Application of reverse micelle sol-gel synthesis for bulk doping and heteroatoms Surface Enrichment in Mo-Doped TiO 2 nanoparticles

TiO 2 nanoparticles containing 0.0, 1.0, 5.0, and 10.0 wt.% Mo were prepared by a reverse micelle template assisted sol-gel method allowing the dispersion of Mo atoms in the TiO 2 matrix. Their textural and surface properties were characterized by means of X-ray powder diffraction, micro-Raman spectroscopy, N 2 adsorption/desorption isotherms at -196 °C, energy dispersive X-ray analysis coupled to field emission scanning electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis spectroscopy, and ζ-potential measurement. The photocatalytic degradation of Rhodamine B (under visible light and low irradiance) in water was used as a test reaction as well. The ensemble of the obtained experimental results was analyzed in order to discover the actual state of Mo in the final materials, showing the occurrence of both bulk doping and Mo surface species, with progressive segregation of MoO x species occurring only at a higher Mo content

Bi2O3/Nylon multilayered nanocomposite membrane for the photocatalytic inactivation of waterborne pathogens and degradation of mixed organic pollutants

Worldwide there is an increasing demand for clean water and sanitation systems and any different solutions are under evaluation, including advanced oxidation processes such as photocatalysis. This work describes the scalable synthesis process of an electrospun composite membrane made of Nylon and embedded α/β-Bi2O3 nanoparticles that can be activated by visible light instead of UV light typically used with other nanomaterials (e.g. TiO2). As a proof of concept, the efficacy of the α/β-Bi2O3 electrospun composite membrane in the visible light inactivation of pollutants and pathogens was demonstrated in a Continuous-flow Photocatalytic Membrane Reactor, highlighting the great potential of this advanced photocatalytic process for clean water and sanitation

Photocatalytic Denitrification of Nitrate Using Fe-TiO2-Coated Clay Filters

In this work, 3D-structured clay filters were prepared and coated with iron-doped tita- nium dioxide (Fe-TiO2) using 3D printing and sol–gel soaking and calcination techniques. Three- dimensional printing was employed to mold and shape the clay filters before annealing. The coated and uncoated filters were characterized for different properties, i.e., morphology, optical properties, and crystalline structure, using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), UV/Vis diffused reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The FESEM images show uniform coatings of round-shaped Fe-TiO2 on the tiny pore of the clay filter. The optical energy band gap of the obtained coating was around 2.8 eV, estimated by Tauc’s plot, compared with 3.2 eV of pristine anatase TiO2. The XRD spectra data processed through XRD software revealed the coatings of TiO2 on the filter surface with the obtained phase of anatase. The photocatalytic performance of bare and coated filters was initially tested for the degradation of indigo carmine (IC) dye and the obtained results suggested the photocatalytic degradation of IC dye by the Fe-TiO2 clay filter compared with the bare filter. Afterward, the deni- trification of nitrate NO3 at various concentrations was performed using Fe-TiO2-coated clay filters and analyzing the total nitrogen (TN) analysis and reduction of NO3 to nitrite (NO2−), nitrogen monoxide (NO), and nitrogen gas (N2). The TN analysis revealed up to 81% denitrification efficiency of the 30 ppm NO3 solution with the photocatalytic response of the Fe-TiO2-coated filter. The results revealed that the Fe-TiO2-coated clay filter has a high potential for denitrification applications under natural sunlight

Single BiFeO3 and mixed BiFeO3/Fe2O3/Bi2Fe4O9 ferromagnetic photocatalysts for solar light driven water oxidation and dye pollutants degradation

