Heterogeneous uptake of carbonyl sulfide onto kaolinite within a temperature range of 220–330 K

Abstract

In this study the heterogeneous uptake of carbonyl sulfide (OCS) onto kaolinite was investigated using a Knudsen cell reactor within the temperature range of 220–330 K. Results showed that OCS could only be adsorbed at Al‐OH sites on kaolinite reversibly within this temperature region. The initial true uptake coefficient was measured to be (1.68 ± 0.12) × 10−7 at 300 K. It showed no observable dependence on the pressure of OCS, while it varied significantly with temperature, and can be expressed as γt = exp(1293/T − 20.0)/[1 + exp(1293/T − 20.0]. The values of ΔHobs and ΔSobs during the adsorption process were −10.7 ± 1.1 kJ mol−1 and −166.3 ± 4.5 J K−1 mol−1, respectively. The activation energy for desorption of OCS on kaolinite was 19.5 ± 1.1 kJ mol−1. The uptake of OCS by kaolinite owing to reversible physisorption may have little influence on the sink of OCS in the atmosphere.