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CHEMICAL PROBLEMS 2025 no. 1 (23) ISSN 2221-8688
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PREPARATION OF VERMICULITE AND POLYPOLYACRYLONITRILE COMPOSITE AND ITS MODIFICATION WITH DIETHANOLAMINE
S.A. Kholmurodova1*, Kh.Kh. Turaev1, R. Alikulov1, A.Kh. Tashkulov1, B.A. Xolnazarov1,
S.G. Yuldashova2, Kh.E. Eshmurodov3
1Faculty of Chemistry, Termiz State University, Termiz, Uzbekistan 2Tashkent Research Institute of Chemical Technology, Tashkent, Uzbekistan 3Department of Medical and Biological Chemistry, Termez branch of Tashkent Medical Academy, Termez,
Uzbekistan
*e-mail: [email protected]. (0RCID.0000-0003-0002-7054).
Received 10.06.2024 Accepted 11.08.2024
Abstract: This article studied the characteristics of vermiculite sourced from the Tebinbulok mine situated within the borders of the Republic of Uzbekistan, as well as the most ^ favorable conditions ^ for its activation through heating and treatment. A 7% solution of hydrochloric acid was used for activation. Activated vermiculite was modified using maleic anhydride and polyacrylonitrile dissolved in acetic acid solution. The properties of the resulting composite were studied. To further increase its sorbent properties, diethanolamine with an amine functional group was added to the composite. A laboratory study of the obtained organic-inorganic composite is presented. The research was carried out in the state connected to the reflux cooler, at a temperature of 60-70°C, with constant stirring. The properties, microstructure, porosity, thermal tolerance, and composition of the samples were analyzed using traditional and empirical methods of physical and chemical analysis, respectively, and IRTracer-100 SHIMADZU (Japan), infrared IR-Fourier, MIRA 2 LMU scanning electron microscope (SEM), elemental analysis, thermogravimetric (TGA and DTA) analysis, and X-ray phase analysis were studied. The results showed that after activation, vermiculite, which is almost chemically stable, was bound to polyacrylonitrile through the OH bonds formed in it, and maleic anhydride acted as a modifier in the binding, polyacrylonitrile vermiculite polymerized in solution It was proved by analysis that it formed one composite with OH- bonds^ formed on its surface. To^ further increase the sorption capacity of this composite with maleic anhydride as a binder, diethanolamine containing an amine functional group was added to it.
Keywords: Vermiculite, activation, polyacrylonitrile, maleic anhydride, modification, sorption, desorption.
DOI: 10.32737/2221-8688-2025-1-3-19
1. Introduction
In recent years, there have been endeavors to develop contemporary and exceptionally efficient sorbents designed for extracting toxic metal ions from diverse industrial waste streams. It is a challenge to manufacture sorbents that would be efficient concerning various pollutants. [1, 2]. "Salt in a porous matrix" composites based on expanded vermiculite are widely used for their properties such as high sorption and heat retention [3]. In a broader sense, the proposed approach helps to accelerate the sorption of methanol, water, and ammonia in composites based on macroporous matrices [3].
Several experiments have shown that mineral sorbents such as zeolite and vermiculite are more effective than organic sorbents for nickel, cobalt, strontium, and other metals under static conditions, and they can be used as high-efficiency filters with high sorption capacity [4]. As the level of pollution in water and land increases due to climate change around the world, ions are created that affect global food security. In 2022 research conducted based on FGBOU HE SPbGUVM, 45 Guppy aquarium fish were taken as research subjects, and when the natural vermiculite sorbent mixture was added to the feed of these fish in the amount of
4%, the amount of lead in the fish body was reduced. showed a significant decrease in the amount [5]. It has also been revealed that up to 45% of waste antibiotics can be removed using vermiculite treated with 7% hydrochloric acid [6]. In addition, the increase in the
mechanochemical activation level of vermiculite can change the hydration state of vermiculite, and it can change from its hydration state to a single or bilayer state. This indicates that the level of sorption of oil product waste is high [7]. One such study conducted by Russian scientists obtained composite materials based on resorcinol-formaldehyde polymer of vermiculite and phosphorous vermiculite, and their sorption characteristics were studied in the example of methylene blue adsorption and strontium extraction from aqueous solutions under static conditions [8]. In the following research work, vermiculite-based sorbents
showed the best results for cleaning hexachlorobenzene, one of the persistent organic pollutants that can have harmful effects on humans and other living organisms [9, 10]. The technology of cleaning highly concentrated solutions using activated vermiculite and granular serpentine sorbent was used to clean soils contaminated by the wastes of copper-nickel production from vermiculite mineral (Monchegorsk, Murmansk region) [11]. A vermiculite-based sorbent was also used to clean Cr (VI) ions and humic acid in the soil [12, 13].
