Abstract
Highly ordered hexagonal mesoporous silica was successfully synthesized from natural Opoka minerals, and an all-atom model of MCM-41 was constructed by simulation. The samples were characterized by XRD, N2 adsorption, FE-SEM, TEM and FT-IR, and its water vapor adsorption/desorption performance were also evaluated. The structural rationality of MCM-41 model was verified by XRD, Connolly volume, and radial distribution function. The adsorption behavior of water molecules on MCM-41 model was simulated by Monte Carlo method, and the adsorption mechanism was discussed at the micro level. Results showed that the synthesized MCM-41 possessed a large surface area of 988 m2/g and pore volume of 1.02 cm3/g, and an average pore diameter of 4.1 nm. The moisture adsorption/desorption content of MCM-41 can be as high as 82 % and 67 %, respectively, with a high adsorption/desorption rate. The simulation results show that the adsorption sites of water molecules on MCM-41 are mainly concentrated on the silanol groups and skeleton defects of the pore surface. With the increase of pressure, the adsorption of water molecules on the surface of MCM-41 pores changes from mono-layer to multi-layer. Meanwhile, microdroplets are formed due to hydrogen bonding, and further capillary condensation occurs in the pores.
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