Oxidation of copper(I) in seawater at nanomolar levels

The oxidation and reduction of nanomolar levels of copper in air-saturated seawater and NaCl solutions has been measured as a function of pH (7.17-8.49), temperature (5-35 degrees C) and ionic strength (0.1-0.7 M). The oxidation rates were fitted to an equation valid at different pH and ionic strength conditions in sodium chloride and seawater solutions: log k((NaCl)) 5.221 + 0.609pH -1915 / T -1.8180 + 0.408I logk((sw)) = 5.036 + 0.514pH -1765/T -1.101 root 1 + 0.233I. The reduction of Cu(II) was studied in both media for different initial concentrations of copper(II). When the initial Cu(II) concentration was 200 nM, the copper(I) productions were 20% and 9% for NaCl and seawater, respectively. The effect of speciation of copper(I) reduced from Cu(II) on the rates was studied. The Cu(I) speciation is dominated by the CuCl2- species. On the other hand, the neutral chloride CuCl species dominates the Cu(I) oxidation in the range of 0.1 M to 0.7 M chloride concentrations. (C) 2009 Elsevier B.V. All rights reserved.