Hydrothermal synthesized kaolin group lamellar/spongy aluminosilicates for enhanced lead vapor capture.

Abstract

Developing high-temperature-resistant adsorbents with superior porous properties is crucial for safely disposing of heavy metal-containing solid waste via pyrolysis. We synthesized aluminosilicates hydrothermally and observed that acidic conditions, especially HCl (pH=2.6), favored sponge-like mineral (NC2.6) formation with a specific surface area of 500.31 m²/g and pore volume of 0.986 cm³ /g, while alkaline conditions (pH=12.0) promoted spherical particle growth. NC2.6 exhibited higher adsorption capacity compared to kaolinite and halloysite in the PbCl₂ vapor adsorption, reaching a maximum of 137.68 mg/g at 700 ℃ (75.91 % stable). We examined the effect of CO₂ and H₂O on adsorption efficiency and explored the mechanisms using DFT and GCMC simulations. From GCMC results, CO₂ negatively impacted PbCl₂ adsorption due to competitive adsorption, while H₂O increased adsorption content (144.24 mg/g at 700 ℃) by converting PbCl₂ into oxides. DFT revealed the presence of CO₂ enhanced the adsorption stability of PbCl₂ via the formation of covalent bonds between O in CO₂ and Pb, and active O on the aluminosilicate surface. H₂O increased PbCl₂ adsorption energy, as O in H₂O occupied an active Al that originally formed a covalent bond with Cl, while the H formed a weak hydrogen bond with this Cl.