electrode and anode of graphite. In the presence of Na₂SO₄, phenol was degraded by H₂O₂ produced at cathode. The results show that phenol degradation rate was 77% in 1h when current density was 75mA/cm², blowing air volume was 5L/min, pH value was 3, and original phenol concentration was 80mg/L. The phenol degradation rate was strongly influenced by Fe²⁺. The phenol degradation rate was raised up to 89% within 10 minutes after 0.2mmol/L Fe²⁺ was added in.At the same time, manganese and cobalt was adulteratited in the gas diffusion electrode. In the example of H₂O₂ production, H₂O₂ production reduced for adulteratiting manganese and cobalt. It was proved that manganese and cobalt can break up H₂O₂. In the example of phenol degradation, phenol degradation rate was less reduced for adulteratiting manganese and cobalt. It is resumed that manganese and cobalt could catalyse H₂O₂ to H₂O and OH.Finally, the full wave tracing of phenol degradation was reviewed in different time, and phenol degradation course was analyzed. Phenol degradation courses with different cathodes were compared.更多还原