Aqueous speciation of sulfuric acid-cupric sulfate solutions

This work presents the development and use of an ion-association multicompo nent equilibrium model and the application of an ion-interaction model deve loped by Pitzer, to simulate the distribution and concentration of chemical species (speciation) in sulfuric acid-cupric sulfate solutions in the 0-20 0 g/l H2SO4 and 0-50 g/l Cu(II) concentration range and 15-70 degreesC temp erature range. The model consists of a set of equations that represent the equilibrium relationships for the ionic reactions and the mass balances for the components present in the system. The effect of ionic strength was tak en into account by correcting the equilibrium constants using a relationshi p proposed by Davies. Several species can be formed at Various pH and tempe rature values, the principal ones being: HSO4-, H+, SO42-, Cu2+, and CuSO4( aq). Simulations show that concentrations are highly dependent on pH. Sulfu ric acid speciates mainly as bisulfate ion (HSO4-) and hydrogen ion (H+) at pH Values lower than 1. Calculations including Davies' relationship show v ery good agreement with experimental Values for the ionic conductivity of t he solution. The conductivity of the aqueous CuSO4-H2SO4 solution decreases as cupric sulfate is added, due to the resulting decrease in hydrogen ion concentration. The model presented in this work can be applied to predict a nd to analyze the solution composition in electrolytic copper processes suc h as leaching, electrowinning and electrorefining, as well as the purificat ion of industrial solutions used in hydrometallurgical processing. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.