Sol-gel preparation of In2O3-Al2O3 supports with controlled textural and structural properties

Novel polypropylene-TiO2:Bi spherical floater for the efficient photocatalytic degradation of the recalcitrant 2,4,6-TCP herbicide

In this work, spherical photocatalytic floaters were fabricated by depositing TiO₂:Bi (TBi) particles on polypropylene (PP) spheres (recycled from beer cans). These particles were deposited on the sphere (TBi-sphere) by the spray coating technique and evaluated their performance for the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) herbicide. SEM images demonstrated that the BTi powders consisted in conglomerated grains with sizes of 20-80 nm and the analysis by X-ray diffraction confirmed the presence of rutile and anatase phases in the BTi. The photocatalytic experiments showed that the TBi and TBi-sphere produced maximum degradation of 90 and 97% for 2,4,6-TCP, respectively, after 4 h under UV-Vis light. The photocatalytic powders/composites were reused 3 times and the loss of degradation efficiency was 3 and 16% for the TBi powder and TBi-sphere, respectively. This means that the TBi-sphere is more stable for the continuous degradation of the 2,4,6-TCP contaminant. The TiO₂:Bi powder was compared with the commercial TiO₂ (P25) and found that the TiO₂:Bi powder had higher light absorption (≈42%) and higher surface area (≈105%) than the P25. Therefore, the degradation percentage for the 2,4,6-TCP was 52% higher in the sample doped with Bi. Also, scavenger experiments were carried out and found that the main oxidizing agents produced for the degradation of 2,4,6-TCP were •OH^- radicals and •O₂^- anions. Other species such as h⁺ were also produced at lower amount. Hence, our results demonstrated that spherical/floatable photocatalytic composites are a viable option to remove herbicide residuals from the water, which is of interest in water-treatment-plants.

Enhancing the eosin-yellowish dye degradation in drinking water by using TiO2 coatings co-doped with Ni and In

This work reports on the structural, morphological, and photocatalytic properties of titanium dioxide (TiO₂) and TiO₂:NiIn (T-NiIn) coatings fabricated by spin coating. The SEM images revealed coatings with average thicknesses of 3.59 and 3.37 μm for the TiO₂ and T-NiIn, respectively. EDS spectra and Raman studies confirmed the presence of TiO₂ co-doped with nickel (Ni) and indium (In) in the coatings. XRD analysis showed the anatase and rutile phases for the TiO₂ coatings, while the T-NiIn coatings presented the rutile and brookite phases. These samples were evaluated in the photocatalytic degradation of the eosin-yellowish (EY) dye. The T-NiIn coatings showed 9.1% higher effectiveness than the undoped TiO₂ coatings after 300 min under UV irradiation. Meanwhile, the T-NiIn coatings exposed to solar light removed 40% more dye than the TiO₂ coatings. Furthermore, T-NiIn coating was the most stable because its effectiveness was reduced by only 1.4% after 4 cycles of reuse. Additionally, the scavenger tests confirmed that the main oxidizing sites were the •OH^- radicals and the superoxides •O₂^-. Thus, the use of coatings based on TiO₂ co-doped with Ni and In is a feasible strategy to increase the degradation of the EY dye in drinking water.