AI Article Synopsis
- Recent research found that pulsed electric fields (PEFs) can help reduce mineral fouling on cation-exchange membranes (CEM) during electrodialysis of Mg(2+)/Ca(2+) rich solutions, but anion-exchange membranes (AEM) still experienced issues due to prolonged pauses.
- The study explored how different current modes affect AEM fouling, revealing that direct current (dc) created stable barriers against fouling, while high-frequency PEFs effectively removed initial mineral deposits.
- However, longer pauses in certain PEF conditions led to the formation of a harmful brucite layer on the AEM-diluate side, which caused further fouling by promoting the formation of undesirable minerals during subsequent runs.
Article Abstract
Mineral fouling of cation-exchange membrane (CEM) was recently reduced by pulsed electric fields (PEFs) during the electrodialysis (ED) of solutions containing high Mg(2+)/Ca(2+) ratios. However, a fouling layer appeared on the diluate side of anion-exchange membrane (AEM) once the pause lapse surpassed certain duration. Recent studies presented a multilayer mineral growth on CEM, but the case of AEM needs yet to be cleared. The current study reveals the mechanisms involved in AEM fouling growth when applying pulse modes of current in comparison with dc current. The results showed that dc current generated steady proton barriers given by water splitting at AEM interfaces that impeded fouling on both membrane sides. The higher frequency of PEF ratio 1 (Ton/Toff=10s/10s) acted removing completely an initial mineral deposit on the concentrate side of AEM, keeping it clean after two and three consecutive runs. Particularly, an undesirable brucite layer was formed on the AEM-diluate side for longer pause lapses as for a PEF ratio 0.3 (Ton/Toff=10s/33.3s) current regime. This structure caused violent water splitting resulting in amorphous magnesium hydroxide formation and consequently in fouling precipitation on the concentrate side during a third run through current exaltation.
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| http://dx.doi.org/10.1016/j.jcis.2012.09.067 | DOI Listing |
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