Fotodegradação do Ácido 2,4-diclorofenoxiacético usando o nanomaterial TiO2@SBA-15 e avaliação da toxicidade dos subprodutos fotocatalíticos pelo teste Allium cepa

Abstract

In this study was investigated the photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) using TiO2 nanoparticles supported on SBA-15 molecular sieve, obtained by the in-situ anchoring (ISA) method. Results obtained by XRD revealed that the incorporation of the TiO2 not destroyed the characteristic structure of the molecular sieve and Raman spectrum showed actives modes for anatase phase of TiO2 nanoparticles anchored onto SBA-15 matrix. SEM images revealed a hexagonal arrangement organized into rope-like structures. UV-Vis spectra showed that TiO2 anchored into SBA-15 exhibited light absorption in the UV region. As catalytic reaction is affected by surface charge of the catalyst and by its interaction with pollutants molecules, zeta potential analysis was performed that revealed a negative surface charge for samples, this charge affected adsorption process. TiO2@SBA-15 catalyst showed a efficiency photocatalytic of 82.11% in the degradation of 2,4-D herbicide in 180 minutes of UV radiation, besides it was not observed considerable loss of the photocatalytic activity when reusing the catalyst for three times, with 82.11%; 74.4% and 74% of photocatalytic efficiency in the 1st, 2nd and 3rd cycle, respectively. The Allium cepa bioassay results showed that 2,4-D initial solution (10-5 M) induce to chromosomal damage and inhibiting the growth of roots, after 24 h of exposition, however residues coming from the photocatalytic assay exhibited similar results to the negative control (distilled water). Therefore, the material TiO2@SBA-15 showed promising as photocatalyst results in the degradation of 2,4-D herbicide.