光电一体化处理氯酚废水

【作者】 叶倩；

【导师】 吴祖成；

【作者基本信息】 浙江大学 ， 环境工程， 2004， 硕士

【摘要】 在经氟树脂改性的新型二氧化铅大面积电极上，开展了有毒难降解有机污染物处理技术的应用基础研究。采用光化学氧化技术、阴阳两极的协同电化学处理技术、光电一体化的复合高级氧化技术对氯酚进行处理。 对模拟污染物—对氯苯酚（CP）进行光催化氧化降解实验研究。对比了不同氧化体系对CP及溶液COD的降解效果；单独UV、单独H₂O₂对CP废水降解能力有限，H₂O₂／UV、UV／H₂O₂／air体系降解率明显提高。增加H₂O₂投加量可以加快UV／H₂O₂反应的初始反应速度。污染物初始浓度增加，氯酚的降解率减少，但是绝对的降解量和降解速率增加。pH值对污染物和COD降解影响较小。 进行电化学氧化降解实验研究。采用的电极和工艺体系对CP的处理显示了很好的催化活性和稳定性。阴阳两极协同工艺（ACE）降解工艺较单独的阳极氧化（AE）工艺更能达到有机物的彻底氧化。ACE工艺能平均提高氯酚降解率15％左右，在反应初期协同作用更为明显。废水COD去处率提高100％，ACE工艺在促进污染物降解的同时，更促进了降解中间产物的降解。 在此基础上发展的光电一体化工艺，存在显著的协同效应，对CP和COD的协同作用的增强因子分别达到了125.3％和129.8％。曝氧速率、电流、pH值、初始浓度、温度等因素对光电一体化降解苯酚都有较明显的影响。而且，联合工艺对中间有毒产物如苯醌也能得到很好的降解。 开展了污染有机物降解机理和动力学的研究。实验借助高效液相色谱、离子色谱等手段对光电化学反应过程中产生的活性物种做了分析鉴定，作用产生的主要为羟基自由基（^·OH）和H₂O2，并作了间接定量测定。通过有机物和COD去除速率与^·OH反应速率显著相关性，证实了羟基自由基对有机物的亲电反应在光电催化降解反应中起重要的作用。从分析降解中间产物出发，通过假设和简化，推导了氯酚部分氧化降解的动力学模型，能很好的说明各影响因素对氯酚降解的影响。更多还原

【Abstract】 This work describes the methodological development of photocatalysis, anodic oxidation, paired electrocatalysis, and their coupling processes with photochemical technology and electrocatalysis, which helped to build up the technical platform of electrochemical methods for environmental application.Photooxidation of chlorophenol (CP) were conducted by the application of three different photochemical processes (UV, H2O2 H2O2/UV UV/ H2O2/air). The effects of reaction conditions such as the dosage of H2O2, initial chlorophenol, initial pH, were investigated in terms of CP degradation and chemical oxygen demand (COD) removal.A novel paired electrocatatlysis in the presence of ferrous ion that named anode-cathode electrocatalysis (ACE) was developed. It was found that CP degradation rate could be enhanced by 15% compared with that of individual anodic oxidation under similar conditions, and the promotion for COD was around 100%. The effects of pH, concentration and current on CP degradation were discussed, based on which the conditions for the synergetic effects were given.The combination of electrocatalysis and UV radiation greatly accelerated the removal efficiency. According to the pseudo-first-order reaction rate constant, the promoting factor for CP and COD abatement was 125.3% and 129.8%, respectively. Operating conditions were optimized to make the main reactions occurred in harmony. Higher removal rate was achieved when current is 0.7 A. Temperature has an effect on the CP degradation. However, considering the overall effect, it is advisable to carry out the process at ambient temperature. UV-assisted method can save the running cost to a certain degree and make the techniques possible for industrial application.The degradation behaviors of CP under process of anode electrocatalysis(AE), ACE and UV-ACE were compared, through which a possible degradation pathway was proposed. Strong oxidant, hydroxyl radical (OH), was generated through the reduction of oxygen on the surface of the cathode. A simplified mathematical model for CP and benzoquinone evolution was developed according to the proposed pathway, which could be well served to explore the influencing factors.更多还原