The formation of Cu(II) complexes with carbonate and bicarbonate Ions in NaClO4 solutions

Abstract

The inorganic behavior of most divalent metals in natural waters is affected by the formation of carbonate complexes. The acidification of the oceans will lower the carbonate concentration in the oceans. This will increase the concentration of free copper that is toxic to marine organisms. To be able to determine the effect of this acidification, reliable stability constants are needed for the formation of copper carbonate complexes. In this paper, the speciation of Cu(II) with bicarbonate and carbonate ions

is investigated as a function of ionic strength and temperature in NaClO4 solutions. To fully examine the system, the dissociation of carbonic acid in the media were examined using the Pitzer equations in NaClO4 solutions to 6.5 mol⋅kg−1 at 25 °C. With this foundation, the stability constants for the formation of Cu(II) carbonate complexes were used to determine the activity coefficients for the complexes (CuHCO+3, CuCO3, Cu(CO3)2−2). Pitzer parameters for these complexes were determined at 25 °C and ionic strength (0 to 1.1 mol⋅kg−1) in NaClO4 solutions. Since the formation of Cu(II) carbonate complexes appear to be linearly related to the values for other metals, it is possible to use the correlations to estimate the carbonate constants for a number of other divalent metals.