The purpose of research. Determining the composition and properties of Tebinbulok vermiculite. Obtaining a composite based on vermiculite and polypolyacrylonitrile and obtaining sorbents by modifying it with diethanolamine, studying their physicochemical sorption properties.
2. Experimental part
2.1. Obtaining a vermiculite composite. To
obtain a polyacrylonitrile-modified vermiculite composite, Tebinbulok mine vermiculite meeting the requirements of GOST 12865-67 (Table 1), polyacrylonitrile in the technical state GOST 11097-86, pure maleic anhydride
meeting the requirements of GOST 11153-75 in the technical state, and TY 2423 were included to bind the amine functional group. A-151-00203335-2003 type of diethanolamine with 98%, which meets the requirements of GOST, was used.
Table 1. Chemical composition of Tebinbulok mine vermiculite
Compo nent SiO 2 MgO Al2O3 Fe2O3 CaO Na2O K2O FeO TiO2 MnO SO3 other
The amount; % mass 38-49 20-23.5 12-17.5 5.4-9.3 0.7-1.5 00 о О) l> 1 <N >n <N >n 0.1-0.3 >n 2.04
(a) (b)
Fig. 1. View of vermiculite from Tebinbulok mine in natural (a) and porous (b) state
Washed, cleaned and dried vermiculite in distilled water was burnt in a Digital Muffle Furnace FHX-05 at a temperature of 900°C in an airless environment. In this case, hydration water between the layers of vermiculite is released [14-15]. The layers of vermiculite swell up again and turn yellow with a beautiful
metallic sheen (Fig. 1).
When the temperature exceeds 150°C, the condensed water between several layers of vermiculite starts to evaporate. This situation, which occurs in chemically more stable vermiculite, can be understood by analyzing its structure (Fig. 2).
Fig. 2. The structure of vermiculite.
Vermiculite consists of hydrated aluminum and magnesium silicate, and when heated to 150-1000 °C, it expands 8-30 times compared to its original volume due to the vaporization of constituent waters in vermiculite layers. After cooling, expanded vermiculite retains its new volume. Expanded vermiculite particles are seen as thin plates separated by air spaces. Their shape, color, brightness, and
composition are closely related to the original raw materials. The water absorption capacity of vermiculite increased dramatically as the bulk density and particle size varied from 64 to 160 kg/m3. As a result, vermiculite has several properties such as low thermal conductivity, high fire resistance, and strong sound absorption [14].
(a) (b)
Fig. 3. IR spectra of Tebinbulok mine vermiculite, natural (a) and porous (b)
In our research, we have studied the activated methods with solutions of hydrochloric acid of different concentrations and performed acidic thermal treatment with hydrochloric acid in the following order. 10 mg
of crushed Tebinbulok mine vermiculite, porous at 900 °C, was placed in a flask with a flat bottom, 250 ml capacity. and 100 ml of 7% HCl acid solution was added and stirred in a magnetic stirrer at a speed of 650 rpm. The
process was carried out in a reflux condenser with the temperature control adjusted to 65-70°C. The mixture was filtered and the remaining acid residue was neutralized with low low-concentration sodium hydroxide solution. The resulting salts were decanted. In all the above cases, vermiculite was washed and cleaned, and dried in a drying oven at a temperature of 80-95 °C for one day. The resulting product is a dark yellow, porous, small granular substance [16] (Fig. 3). The reaction yield is 91%.
In Fig. 4, we can see the analysis of infrared spectra obtained after processing and
activating Tebinbulok mine vermiculite in 15% sulfuric acid and 7% hydrochloric acid. Deep peaks in the 3361.93 cm-1 vibrational regions of hydrochloric acid-treated vermiculite, shown in black lines, and 3384.11 cm-1 vibrational regions in the IR spectra of sulfuric acid-treated vermiculite, represented in red lines, increase the degree of hydration during activation in the outer layers of vermiculite. appeared to belong to the resulting H-bonded, valence-vibrating, extensive, and intense OH bonds. The presence of Si-O- valence bonds was seen in the vibration fields of 1060.85 cm-1 in black lines and 1039.63 cm-1 in red lines.
