Thermodynamic Study of Iridium in HCl: The Effect of Concentration

Abstract

In this work, the dissolution of iridium was studied through a thermodynamic theoretic study with different concentrations of hydrochloric acid (HCl) and Iridium (Ir). Three different acid conditions and three different concentrations of iridium were analyzed: 1, 0.1 and 0.01 M HCl and 0.86, 0.021 and 0.002 M of iridium. The system 1 M HCl was the only one that presented soluble species of Ir. Results showed that as the Ir concentration diminished from 0.86 to 0.002 M, the pH range where it is possible to obtain Ir soluble species, increased (from 0-1.2 to 0-2). The presence of two Ir species (valences III and IV) for 0.021M and 0.002 M Ir concentrations was determined from the Pourbaix diagrams; while for the 0.086 M concentration, only the Ir (IV) species was observed. The Pourbaix diagrams showed that it is possible to obtain the species iridium (IV) from a potential range of 0.823 V vs SHE to 1.422 V vs SHE and at a pH between 0 and 1.2 in the 1 M HC1 solution.