The oxidation of Cu(I) with H sub 2 O sub 2 in natural waters

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90349-9· OSTI ID:7266140

Sharma, V K; Millero, F J ^[1]

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1. Univ. of Miami, FL (USA)

The oxidation of Cu(I) with H{sub 2}O{sub 2} in seawater and in NaCl solutions has been measured as a function of pH (6 to 9), temperature (5 to 45{degree}C), ionic strength (0.5 to 6 m) and composition. The seawater rate constants, k (M{sup {minus}1} s{sup {minus}1}), for the oxidation d(Cu(I))/dt = {minus}k(Cu(I))(H{sub 2}O{sub 2}) have been fitted to the equation log k = 11.55 {minus} 2,250/T {minus} 3.71I{sup {1/2}} + 2.06I with a {sigma} = 0.04. The energy of activation was 43.1 {plus minus} 1.0 kJ mol{sup {minus}1}. At a constant ionic strength (I = 1, 3, and 6 m) in NaCl-NaClO{sub 4} mixtures, the Cl{sup {minus}} dependence has been attributed to the oxidation of various forms of Cu(I) in the solution. At a fixed Cl{sup {minus}} concentration, the addition of Mg{sup 2+} causes the rate to decrease, and the addition of HCO{sup {minus}}{sub 3} causes the rate to increase. The increase due to HCO{sup {minus}}{sub 3} may be due to the formation of CuHCO{sup 0}{sub 3} which has a faster rate of oxidation than CuCl{sup 0}. The decrease caused by Mg{sup 2+} may be due to the slow exchange of MgEDTA or MgCO{sub 3} with Cu{sup 2+}, which may cause the overall oxidation rates of Cu(I) to be slower due to back reactions of Cu(II) with H{sub 2}O{sub 2}. Empirical equations for the rate of oxidation of Cu(I) with H{sub 2}O{sub 2} in natural waters are given. The H{sub 2}O{sub 2} results are compared with the kinetics of Cu(I) oxidation with O{sub 2} in natural waters. At the levels of O{sub 2} (200 {mu}M) and H{sub 2}O{sub 2} (0.1 {mu}M) in surface sea waters, the oxygen oxidation is 130 times faster than peroxide oxidation. In rainwaters, however, the concentration of hydrogen peroxide (100 {mu}M) is great enough so that H{sub 2}O{sub 2} is the dominant oxidant for Cu(I).

• OSTI ID: 7266140
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:9; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COPPER
OXIDATION
HYDROGEN PEROXIDE
ACTIVATION ENERGY
CHEMICAL REACTION KINETICS
SEAWATER
COPPER COMPOUNDS
COPPER IONS
GEOCHEMISTRY
IONIC COMPOSITION
PH VALUE
SODIUM CHLORIDES
THERMODYNAMIC ACTIVITY
ALKALI METAL COMPOUNDS
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
ELEMENTS
ENERGY
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
IONS
KINETICS
METALS
OXYGEN COMPOUNDS
PEROXIDES
REACTION KINETICS
SODIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
WATER
580000* - Geosciences