电絮凝中传质过程数值模拟的研究

发布时间：2018-06-15 01:36

本文选题：电絮凝 + 质量传递　；参考：《江苏科技大学》2015年硕士论文

【摘要】：近年来,重金属废水污染事件频繁发生,电絮凝(EC)是处理重金属废水的一个重要技术。它也常常被用于难降解有机物废水的处理。EC过程是由电极电化学反应、物质质量传递、水解反应和吸附反应等多个过程组成,各个过程之间形成相互影响、相互作用的耦合关系。正是各过程之间复杂的耦合关系使得实验研究和工艺改进的难度增大,制约了机理研究的进一步深入。由于EC过程由絮体的产生,絮体的运移及絮体的吸附三个过程组成,而絮体的产生及分布过程对污染物的去除效率产生重要的影响,因此本文建立了EC过程中电极电化学反应和水解反应模型,同时建立了EC电解和水解产物的质量传递和动量传递模型,并计算求解,对连续电絮凝过程中各物种的产生和传质规律进行研究。研究发现,电解产生的Al3+主要分布在阳极附近,OH-分布在阴极附近,沿流程方向两离子的量都逐渐地减少。在电解槽的前段,离子的浓差极化较弱,水解反应为控制步骤;在电解槽的中段和后段,离子的浓差极化较强,传质为控制步骤。随着电流密度的增大,Al3+和OH-的浓度也增加;在无水解的情况下,离子的浓差极化较弱,整个电解槽溶液显弱碱性。水解产物中溶解铝主要分布在两电极附近,而絮体铝主要分布在两电极中间位置,同时整个电解槽中絮体铝占主要地位。沿流程方向,絮体铝占总铝的百分比逐渐增加,溶解铝占总铝的百分比逐渐减小。研究还发现,在电迁移和对流的共同作用下絮体主要分布在电解槽后段的极板间的中间位置,而靠近阴极区域絮体的量几乎为0。沿着流体流动方向絮体的量增大,电解通道中絮体的生成量随电流密度和停留时间的增加而增加,而在初始pH值为5-7的范围几乎不发生变化。同时发现电解槽通道中,垂直于电极方向上,絮体的分布不受停留时间、电流密度及初始pH的影响。
[Abstract]:In recent years, heavy metal wastewater pollution incidents occur frequently, and electroflocculation (ECC) is an important technology to treat heavy metal wastewater. It is also often used in the treatment of refractory organic wastewater. EC process is composed of electrochemical reaction of electrode, mass transfer of substance, hydrolysis reaction and adsorption reaction. The coupling of interactions. It is the complicated coupling relationship between the processes that makes the experimental research and process improvement more difficult, which restricts the further study of mechanism. The EC process consists of three processes: floc generation, floc transport and floc adsorption, and the floc generation and distribution process have an important effect on the removal efficiency of pollutants. In this paper, the electrochemical reaction and hydrolysis reaction model of electrode in EC process is established, and the mass transfer and momentum transfer model of EC electrolysis and hydrolysate are established, and the solution is calculated. The generation and mass transfer of species during continuous electrocoagulation were studied. It is found that the Al3 produced by electrolysis mainly distributes in the cathode near the anode, and the amount of the two ions decreases gradually along the flow direction. In the front section of the electrolyzer, the concentration polarization of the ion is weak, the hydrolysis reaction is the control step, and the concentration polarization of the ion is stronger in the middle and the later part of the cell, and the mass transfer is the control step. The concentration of Al3 and OH- also increased with the increase of current density, and the concentration polarization of ions was weak without hydrolysis, and the whole electrolytic cell solution showed weak alkalinity. The dissolved aluminum in the hydrolyzed product mainly distributes near the two electrodes, while the floc aluminum mainly distributes in the middle position of the two electrodes, and the floc aluminum occupies the main position in the whole electrolysis cell. Along the flow direction, the percentage of floc aluminum to total aluminum increases gradually, while the percentage of dissolved aluminum to total aluminum decreases gradually. It is also found that the floc mainly distributes in the middle position between the polar plates in the back section of the electrolytic cell under the combined action of electromigration and convection, and the amount of floc near the cathode area is almost 0. The amount of floc in the electrolytic channel increases with the increase of current density and residence time, but almost does not change in the range of initial pH value of 5-7. At the same time, it is found that the distribution of floc is not affected by residence time, current density and initial pH in the electrolytic cell channel perpendicular to the electrode direction.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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