Mechanisms of Reaction Between Co(II) Complexes and Peroxymonosulfate

Dror Shamir, Dan Meyerstein, Dmitry Katsaran, Lyudmila Pochtarenko, Guy Yardeni, Ariela Burg, Yael Albo, Haya Kornweitz, Israel Zilbermann

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Advanced oxidation technologies often use peroxymonosulfate in the presence of CoIIaq. It is commonly assumed that the reaction of Co(H2O)62+ with HSO5 yields CoIIIaq and SO4.−. DFT results point out that first CoII(SO5)(H2O)2 is formed. The homolysis of CoII(SO5)(H2O)2 to yield (H2O)CoII(SO5)OH.+SO4., is exothermic but has a large activation energy. However the cobalt is not oxidized in this reaction. CoII(SO5)(H2O)2 reacts with a second HSO5 to form CoII(SO5)2(H2O)2− that decomposes via disproportionation of the monoperoxysulfate ions without oxidation of the central cobalt ion. Surprisingly even in the presence of ligands, L, that stabilize CoIII, i. e., pyrophosphate; tri-polyphosphate and ATP, the experimentally observed reaction mechanism involves the formation of LCoII-OOSO3aq which then reacts with another HSO5 to form LCoII-(OOSO32−)2. The latter complex decomposes via disproportionation of the monoperoxysulfate ligands followed by oxidation of the central cobalt cation. Alternatively, in the presence of excess CoIILaq, LCoII-OOSO3aq reacts with CoIILaq to form 2CoIIILaq. These results point out that the mechanism of advanced oxidation processes initiated by a mixture of Co(H2O)62+ and HSO5 must be re-considered.

Original languageEnglish
Article numbere202100646
Pages (from-to)e202100646
JournalEuropean Journal of Inorganic Chemistry
Issue number1
StatePublished - 11 Jan 2022


  • Catalytic processes
  • Cobalt(II)
  • Fenton like mechanism
  • Oxidation Processes
  • Peroxymonosulfate


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