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Study to determine the effectiveness of the cleaning unit sub-micron particles with a Movable nozzle were conducted in a wide range of gas flow velocity and the flow rate of the fluid. In studies of gas flow rate in the working area changed in the range from 10 m/s to 20 m/s at constant values of the density of irrigation. The dependence of the efficiency capture of sub-micron particles from the gas flow rate obtained in irrigation density 40 m 3/m 2 h, as described in Figure 2.
As you can see from the chart, increase gas flow rate, as can be seen from the theory of dust deposition [1], leads to an increase in the efficiency of dust collecting system. Studies on determination of the efficiency of dust collecting system ofgas flow rate, can be divided into two series. At speeds of10 4 15 m/s cleaning efficiency is growing slowly,
and at a speed of15 m/s and density of30 irrigation m 3/m 2 h reached 60%. Nozzle elements were used, the size of 6 x 6 mm and weighs 0.6 oz. At speeds over 15 m/s, monitored the UPDF this attachment to the upper restrictive Grill.
In the field of speeds 15^20 m/s used cylindrical body size 6 x 6 mm nozzle and weight « 1 g, which gave an opportunity to raise the speed of up to 20 m/s. Increase speed of 15 m/s to 20 m/s has been accompanied by a sharp increase in the efficiency of the capture of fine aerosols and collection efficiency reaches 90% value. While hydraulic resistance amounted to 4.4 kPa. Thus, the results obtained show that precipitation apparatus with a Movable nozzle can be used for the capture of submicron aerosol particles with high efficiency and low energy consumption.
References:
1. Rakhmonov T. Z., Levsh V. I., Vagapov I. H. Centrifugal effect in gas-liquid separators/Scientific -technical «Uzbek Journal of oil and gas», - Tashkent, - 1999. - No 4. - P. 25-28.
2. Boyko S. I., Litvinenko A. V., Adzhiev A. Y., Gritsay M. A., Morozov B. M., Prusachenko S. N. Separation systems for units of oil gas treatment//Gas industry. - Moscow, - 2009. - No 7. - P. 32-36.
3. Ujov V. N., Valdberg A. Y., Myagkov B. I., Reshidov I. K. Purification of industrial gases from dust. - M: «Chemistry», -1981.
4. Symposium on Separation Science and Technology for Energy Applications, Gatlinburg, Tenn., Oct. 18-22, -2009.//Separ. Sci. and Technol. - V. 45, - No 2. - P. 1167-1181.
DOI: http://dx.doi.org/10.20534/AJT-16-11.12-81-85
Yunusov Furkat Umarovich, PhD, National University of Uzbekistan, Tashkent, Uzbekistan, E-mail: [email protected] Kabulov Bahodir Jabborovich, Professor, Tashkent State Technical University, State unitary enterprise "Science end progress", Tashkent, Uzbekistan, Akbarov Khamdam Ikramovich, Professor, National University of Uzbekistan, Uzbekistan, Tashkent, Makhmudov Ravshankhon Yunuskhonovich, Senior researcher, Tashkent State Technical University, State unitary enterprise "Science end progress", Tashkent, Uzbekistan
The study of the structural characteristics of polycaproamide-silica nanocomposite material obtained by the sol-gel method
Abstract: This article provides the structural-morphological studies of the polycaproamide-silica nanocomposite materials, obtained by the sol-gel method based on tetraethoxysilane, polycaproamide and glycerol, by the nitrogen porometry. A significant effect of glycerol on the final structure of the hybrid polycap-roamide-silica nanocomposite materials is shown. The values of the surface fractal dimension were defined on the basis of the results.
Keywords: sol-gel, polycaproamide, silica, nanocomposite material, nitrogen porometry, morphology, fractal dimension.
Introduction. The general approach for the synthesis of hybrid polycaproamide-silica nanocomposite materials is the sol-gel method. The mild conditions of conducting the process of hydrolytic polycondensation of silica precursor, as the one alkoxysilanes are most often used, allow the functional monomers, polymers and even biopolymers enter into the reaction system. Such various components of inorganic and organic nature can be mixed in nanometer scales leading to the formation of hybrid polycaproamide-silica nanocomposite materials [1-2].
The sol-gel technology takes a special place on the synthesis of nanocomposite materials and it allows to solve many problems in the creation of such materials by the help of the molecular design. The sol-gel method offers the several advantages, such as the one-step synthesis and the preparation of multicomponent products. The use of the sol-gel technology in the preparation of nanocomposite materials allows to obtain, for example, sorbents having a functionality not only on the surface but also within the matrix. This fact determines the appearance of additional active sites, responsible for the intermolecular interaction in separations, in the sorbent and gives the sorbent new properties [3-4].
A feature of these materials is that on the one hand they can be used as those which are obtained as monolith or microsphere particles. On the other hand, they can serve as starting material for producing porous silica by burning or extraction of the polymer component, or for obtaining porous carbon sorbent by carbonizing the starting material with further leaching of silica [5-6].
