Efeito da substituição do cátion A (A= Ca, Sr, Ba) em ASnO3 e do cátion B (B= Sn, Zr) em Ba(B1-XB’X)O3 na descoloração do corante verde de malaquita

Abstract

The textile industries have contributed directly to the contamination of the environment, mainly due to the disposal of the effluents that are generated in the fiber dyeing process. Contamination of water by textile effluents causes visual pollution. In addition, many dyes or their by-products are carcinogenic and / or mutagenic to aquatic biodiversity. Treatment of contaminated effluents can occur by physical, biological or chemical processes. Among the chemical processes, it is possible to highlight heterogeneous photocatalysis,where mixed metal oxides of the general formula ABO3, called perovskite, act as photocatalysts.In this context, the present work had as objective boast synthesis and characterization of pure and modified oxides based on ASnO3 (A = Ca, Sr and Ba) e BaZrxSn1-xO3 (x = 0; 0,5 and 1) aiming to evaluate the photocatalytic capacity of these materials in the discoloration of this material. Malachite green dye.The synthesis and structural characterization of alkali metal stannates and zirconates substituted by the polymeric precursor method was performed. The synthesized oxides were characterized by X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and UV-Visible Absorption Spectroscopy.CaSnO3, SrSnO3, BaSnO3, BaZr0.5Sn0.5O3 and BaZrO3- based perovskites were successfully obtained by the polymeric precursor method, confirmed by XRD standards. A shift to smaller theta values was observed for samples containing the largest ionic radius at site A(Ca=100 pm ; Sr=118 pm; Ba=135 pm) and the highest amount of Zr^4+ at site B of the structures.Infrared presented bands referring to the presence of carbonates.The Raman spectra of these materials showed higher symmetry in the lowest symmetry forming region in the lattice modifier region, due to the simultaneous occupation of the Zr^4+ and Sn^4+ cations in the modified perovskite crystalline system.From the absorption spectra in the UV-Vis region, the band gap values ranging from 3.25 to 5.01 eV were calculated by the TAUC method. due to the increase of ionic radius (cation A) and the amount of Zr^4+ (cation B) modifying the band structures of materials.All samples (ASnO3 and BaZrxSn1-xO3) showed excellent performance in the discoloration of malachite green dye.BaSnO3 practically did not change its efficiency with the dye concentration variation and BaZr0.5Sn0.5O3 obtained better result in a shorter time 77.55% (5 ppm) and 75.62% (15 ppm) in 2h, the distortions caused at site B had a positive effect on photocatalysis, as did the increase in the ionic radius of cation A, even tripling the dye concentration practically maintained the performance.