Temperature effects on ion migration and energy consumption during brackish water electrodialysis desalination

Electrodialysis (ED) is a well-established brackish water (BW) desalination technology based on the selective electro-transfer mechanism of ions for meeting freshwater demands in scarce water regions. While the influence laws of water temperature difference caused by changing seasons on the performance of BWED need to be clarified further. This study examined the effect of temperature on the desalination efficiency and energy consumption of BWED by controlling the water temperature with a constant temperature tank. Results showed that higher temperature significantly increased the current density and salt flux of BWED, but also caused a decrease and then an increase in energy consumption. The apparent activation energy of BWED system in low temperature range is about 40 % higher than that in high temperature range, indicating that higher temperature is contributed to reduce the ion transport resistance. While higher temperature increased ion diffusivity and membrane pore size, with a corresponding rise in LCD of similar to 0.41 mA/cm(2) and an increase in desalination ratio of similar to 7.75 % for increment of every 10 degrees C, thus enhanced reverse salt diffusion. The running parameters of BWED system should be regularly regulated with the seasonal temperature based on the trade-off between desalination efficiency and energy consumption to ensure an efficient operation.