Photocatalytic visible-light-driven removal of the herbicide imazapyer using nanocomposites based on mesoporous TiO2 modified with Gd2O3

Abstract

In this work, mesoporous Gd 2 O 3 -TiO 2 nanocomposites synthetized by a sol-gel with vary Gd 2 O 3 concentration were investigated for photo-destruction of imazapyr herbicide waste. Textural, structural and surface properties of the synthetized nanocomposites are verified by N 2 physisorption, X-ray diffractometry, HRTEM and various spectroscopic techniques (FTIR, DRS UV-Vis, Raman, PL and XPS). HRTEM micrographs of the calcined Gd 2 O 3 -TiO 2 revealed the existence of a mesoporous matrix consisting of homogeneously distributed TiO 2 nanoparticles (NPs, 12 nm) which are decorated with Ga 2 O 3 nanoparticles. It was found a reverse correlation between the amount of Gd 2 O 3 concentration and the TiO 2 nanoparticle size: the formation of smaller TiO 2 nanoparticles was favored by the use of high Gd 2 O 3 concentration. The photocatalytic efficiency of the synthetized Gd 2 O 3 -TiO 2 nanocomposites was appraised in the photo-destruction of imazapyr herbicide below visible-light irradiation. The best herbicide destruction was achieved using 3%Gd 2 O 3 -TiO 2 photocatalyst and degraded the imazapyr herbicide 20.5 and 8.2 times faster than a commercial P25 and non-promoted TiO 2 , respectively, indicating that modification of TiO 2 with Gd 2 O 3 led to a significant improvement of photocatalyst efficiency. This was explained as due to a lessening of the apparent optical bandgap and the formation of a large amount of surface defect states favoring the separation between electrons and holes. Besides its high efficiency, the 3%Gd 2 O 3 -TiO 2 photocatalyst demonstrated to be recyclable and stable in the visible-light-driven photocatalytic destruction of imazapyr herbicide.