Preparation, characterization of recyclable ammonia phosphotungstate and degradation of chlorothalonil.

In this study, insoluble ammonium phosphotungstate (NH₄ PW), which is a photocatalyst, was used to degrade the herbicide chlorothalonil present in aqueous solutions. NH₄PW was prepared by both the immersion method (NH₄ PW¹ ) and the reflux method (NH₄PW² ), and preparing conditions were optimized for degrading chlorothalonil present in aqueous solutions. NH₄PW grain sizes are relatively small and well dispersible, when compared with phosphotungstic acid by scanning electron microscope images, while still maintaining the original Keggin structure as can be seen from the results obtained by X-ray diffraction, UV-visible spectra and Fourier transforming infrared spectrum. The efficiency of NH₄PW prepared by both methods in degrading chlorothalonil was evaluated. The degradation efficiency of NH₄PW¹ and NH₄ PW² can reach 73.64% and 55.21%, respectively, under the following conditions: 0.05 g of NH₄PW catalysts, 180 min of exposure to UV light and chlorothalonil concentration of 5 mg/L. Moreover, these catalysts showed excellent reproducibility and stability. Catalytic properties did not change significantly when they were calcinated for more than 4 h. Ion chromatographic analysis of the samples further indicated that dissociation occurred in the molecular skeleton of chlorothalonil during the degradation process. The results suggest that ammonium phosphotungstate can be used as a photocatalyst to accelerate the degradation of chlorothalonil present in aqueous solutions and the degradation mechanism of chlorothalonil is discussed in detail in the text. [ABSTRACT FROM AUTHOR]