Fig. 4. IR spectroscopy analysis of vermiculite activated with 15% sulfuric acid (red lines) and 7%
hydrochloric acid (black lines).
2.2. Porous and activated vermiculite was modified using polyacrylonitrile. Maleic anhydride was used to etch polyacrylonitrile and vermiculite composite. Maleic anhydride dissolved in acetic acid easily enters and intercalates between layers of vermiculite. Polyacrylonitrile is polymerized with the help of maleic anhydride and forms a whole composite with vermiculite. The initiation of solution polymerization was initiated after adding a small amount of initiator [17]. The experiment was carried out in a magnetic stirrer at a temperature of 348 K with distillation with a deflegmator connected and under constant stirring. Polymerization first occurs in water and precipitates as the molecular weight increases. After the polymerization was completed, it was
filtered and dried in a drying oven at 70°C for one day [15].
2.3. The sorbent properties of the obtained composite were studied. Vermiculite, which is a natural sorbent, has a SAS value of 0.8 mg-eq/g, while this composite has a value of 4 mg-eq/g. This value was determined by the sorption of copper ions from a 0.1 N solution of CuSO4. 30 mg of ionite was taken and placed in 10 ml of solution. The concentration of the solution left for one day was measured in a UF spectrometer. The standard solution, that is, the solution without ionite, and the solution that was in the sorbent for one day, were examined. By putting the results into the following formula, the value of ionite sorption amount was determined.
_ _ Vo,i • (Co,i Ct)
4e =
Here: qe is the amount of ion absorbed by the ionizer; mmol/g Vo,i - solution volume; l C0i- initial concentration of the solution; mmol/l C0i- equilibrium concentration; mmol/l m- dry ionite mass; g.
Based on this formula, the amount of Cu(II) ions and Zn(II) ions absorbed into the sorbent was found. The highest reaction yield and static exchange capacity were obtained
Table 2.The influence of the mole amounts of the initial substances on the physico-chemical ____________________________properties of the obtained sorbent___________________
Vermiculite, Polyacrylonitrile and Maleic Anhydride Reaction product, % Static exchai in 0.1 N solut ige capacity tion, mmol/g
CuSO4 ZnSO4
2:2:0.5 78% 2.6 2.1
1:1:1 80% 3.5 2.9
1:2:0.5 94% 4.1 3.01
m
when the ratio of starting materials, vermiculite: polyacrylonitrile: maleic anhydride - 1:2:0.5 was obtained. It was determined that the amount of ions absorbed by the obtained sorbent is equal to qe=4.1 in the solution containing Cu (II) ion, and qe=3.01 in the solution containing Zn(II) ion [16]. The results of the study of the physico-chemical properties of the obtained sorbent are presented in Table 2.
To further increase the sorption capacity of the obtained sorbent, an amine functional group was added to this sorbent. For this, diethanolamine containing an amine group was exposed to a sorbent in a mass ratio of 1:0.2. The reaction was carried out in a fume hood at a temperature of 338 K with continuous mechanical stirring. When the mixture became tar-like, we poured it into a large porcelain container, dried it with the help of artificial wind, and crushed it. The obtained product is a solid, porous substance of light brown color. The static exchange capacity of the sorbent modified with diethanolamine was studied. This value was found to be equal to qe=10. Initial and final solutions of ionic solution of Cu (II) were examined in the UF spectrophotometer of
the Japanese company SHIMADZU [17, 18]. Zn(II) ion was detected by complexometric titration using the optical densities of the standard and test solution to determine the amount of static exchange in the available solutions. This value was equal to qe=5.5. The investigation was carried out at temperatures of 338 K, 353 K, and 318 K. The best optimum temperature for reaction yield was found to be 338 K. The reaction yield at this temperature was 95.5%. Table 3 presents the results of the study of the synthesis of vermiculite-based sorbent modified with polyacrylonitrile and diethanolamine (VT-PANDEA) on the dependence on temperature and other physicochemical processes [19].
