| Summary: | 碩士 === 國立交通大學 === 應用化學研究所 === 85 ===
The use of pure water, whether for washing, cooling or as solvent, is essential in the process industry. This is especially true in the field of semi-conductor where the purity requirement for water is severe and its consumption is in large quantity. Ion exchange is known to be the most effective method of deionization as one of several steps carried out in purifying water. There has been few studies on the kinetics of ion exchange accompanied by chemical reaction. The aim of this work is to carry out the study on the kinetics of anion ex- change accompanied by chemical reaction.
Batch system is employed in the kinetics study. Ten experiments on Cl-OH exchange were conducted for the purpose of studying the effect of stoichiometric ratio/stirring rate and resin size. To examine the kinetics of heterovalent exchange, three experiments for SO4-OH exchange were also carried out. For consideration of practical application, five column runs with pure HCl, pure H2SO4 and mixture of HCl and H2SO4 as feed solution.
Results of batch experiments indicate 1. Increase the stoichiometric ratio of resin and solution results in higher rate. 2. Increasing stirring rate tend to reduce film thickness and hence increase the rate of exchange. 3. Smaller resin particle yields higher rate, this is consistent with the film diffusion model employed in this study. 4. Rate of SO4-OH exchange is higher than Cl-OH due to the larger value of Dnci compared to DH2SO4. The exchange being irreversible, higher selectivity of sulfate ion over chloride ion has no effect on the rate of exchange.
Results of column runs show : 1. Due to the higher selectivity of sulfate ion, the chloride ion is displaced and break-through occurs earlier. 2. The lower the flowrate employed, the sharper the breakthrough curve hence higher resin utilization.
This study is undertaken with the use of theoretical derived equations and experiments conducted under various operating conditions. The kinetics data and parameters as determined in this work will be useful in the application of manufacturing pure water by fixed bed ion exchange.
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