Effective Photodegradation of 2,4-Dichlorophenoxyacetic Acid on TiO 2 Nanocrystals Anchored on SBA-15 Mesoporous Material

This study investigated the photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) using TiO 2 nanoparticles supported on SBA-15 molecular sieve, obtained by the in situ anchoring (ISA) method. Results obtained by X-ray diffraction (XRD) revealed that the incorporation of the TiO 2 did not destroy the characteristic structure of the molecular sieve. Raman spectrum showed active modes for anatase phase of TiO 2 nanoparticles anchored onto SBA-15 matrix. Scanning electron microscopy (SEM) images illustrated an arrangement organized into rope-like structures. UV–Vis spectra indicated that TiO 2 anchored into SBA-15 exhibited light absorption in the UV region. Zeta potential analysis was performed that revealed a negative surface charge for samples, which affected the adsorption process. TiO 2 /SBA-15 catalyst showed an efficiency photocatalytic of 82.11% in the degradation of 2,4-D herbicide in 180 min of UV radiation. Moreover, considerable loss of the photocatalytic activity was not observed when reusing the catalyst three times, with 82.11%, 74.4%, and 74% of photocatalytic efficiency in the first, second, and third cycles, respectively. The Allium cepa bioassay demonstrated that 2,4-D initial solution (10 –5 M) induced chromosomal damage and inhibited the growth of roots, after 24 h of exposition. However, the residues coming from the photocatalytic assay exhibited similar results to the negative control (distilled water). Therefore, the material TiO 2 /SBA-15 showed promising results in the degradation of 2,4-D herbicide.