(210c) High Surface Area Magnetic Photocatalyst

Photocatalytic oxidation is a technique to convert hazardous organic contaminants to carbon dioxide, water and mineral acids. Several obstacles arise when applying this technology to full-scale operations. Supported photocatalysts in packed beds and on other support materials tend to have slow reaction rates with respect to slurry reactors, yet the slurry reactors require a challenging recovery technique. Magnetic photocatalysts have the benefit of recoverability or even confinement/agitation using an oscillating magnetic field, hence avoiding the mass transport-related reactor inefficiencies. Previous work included development of a magnetic photocatalyst consisting of a barium ferrite core coated with silica and subsequently with titanium dioxide nanoparticles resulting in a material with a specific surface area of 30 m2/g primarily due to the titanium dioxide. A new higher surface area photocatalyst was developed consisting of silica-coated strontium ferrite and Degussa P25 titanium dioxide dispersed in an acid catalyzed silica xerogel. Three types of this photocatalyst developed by modifying the concentration of hydrofluoric acid had measured BET surface areas of 177, 256, and 496 m2/g. These photocatalysts were assessed for their photocatalytic activity by oxidizing a 10 mg/L phenol solution. Resulting pseudo-first order reaction rate constants for reduction in nonpurgeable dissolved organic carbon were found to be 0.189, 0.396, and 0.513 hr-1 for the lowest to highest surface area photocatalyst compared to 0.194 hr-1 for an equal mass of Degussa P25.