Reticulated ZnO Photocatalyst: Efficiency Enhancement in Degradation of Acid Red 88 Azo Dye by Catalyst Surface Cleaning

The reticulated ZnO photocatalysts fabricated by replicating the shape of a polyurethane sponge through the ZnO powder slurry impregnation method were used in the degradation of Acid Red 88 dye molecules in an aqueous environment. In terms of color change percentage and total organic carbon content, the efficiencies of the catalysts were determined for a fixed dye concentration (50 mg/L) and time (180 min) as a function of wavelength (365 and 254 nm) and reusability (up to five runs). The catalysts were cleaned between each consecutive run in deionized water under ultraviolet light irradiation overnight. The highest color removal percentage (79%) was reached after the first cleaning process (i.e., for the second run) when the wavelength was 254 nm. After the fifth run, this value slightly dropped to 64% with the relatively low mineralization degree of 14.4%. The same trend was also observed for the 365 nm wavelength, where the color removals were changed from the maximum value of 63 to 50%. The efficiency enhancement for the second runs is attributed to hydroxyl enrichment of the ZnO surfaces during irradiation in water.