scholarly journals Nanostructured mesoporous g-Fe2O3: a novel photocatalyst for degradation of organic pollutants

2021 ◽  
Vol 22 (1) ◽  
pp. 101-109
Author(s):  
A.B. Hrubiak ◽  
O.Yu. Khyzhun ◽  
B.K. Ostafiychuk ◽  
V.V. Moklyak ◽  
Yu.V. Yavorskyi ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Mesoporous Structure ◽  
Molar Concentration ◽  
Average Particle ◽  
Pore Size Distributions ◽  
Sol Gel Synthesis

The  modified sol-gel synthesis technique was used to created of nanostructured maghemite (γ-Fe2O3). It has been shown that the molar concentration of the original precursors during synthesis affects on the average particle sizes, specific surface area, pore size distributions, optical and conductivity properties. The XPS metod allowed to establish features of electronic structure of the synthesized materials. Optimal conditions for the synthesis of nanostructured maghemite with mesoporous structure were selected. The mechanism of electrical conductivity formation for synthesized mesoporous materials was established. The width of the band gap is determined and its dependence on the molar concentration of precursors is established. The positive correlation between the specific surface area of γ-Fe2O3 samples and photocatalytic activity was installed - the photocatalytic activity of synthesized γ-Fe2O3 increase with growth of specific surface area of γ-Fe2O3 samples.

Sol-gel Synthesis of a Novel χSm2Ti2O7/HZSM-5 Composite Photocatalyst for the Promoted Activity on RBR X-3B Degradation

2017 ◽  
Vol 14 (1) ◽  
pp. 17-25
Author(s):  
Wenjie Zhang ◽  
Jiao Yang ◽  
Ling Du
Keyword(s):  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Bandgap Energy ◽  
Powder Materials ◽  
Sol Gel Synthesis ◽  
Adsorption Desorption

Background: Pyrochloro structured Sm2Ti2O7 has photocatalytic activity on degradation of organic substances and on hydrogen evolution from water. Powder materials usually encounter the obstacle of separating from treated water. HZSM-5 zeolite is a kind of porous structured material with large surface area. Its role as a support for Sm2Ti2O7 is interesting. Methods: The supported Sm2Ti2O7 was synthesized using sol-gel method. The composite χSm2Ti2O7/HZSM-5 was characterized by XRD, SEM, TEM, FT-IR/FIR, UV-Vis DRS, N2 adsorption- desorption and XPS measurements. Photocatalytic degradation of Reactive Brilliant Red X-3B (RBR X-3B) was measured to evaluate the activity of the composite. Results: Sm2Ti2O7 is in the pyrochlore phase after loading on the surface of HZSM-5 zeolite. The crystal cell of pyrochlore Sm2Ti2O7 continuously expanses with decreasing Sm2Ti2O7 loading content in the composite. Bandgap energy of Sm2Ti2O7 is enlarged after supporting. The specific surface area of Sm2Ti2O7 was enlarged from 9.8 m2/g to 93 m2/g after loading. Both of the adsorption capacity and photocatalytic activity of the χSm2Ti2O7/HZSM-5 are greater than those of pure Sm2Ti2O7. After 120 min of irradiation, 73.1% of the initial RBR X-3B molecules are decomposed on 70%Sm2Ti2O7/HZSM-5, and only 27.7% of the dye is decomposed on the bare Sm2Ti2O7. Conclusion: Sm2Ti2O7 crystal growth is constrained after loading due to dispersion of Sm2Ti2O7 on the surface of HZSM-5. The specific surface area of Sm2Ti2O7 is significantly enlarged after loading. All the supported samples have greatly enhanced photocatalytic activity as compared to the bare Sm2Ti2O7.

TiO2 composite films on different substrates with enhanced visible light photocatalytic performance

2020 ◽  
Vol 13 (07) ◽  
pp. 2051037
Author(s):  
Ke Han ◽  
Guobao Li ◽  
Fang Li ◽  
Mingming Yao
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Photocatalytic Performance ◽  
Sol Gel ◽  
Composite Films ◽  
Methyl Green ◽  
Photogenerated Electrons

For the sake of improving the photocatalytic performance of TiO2, we prepared the B/Ag/Fe tridoped TiO2 films on common glass and stone substrates by the sol–gel method. In this work, the optical absorption, recombination of photogenerated electrons (e−) and holes (h[Formula: see text]), crystal types, thermal stability, composition, specific surface area and photocatalytic activity of the modified TiO2 films were investigated. The results indicated that B/Ag/Fe tridoping not only enhanced the absorption of visible light by TiO2, but inhibited the recombination of electron–hole (e−/h[Formula: see text]) pairs. The tridoping also promoted the formation of anatase and prevented the transformation of anatase to rutile at high temperature. The composite TiO2 has a large specific surface area, about three times that of pure TiO2. The photocatalytic activity of the TiO2 films were evaluated by methyl green (MG) and formaldehyde degradation. In all samples, the B/Ag/Fe tridoped TiO2 film exhibited the highest degradation rate of MG under both ultraviolet and visible light irradiation. The improvement of photocatalytic performance of TiO2 films is due to the synergistic effect of the B/Ag/Fe tridoping, which enhances the absorption of visible light and prolongs the lifetime of e−/h[Formula: see text] pairs and facilitates transfer of interface charge.

