Oxidation of copper(I) in seawater

Abstract

The oxidation of Cu(I) in air-saturated solutions of sea water has been measured as a function of pH (5.3-8.6), temperature (5-45 /sup 0/C), and salinity (5-44). The overall rate constant k (kg mol/sup -1/ min/sup -1/) d(Cu(I))/dt = -k(Cu(I))(O/sub 2/) has been fitted to log k = 10.73 + 0.23 pH - 2373/T - 3.33I/sup 1/2/ + 1.45I with a standard error of 0.08 in log k. The energy of activation was found to be 45.6 +/- in 1.7 kJ mol/sup -1/. The strong chloride dependence of the rates has been attributed to the effect of temperature and ionic strength on the oxidation of Cu/sup +/ and CuCl/sup 0/ species. At a given Cl/sup -/ concentration, the rates of oxidation in sea water are lower than in NaCl or NaCl-NaClO/sub 4/ mixtures. These differences in sea water are due to a decrease in the rates due to Mg/sup 2 +/ and Ca/sup 2 +/ and the increase in the rates due to HCO/sub 3//sup -/. Possible causes of these effects are discussed.