Current efficiency in an electrodialyzer is decreased by water leakage, electric permeance, permeance with concentration difference, membrane fouling, current leakage and electrolysis. And currentefficiency η* can be divided into respective influencing factor to clarify these effects on current efficiency, and η* is expressed: η*=η
q·ηH
2O·η
m·η
1·η
e.
In this report, effects of η
q, ηH
2O and η
m on η* are studied theoretically and experimentally.
The results of the study have clarified that η
q is expressed as functions of and where is the ratio of flow rate of leakage to raw water and is the ratio of desalinated salt weight of leakage to raw water, that ηH
2O is expressed as only a function of current density in the temperature range of 15-45°C on the condition that the concentration of the raw water and desalinated water are respectively invariable, for example, in case of desalination from seawater, ηH
2O has constant value (about 0.88) in range of
i>2A/dm
2, and that ηm in case of non-membrane fouling is 0.96 in view of membrane transport number, but ηm in case of membrane fouling by Cl
2 is 0.81 for the operation time from 15 to 17 h.
Therefore, the maximum value of η* in case of desalination (500 ppm: T. D. S. concentration of desalinated water) from seawater is about 0.85.
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