Utilization of Element-doping Titania-impregnated Granular Activated Carbon in a Plug-flow System for Removal of BTEX

Abstract

The use of an activated carbon (AC) system alone has the limitation that the pollutants are not eliminated but only transferred to another phase with the consumed AC becoming hazardous waste itself. Therefore, the present study investigated the feasibility of using a combined system of granular AC (GAC) with S-doped visible-light-induced TiO2 (GAC/S-doped TiO2) to clean monocyclic aromatic hydrocarbons (MAHs) with concentrations at ≤3 mg m-3, using a continuous air-flow reactor. This study conducted three different experiments: an adsorption test of pure GAC and GAC/S-doped TiO2; a long-term adsorptional photocatalytic (AP) activity test of GAC/S-doped TiO2; and an AP activity test of GAC/S-doped TiO2 under different conditions. For the AP activity test, three parameters were evaluated: various weights of GAC/S-doped TiO2 (0.9, 4.4, and 8.9 g); various flow rates (FRs) (0.5, 1 and 2 L min-1); and various input concentrations (ICs) of the target MAHs (0.1, 1, 2 and 3 mg m-3). The adsorption efficiencies were similar for the pure GAC and GAC/S-doped TiO2 reactors, suggesting that S-doped TiO2 particles on GAC surfaces do not significantly interfere with the adsorption capacity of GAC. Benzene exhibited a clear AP activity, whereas no other target MAHs did. In most cases, the AP efficiencies for the target MAHs did not significantly vary with an increase in weight, thereby suggesting that, under the weight range tested in this study, the weights or FRs are not important parameters for AP efficiency. However, ICs did influence the AP efficiencies.

Keywords

• photocatalytic activity
• visible-light irradiation
• element-doping
• granular activated carbon
• plug-flow system