COPPER-AMINE SPECIATION - AN ELECTROCHEMICAL INVESTIGATION OF THE SELECTION OF VOLATILE AMINES FOR STEAM-GENERATOR WATER

Addition of volatile amines for pH control to steam generator water of power plants to protect the steam water system from corrosion is call ed all volatile treatment (AVT) of steam generator water. Metal ion co ncentrations in steam generator water will generally be in the mu g l( -1) range. Pseudopolarography in combination with differential pulse a nodic stripping voltammetry copper speciation studies (at 50 mu g l(-1 ) copper concentration) were carried out in aqueous media containing f our important amines, viz. 3-methoxypropylamine (3MPA), 1-dimethylamin o-2-propanol (DMPA), 2-dimethylaminoethanol (DMAE) and piperidine (Pip ), all having a large potential for use as AVT reagents. The copper-am ine complexes were identified and their log stability constants (log K ) values were as follows: [Cu(I)(3MPA)(2)]: 10.47; [Cu(II)(OH)(2)(DMPA )(2)]: 20.33; [Cu(II)(OH)(2)(DMAE)(2)]: 20.51; [Cu(I)(Pip)]: 8.29; [Cu (I)(Pip)(2)]: 9.89; [Cu(I)(OH)(2)(Pip)(2)]: 16.67. Electroreduction me chanisms of these identified species at a hanging mercury drop electro de were studied. The ability of some of the amines to influence the st epwise reduction/oxidation of copper results in impeding its transport in dissolved form in the steam generator water. Hence it is recommend ed that only those amines that do not stabilize Cu(I) in solution be s elected for use as AVT reagents for ensuring better performance of ste am water circuits in power industries.