Hollow-structured pollucite microspheres and the formation mechanism

Abstract

Pollucite (CsAlSi2O6·nH2O) with ANA zeolite structure could be synthesized by using metakaolin (MK), silica fumes (SF) and CsOH·H2O under hydrothermal conditions without any surfactants and seeds. Hollow-structured pollucite microspheres were obtained when the Si/Al molar ratio was above 2.0. The as-prepared hollow-structured microspheres were observed to have hierarchically structure with hollow inner and micro to mesoporous shell. Results showed that the earlier generated cesium aluminum silicate precursors through the rapid reaction of MK and CsOH could be deposited on the surface of SF microspheres to form a core-shell structure. Then further dissolution of SF microspheres in core led to the formation of hollow-structured pollucite microspheres. Self-sacrifice template effect of SF microspheres with relatively lower dissolution rate than MK was proposed to explain the formation of hollow microspheres. It is observed that the adsorption capacity of hollow-structured pollucite microspheres for methylene blue (MB, 50 mg/L) at 20 °C could reach to 52.44 mg/g, which higher than that of MK or SF. Hollow-structured pollucite microspheres might be applied as adsorbent, catalyst carrier and micro-reactor.