Facile synthesis of activated carbon/titanium dioxide composite and its application for adsorptive/photocatalytic removal of gaseous toluene

The practical utility of activated carbon/titanium dioxide (AC/TiO₂) composite has been investigated for the abatement of a common aromatic volatile organic compound (VOC), toluene. The adsorption and photocatalytic performance of the prepared AC/TiO₂ composites (ACT-x: x as the theoretical mass ratio (in percent) of AC over TiO₂ ranging from 0% to 10%) is evaluated individually against gaseous toluene using a packed flow tube reactor under varying operational conditions (e.g., relative humidity and gaseous pollutant composition). The presence of AC in the composite significantly increases the adsorption capacity (Q) such as 1.71 mg g⁻¹ for ACT-10 relative to 0.01 mg g⁻¹ for ACT-0. The ACT-5, with 3.6% C, exhibits the maximum photocatalytic removal efficiency (X_T = 93.77%), quantum efficiency (QE; 1.63 × 10⁻⁴ molecules photon⁻¹), space time yield (STY; 1.99 × 10⁻⁵ molecules photon⁻¹ mg⁻¹), and specific clear air delivery rate (SCADR; 686.2 L h⁻¹ g⁻¹) among all the ACT compositions tested. ACT-5 exhibits enhanced potential for adsorption and in-situ degradation-desorption to facilitate the removal of VOCs with the reduced yield of by-products. The in-situ diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography-mass spectrometry analyses indicate the formation of several intermediate by-products during the photocatalytic degradation process, including benzyl alcohol, benzaldehyde, benzoic acid, phenol, and alkane species. In addition, the photocatalytic performance of ACT is demonstrated to be superior to those of other TiO₂-based photocatalysts. Accordingly, the ACT composite is recommended as a promising medium for the abatement of aromatic VOCs in indoor air.