Experimental study on factors affecting the quality of ice crystal during the freezing concentration for the brackish water Original Research Article

In my study, the unidirectional-freezing method that ice growth layered from top to bottom was employed to investigate the controlling factors on the quality of ice. The method of crushing ice and centrifugation (CIAC) was introduced, trying to further improve the quality of ice. The results showed that the quality of ice was mainly influenced by controlling factors. The desalination rate positively correlated with freezing temperature and amount of seed ice; while negatively correlated with freezing rate, the solid fraction, solution concentration and the surface area of the freezing container. The initial temperature of solution had no effect on the quality of ice. CIAC based on the traditional freezing-concentration method further improved the quality of ice by breaking the “ice-salt pocket” and releasing the brine. Because crushing ice can lead to the breakage of this structure and the release of brine, while centrifugation accelerated the process, and further improved the quality of ice, especially for the ice with a higher TDS concentration. Within the concentration scope of brackish water samples (1320 ppm to 8350 ppm), the freezing method could remove 57.88%–48.38% of TDS, while the method of the CIAC could further remove 30.91%–47.28% of the TDS (with the similar solid fraction (Fs)), and thus greatly improved the quality of ice.