Transformation of Al(NO
3
)
3
∙9H
2
O (upon heating in the range of 20–1200 °C) into blends of amorphous and crystalline boehmite (210–525 °C), amorphous alumina and crystalline γ-Al
2
O
3
(850 °C), ...and crystalline α-Al
2
O
3
(1100 °C) was analyzed using X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), infrared (IR) spectroscopy, thermogravimetry, and low-temperature nitrogen adsorption. Boehmite consists of nanoparticles of 6–10 nm in diameter, and part of them has crystalline structure observed in HRTEM images, despite they are XRD amorphous. The nanoglobules are surrounded by amorphous aluminum hydroxide with chains of –AlO(H)–O–AlO(H)– of 1–5 nm in length. Heating of samples at 350–525 °C gives mesoporous aluminum hydroxide with a relatively narrow pore size distribution. An increase in calcination temperature to 850 °C decreases the porosity of alumina composed of amorphous and crystalline (γ-Al
2
O
3
) phases. Calcination at 1100 °C gives α-Al
2
O
3
with strongly decreased porosity of aggregates.
Glucose, lactose, and saccharose were used as precursors to prepare chars at 400 °C then activated at 800 °C or 1000 °C in closed vessels with controlled amounts of oxygen penetrating through ...nanopores in the vessel walls. There are correlations between the porosity, amounts of residual O- and H-containing functionalities, and electroconductivity of amorphous carbons studied. The pore size distributions calculated using the nitrogen adsorption isotherms and TEM images show that all carbons are mainly nanoporous with certain contribution of narrow mesopores (at pore half-width
x
< 5 nm). Oxidizing activation by oxygen penetrating into the closed vessels with chars through nanopores can more strongly change the outer layers of char particles than the inner pores. Therefore, despite relatively great burn-off degree, the textural characteristics are relatively low for activated carbons.
The photocatalytic activity of four titanium dioxide samples (TiO2-P25 Degussa, PC105 Millennium, PC500 Millennium, and Anatase) was studied in the degradation of dyes (Congo Red (CR), Methyl Orange ...(MO), and Direct Red 23 (DR23)) using cost-effective smartphone-based analysis. The obtained kinetic curves are well described by the first-order kinetic model. It was established that the phase composition, the size of the particles, and the specific surface area of the catalyst have a significant effect on the photocatalytic activity of the studied TiO2 samples. It was investigated that the Millennium PC500 sample is the most effective photocatalyst due to a large specific surface area and a small particle size (8 nm). TiO2-P25 Degussa and Anatase also demonstrate a high photocatalytic activity in the degradation of CR and DR23 dyes, which can be explained by the accelerated process of electron transfer between the anatase and rutile phases. For the PC105 sample, a higher CR photodegradation efficiency is observed compared to PC500. It can be concluded that heterogeneous photocatalysis is an effective method for the removal of toxic dyes from wastewater. With the use of smartphone-based analysis, it is possible monitoring the photodegradation kinetics in real-time.
The E. coli inactivation using hydrogen peroxide (H2O2) and cobalt ferrite granulated catalyst was investigated in a fixed-bed flow reactor. CoFe2O4 catalyst was synthesized by the co-precipitation ...method, granulated, and annealed at 1150°C. X-ray diffraction analysis was used to identify the crystal structure of the catalyst. CoFe2O4 catalyst demonstrates good catalytic activity for bacteria inactivation in the presence of H2O2. An increase in the hydrogen peroxide concentration increases the inactivation efficiency. The reactor demonstrates the E. coli inactivation of 99.94% at the H2O2 hydrogen peroxide concentration of 15 mM and initial bacterial concentration of 6·103 CFU/L. The water disinfection using a fixed-bed reactor demonstrates the broad prospects for industrial use.
The paper presents a simple one-step "green" approach to the synthesis of magnetite nanoparticles. The magnetite nanoparticles were synthesized using fruit extract obtained from grape peels and grape ...pulp. The formation of magnetite nanoparticles was confirmed by X-ray diffraction analysis (XRD), infrared spectroscopy (IR), Mössbauer spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The crystallites sizes of magnetite nanoparticles are 7 and 14 nm for Fe3O4-peel and Fe3O4-pulp samples, respectively. Scanning electron microscopy images show that the samples consist of agglomerated nanoparticles. The synthesized magnetite nanoparticles showed good prospects for their use in magnetic hyperthermia. SAR values of 0.488 W/g and 1.330 W/g for Fe3O4-peel and Fe3O4-pulp samples, respectively. The synthesized magnetic nanoparticles show excellent colloidal stability in the aqueous solutions. The maximum hyperthermia temperatures are 42.28 °C and 42.48 °C for Fe3O4-peel and Fe3O4-pulp samples, respectively. Studies of the catalytic activity of magnetite were performed in decomposition of hydrogen peroxide in a batch mode. The degrees of H2O2 decomposition are 67.5% and 65.25% for the Fe3O4-peel and Fe3O4-pulp samples respectively. The high catalytic activity of the synthesized samples makes them promising candidates for the decomposition of hydrogen peroxide in wastewater disinfection.
The results of electrochemical studies of nanoporous carbon as electrode material for electrochemical capacitors (EC) are presented in this work. Nanoporous carbon material (NCM) was obtained from ...the raw materials of plant origin by carbonization and subsequent activation in potassium hydroxide. It is established that there is an optimal ratio of 1:1 between content of KOH and carbon material at chemical activation, while the maximum specific capacity of NCM is 180 F/g. An equivalent electrical circuit, which allows modeling of the impedance spectra in the frequency range of 10
−2
to 10
5
Hz, is proposed, and a physical interpretation of each element of the electrical circuit is presented.
The influence of magnetic induction heating on the catalytic activity of cobalt ferrite has been investigated. The cobalt ferrite has been obtained by flow co-precipitation method using metal salts ...as precursors and sodium hydroxide as precipitant. The catalytic activity of CoFe
2
O
4
has been studied in the H
2
O
2
decomposition. The influence of the catalyst dosage and its annealing temperature on the H
2
O
2
decomposition has been studied. The impact of induction heating on cobalt ferrite activation has been elucidated. It is shown that the CoFe
2
O
4
catalyst, annealed at 400 °C, exhibited the highest catalytic activity under induction heating in the H
2
O
2
decomposition for 20 mM H
2
O
2
solution. Induction heating is proposed as a promising approach for use in water purification technology.
The article investigates the effect of thermal modification of porous carbon material (PCM), obtained from plant feedstock, on its morphology and fractal structure by small-angle X-ray scattering ...(SAXS) method. The analysis of the scattering intensity curves serve the basis for calculating the parameters of the PCM porous structure: the Porod constant, the Porod invariant, average pore radius, specific surface area, and mass and surface fractal dimensions. It has been found out that the PCMs obtained have fractal structure, formed from mass and surface fractals, the sizes of which increase at the growth of temperature and modification time.
PACS
81.05.Uw; 61.05.cf; 82.47.Aa
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