Conversion of hypochlorite at a hydrogen gas-diffusion anode

L.J.J. Janssen

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    Abstract

    To study the conversion of hypochlorite into chlorate in a strongly acidic soln. and without simultaneous formation of oxygen, the chem. chlorate formation and the conversion of hypochlorite at a gas-diffusion anode in a weakly alk. soln. contg. NaCl and NaClO were detd. During electrolyses H+-ions are produced on the gas-diffusion anode by oxidn. of hydrogen mols. and the soln. layer adjacent to this anode will be very acidic. The rate of the redn. of hypochlorite on the hydrogen GDE at E = 1.00 and 1.10 V is detd. by mass transfer of hypochlorite. If a large part of the HClO formed is converted into chlorine, the rate of redn. of hypochlorite to chloride is clearly smaller than that corresponding to the rate of mass transfer of hypochlorite, since chlorine diffuses to and from the electrode surface of the GDE. Moreover, the rates of the hypochlorite conversion at 1.00 and 1.10 V are practically equal. These potentials are, resp., below and just above the equil. electrode potential for the reaction 2Cl-.dblharw. Cl2 + 2e- assuming a chlorine pressure of 1 atm and a chloride concn. of 0.5M. If a large part of the HClO formed is converted into chlorine, the rate of redn. of hypochlorite to chloride is clearly smaller than that corresponding to the rat of mass transfer of hypochlorite, since chlorine diffuses to and from the electrode surface of the GDE. Moreover, the rates of the hypochlorite conversion at 1.00 and 1.10 V are practically equal. These potentials are, resp., below and just above the equil. electrode potential for the reaction 2Cl .dblharw. Cl2 + 2e- assuming a chlorine pressure of 1 atm and a chloride concn. of 0.5M. Consequently, it is more likely that hypochlorous acid is reduced directly to chloride. Formation of chlorate does not take place under these conditions. This may be due to the fast redn. of hypochlorous acid to chloride. Unfortunately, the method used is not useful for study of chem. chlorate formation in strongly acidic soln
    Original languageEnglish
    Pages (from-to)848-850
    JournalJournal of Applied Electrochemistry
    Volume23
    Issue number8
    DOIs
    Publication statusPublished - 1993

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