Synthesis and Structural Characterization of SiO2-Al2O3 Xerogels

2007 ◽  
Vol 336-338 ◽  
pp. 2286-2289
Author(s):  
Fei He ◽  
Xiao Dong He ◽  
Yao Li
Keyword(s):  
Structural Change ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Supercritical Drying ◽  
High Specific Surface Area ◽  
Molar Ratio

Low-density xSiO2-(1-x)Al2O3 xerogels with x=0.9, 0.8, 0.7, 0.6 (mole fractions) were prepared by sol-gel and non-supercritical drying. Silica alkogels, which were the framework of binary composite materials, formed from tetraethyl orthosilicate (TEOS) by hydrolytic condensation with a molar ratio of TEOS: H2O: alcohol: hydrochloric acid: ammonia =1: 4: 10: 7.5×10-4: 0.0375. Aluminum hydroxide derived from Al(NO3)3·9H2O and NH4OH acting in the alcohol solution under the condition of catalyst. After filtrating and washing, the precipitation was mixed into silica sols to form SiO2-Al2O3 mixed oxide gels with different silicon and aluminum molar ratio. The structural change and crystallization of the binary xerogels were investigated after heat treatment at 600 for 2 h by the means of X-ray diffraction. Nitrogen adsorption experiment was performed to estimate specific surface area, porous volume and pore size distribution. The structural change of xerogels was observed by FT-IR spectroscopy. The resulting mixed xerogels possess of mesoporous structure which is characteristic of cylindrical pores, high specific surface area of 596-863 m2/g and a relatively narrow pore distribution of 2.8-30 nm. Al2O3 is introduced into the SiO2 phase and some of Al-O-Si bonds form.

scholarly journals Towards Macroporous α-Al2O3—Routes, Possibilities and Limitations

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1787
Author(s):  
Simon Carstens ◽  
Ralf Meyer ◽  
Dirk Enke
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Surface Areas ◽  
Alumina Membranes ◽  
Sol Gel Process ◽  
Specific Surface Areas ◽  
Α Al2o3 ◽  
Sol Gel Synthesis

This article combines a systematic literature review on the fabrication of macroporous α-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that γ-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for α-Al2O3 amounts to 16–24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

scholarly journals Structural, photocatalytic and surface analysis of Nb/Ag codoped TiO2 mesoporous nanoparticles

2020 ◽  
Vol 96 (3) ◽  
pp. 728-741
Author(s):  
Mahtab Gorgani ◽  
Behzad Koozegar Kaleji
Keyword(s):  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Band Gap Energy ◽  
Xenon Lamp ◽  
X Ray ◽  
Mesoporous Nanoparticles

Abstract In this study, several TiO2 mesoporous nanoparticles with different mol% of niobium and silver were synthesized using the sol–gel method. The crystalline phase, chemical state, photocatalytic and optical properties, specific surface area, and morphology of mesoporous nanoparticles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis reflective spectroscopy (UV–Vis), Brunauer–Emmett–Teller-specific surface area (BET) and field emission scanning electron microscopy (FESEM). With increasing calcination temperature, the photocatalytic activity of the samples gradually increased due to the improvement of crystallization of the anatase and rutile phases. Nb/Ag codoping sample calcined at 550 °C has reduced the band gap energy (3.17 eV to 3.06 eV) and improved the photocatalytic properties of samples under visible light (xenon lamp, 200 W for 1 h and 2 h). Doped TiO2 mesoporous nanoparticles were shown to have the highest photocatalytic activity as compared with the pure TiO2 nanoparticles. The best photocatalytic efficiency of codoped TiO2 mesoporous nanoparticles was observed for the TNA3 sample calcined under 550 °C, containing molar contents of Nb (0.5 mol%) and Ag (1 mol%) dopant ions with 95.60% efficiency.

scholarly journals Sol-Gel Synthesis of Nonstoichiometric Titanium Dioxide for Photo-Oxidation of Toxic Organic Substances

2020 ◽  
Author(s):  
I. B. Dorosheva ◽  
A. A. Rempel ◽  
A. A. Valeeva ◽  
I. A. Weinstein
Keyword(s):  
Titanium Dioxide ◽  
Specific Surface ◽  
Band Gap ◽  
Surface Area ◽  
Specific Surface Area ◽  
Anatase Phase ◽  
Sol Gel ◽  
Bet Method ◽  
Sol Gel Synthesis ◽  
Toxic Organic Substances

