اثر پیکربندی در انتقال جرم در یک نوع فیلتر پرس سلولی الکتروشیمیایی

Effect of configuration (structure of electrode, interelectrode gap, positions of inlet and outlet, volume of the cell and additional nets) on mass transfer characteristic of a filter-press type electrochemical cell has been studied. The mass transfer coefficients on the electrodes were obtained by using the well-known technique based on the determination of limiting diffusion current. It is found that mass transfer coefficients with mesh electrode are greater than that of with plate electrode. Mass transfer coefficient is decreased with interelectrode gap. While interelectrode gap achieved a certain value (7 mm), mass transfer coefficient is steady, no more declining. Mass transfer characteristic for different positions of inlet and outlet are different and dimensionless number groups correlated equations are obtained by experiment. Mass transfer characteristic is the best when inlet located on the top and outlet on the bottom of the cell respectively. While magnified the volume of the cell to eight times, mass transfer characteristic changes little. Mass transfer characteristic without nets is lower than that of with additional nets in the exit region, but higher than that of with additional nets in the entry region.

Traditional treatment technique is not of content with higher and higher requires of environmental protection for organic wastewater [1], which has abundant source, many sorts, low biodegradation and high toxicity. Studying and developing efficient technology for organic wastewater treatment have become the hotspots of research in both industry and academe [2]. Recently, electrochemical oxidation method is becoming a new alternative for wastewater treatment and replacing the traditional processes in view of electro-generated hydroxy radical and other strong oxidant, which may degrade or even mineralize toxic and non-biodegradable organic pollutant efficiently. Many researchers have paid a great attention to electrochemical oxidation. But so far, electrochemical oxidation technology has not been commercialized because of low current efficiency, high-energy consumption and large operating costs. Consequently, how to enhance mass transfer characteristic and current efficiency, develop efficient electrochemical cell for organic wastewater treatment is still a very urgent problem [3]. With the development of expanding anode [4] and porous electrode [5], mass transfer characteristics of a filter-press type electrochemical cell will be improved. In view of their uniformity of potential distribution, strong reliability, simple structure, flexible modularity, adaptability to monopolar or multipolar, low maintaining costs, facility of adding solid electrode, promoter and baffles, easy expelling of gas, control of temperature and flow, the traditional filter-press type electrochemical cell applied to organic wastewater treatment has attracted much attention [6, 7]. Two different mechanisms can be distinguished for electrochemical oxidation of organic pollutant: (1) Direct anode oxidation, electrochemical combustion [R + M (OH·)

Mass transfer coefficients with mesh electrode are greater than that of with plate electrode. Mass transfer coefficients decrease with the increase of interelectrode gap. When interelectrode gap reaches a certain value (7 mm), mass transfer coefficient is not decreased any more. Positions of inlet and outlet have significant effect on mass transfer characteristic. While inlet 2/outlet 4 was selected, mass transfer characteristic is the best. According to experimental data, it is obtained dimensionless groups mass transfer correlate equation. For each position of inlet and outlet, the following correlations are obtained: inlet 1 outlet 1 and inlet 1 outlet 2, Sh