Currently the water (hydrolytic) and the waterless (non-hydrolytic) sol-gel processes are used for the production of silica from the alkoxysilanes (tetraethoxy-or — tetramethoxysilanes). The hydrolytic path, become traditional, is based on the hydrolysis reactions catalyzed by acid or base and the condensation of the products of hydrolysis occurring in organic solvents in the presence of water. In the waterless sol-gel process the formation of Si-O-Si siloxane bonds is due to the condensation reactions between substituted and unsubstituted alk-oxysilanes with the separation of low molecular weight compounds [7-9].
The objects and the methods of the research. We carried out a one-pot sol-gel process in a reaction system, consisting of tetraethoxysilane (TEOS), polycaproamide (PCA) and alcohols (ethanol and glycerol) dissolved in
formic acid, and obtained polycaproamide-silica nanocomposite material.
For that the 5% polycaproamide solution in formic acid was prepared. Further, the calculated amount of ethanol and glycerol, and then tetraethoxysilane were introduced into polycaproamide solution. The solution was subjected to ultrasonic treatment in an ultrasonic bath for 3 minutes for a better homogenization.
Depending on the ratio of the components in the sol-gel reaction, after a time the formation of clear gel was begun. After complete maturation and aging, the gel was dried to the xerogel state. The dried xerogel has been used for the subsequent studies.
The structural analysis was performed by the nitrogen porometry (the specific surface area and pore size analyzer Autosorbl firm «Quantachrome Corp», USA).
Before carrying out the analysis the samples (~ 0,060,07 g) were subjected to degassing at 110OC for 4 hours.
The BET equation was used for processing the obtained data [10]:
P / P 1 . (C -1) P
P
(1)
V (1 - P / P ) VC VC
a V o / m m
where V — value adsorption at a relative pressure P/Po, cm 3/g;
Vm — capacity monolayer cm 3/g; C — constant depending on the temperature. Sp — specific surface calculated according to the formula:
Ssp = V ■ Um ■ N-10-20 (2)
where am — area occupied by a nitrogen molecule, which is equal to 0.162 nm 2,
N — Avogadro's number, equal 6,02x10 23 Results and discussion. The analysis results listed in Table 1 indicate a significant effect of glycerol on the final structure of polycaproamide-silica hybrid nanocomposite materials. The specific surface Sp of the sample prepared without the addition of glycerol is 4.7 m 2/g, while the addition of glycerol at the ratio of 0.80 mol to the amount of TEOS leads to the increase of the specific surface of the samples 15 times, and at a ratio of 1.30-30 times. Accordingly, the values of pore volumes V changes. However, the pore diameter dp of the sample (1) prepared without the addition of glycerol is greater than in the samples obtained with the addition of glycerol.
It attracts attention the numerical values of the constant C. The numerical values of the constant C for the
sorbent obtained without the addition of glycerol is 17,014, which is peculiar to the sorbents with hydrophobic surface.
The constant determined from the BET equation (1) reflects the degree of interaction between the nitrogen molecules with adsorbent surface and depends on the nature of the surface. The lowest values of the constant C correspond to the minimum energy of interaction with the non-polar surface. By increasing the energy of the interaction that occurs between the nitrogen molecule and the polar surface, the value of the constant C increases and the more the polarity, the greater the value of the
constant C. The value of found constant C = 17.01 for a sorbent (Table 1) shows the adsorption on the low-energy surface and indicates the interaction of nitrogen with hydrocarbon chains of PCA.
For the samples obtained in the presence of glycerol, the values of the constant C are greater than 50, which indicate the presence of the polar NH2 groups (Table 1, sample 2 and 3). From this it follows that the processes taking place by the different mechanisms in the synthesis of the sorbents lead to the formation of interfacial surface containing the functional groups of different nature.
Table 1. - The structural characteristics of polycaproamide-silica nanocomposite materials defined by the nitrogen porometry
Sample molar ratio of glycerol, mole/mole Structural characteristics
Sy m2/g V, cm 3/g d , nm p Constant C
Before calcination
1 - 4,7069 0,01475 12,5300 17,014
2 0,80 70,8000 0,1539 8,6943 52,379
3 1,30 146,5700 0,2998 8,1831 56,761
After calcination
1 - 463,25 0,2305 1,99 -
2 0,80 454,45 0,5285 4,65 140,210
3 1,30 562,00 0,7354 5,22 -
This difference is clearly associated with a hydro-philic surface, that is, the presence of polar groups. Thus, it should be noted that after the calcination of the synthesized hybrid polycaproamide-silica nanocomposite materials the silica sorbents are formed both with the high specific surface area and the higher values of the pore volume, whereas from the hybrid material prepared without the addition of glycerol microporous silica with dp=1.99 nm is formed, while from the hybrid materials synthesized with the addition of glycerol mesoporous silicas with the pore diameters of 4.65 and 5.22 are obtained (Table 1).
