The rate of reduction of copper(II) with hydrogen peroxide in seawater

Frank J. Millero, V. K. Sharma, Barbara Karn

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

The rates of reduction of copper(II) with H2O2 have been measured in seawater solutions as a function of pH (6–9), temperature (5–45°C) and salinity (5 to 35). The rate constants, k, for the reduction d[Cu(II)]/dt=−k [Cu(II)][H2O2] have been fitted to the equation log k=2.12+1.29 pH—6534/T+2.72 I1/2 with σ=0.13 in log k. At a given salinity, the rates increase as a function of [H+] to the 1.3±0.1 power. Speciation calculations indicate that this slope is related to the concentration of Cu(OH)2 which is reactive to reduction with H2O2. The increase in the rates with increasing ionic strength or salinity is due to the increasing Cl concentration. The rates increase with increasing chloride to the 1.8±0.2 power. The pH and Cl results indicate that in seawater the reactive species may be Cu(OH)2Cl22−. The reaction of the dichloro Cu(II) complex leads to the formation of the dichloro Cu(I) complex, that is resistant to oxidation with O2 and H2O2. Measurements in the major sea salts indicate that the rates in seawater are nearly the same as in NaCl at the same level of Cl and HCO3. Measurements in NaCl with increasing levels of NaHCO3 and NaH(OH)4 at the same pH indicate that CuCO3 and Cu(CO3)22− are non-reactive, while CuB(OH)4+ is reactive to reduction with H2O2.

Original languageEnglish (US)
Pages (from-to)71-83
Number of pages13
JournalMarine Chemistry
Volume36
Issue number1-4
DOIs
StatePublished - Jan 1 1991

ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology

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