Discussion on the formation mechanism of chlorates in sodium hypochlorite products
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Dear sea friends: The sodium hypochlorite products manufactured by our company are primarily used for disinfection in water treatment plants (as a replacement for liquid chlorine in such processes). Sodium hypochlorite products are currently governed by the standard GB19016-2013 \"Standards for Sodium Hypochlorite\". The key performance parameters are as follows: Item – Parameter; Effective chlorine (as Cl) – ω/% ≥ 10.0; Free alkali (as NaOH) – ω/% 0.1–1.0; Iron – ω/% ≤ 0.005; Heavy metals (as Pb) – ω/% ≤ 0.001; Arsenic (As) – ω/% ≤ 0.0001; Color – light yellow. At present, some water treatment plants have set additional requirements for these products; in addition to complying with the standard GB19016-2013, specific limits are also imposed on bromate and chlorate levels. I have a few questions for the forum members: 1. Besides being introduced from the raw materials, do bromates and chlorates in sodium hypochlorite products also form during the chlorination reaction? 2. If bromates or chlorates are formed in the chlorination reaction, what is the mechanism behind their formation? 3. How can the formation of bromates and chlorates be reduced or eliminated in sodium hypochlorite production?
In the ion-exchange membrane process for producing caustic soda, chlorine reacts with sodium hydroxide that has been reverse-osmosis-treated in the anode chamber: 3Cl2 + 6NaOH = 5NaCl + NaClO3 + 3H2O
In the chlor-alkali process, sodium hypochlorite is produced by the absorption of chlorine gas by an alkaline solution, which contains trace amounts of chlorate. As for bromates, I think they are present in the raw materials. This is just my humble opinion; I welcome feedback from all fellow sailors, as the main goal is to engage in exchanges and learning.