Adsorption-desorption characteristics of water vapor on functional cattle bone-originated apatites powders with mesopores

Microcrystals of cattle bone-originated apatites (r-HAp) were prepared by the dissolution-precipitation and freeze-drying processes. The r-HAp particles obtained gave 128 m(2).g(-1) specific surface area and 0.376 cm(3).g(-1) total pore volume and strong basic surface with mesopores. All the adsorption isotherms of water vapor at 288-308 K for the r-HAp powders obeyed IV-type in a classification of the BDDT In the repeated adsorption-desorption operations, an adsorption hysteresis resulting from mesopores was recognized. The amounts of water vapor adsorbed obtained in the first adsorption operation were larger than those in the second adsorption operation, indicating that some portion of water vapor adsorbed to be irreversible adsorption. The water vapor-adsorption heats for the r-HAp were 45-60 kJ.mol(-1), whose values were higher than natural diatomite. The amounts of water vapor adsorbed for the r-HAp were larger than those for the adsorbents, such as natural diatomite, aerosol silica, and activated carbon, at the relative partial pressures of 0-0.7.