Efficient construction of calcium fluoride nanoaggregates for enhanced water vapor adsorption

Abstract

Calcium fluoride (CaF2) is an ideal adsorbent for the dehydration of gaseous hydrogen fluoride (HF) containing water vapor. In this work, a novel CaF2 absorbent, spherical CaF2 nanoaggregates (NAs) with a closely packed structure, was proposed and efficiently fabricated by spray drying technology. As the building blocks of CaF2 NAs, the CaF2 nanoparticles (NPs) were prepared by the addition of excess calcium ions (Ca2+) or fluorine ions (F−) in the synthesis. The results indicated that the CaF2 NPs synthesized by excess Ca2+ and the corresponding NAs exhibited much better water vapor adsorption properties than their counterparts by excess F−, owing to higher zeta potentials. More importantly, whether excess Ca2+ or F−, CaF2 NAs had further enhanced water vapor adsorption capacity compared to primary CaF2 NPs, possibly owing to their unique nano-micro secondary structures and higher surface areas. This work has great potential in the development of high-performance absorbents for separating moisture from corrosive gas HF.