# Characterization of CO2 Adsorption Behavior in Pyrolyzed Shales for Enhanced Sequestration Applications

## TL;DR

This study explores how pyrolyzed shale can be used as a low-cost material for capturing and storing CO2, offering a sustainable solution for reducing carbon emissions.

## Contribution

The study introduces a novel, low-cost shale-derived sorbent with high CO2 adsorption capacity and identifies the mechanisms behind its performance.

## Key findings

- Spent shale achieved a CO2 sorption capacity of 1.62 mmol/g, outperforming many commercial sorbents.
- CO2 adsorption behavior was best modeled by Sips and Toth isotherms, indicating multilayer and heterogeneous processes.
- Adsorption mechanisms involved both diffusion and chemisorption, as revealed by kinetic modeling.

## Abstract

Mitigating climate change through the reduction of atmospheric CO2 emissions remains a critical global priority. Solid adsorbents, particularly shales, have become promising options for CO2 storage due to their favorable structural and chemical properties. In this study, a solid sorbent was developed by pyrolyzing shale at 800 °C under a nitrogen (N2) atmospheric condition, yielding spent shale. The key physicochemical properties influencing CO2 sorption were characterized using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Brunauer–Emmett–Teller (BET) surface area analysis, and Temperature-Programmed Desorption (TPD). Mineralogical analysis revealed the presence of quartz, feldspars, clays, and carbonate minerals. The spent shale exhibited surface areas of 30–34 m2/g and pore diameters ranging from 3 to 10 nm. TPD results confirmed the presence of active adsorption sites, with a maximum CO2 sorption capacity of about 1.62 mmol/g—surpassing several commercial sorbents. Adsorption behavior was best described by the Sips and Toth isotherm models (R2 > 0.99), indicating multilayer and heterogeneous adsorption processes. Kinetic modeling using both pseudo-first-order and pseudo-second-order equations revealed that CO2 uptake was governed by both diffusion and chemisorption mechanisms. These findings positioned spent shale as a low-cost, efficient sorbent for CO2 storage, promoting circular resource utilization and advancing sustainable carbon management strategies. This novel shale-derived material offers a competitive pathway for carbon capture, storage, and sequestration applications.