A simple synthesis route is presented to obtain single BiFeO3 and mixed BiFeO3/Fe2O3/Bi2Fe4O9 photocatalysts. The obtained samples were characterized to analyze their structural, magnetic, optical and physical– chemical properties. The role of additional phases, i.e. Bi2Fe4O9 and Fe2O3 in the BiFeO3 structure, was analyzed by investigating sunlight-driven water oxidation and degradation of different dye pollutants. The achieved results suggest formation of BiFeO3/Fe2O3/Bi2Fe4O9 heterojunction-like interfaces, that induce lower e−/h+ recombination rate, thus enhancing photoactivity than bare BiFeO3. Additionally, BiFeO3/Fe2O3/Bi2Fe4O9 has exclusive feature of being magnetically separated from treated media and its stability was demonstrated for at least 3 cycles of dye degradation

Insight on the Properties of Pumice Mineral for the Combined Adsorption Distillation of Membrane Reject Water

The current study evaluated the use of pumice, a volcanic mineral and common sand, in treating reverse osmosis membrane reject water (ROR) using a novel combined adsorption distillation (CAD) method. The CAD method is developed to separate the dissolved solids through adsorption distillation, i.e., leaving the vaporized distillate as freshwater and concentrated brine. The adsorption potential of pumice and sand was investigated at different adsorbent doses, i.e., 2, 5, and 10 g, and consecutive CAD adsorbent backwashing cycles. The improved results were achieved at a 10 g pumice dose. However, its adsorption efficiency declined in longer CAD cycles, i.e., due to the separated deposition of solids. After backwashing, the adsorbed and accumulated salts were slightly removed, and pumice adsorption capacity was maintained for up to 20 cycles of CAD. The properties of the pumice, i.e., before and after five CAD cycles and after backwashing, were characterized with scanning electron microscopic (SEM), elemental disruptive spectroscopy (EDS), and X-ray diffraction (XRD), which revealed that the porous structure of the pumice was completely accumulated with deposits of ionic salts, which were slightly washed away after backwashing, but accumulation remained continued in post-CAD cycles. The explored method revealed a high potential of pumice in water filtration

Insights on the role of β-Bi2O3/Bi5O7NO3 heterostructures synthesized by a scalable solid-state method for the sunlight-driven photocatalytic degradation of dyes

A simple, solvent-free and scalable route for the synthesis of nanostructured Bi5O7NO3 and Bi2O3 polymorphs photocatalysts and their heterostructures is here presented. Morphology, porosity and crystal phases were tuned by controlling the thermal decomposition of Bi(NO3)3:5H2O, by using different calcination temperatures and cooling processes. Bi5O7NO3 layered nanosheets, highly porous β-Bi2O3/Bi5O7NO3 heterostructured nanoflakes and micrometric sheets of α-Bi2O3 were obtained at temperatures of 400 °C, 425–450 °C and 525 °C with a slow cooling rate, respectively. Moreover, in contrast to previous reports on Bi5O7NO3, the role on the visible-light driven photocatalytic activity of Bi5O7NO3 due to the formation of a stable heterojunction with β-Bi2O3, which here was identified to be also formed by a rapid cooling after calcination at 400 °C, was deeply investigated and demonstrated. All the samples were fully characterized by X-ray Diffraction, Field-emission scanning electron microscopy, UV–vis spectroscopy, N2 adsorption and X-ray Photoelectron Spectrometry analyses. The role of oxygen vacancies, which indicate structural defects and/or sub-stoichiometric forms of Bi5O7NO3 or Bi2O3 in the photocatalysts surface, was also analyzed and correlated to their photo-response. Simulated sunlight-driven degradation of organic dyes with different functionalities, i.e. a cationic dye (Rhodamine B) and an anionic one (Indigo Carmine), was investigated and proved to be optimized due to an efficient synergy between suitable amounts of Bi5O7NO3 and β-Bi2O3 in the heterostructured samples. An improved charge carriers separation at the heterojunction interphase and an enhanced formation of reactive oxygen species in these materials were additionally confirmed by both photocatalytic water oxidation experiments with O2 evolution and mineralization of a refractory anionic dye, i.e. Remazol Brilliant Blue R. The latter was reached with an optimum photocatalyst/ dye weight ratio of 33, which is about 2–3 times lower than previous literature results