Thermodynamics and mechanisms of adsorption of iodide on zirconia

Here we present a comprehensive experimental and computational study of adsorption of I - to ZrO 2 particles in water. With batch experiments and a new quantitative spectrophotometric method, the Henry isotherm and the thermodynamic quantities of the Van’t Hoff equation for adsorption of I - were determined. DFT calculations with periodic models were performed to understand molecular and dissociative water adsorption and I - adsorption considering adsorbate exchange at the surface to mimic the real system. The DFT calculations show that I - competes with H 2 O and HO – for the same adsorption sites. I - is able to displace molecularly adsorbed H 2 O, but not the adsorbed HO – which ultimately provide the bonding environment for I - at the surface of the oxide. The number of adsorbate binding sites is obtained from the Henry isotherm here used as a limiting case of the Langmuir model. This is possible because, as demonstrated by the DFT data, Δ H ads is close to constant with increasing coverage of I. The isotherm predicts the formation of a partial overlayer of I-atoms which is also suggested by the DFT data. The Δ H ads and Δ S ads determined from experimental data and the Van’t Hoff equation agree with the proposed mechanisms from DFT.