恒电位和恒电流下苋菜红在ACF上的电化学脱色

【作者】 周艳伟；

【导师】 杨卫身；

【作者基本信息】 大连理工大学 ， 环境工程， 2004， 硕士

【摘要】 染料废水具有组成复杂、色度高，COD、TOC含量高，悬浮物多，水质、水量变化大，难降解物质多等特点，是难处理工业废水之一。电化学水处理方法作为一种环境友好技术，具有无需或少量投加化学药剂，不产生二次污染，后处理简单，占地面积小，管理方便等优点，在染料废水处理领域，越来越受到人们的重视。 目前，电化学方法处理染料废水的研究多数是在给定槽压或恒流供电方式下，以考察电极材料、槽压、电流密度、电解质浓度、pH或传质速率等控制条件对脱色率、有机物去除率、电流效率以及能耗的影响为主要内容，而在恒电位或恒电流模式下，电极电位或电流密度对染料脱色行为影响的研究鲜有报道。对于异相界面电极反应，电极电位决定了反应的难易程度，而电流密度在一定程度上决定了反应速率。同时，大部分研究采用了无隔膜电解槽，由于阴、阳极反应的相互干扰，想确定电氧化或电还原在染料降解脱色过程中所起的作用是相当困难的。 本论文以建立一种能够考察电极电位和电流密度如何影响某一染料在某一电极上电化学脱色行为的实验模式为目的，在恒电位和恒电流模式下，采用由阳离子交换膜分隔的双室电解槽，以ACF为工作电极(阳极或阴极)，考察了电极电位和电流密度对偶氮染料苋菜红电化学脱色行为，即脱色机理、脱色动力学和色度、COD、TOC的去除的影响。 研究结果表明本实验模式可成功地完成电极电位和电流密度对苋菜红在ACF电极上电化学脱色行为影响的研究。实验条件下(pH=6.4)，苋菜红在ACF电极上的氧化电位和还原电位分别为0.6V和-0.2V。恒电位模式下，当电位为-0.2V～-0.8V时，电还原是脱色的主要原因；当电位为-0.1V～0.5V时，脱色是由于苋菜红在ACF上的吸附，吸附不受ACF极化的影响；当电位为0.6V～1.4V时，脱色以苋菜红的电氧化为主。恒电流模式下，当阴极电流密度为-0.844mA/cm~2～-1.13 mA/cm~2时，脱色的主要原因是苋菜红的阴极还原；当电流密度为-0.813 mA/cm~2～0.0625 mA/cm~2时，脱色源于苋菜红在ACF上的吸附，吸附不受ACF极化的影响；当阳极电流密度0.125 mA/cm~2～0.5mA/cm~2时，主要是苋菜红电氧化导致脱色。 苋菜红的电氧化和电还原降解脱色过程遵循准一级反应动力学；恒电位阴极还原和恒电流阳极氧化时，脱色速率常数分别同电极电位或电流密度呈线性相关。更多还原

【Abstract】 Dye wastewater is characterized by complicated components, strong color, highly fluctuating pH, high COD, TOC concentration and suspend solids, low biodegradability, and widely varied quality and quantity, so it has been rather difficult to treat dye wastewater. As an eco-friendly technology, electrochemical method added little or no additional chemicals without secondary pollutants for wastewater treatment. In recent years, there has been increasing interest in the use of electrochemical methods for the treatment of dye wastewater.Most study on dye wastewater treatment with electrochemical method was conducted with cell voltage or current constantly controlled and the parameters of voltage, current density, wastewater conductivity, pH, current efficiency and energy consumption were evaluated. However, there are few reports on the relationship between the decolorization and the potential and current density. It is known that potential and current density are the fundamental factors for the electrochemical process. So it is necessary and important to evaluate the effect of potential and current density on the decolorization of dye wastewater. Besides, a great number of experiments were performed in a single compartment electrolytic cell. As a result, it is difficult to make sure the pure contribution of electrooxidation and electroreduction for the decolorization of dye wastewater because of the cross- interference of the anode and cathode.The objective of this study is to estimate an experimental model for the investigation of the effect of the potential and current density on the decolorization of dye wastewater. Activated carbon fiber (ACF) was used as anode or cathode under potentiostatic and galvanostatic model, respectively. Amaranth, a kind of azo dye, was chosen as the model compound. The electrolytic cell was designed as a two-compartment cell separated by cation selective membrane. The effect of potential and current density on the decolorization kinetics, color, total organic carbon (TOC) and chemical oxygen demand (CODcr) removal ratio were analyzed.The results obtained were shown as: (1) The Amaranth water was oxidized on ACF at the potential of 0.6V and reduced at the potential of -0.2V. (2) In the range of -0.1V~0.5V and -0.813 mA/cm2~0.0625 mA/cm2, the decolorization results from the adsorption of Amaranth on ACF and the adsorption behavior is insignificantly affected by electric polarization; (3) In the range of -0.2V~-0.8V and -0.844 mA/cm2~-1.13 mA/cm2, the electroreduction plays an important role in the decolorization.Furthermore, the decoloring process follows pseudo-first order kinetics; (4) In the range of 0.6V~1.4V and 0.125 mA/cm2~0.5 mA/cm2, the electrooxidation results in the decolorization and the decoloring process also follows pseudo-first order kinetics.更多还原