Photocatalytic efficiencies of alternate heterogeneous catalysts: Iron modified minerals and semiconductors for removal of an azo dye from solutions

Photocatalytic degradation of reactive dye solutions have been compared using two types of heterogeneous catalysts, i.e., semiconductors and iron modified clays. Decolorization and mineralization efficiencies of the catalysts were performed in a slurry batch reactor with UVA and UVC (365 and 254 nm, respectively) light sources using reactive azo dye solutions. Two natural minerals (zeolites and beidellites) modified with Fe³⁺, Fe²⁺and semiconductors (TiO₂-P25 and ZnO) were used as photocatalysts. Iron modified minerals produced similar results compared to homogeneous photo-Fenton reactions under UVC radiation. Fe²⁺-beidellite and Fe³⁺-zeolite showed the best efficiency for dye removal with 98.5% at 75 min and 96.3% at 90 min, respectively, which is higher than the other iron modified minerals under UVA radiation. ZnO and TiO₂ exhibited initial dye removal rates under UVA as 98.9% and 95.5% at 45 min, respectively. Mineralization efficiencies for TiO₂, ZnO and Fe²⁺-beidellite, Fe³⁺ -zeolite under UVA were 86.2%, 74.5% and 76.9%, 67.8%, respectively. However mineral catalysts performed 99% dye removal rates within 15 min with respect to semiconductor catalyst values (over 97% within 45min) under UVC radiation. Mineral catalysts and TiO₂ provided higher initial TOC removal rates as 92% in 60 min under UVC radiation.