Effect of thermal annealing on structural, morphological, optical, and photocatalytic activity of Ag3PO4 in the 17α-ethinylestradiol degradation

Abstract

The improper disposal of pharmaceuticals can disrupt aquatic ecosystems in rivers and lakes, as well as impact human and animal health. Consequently, heterogeneous photocatalysis stands as a promising technology to mitigate or even eradicate these pollutants from aquatic systems. Silver phosphate crystals (Ag3PO4) exhibit exceptional photocatalytic and bactericidal properties. Ag3PO4 crystals were synthesized using the precipitation method, followed by a 6h heat treatment at temperatures of 100, 200, 300, 400, and 500 °C. X-ray diffraction data showcase structures with outstanding crystallinity, which remain stable even under fluctuating temperatures. Scanning electron microscopy images reveal shifts in material morphology as the temperature rises. Diffuse reflectance spectroscopy unveils optical band energy values ranging from 2.33 to 2.41 eV for the materials. Conversely, both Raman and infrared spectra indicate a reduction in bands linked to phosphate groups. Lastly, Ag3PO4 crystals exhibited remarkable performance in the photodegradation of 17α-ethinylestradiol (EE2) during a 280 min test, achieving removal rates of 77.5 %, 71.2 %, 92.4 %, 82.0 %, 41.3 %, and 92.5 % for crystals treated at 25, 100, 200, 300, 400, and 500 °C, respectively. Ag3PO4 crystals treated at 200 and 500 °C demonstrated the highest photocatalytic efficiency, attributed to their enhanced structural and morphological properties.