Investigating the photocatalytic role of Ag₃PO₄ and CdS composites based on CNTs to degrade methyl orange under visible light

Abstract

Wastewater treatment, if done at a high efficiency and a low price, can be widely used as a strategy to deal with water shortage to a great extent. Advanced oxidation process is one of the best methods of removing colour contaminants from water, and the photocatalytic process, which functions based on semiconductors, is known as an advanced oxidation method. In this research, Ag 3 PO 4 /CdS/CNT (Ag/Cd/CN) photocatalyst was prepared using a simple precipitation method with different ratios and Ag/Cd/ CN (3:1:15 wt%) nanocomposite showed the best result, so it was finally used to remove methyl orange from water in visible light irradiation. The prepared photocatalyst was detected by fourier transform infrared spectroscopy and X-ray diffraction spectroscopy analyses. In addition, the morphology of the prepared photocatalyst was investigated and it determined that cadmium sulphide and silver phosphate particles were spread evenly on carbon nanotubes. According to the results of diffuse reflectance spectra analysis, the band gap of the optimum photocatalyst declined from 2.38 eV to 1.97 eV, in comparison with silver phosphate, and the decrease in photoluminescence resulted in the nanocomposite particles being coupled successfully. The distribution of the particles' sizes was analysed by DLS. Furthermore, BET determined mesopores in the prepared nanocomposite. This experiment was designed by Design Expert 7, where the pH parameters, photocatalyst amount, and time were all optimized. As a result, 0.4 g/L of the photocatalyst, prepared in pH = 2.5 and in 60 min, managed to degrade methyl orange (MO) by 98%. The best result was obtained at 45 °C. The prepared photocatalyst showed high stability in dye removal after being used for five cycles.