Sorption of Water by Sodium, Copper, and Magnesium Sulfates Dispersed into Mesopores of Silica Gel and Alumina
Russian Journal of Physical Chemistry A
, E-ISSN: 1531-863X
Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences, pr. akademika Lavrent'eva 5, Novosibirsk, 630090, Russian Federation
Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russian Federation
New composite sorbents [Na2SO4/(KSK silica gel), CuSO4KSK, MgSO4/KSK, and MgSO4/alumna] were synthesized. The sorption equilibrium of these sorbents with water vapor was studied at pressures from 10 to 50 mbar and temperatures from 20 to 300degreesC. It was established that the sorption equilibrium and phase composition of Mg, Na, and Cu sulfates dispersed into pores of KSK silica gel are determined by the concentration of the salt in the composite. At low concentrations of the salt, it exists in the pores in the farm of an XRD-amorphous phase, whose composition changes monotonically with the water vapor pressure and the temperature (bivariant system). In the pores of systems containing high concentrations of Mg and Na sulfates, a crystalline phase of the salt is formed. The dispersity, of this phase is determined by the size of the pores in silica gel, 10-25 rim. The sorption of water vapor by these systems is accompanied by the formation of a salt crystal hydrate with a fixed composition (univariant systems). As the sorption of water vapor proceeds still further, a salt solution is formed in the pores, and the system becomes bivariant. Depending on the nature of the salt, the crystalline phase is formed at a salt concentration of 15 to 25 wt %. The characteristics of the sorption of water vapor by dispersed sulfates were compared with those reported for Ca and Li halides dispersed in the same matrices.