Copper, electrostatic charge effect

The effect of surface electrostatic charge on a material on the attachment of the decay products of radon has been known since pioneering work on atomic structure by Rutherford. Extensive research into this area for the radon and thoron progeny has been conducted in this laboratory for environmental monitoring purposes. Several authors have reported on the effect of electrostatic charge on the collecting characteristics of copper for the radon progeny for exploration purposes (Card and Bell, 1979). 

As often is the case (see Chapter 2, Sections 2.2.6 and 2.7), the molecular mechanics analysis above does not include any electrostatic interaction energies. To include these, the charge distribution and the charge compensation by ion-pairing to counter ions (perchlorate) have to be known. Model calculations indicate that an effective charge of around +1.6 per copper site, a value that is expected from thermodynamic considerations, leads to electrostatic repulsion energies of ca. 17 kJ mol-1 and 10 kJ mol-1, respectively, for the folded and stretched conformers. In agreement with the experiment (EPR spectra), this qualitative analysis indicates a preference for the folded structure of A, and for the stretched structure of B1 201. 

On the other (copper) electrode the electrolytic solution pressure is lower than the osmotic pressure of the cations in the solution and therefore cupric ions from tho solution are deposited, thus giving the metal a positive charge, while the solution becomes negative due to the excess of anions (SO ). Both kinds of charges Cu++ and SO - are attracted and form again the electrical double layer. In this case, however, the double layer has an opposite effect than at the zinc electrode as it facilitates the transfer of the cupric ions from the electrode to the solution and prevents them being transferred in the opposite direction. Equilibrium will be attained, when the electrostatic forces of the double layer and the solution pressure of copper together will counterbalance the osmotic pressure of the cupric ions in the solution. 

This factor of 106 is much too large to be explained only on the basis of an electrostatic effect that arises from the reaction of a negatively charged hydroxide ion with a positively charged copper(II) complex (25). It is therefore necessary to postulate that the copper(II) ion which is coordinated to the nitrogen atom of the amino group also interacts directly with the ester group (structure XXXVI). 

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