Nanocomposites Prepared via Acid Treatment from Calcium Silicate for Enhanced CO₂ Fixation

Abstract

Xonotlite, with a chemical formula of Ca₆(Si₆O₁₇)(OH)₂, has been widely used as a thermal insulation material due to its high porosity and chemical/physical stabilities. As a potential recycle use of Xonotlite, CO₂ fixation is promising when considering its high alkali content and macroporous structure. In this study, Xonotlite was chemically activated to form nanocomposites of silica and calcium salt by optimizing an acid treatment. It was found that Xonotlite treated with acetic acid at 1.0 mol/L keeps the original macroporous structure of Xonotlite, and simultaneously segregates calcium salt on the surface of the residual silica. The nanocomposite of silica and calcium salt exhibits the capability of CO₂ fixation and high cycle stability thanks to the unique structural feature of the composite.