Sorption kinetic of water vapour of MX80 bentonite submitted to different physical–chemical and mechanical conditions

Abstract

The clay materials are widely used in industrial processes. One significant application is as a solid desiccant agent or as a dehydrator of gases. In this case, it is fundamental to investigate on the sorption kinetics of water vapour. The main aim of the current study has been to present an experimental–theoretical study on the sorption kinetics of water vapour, using as reference material MX80 bentonite. This clay mineral was submitted at different physical, chemical and mechanical conditions. Then 0.5g of the modified-sample previously dried for 24h at 110°C was placed in plastic desiccators (2l) under isothermal conditions and atmospheric pressure, here the relative humidity was controlled by a supersaturated salt solution. This instrumental system allowed us to study the sorption kinetics of water vapour of MX80 bentonite where the control parameters were the interlayer cation (bentonite exchanged with Na, Li, K, Mg, Ca), mechanical compaction (uni-axial system at 21, 35 and 63MPa), drying temperature of sample (110, 150, 250 and 500°C), relative humidity (61, 75, 87 and 95%) and the amount of the sample (0.5, 1, 2, 3, 4 and 5g).Thanks to a kinetic model of second order it was possible to estimate that the sorption kinetic of water vapour of MX80 bentonite depends directly on the relative humidity, the interlayer cation and amount of the sample. In contrast, the sorption kinetics of water vapour was lightly affected by the mechanical compaction. Finally, the sorption kinetics of water vapour was modified by the drying temperature of sample exclusively when this is very high (for example, 500°C).