Free chlorine testing status
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This post was last edited by sunjl1981 on 2013-1-6 at 21:44. After vacuum dechlorination under alkaline conditions, sodium sulfate was added; the ORP measurement showed a negative value. After the mixture was sent to a membrane-based nitrate removal system, acid was added for testing, and the values remained high, around +240. What could be the reason? I would appreciate any advice from experienced users -
Vacuum dechlorination should take place under acidic conditions; after passing through the dechlorination tower, an alkali is added to adjust the pH, followed by the addition of sodium sulfite to remove free chlorine. If you perform vacuum dechlorination under alkaline conditions, free chlorine reacts with the base to form sodium hypochlorite and sodium chlorate. After adding sodium sulfite, sodium hypochlorite is removed, and the potential becomes negative. After nitrate removal using membrane technology, acid is added, and sodium chlorate reacts with hydrochloric acid to produce sodium hypochlorite again.
Vacuum dechlorination is carried out under acidic conditions; under alkaline conditions, free chlorine is converted into chlorates, and acid needs to be added for membrane-based nitrogen removal, as chlorates decompose to produce free chlorine
Reply to 3# marongqiang: We are also facing the same situation at the moment. After vacuum dechlorination, the pH value is adjusted to around 11, and sodium sulfite is added to remove hypochlorous acid. It is necessary to ensure that the hypochlorous acid content in the lightly salted water is zero; meanwhile, it is important to check the hydrochloric acid you use to see if the level of free chlorine in it exceeds the permissible limits.
Dechlorination takes place under acidic conditions; we add high-purity hydrochloric acid before entering the dechlorination tower, and then we add alkali and sodium sulfite to the dechlorinated brackish water