Titanium dioxide (TiO2) was synthesized by sol-gel method at different values of pH = 3, 7, 8, 9, or 10. X-ray phase analysis has shown that in an acid rout, an anatase phase had crystallized, and in an alkaline rout an amorphous phase of TiO2 was achieved. After annealing for 4 hours at 350∘C, all samples were transformed into anatase phase. The particle size in the different samples varies from 7 to 50 nm depending on the pH. The diffuse reflectance spectra revealed a high value of the band gap width in the range from 2.9 to 3.4 eV and its narrowing after annealing to the range from 2.8to 3.1 eV. The specific surface area measured by BET method was changing from 80 up to 140 m2 /g. Keywords: Titanium dioxide, nanostructure, photocatalysis, band gap, specific surface area

Novel 0D-nanocarbon-silica ceramic composites: sol–gel synthesis and high-temperature evolution

2020 ◽  
Vol 49 (21) ◽  
pp. 7144-7154 ◽  
Author(s):  
Alexander Ott ◽  
Simone Rogg ◽  
Stefan Lauterbach ◽  
Hans-Joachim Kleebe ◽  
Christian Hess ◽  
...  
Keyword(s):  
High Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Ceramic Composites ◽  
High Specific Surface Area ◽  
Gel Method ◽  
Sol Gel Synthesis ◽  
Silica Ceramic

Novel mesoporous, high specific surface area (up to 562 m2 g−1) 0D-nanocarbon-based silicon-containing ceramic composites were produced by a straightforward sol–gel method followed by polymer-to-ceramic transformation.

scholarly journals Cost-effective sol-gel synthesis of porous CuO nanoparticle aggregates with tunable specific surface area

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lars Dörner ◽  
Claudia Cancellieri ◽  
Bastian Rheingans ◽  
Marc Walter ◽  
Ralf Kägi ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Cost Effective ◽  
Nanoparticle Aggregates ◽  
Sol Gel Synthesis ◽  
Cuo Nanoparticle

The Degradation and BMP Release Dynamics of Silica-Based Xerogels Modified by Adding Calcium and Magnesium or Sintering Process

2012 ◽  
Vol 151 ◽  
pp. 378-382 ◽  
Author(s):  
Xiao Sheng Li ◽  
Wei Lin ◽  
Feng Lan Xing
Keyword(s):  
Electron Microscope ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Diameter ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Mesoporous Structure ◽  
Silica Xerogel ◽  
Calcium And Magnesium

A new mesoporous silica xerogel used as biodegradable material was synthesized by improved sol-gel methods. The xerogel’s degradation character and property of releasing character for bone morphological protein (BMP)were modified by adding calcium (Ca) and phosphor (P) elements into pure silica xerogel, and uesing sintering processes, as well as adding magnesium (Mg) into silica xerogel. The differential thermal and thermogravimetric analysis (DTA-TG), X-Ray diffraction analysis(XRD), Fourier infrared spectrum analysis (FITR), N2 adsorption-desorption analysis, Scanning electron microscope(SEM) and Transmitting electron microscope (TEM) observation were used to measure the thermal effects, crystalline state, pore diameter and specific surface area, surface morphology and inner structure of the xerogels. The xerogel’s degradability and BMP release were studied by simulated body fluid (SBF) immersion. The results indicated that the synthesized xerogels were mesoporous structure with pore diameter around 3 nm and the big specific surface area about 1000 m2/g.They were non crystall with hydroxyl and micro-molecular silica-oxygen groups. Xerogels dried at low sintering temperature degraded completely in 42 days in bursting manner and degraded in linear curves with sintering temperature increased as well as adding calcium and magnesium into xerogels. The BMP release behaviour from the Mg-xerogel dried naturally was in controlled manner.

Synthesis of Three-Dimensionally Ordered Macroporous Co/SiO2 Catalysts by Sol-Gel Method

2013 ◽  
Vol 634-638 ◽  
pp. 620-623 ◽  
Author(s):  
Jittima Junsawat ◽  
Nichakan Phumthiean ◽  
Payoon Senthongkaew ◽  
Supakit Achiwawanich
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ordered Macroporous ◽  
Sol Gel Synthesis

A preparation of novel cobalt-based catalyst on three-dimensionally ordered macroporous (3DOM) silica supporter using poly (methyl methacrylate) monolith as a template has been studied. Monodispersed PMMA colloids were synthesized via an emulsion polymerization, resulting in PMMA spheres with the diameter of 390-400 nm. Two processes were employed for the 3DOM Co/SiO2catalyst fabrications, a single-stage sol-gel synthesis (SG) and incipient wetness impregnation method (IM) on synthesized 3DOM SiO2. Both catalysts were characterized using X-ray Diffraction (XRD), X-ray Absorption Spectroscopy (XAS), Scanning Electron Microscope (SEM) and specific surface area analysis. The XRD and XAS results showed that the doped Co in the 3DOM Co/SiO2(SG) were the mix phase of Co(NO3)2and Co3O4, while, only Co3O4was found in the 3DOM Co/SiO2(IM). The SEM micrographs revealed that both catalysts feature periodic macroporous structure with mean pore diameter of 300-350 nm. Specific surface area of the 3DOM Co/SiO2(IM) and the 3DOM Co/SiO2(SG) catalysts are 195 m2/g and 286 m2/g, respectively.

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