Thermodynamic study of Iridium in HCl: The effect of concentration

In this work, the dissolution of iridium was studied through a thermodynamic theoretic study withdifferent concentrations of hydrochloric acid (HCl) and Iridium (Ir). Three different acid conditionsand three different concentrations of iridium were analyzed: 1, 0.1 and 0.01 M HCl and 0.86, 0.021and 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 itis 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 Pourbaixdiagrams; while for the 0.086 M concentration, only the Ir (IV) species was observed. The Pourbaixdiagrams showed that it is possible to obtain the species iridium (IV) from a potential range of0.823 V vs SHE to 1.422 V vs SHE and at a pH between 0 and 1.2 in the 1 M HC1 solution.