A Comparative Study of Supported Sulfonic Acids Derived from CdO and CaO for the Reactive Adsorption of o-Xylene

The recovery and control of volatile organic compounds (VOCs) have gained significant attention. Supported sulfonic acid materials show potential in converting aromatic VOCs into non-volatile sulfonic acid derivatives. However, their effectiveness is closely tied to the anchoring state of the sulfonic acid groups. In this study, two supported sulfonic acids, SSA@CdO and SSA@CaO, were synthesized via the respective reactions of CdO and CaO with chlorosulfonic acid to investigate how the properties of the supports influence sulfonic acid anchoring and reactivity toward o-xylene. Comprehensive characterization and performance tests revealed that sulfonic acid groups on CdO were covalently bonded, forming positively charged sites ([O0.5Cd–O]ɗ−–SO3Hɗ+) with high loading (9.7 mmol/g), enabling excellent o-xylene removal (≥95.6%) and adsorption capacity (51.67–91.59 mg/g) at 130–150 °C. In contrast, ion-paired bonding on CaO formed negatively charged sites ([O0.5Ca]+:OSO3H−), which were inactive in electrophilic sulfonation. This work provides new insights for enhancing supported sulfonic acid materials in VOC treatment.