Characterization and the photocatalytic activity of TiO2 immobilized hydrophobic montmorillonite photocatalysts: Degradation of decabromodiphenyl ether (BDE 209)

A novel TiO2 immobilized hydrophobic montmorillonite photocatalysts were designed and prepared for the advanced oxidation of persistent organic pollutants in water, which combined the pre-adsorption and concentrated effects for aqueous micro-organic pollutants with the photocatalytic destruction of organic pollutants. The photocatalysts were synthesized by immobilizing TiO2 onto surfactant-pillared montmorillonite via ion exchange reaction between sodium montmorillonite with cation surfactant, cetyl trimethyl ammonium bromide (CTMAB). The Degussa P25 catalyst loading amounts varied between 20 and 80%. The composition and texture of the prepared composites were characterized with X-ray powder diffraction, scanning electron microscope, and energy-dispersive spectrometry. The adsorption performance and photocatalytic activities of prepared composite photocatalysts were evaluated using decabromodiphenyl ether (BDE 209) as a model pollutant in aqueous solution. The results were found that these composite photocatalysts can effectively degrade BDE 209, and the complete removal can be achieved within 180 min of irradiation. The removal efficiency of BDE 209 increased with the percentage of immobilized TiO2 on the hydrophobic clay. Highly hydrophobic substrates (BDE 209) can effectively adsorb (concentrate) in or near the hydrophobic surfactant regions of TiO2 immobilized CTMAB-pillared montmorillonite photocatalysts. The degradation pathways involving photochemical debromination and hydroxyl radical addition are proposed based on the identification of specific by-products.