Binding of the Cationic Dye, Janus Green B, as a Measure of the Specific Surface Area of Crystalline Silica in Aqueous Suspension

Silica gel supported titanium dioxide photocatalysts were prepared by sintering TiO2/SiO2 mixtures under variations of TiO2 content, calcination temperature and calcination time. The method allowed to obtain catalyst samples, which can be used in aqueous suspension and which were found to be easily separated by decantation after the photocatalytic treatment. The photocatalytic efficiency of the catalysts was tested by carrying out the photooxidation of the textile dye Acid Red 88 (AR88) in aqueous solution, used as “model” water pollutant. The obtained photoefficiency results were correlated to catalyst physicochemical characteristics, as determined by Inductively Coupled Plasma (ICP) analysis, X-ray diffraction, specific surface area (BET) and scanning electron microscopy (SEM). No positive correlation has been observed between titanium dioxide content and photocatalytic efficiency. The decrease of photocatalytic activity at high calcination temperature (1000 °C) is attributed to the phase transition anatase/rutile as well as to the decreasing specific surface area. According to SEM analysis, no significant fixation of TiO2 on silica is observed for catalysts prepared at low temperature (400 °C). The observed photocatalytic activity is consequently due to free TiO2 particles. The best efficiency is observed for photocatalyst prepared at 800 °C and containing around fifty percent titanium dioxide.

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EFFECT OF PHYSICOCHEMICAL PROPERTIES OF d-METAL OXIDES ON SUNFLOWER OIL TRANSESTERIFICATION

Bulletin of the National Technical University «KhPI» Series New solutions in modern technologies ◽

10.20998/2413-4295.2021.02.16 ◽

2021 ◽

pp. 113-120

Author(s):

Yurii Melnyk ◽

Stepan Melnyk ◽

Halyna Mahorivska ◽

Viktor Reutskyy

Keyword(s):

Specific Surface ◽

Metal Oxides ◽

Surface Area ◽

Specific Surface Area ◽

Sunflower Oil ◽

Aqueous Suspension ◽

Surface Acidity ◽

Weak Acid ◽

Transesterification Reaction ◽

Acidity And Basicity

The physicochemical indicators of d-metal oxides (NiO, CuO, MnO, FeO, PbO, ZnO) which are heterogeneous catalysts for the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol have been determined. The available specific surface area, surface acidity and basicity, as well as the hydrogen potential change of the catalyst suspension in water were determined for the oxides. The available specific surface area of the oxides was determined by titration of their aqueous suspension with a solution of methylene blue with a predetermined concentration. The surface acidity and basicity of the catalysts were determined by back titration of samples treated with an aqueous solution of ammonia and acetic acid, respectively. It was found that all investigated d-metal oxides have a low specific surface area. The value of specific surface area is in the range of 0.6-1.5 m2/g. The surface acidity and basicity of the catalysts is 0.13-0.27 mmol/g and 0.019-0.066 mmol/g, respectively. It is shown that the change in the aqueous suspension hydrogen potential of the investigated catalysts relative to the distilled water pH is maximum for NiO and ZnO and it is 0.6-0.65, while for CuO this change is the smallest and it is only 0.3. The character of the pH change curves and the pH values of the oxides suspension in equilibrium condition indicate the presence of weak acid sites in the studied catalysts. The indicated catalysts characteristics are compared with the results obtained in the transesterification process of sunflower oil triglycerides by ethanol and butan-1-ol. It was found that there is a correlation between the surface acidity of catalyst and the reaction initial rate of triglycerides transesterification by ethanol and butan-1-ol. At the same time, such a correlation is absent for the surface basicity of the catalysts. This is consistent with the data on the catalysis of the triglyceride transesterification reaction only by strong major active sites. It is concluded that the transesterification reaction of sunflower oil triglycerides by ethanol and butan-1-ol occurs predominantly on the weak acid centers of the d-metal oxides.

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The Simplest Way to Iodine-Doped Anatase for Photocatalysts Activated by Visible Light

International Journal of Photoenergy ◽

10.1155/2011/685935 ◽

2011 ◽

Vol 2011 ◽

pp. 1-13 ◽

Cited By ~ 18

Author(s):

Václav Štengl ◽

Tomáš Matys Grygar

Keyword(s):

Photocatalytic Activity ◽

Visible Light ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Aqueous Suspension ◽

Organometallic Compounds ◽

Orange Ii ◽

Iodine Doping ◽

Doped Titania

Iodine-doped TiO2was prepared by thermal hydrolysis of aqueous solutions of the titanium peroxo-complex, which includes no organic solvents or organometallic compounds. The synthesized samples were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), infrared spectroscopy (IR), specific surface area (BET), and porosity determination (BJH). The morphology and particle size was determined by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). All prepared samples have a red-shifted band-gap transition, well crystalline anatase structure, and porous particles with a 100–200 m2 g−1specific surface area. The photocatalytic activity of iodine-doped titania samples was determined by decomposition of Orange II dye during irradiation at 365 nm and 400 nm. Iodine doping promotes the titania photocatalytic activity very efficiently under visible light irradiation. The titania sample with 0.32 wt.% I has the highest catalytic activity during the photocatalyzed degradation of Orange II dye in an aqueous suspension in the UV and visible regions.

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Hydrothermal and mechanochemical synthesis of crystalline CaCO3

Adsorption Science & Technology ◽

10.1177/0263617417704298 ◽

2017 ◽

Vol 35 (7-8) ◽

pp. 668-676 ◽

Cited By ~ 3

Author(s):

J Skubiszewska-Zięba ◽

B Charmas ◽

H Waniak-Nowicka

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Aqueous Suspension ◽

Microwave Treatment ◽

Porous Structures ◽

X Ray Diffraction ◽

X Ray ◽

Saturated Water ◽

Crystallite Sizes

Mechanochemical and microwave-assisted hydrothermal (MicroWave Treatment [MWT]) procedures were applied to prepare crystalline CaCO3. Mechanochemical process was carried out at different speeds of rotation (500 or 850 rpm/min), different duration times (30 or 60 min) and in the aqueous suspensions or in dry state. MWT synthesis was conducted in a saturated water vapour or under the layer of water. The crystalline and porous structures of the prepared samples as well as their morphology were investigated using N2 adsorption, X-ray diffraction and scanning electron microscopy methods. As a result, the calcium carbonate samples in the form of calcite were obtained. The materials prepared by the mechanochemical route performed in the aqueous suspension are characterized by smaller crystallite sizes as compared to those obtained without the addition of water. The samples obtained hydrothermally have the largest size of crystallites. Powders prepared by energetical milling possess higher values of specific surface area in relation to the parameter for those synthesized hydrothermally. In the process of hydrothermal treatment, macroporous structure of the prepared materials is created. With the increasing specific surface area of the sample, the size of the crystallites decreased.

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