Abstract
Experimental kinetic data on the adsorption and desorption of water vapors on molybdenum disulfide in relative humidity ranges of the gas phase from zero to 100% are presented. Microsized layered molybdenum disulfide powders (manufactured by Climax Molybdenum Co., USA) were used in the experiment. The adsorption–desorption kinetics of water vapors was studied by the gravimetric method. In the continuous automatic mode, the weight changes in the test sample and the process rate were recorded. An air stream with a relative humidity of 100% was used for water vapor adsorption. Desorption was studied under decrease in the partial pressure of air flow water vapors to 55% of the relative humidity in isothermal and nonisothermal conditions (temperature increase and decrease in the range 20–130°C). The time dependence of the adsorptive process of water vapors in a flowing system with 100% humidity of the gas phase is close to parabolic. The dependence of adsorption on water vapor pressure (V = f(Pi) is S-shaped with the bend point in the region of transition to condensation-induced filling of absorption volumes. The desorption rate exceeds the adsorption rate. The adsorption potential theory of Polanyi, Dubinin, and Radushkevich was used to assess the bonding energy between the water molecules and nonuniform MoS2 porous structure. The change in the adsorptive forces and the Pi/Ps ratio depending on the change in adsorbate volume were characterized. Adsorption isotherms for water vapors were plotted at 30 and 50°C. The graphical integration method was applied to determine the differential rate of forming the water adsorption volumes (dVi) at water partial pressures 0 < Pi < 5 kPa. The kinetic features of the stepwise process are shown to depend on the potential energy of interaction between the adsorbed volumes and adsorbent. The nature of the adsorption process does not change in temperature changes. The coordinates of intensive formation of the adsorption volume changed towards increase in the partial pressure of water vapors.
Published Version
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