Research on the feasibility of continuous generation of chlorine dioxide by membrane electrolysis method

• Main Authors: Yu-Cher Tsai, 蔡煜哲
• Other Authors: Yung-Hsu Hsieh
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/04747055920367960340

碩士 === 中興大學 === 環境工程學系所 === 99 === Well known as a powerful water disinfectant with fewer disinfection by-products than chlorine, Chlorine dioxide (ClO2) has been widely used for treating potable water in western countries. Yet until today, ClO2 has not been used in practice as disinfectant in purifying potable water in Taiwan. Instead, the application of ClO2 in water purification remains to date at the stage of research. The major reason is the lack of guideline and standard operation procedure (SOP) for the use as well as analysis of this novel disinfectant. In the future, the ClO2 is expected to be more and more widely used as a disinfectant not only for potable water but also for food, medicine, environment, medicine, and so forth. As a result, more and more relevant research will surely be conducted in Taiwan as well as in foreign countries. A new electrochemistry technology has been widely used in generating ClO2 because of its advantage of high purity production, simple dosing and continuous generation. This research is followed the outcome of previous study of this University on the production of chlorine dioxide by membrane electrolysis method this research. That study explored how different composition of anolyte in operating cell can affect the production of ClO2. According to the research, a ClO2 solution at 302 mg/L of concentration and 91 % of purity respectively can be achieved in 20 minutes of electrolysis operation conducted in mixed anolyte of 2 % NaCl and 6 % NaClO2 along with catholyte of 0.5 ％ NaOH in condition of 12 V operating voltage.（YANG，2010） This study went further to explore two issues: the impact of temperature upon ClO2 production and the potentiality of continuous ClO2 production in certain concentration. The outcome of study demonstrates that along with the adjusted rise of initial temperature of electrolysis solution and that of cooling water, the initial current, top current, top temperature as well as ClO2 concentration all go up accordingly. When the controlled temperature reaches 30 ℃and cell top temperature arrives at 52℃, one can harvest a ClO2 at as high as 907 mg/L of concentration and 98% of purity. As for the issue of continuous ClO2 production in certain concentration, the research shows that ClO2 production concentration goes down while the production time range tends to be prolonged, when the electricity current is lowered in a context of fixed current and extra dosing. With the electricity current fixed at 20 A, the top production concentration falls into the category between 35 mg/L and 40 mg/L and the production concentration remains in this domain in 30 ~ 45 minutes after the process starts. The anolyte in operating cell is replaced with a view to sustaining production concentration. As the replacement volume is higher than 50%, the greater is the replaced volume, the more concentrated is the generated ClO2 solution, as the research suggests initially. However an obvious gap in production concentration is observed shortly after the replacement is made. On the other hand, when the replacement volume is lower than 50%, gap in generation concentration is less evident but the subsequent concentration is not accelerating as expected. It is concluded accordingly the conceived continuous ClO2 generation in certain concentration seems not be able to be achieved by adding once for all the dose of electrolysis solution in present experimental generation process.