Removal of Hazardous Hydrogen Fluoride from Water Through Homogeneous Nanostructured CaO-SiO.sub.2 Sorbents: Optimization of Binder

In this study, we prepared a homogeneous dispersion of CaO-SiO.sub.2 sorbent with advanced nanostructures as an efficient solid-reducing agent for the elimination of hazardous chemicals. The hydrophobic properties of SiO.sub.2 ceramic particles are of interest for reducing the limitations and enhancing the chemical properties of highly hygroscopic materials. Nano-sized SiO.sub.2 is introduced and composited with CaO through a facile synthetic route. The structural and microstructural characteristics and elemental compositional analyses confirm the uniform distribution of the CaO-SiO.sub.2 nanocomposite. The as-prepared nanocomposites have particle sizes in the range of ~ 20-100 nm. Optimization of the composition reveals that the 60 wt% CaO-SiO.sub.2 can be considered as an efficient solid-reducing agent for the hydrogen fluoride (HF) removal process. In order to identify the catalytic effect and binder ratio, the specific surface area and HF removal performance was investigated and compared to CaO-SiO.sub.2 nanostructures with individual CaO catalyst. The higher amount of HF concentration was absorbed by CaO-SiO.sub.2 catalyst than the CaO only. In the first 2.5-h reaction, the outlet HF concentration is rapidly increased to 380 ppm by using CaO catalyst as a HF sorbent. However, the outlet HF concentration is sluggishly increased up to 180 ppm, when nanostructured CaO-SiO.sub.2 catalyst used as a sorbent in RE-RCS. It has been found that the addition of hydrophobic properties of SiO.sub.2 has prevented the reaction between water/moisture and CaO in CaO-SiO.sub.2 catalyst system, which is a major reason for enhancement in HF removal process. Furthermore, the CaF.sub.2 byproduct can be effectively used in the ceramic industry and building material applications.