Investigations on adsorption and transport behaviour of carrier-free silver, gold and platinum in quartz columns under vacuum conditions

The adsorption enthalpy of silver and gold atoms on fused silica surfaces was measured using vacuum-thermochromatography. Carrier-free silver, gold and platinum nuclides were produced by irradiation of cadmium, lead and mercury targets at the Swiss Spallation Neutron Source SINQ, followed by a thermochromatographic separation. For the calculation of the adsorption enthalpy from experimental data a thermodynamic model and a kinetic model (Monte Carlo simulation) were used. Our measurements revealed an adsorption enthalpy of -279 +/- 10 kJ/mol for gold, -232 +/- 13 kJ/mol for silver and an upper limit of -430 kJ/mol for platinum. These values, determined by the thermodynamic model, are in good agreement with literature values based on the same model. Additionally, Monte Carlo simulations have been performed to demonstrate the influence of temperature and size of quartz columns on the transport of model-isotopes with different half-lives.