Enhancing the thermal stability of activated carbon in VOCs adsorption by incorporation of silicon-doped CQDs

As a widely utilized adsorbent for volatile organic compounds (VOCs) from industrial waste gases, activated carbon (AC) poses a risk of fire due to its tendency of spontaneous combustion under oxidizing conditions. The introduction of carbon quantum dots (CQDs) into AC via immersion method can improve its thermal stability thus reducing the fire risk. Meanwhile, it can further enhance its VOCs adsorption performance. The Si-doped CQDs modified AC was synthesized and characterized using TEM, FT-IR, and XRD. After modification, a significant presence of crystalline structures and compact structures were observed on the surface of AC, resulting in increased intermolecular forces and suppressed thermal decomposition of AC. The natural tendency and thermal safety of modified AC were studied by thermal analysis. The spontaneous combustion results showed that after toluene adsorption, the autoignition temperature of Si-doped CQDs modified AC was 59.7 ℃, much higher than that of AC. The activation energy increased from 31.90 kJ·mol −1 to 69.97 kJ·mol −1 . The relative fire safety factor of Si-doped CQDs modified AC was 1.3, superior to unmodified AC, significantly reducing the thermal safety risk. The thermal investigation during the toluene adsorption of AC were studied by μRC. The study showed that the heat released by the modified AC at different temperatures was significantly lower than the unmodified AC. The Si-doped CQDs modified AC effectively increased the thermal stability of the AC and significantly reduced the propensity for fire hazard of VOCs adsorption by AC.