Influência do método de síntese nas propriedades estruturais, morfológicas, ópticas e atividade fotocatalítica de Ag3PO4 na degradação do corante RB e AM sob irradiação de WLEDs

Abstract

The silver orthophosphate (Ag3PO4) sub-microcrystals (PM) was synthesized by the precipitation method. After that, aliquots of the PM sample were extracted and subjected to the heat treatment without air flow at 150 °C for 6 h to samples was named (PM-C).In addition, aliquots of the PM sample were submitted to hydrothermal treatment at 150 °C for 6 h. The samples named as (PM-H). This work presents the microstructural analysis, morphology, optical properties, quantum apparent efficiency and photocatalytic activity of PM, PM-C and PM-H samples in degradation of the dye Rhodamine B (RhB) and methyl orange (MO) under WLEDS. In the characterization of the catalytic solids, the X-ray diffraction patterns (XRD), demonstrated that the synthesized samples presented good crystallinity and were used in the Rietveld refinement applying the program Fullprof in the indexing of phases and microstructural analysis. Results indicated that the degree of microstrain, crystallite anisotropic size and partial orientation preference varied between PM, PM-C and PM-H treatment methods. The results obtained by the Williamson-Hall method as well as the visualization of the mean apparent crystallite size distribution obtained from the refinement of the spherical harmonic coefficients showed a slight similarity to the particle morphologies visualized by field emission scanning electron microscopy( SEM-FE). Quantitative analysis of the phases present in the PM-C and PM-H samples was implemented in the refinement routine and evidenced the presence of Ag-NPs in the samples treated by thermal and hydrothermal routes. Results of Raman and FTIR spectra showed the symmetric and asymmetric groups characteristic of Ag3PO4. UV-Vis Diffuse Reflectance Spectroscopy (DRS) revealed PM, PM-C and PM-H samples to have EBG with 2.23, 2.15 and 2.16 eV respectively. The best photocatalytic binder was obtained with PM-C (> 95 percent) in the degradation of RhB and MO dyes. Sub-microcrystalline Ag3PO4 demonstrated good catalytic activity during reuse, especially for PM-C sample under WLEDs radiation. It was possible to evaluate during the three catalytic cycles the influence of the light source (WLEDs), the plasmatic effect of the Ag-NPs on the surface of PM-C and PM-H samples, as well as the effect of the chromophores groups on the photocatalytic performance of the synthesized samples.