Bleaching Kinetic and Mechanism Study of Congo Red Catalyzed by ZrO2 Nanoparticles Prepared by Using a Simple Precipitation Method.

Bleaching of Congo red catalyzed by ZrO2 nanoparticles was study under UV and sunlight irradiations. The nanoparticles of ZrO2 have been synthesized by controlled precipitation method. The concentration of ZrOCl2 and ammonia reactants and the calcinations temperature of ZrO2 were optimized for the control of nanoparticles size. Characterization of the prepared nanoparticles was studied by using XRD patterns, TEM images and FT-IR spectra. The tetragonal phase of zirconium oxide was obtained at 550 °C and show the most catalytic effect in dye degradation. The various parameters such as the irradiation time, amount of nanophotocatalyst, pH of samples, and initial concentration of Congo red were studied to find desired conditions of photodegradation process. The degradation 98% was achieved at pH 7 catalyzed by 0.7 g/L if ZrO2 nanoparticles in duration time of 125 min. The effect of iso-PrOH, hydrogen peroxide and inorganic anions was studied on the degradation efficiency of dye. The degradation 98% was obtained in the presence of prepared nanosized zirconia in comparison with degradation 65% catalyzed by commercially zirconia.