【作者】 王执伟；

【导师】 刘惠玲；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 硕士

【摘要】 氯酚类化合物具有致癌、致畸、致突变效应,毒性大,难生物降解,在环境中降解周期长,给自然环境造成了很大危害,被许多国家视为优先控制污染物。近年来,电催化还原法处理氯酚类化合物因具有高度灵活性、易于控制、成本小、不产生二次污染等优点,引起了研究者的广泛重视。本文以钯/泡沫镍电极为电还原阴极,以对氯苯酚、2,4-二氯酚为目标物,研究电极的制备工艺及氯酚类化合物脱氯反应的影响因素。本文采用恒电流沉积法,从沉积电流、沉积温度、氯化钯沉积液浓度、沉积时间四个方面考察对电极脱氯性能的影响,优化钯/泡沫镍电极的制备工艺条件。脱氯实验表明随着沉积电流的增加,电极的脱氯性能先增加后减小;随着沉积温度的升高,电极的脱氯性能变化不大;随着氯化钯沉积液浓度的升高,电极的脱氯性能增强;随着沉积时间的延长,电极脱氯性能出现波动现象。在综合考虑电极的脱氯性能、成本、能耗等方面得出最佳的钯/泡沫镍电极制备工艺条件为:沉积电流为6mA、沉积温度为40℃、氯化钯沉积液浓度为1mmol/L、沉积时间为120min(沉积至溶液为无色),并且在该条件下所制备的电极具有良好的脱氯稳定性和重复使用性。借助X-射线光电子能谱(XPS)、扫描电子显微镜(SEM)、X-射线衍射(XRD)等表征手段对电极的元素组成及价态、表面形貌、晶体结构进行分析,实验结果表明,在最佳制备条件下所得的钯/泡沫镍电极确实有钯颗粒负载,并且在基体表面分布均匀,粒径较小,结构紧密,比表面积较大,具有一定空间延伸性。以对氯苯酚、2,4-二氯酚为目标物,从目标物的初始浓度、工作电流、溶液温度三方面探讨最佳脱氯条件。在综合考虑目标物的去除率及电流效率得出最佳脱氯条件为:对氯苯酚的初始浓度为1.0mmol/L、工作电流为5mA、溶液温度为50°C,在此条件下,电化学还原脱氯80min对氯苯酚的去除率即可达到100%;2,4-二氯酚的初始浓度为0.5mmol/L、工作电流为5mA、溶液温度为40°C,在这样的脱氯条件下,反应180min,2,4-二氯酚的去除率可达62.6%。动力学研究表明在最佳脱氯条件下,对氯苯酚和2,4-二氯酚的电催化还原反应均符合准一级反应动力学过程。更多还原

【Abstract】 Chlorophenols compounds with great toxicity are carcinogenic, teratogenic, mutagenic, and difficult to be biodegraded. Their degradation period in the environment is long, and they have caused great damage to the natural environment. So chlorophenols compounds have been listed as priority control of pollutants by many countries. In recent years, more and more investigators have paid attentions to the electrocatalytic hydrodechlorination to deal with chlorophenols compounds, because this method has many advantages such as high flexibility, easy to control, low cost, non-secondary pollution and so on. In this article, palladium-modified nickel foam electrodes were prepared and used as cathode to degrade 4-chlorophenol and 2,4-dichlorophenol. Preparation conditions of electrodes and the influencing factors of disposing chlorophenols compounds were investigated.The preparation technology of the palladium-modified nickel foam electrodes, using the method of constant current electrodeposition, had been optimized in this paper. The preparation conditions, including the deposition current, the deposition temperature, the deposition time and the concentration of PdCl2 solution, were investigated. Experimental results showed that along with the increase of the deposition current, the dechlorination property of Pd/Ni-foam electrode rose firstly, then droped. The increase of deposition temperature could not bring about bigger influence on the dechlorination property. With rising of the concentration of PdCl2 solution, the property got better, but fluctuated with the extension of deposition time. Considering the dechlorination property of electrodes, cost and energy consumption, the best preparation technology conditions were 6mA(deposition current), 40℃(deposition temperature), 1.0mmol/L(concentration of PdCl2), 120min(deposits time, until the yellow PdCl2 solution turned colorless) and the Pd/Ni-foam electrode had good stability and reusability.Some modern physical methods, such as X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), X-ray diffraction(XRD) and so on, were used to characterize the elements and valence, surface morphology and crystal structure of the Pd/Ni-foam electrode. The results indicate that Pd particle had loaded on the surface of Ni-foam substrate and presented micro sizes, uniform distribution, close structure, large specific surface area, and certain space extensibility at the best preparation condition.The effects of initial concentration, current intensity and temperature on the hydrodechlorination of 4-chlorophenol and 2,4-dichlorophenol were examined in the aqueous. Relatively high initial concentration(1mmol/L), moderate current intensity (5mA), and temperature(50℃) were beneficial to improve the hydrodechlorination of 4-chlorophenol in consideration of the removal rate and current efficiency. Under the optimized conditions, 1mmol/L of 4-chlorophenol could be removed rapidly with the rate of 100% after 80min electrolysis. For 2,4-dichlorophenol, the optimized conditions were 0.5mmol/L, 5mA and 40°C, the removal rate reached 62.6% after 180min electrolysis. The degradation of 4-chlorophenol and 2,4-dichlorophenol on Pd/Ni-foam electrode is in good agreement with the fisrt-odrer reaction kinetics equation.更多还原