Enhanced Fe-TiO2 Solar Photocatalysts on Porous Platforms for Water Purification

Abstract

In this study, polyethylene glycol-modified titanium dioxide (PEG-modified TiO2) nanopowders were prepared using a fast solvothermal method under microwave irradiation, and without any further calcination processes. These nanopowders were further impregnated on porous polymeric platforms by drop-casting. The effect of adding iron with different molar ratios (1, 2, and 5%) of iron precursor was investigated. The characterization of the produced materials was carried out by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Optical characterization of all the materials was also carried out. SEM showed that pure TiO2 and Fe-TiO2 nanostructures presented similar nanosized and spherical particles, which uniformly covered the substrates. From XRD, pure TiO2 anatase was obtained for all nanopowders produced, which was further confirmed by Raman spectroscopy on the impregnated substrates. XPS and UV–VIS absorption spectroscopy emission spectra revealed that the presence of Fe ions on the Fe-TiO2 nanostructures led to the introduction of new intermediate energy levels, as well as defects that contributed to an enhancement in the photocatalytic performance. The photocatalytic results under solar radiation demonstrated increased photocatalytic activity in the presence of the 5% Fe-TiO2 nanostructures (Rhodamine B degradation of 85% after 3.5 h, compared to 74% with pure TiO2 for the same exposure time). The photodegradation rate of RhB dye with the Fe-TiO2 substrate was 1.5-times faster than pure TiO2. Reusability tests were also performed. The approach developed in this work originated novel functionalized photocatalytic platforms, which were revealed to be promising for the removal of organic dyes from wastewater.

Floating TiO2-Cork Nano-Photocatalysts for Water Purification Using Sunlight

“…The TiO 2 nanopowder synthesized without cork substrates was also observed by SEM (Figure S2), revealing that, as observed for the TiO 2 nanopowder synthesized with cork substrates, the microwave synthesis resulted in very fine nanoparticles, in agreement with an analogous study [23].…”

“…Observed through the [111 ] zone axis, the angle inferred between both ( 101) and ( 011) is 82° in accordance with the theoretical value reported for pure TiO2 anatase (JCPDS 21-1272). The TiO2 nanopowder synthesized without cork substrates was also observed by SEM (Figure S2), revealing that, as observed for the TiO2 nanopowder synthesized with cork substrates, the microwave synthesis resulted in very fine nanoparticles, in agreement with an analogous study [23].…”

“…where A 0 is the initial absorbance of the RhB solution before irradiation and A t is the absorbance of RhB solution after a certain exposure time (t) [23,97]. Blank experiments (only RhB solution) were also carried out under solar simulating light and natural sunlight (Figures 9c and 10c).…”

“…It was also observed by TEM and SEM that these particles formed agglomerates. Such agglomerates influence the specific surface area of the nanoparticles and, consequently, their photocatalytic activity [23,110,111]. Several approaches and synthesis parameters can be used to minimize their formation including pH of the solution, addition of surfactants, among others.…”

“…Different materials and, more frequently, metal oxide semiconductors have been studied for the development of efficient photocatalysts, including WO 3 [13], Fe 2 O 3 [14], ZrO 2 [15], SrTiO 3 [16], ZnO [17,18] and TiO 2 [19][20][21][22][23][24]. Among these semiconductors, TiO 2 has been extensively studied for photocatalysis since it is the most promising material for industrial use [25], due to its physical and chemical stabilities, low-cost, non-toxicity and strong oxidation potential to decompose organic pollutants [20,[26][27][28][29].…”