Carbon dioxide adsorption on shale: A comparative study of isotherm models across diverse samples and temperatures

Abstract

In order to address one of the most serious environmental concerns of our day, reducing carbon footprints, the globe has turned its attention to carbon dioxide (CO2) storage as a potential solution. Because of its unique features, shale is one of the most intriguing options in this area. Adsorption is the method through which CO2 is stored in shale, particularly in its supercritical condition. Adsorption isotherm models can be used to deduce the behaviour and mechanisms of this adsorption. Langmuir, Freundlich, Dubinin-Astakhov (D-A), and Brunauer-Emmett-Teller (BET) models are among the many available for CO2 modelling on shale. We attempted to fit these models to experimental data gathered from literature sources in this study, concentrating on four separate shale samples from various places in China. Among these samples are LMX1 and LMX2 from the Silurian Longmaxi Formation, WF1 from the Ordovician Wufeng Formation in the Sichuan Basin, and YC from the Ordos Basin's Yanchang Formation. The total organic carbon (TOC) content of these shales, three marine and one continental, ranged from 3.19 to 4.27. The experimental data used to fit the model was obtained at three different temperatures: 35, 45, and 55°C. The Langmuir and D-A models offered the best fit for the data across all samples and temperature. R2 values 0.93429 (for YC rock at 35°C) to 0.99287 (for WF1 at 35°C) for Langmuir and 0.88879 to 0.99201 LMX1 at 35°C. The theoretical underpinnings of these models, which account for the physical properties and adsorption dynamics of supercritical CO2 on shale, are responsible for their performance. Finally, this study adds to our understanding of CO2 adsorption on shale, giving useful insights for future research and potential practical uses in CO2 storage. More research is needed, however, to completely understand the mechanisms and influencing factors of CO2 adsorption in various types of shale, as well as to develop the models used to forecast this behaviour.