The consideration the isotherms of adsorption and desorption of nitrogen for considered polycaproamide-silica hybrid nanocomposite sorbents is showed that they can be attributed to the various types of the sorbents. Since the adsorption isotherm of nitrogen of the hybrid material before calcinations, obtained without the addition of glycerol (Fig. 1), is most likely related to the isotherm of the type III [11], which is typical for non-porous and macroporous sorbents. Indeed, as it can be seen from the figure, both adsorption and desorption isotherms of nitrogen of this sorbent are almost adjacent to the axis of the relative pressure of nitrogen P/Pg.
200
150
M
ioo
50
l | I I I I I i^r-1—I—1—I—1—I—1—r
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 P/P0
Figure 1. The adsorption and desorption isotherms of nitrogen on non-calcinated polycaproamide-silica nanocomposite materials
1 - in the absence of glycerol; 2 - at a molar ratio of TEOS: Glycerol 1: 0.80; 3 - at a molar ratio of TEOS: Glycerol 1: 1.30
After calcinations of this sample, the adsorption and desorption isotherms of nitrogen are already related to the isotherm of the type I. In this case, as it can be seen from Figure 2 the Sample 1, there is a horizontal plateau, the beginning ofwhich is coming to an axis of the relative pressure P/Po is almost at right angles. Adsorption and desorption isotherms of nitrogen at polycaproamide-silica nanocomposite materials obtained with the addition of glycerol with different molar ratio, are type IV, which are characterized by the presence of the hysteresis loop (Fig. 1, 2-3). Moreover, these samples after calcination, the nitrogen adsorption isotherm and desorption retain S-shaped (Fig. 2, 2-3).
Based on the results obtained, by nitrogen porosimetry values defined surface fractal dimension D (Table. 2).
In Table 2 data indicates that the values of fractal dimension of polycaproamide-silica nanocomposite materials obtained under the same conditions of sol-gel process and the same molar ratio TEOS reagents PCA and etha-nol, but with different content of glycerin or its absence, are the numerical values of fractal dimension D in the range of 2 <D <3, the relevant surface fractals [12-13].
Table 2. - Surface fractal dimension D for polycaproamide-silica nanocomposite materials
The molar ratio of the starting components The value of D
Before calcination After calcination
TEOS PCA Ethanol Glycerin
1 0.S0 10.б0 - 2.4180 2.95бб
1 0.S0 10.б0 0.80 2.4087 2.б880
1 0.S0 10.б0 1.30 2.4981 2.б199
Thus, the structural characteristics and morphology development of end-surface properties play glycerol ad-
of polycaproamide-silica nanocomposite materials indi- ditive. Moreover, the more added the glycerol, especially
cate complex interactions occurring in the sol-gel pro- branched formed surface of the final product. cess in which a major role, as shown in an article in the
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500 450 400350300 250 200150100 50
0_l—1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—I—1—г
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 P/P0
Figure 2. Adsorption and desorption isotherms of nitrogen on calcinated polycaproamide-
silica nanocomposite materials 1 - in the absence of glycerol; 2 - at a molar ratio of TEOS: Glycerol 1: 0.80; 3 - at a molar ratio of TEOS: Glycerol 1: 1.30
Thermodinamical properties of mechanical mixtures and nanocompositions diacetatcellulose-silica
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DOI: http://dx.doi.org/10.20534/AJT-16-11.12-85-88
Yarkulov Akhror Yuldashevich, teacher department of «Physical chemistry» of the National University of Uzbekistan named of Mirzo Ulugbek
E-mail: yaaxror@ rambler.ru.
Umarov Bakhrom Smanovich, senior teacher of "Department of physical chemistry" of the National University of Uzbekistan named of Mirzo Ulugbek.,
E-mail: [email protected].
Akbarov Khamdam Ikramovich, doctor of sciences, professor, department of "Physical chemistry" of the National University of Uzbekistan named of Mirzo Ulugbek
E-mail: [email protected]
Thermodinamical properties of mechanical mixtures and nanocompositions diacetatcellulose-silica
Abstract: With using of microbalance Mak-Ben sorbtion of water steams by nanocompositions and mechanical mixtures of diacetatcellulose (DAC)-silica has been investigated. On the base of isotherms of sorbtion of water steams values of the middle free energy of mixing and Gibbs energy have been calculated. By theory of polymolecular adsorption (theory of Braynayr-Emmet-Teller) BET "water" surface and parameters of capillary-porous structure of investigated samples were determined. On the base of results of comparison of thermodinamical parameters conclusions were made about particulates of interactions of mechanical mixtures and nanocompositions DAC-silica.
Keywords: nanocomposition, sorbtion, isotherma, Gibbs energy, theory BET, capillary-porous structure, theory of De Bur-Zviker.
Nanocomposites are materials including in their stable chemical bonds. Such materials are used as en-composition particles both organical (molecules or mac- ergetical nanomaterials, at production of sensor, spe-romolecules) and inorganical compounds dispergated to cial types of ceramics, thin-films structures and optical nanodemension level and forming between themselves surfaces and are characterized by properties charply
