ADSORPTION OF CHLOROPLATINIC ACID AND CHLOROIRIDIC ACID ON COMPOSITE OXIDES

The objective of the present study is to investigate the adsorption of chloroplatinic acid and chloroiridic acid on alumina, titania, and composite oxides formed from alumina and titania. The adsorption results were analyzed by using the Langmuir equation. The adsorption kinetics and adsorption equilibrium amounts indicate that the metal ions have a higher affinity for alumina compared to titania; the difference is more significant in the case of Ir. It was also observed that the presence of titania inhibits aluminum dissolution when the TiO2-Al2O3 supports are brought in contact with acidic impregnation solutions. The adsorption results suggest that the metal ion can be selectively partitioned to alumina present in a Al2O3-TiO2 composite oxide. This selective adsorption process was explored by using temperature-programmed reduction. Our results suggest that the metal weight loading determines the selectivity of this partitioning.