【作者】 陈小龙；

【导师】 王家德；

【作者基本信息】 浙江工业大学 ， 环境科学与工程， 2015， 硕士

【摘要】 电镀废水作为一种典型的重金属废水,其产生量大、危害性强的特点,对环境造成日益严重的污染。其中金属络合物性质稳定、毒性强,难以通过沉淀法直接去除。电化学氧化可对重金属络合物进行有效破络合处理,并能有效改善废水的可生化性。但仍存在电化学反应的传质问题,限制了电氧化的处理效率和电流效率。本文引入超重力概念,设计了一种新型的网板式超重力电化学反应器(RMDE-HER),强化电氧化反应过程。通过电极旋转产生离心力,促进电极表面液膜快速更新,强化电氧化传质过程,提高处理效率和电流效率,降低能耗;避免了普通平板电极中电流密度分布不均匀的问题。以含Cu、Ni和Cr金属络合物的实际电镀废水为实验对象,重点考察了电流密度、旋转电极转速和溶液pH值等宏观工艺参数对RMDE-HER处理效率的影响。研究结果表明:增大电流密度能提高破络合率,但当其超过10 mA·cm-2时,将明显降低破络合负荷提高能耗。破络合率随着旋转电极转速增加而增加,但当转速从200 rpm增至400rpm时,传质效果未继续增强甚至有削弱的趋势。在pH=3.0-12.6范围内具有较好的破络合效果,酸性或碱性条件均促进破络合作用,均比中性条件下破络合效果好。由于酸性溶液抑制了析氧副反应,而碱性条件促进生成·OH、·HO2等活性基团。Cu金属络合物的去除遵循一级反应动力学模型,在pH=11.0时反应速率最快,其反应速率常数为-0.0448 min-1。在最佳工艺条件电流密度为10 mA·cm-2、旋转电极转速为200 rpm和pH=11.0条件下,电解90 min后,Cu、Ni和Cr金属络合物破络合率分别达到98.09%、95.57%和96.10%,其对应破络合的电能消耗分别是106.04 k W·h·kg-1、518.29 kW·h·kg-1和938.12 kW·h·kg-1。另外,RMDE-HER可有效改善难生物降解废水的可生化性;考察了电流密度和转速对实际废水的CODCr和B/C比值的影响。在最佳工艺条件电流密度为10 mA·cm-2和旋转电极转速为200 rpm下,电解90min后,废水的B/C比值从0.20提高至0.48,也可有效降低CODCr;具有较好的改善废水的可生化性的效果。更多还原

【Abstract】 Electroplating wastewater, which is a typical heavy metal wastewater, might render increasingly serious pollution to the environment for its huge emissions and serious toxicity. Compared to metal ions, which is easily removed from wastewater, metal complexes couldn’t be precipitated directly.In this paper, a higee electrochemical reactor with rotating mesh disc electrodes(RMDE-HEC) was designed under the foundation of high gravity(higee). In this reactor, the mass transfer was enhanced by rotating disc electrodes. The centrifugal force generated from the rotating electrodes which promoted the thin liquid film on the electrodes updating faster. Hence, the treatment efficiency and current efficiency of electro-oxidation was enhanced, much less special energy consumption could be obtained by improving the current efficiency and treatment efficiency. Instead of a non-uniform current density was exist in the common electrodes, the current density on the rotating disc electrodes was uniform.Electroplating wastewater with metal complexes of Cu, Ni and Cr was treated using the RMDE-HER. The effect of current density, rotation speed of rotating electrodes and the p H of solution to the treatment effective of RMDE-HER was investigated with focusing on destruction rate of metal complexes. The results shown that,the destruction ratio of metal complexes improved with the increasing of the current density. The lower current efficiency caused much more energy consumption when the current density over 10 m A·cm-2. The mass transfer coefficient in the reactor was first increased with the rotation of rotating electrodes increasing, and then remained unchanged during the rotation speed of rotating electrodes over 200 rpm. The efficiency of destruction of metal complexes was good in a wide range of p H from 3.0 to 12.6, and the efficiency on the condition of acidity or alkaline was higher than that on the condition of neutral. The acid solution could weaken the secondary reaction of O2 evolution; and more hydrogen peroxide and ·HO2 activity species would be generated in a alkaline solution. On the condition of p H=11.0, the reaction rate was the fastest, first-order rate constant of it was-0.0448 min-1. On the optimal condition of current density of 10 m A·cm-2, rotation speed of 200 rpm and p H=11.0, after 90 min electrolysis, the destruction ratio of Cu, Ni and Cr were 98.09%, 95.57% and 96.10%, respectively. The specific energy consumption of Cu, Ni and Cr metal complexes were 106.04 k W·h·kg-1, 518.29 k W·h·kg-1 and 938.12 k W·h·kg-1.In addition, the RMDE-HER was used to pretreat wastewater with refractory biodegradable organic to enhance the biodegradability of the wastewater. The effect of current density and rotation of rotating electrodes on CODCr and the value of B/C was studied. The results indicated that the effect of wastewater pretreatment by electro-oxidation was good. On the optimal condition of current density 10 m A·cm-2 and rotation speed 200 rpm, after 90 min electrolysis, the B/C value of the wastewater improved from 0.20 to 0.48; and the CODCr of it decreased at the same time.更多还原