A comparative study of acid-activated non-expandable kaolinite and expandable montmorillonite for their CO_2 sequestration capacity

This study aims to improve the pore volume and specific surface area of kaolinite (Kaol) and montmorillonite (Mt) through low-temperature acid treatment to address their limited adsorption capacity. Clay mineral samples underwent sulfuric acid activation at various concentrations and durations. SEM analysis indicated acid activation improved kaolinite pore structure, increasing specific surface area, while montmorillonite exhibited reduced grain size and higher porosity, resulting in greater pore volume and surface area. EDX analysis revealed changes in chemical composition, including a 10% increase in silica and a 13% reduction in aluminium in kaolinite, whereas montmorillonite exhibited a 13% aluminium increase and 9.5% higher silica content. Kaolinite’s XRD pattern remained unchanged, resisting 2.5 M acid activation, while montmorillonite displayed modified patterns, indicating interlayer conversion with increased acid concentration. BET analysis confirmed higher sulfuric acid concentration increased pore volume and surface area, while FTIR analysis showed stable Si–O stretching peaks with changing intensity after 8 h. Montmorillonite exhibited Al–OH and Mg–OH bands, decreasing with higher acid concentration, and Si–O–Fe and Si–O–Al bonds disappeared with acid activation. Thus, the results indicate significantly enhanced pore volume and specific surface area after acid activation, accelerating CO_2 adsorption rates. This activation demonstrates a direct relationship between acid concentration and reaction time with clay minerals’ pore characteristics. These clay minerals can be used as adsorbents for CO_2 in carbon capture technology, aiding the global goal of achieving ‘net zero’ emissions by 2050.

本研究旨在通过低温酸处理提高高岭石（Kaol）和蒙脱石（Mt）的孔体积和比表面积，以解决它们吸附能力有限的问题。粘土矿物样品在不同浓度和时长下进行了硫酸活化。扫描电子显微镜（SEM）分析表明，酸活化改善了高岭石的孔隙结构，增加了比表面积，而蒙脱石则呈现出粒径减小和孔隙率提高的现象，从而导致更大的孔体积和表面积。能谱分析（EDX）显示化学成分发生了变化，高岭石中二氧化硅含量增加了10%，铝含量减少了13%，而蒙脱石中铝含量增加了13%，二氧化硅含量提高了9.5%。高岭石的X射线衍射（XRD）图谱在2.5 M酸活化下保持不变，而蒙脱石的图谱发生了改变，表明随着酸浓度增加发生了层间转化。比表面积分析（BET）证实较高的硫酸浓度增加了孔体积和表面积，而傅里叶变换红外光谱（FTIR）分析显示，8小时后Si - O伸缩峰强度发生变化但保持稳定。蒙脱石呈现出Al - OH和Mg - OH谱带，随着酸浓度升高而减弱，并且Si - O - Fe和Si - O - Al键在酸活化后消失。因此，结果表明酸活化后孔体积和比表面积显著提高，加速了二氧化碳的吸附速率。这种活化表明酸浓度和反应时间与粘土矿物的孔隙特征之间存在直接关系。这些粘土矿物可在碳捕集技术中用作二氧化碳的吸附剂，有助于实现到2050年全球“净零”排放的目标。