Tab
e 3. Dependence of VT-PANDEA sorbent on physical and chemical conditions
Temperature, K Reaction product, % Static exchan in 0.1 N solut ige capacity ion, mmol/g
CuSO4 ZnSO4
318 82 7.5 5.3
338 95.5 10 6.5
353 85 6.3 4.5
3. Results and its discussion
3.1. Roman spectroscopy analysis. To study the composition of vermiculite-based composite sorbent modified with polyacrylonitrile and diethanolamine, Roman IR-spectroscopy
analysis was conducted (Fig. 5). Analyzes were performed on a Japanese Shimadzu instrument in the 0 to 3500 cm-1 field.
Fig. 5. A novel spectroscopy analysis of the VT-PANDEA ionite.
In the curve of Roman spectroscopic analysis of the vermiculite-based composite ionite modified with polyacrylonitrile and an amine group introduced through diethanolamine, the highest and broadest peak was recorded in the vibration region of 1376.49 cm-1. These vibrational fields belong to strongly intensively bound OH ions. It leads to the conclusion that the bonds between -OH ions formed on the surface of vermiculite mineral and -COOH carboxyl groups in the polymer of polyacrylonitrile formed in the presence of maleic anhydride caused the peaks in this area. 3250.83 cm-1 represented the valence vibrational peaks given by O-H bonds, formed by crystal waters in the composite and a wide and intense H-bond [20].
Fig. 6. Novel spectroscopic analysis of VT-PANDEA ionite sorbed Cu(II) ions from 0.1 N solution.
3.2. Novel spectroscopic analysis of VT-PANDEA composite sorbent. The VT-
PANDEA composite sorbent, which absorbed Cu(II) ions from a 0.1 N solution of CuSO4*5H2O, was dried at room temperature, crushed, and analyzed by Roman spectroscopy (Fig. 6).
The novel spectra of the sorbent absorbing Cu(II) ions were obtained in the field range from 0 to 3500 cm-1. VT-PANDEA ion analysis (Fig. 5) and Roman spectrum analysis of the same ionite that sorbed Cu(II) ions from solution (Fig. 6) were compared. From the analysis, it can be seen that the device recorded several broad and intense peaks resulting from the absorption of Cu(II) ions into the VT-PANDEA composite. Several intense peaks were noted in the analysis, Men(CO)m in the vibrational region of 1932.51 cm-1 and 1864.96 cm-1 in three intense regions, formed between the Cu(II) ion and ionite with valence vibration [20]. We can observe the gardens of the complex. Bonds of R-COO- anion and C=O
group were formed in 1400.05 cm-1 vibration areas of scanning and 1764.40 cm-1 areas. The peak of moderately intense valence-bonded -NH2 groups were recorded at the widths of 2077.11 cm-1 and the vibration fields of 2187.96 cm-1. In the region of 2339.69 cm-1 of the analysis, there are moderately intensive, valence-vibrating -C=N group bonds. At 3140.62 cm-1, the peaks of highly intense, valence-vibrating -N-H bonds, and at 3237.602 cm-1 peaks of broad and intense, valence-vibrating -OH groups forming H bonds were recorded. These -OH bonds were formed on the surface of polyacrylonitrile composite and vermiculite [21-22].
3.3. SEM analysis of VT-PANDEA sorbent.
Using a scanning electron microscope (SEM) and elemental analysis, the 10pm, 50pm, and 100pm surface sections of polyacrylonitrile and vermiculite composite modified with diethanolamine were compared and analyzed and percentages of elements are shown in Table
4.
Fig. 7. SEM analysis of polyacrylonitrile and vermiculite composite ionite (VT-PANDEA) modified with diethanolamine a)10pm b)50pm and energy dispersive spectroscopy.
It can be observed from the 10pm and 50pm magnified images of the VT-PANDEA composite sorbent and the energy dispersive spectroscopy analysis that the surface
morphology of the substances did not show the remains of the initial substances.
It is visible that the silicate layers of the vermiculite, which formed the basis of the sorbent, and the pores between the layers were not damaged. Fig. 7(a) SEM images show mega layers of vermiculite and particles of polyacrylonitrile and diethanolamine attached to it [23].
In the 100 pm magnified images of the analysis of the sorbent surface morphology
taken from four different focal points (Fig. 7), the pores on the surface and between the layers are visible. Figure 7(a) SEM images show mega layers of vermiculite and particles of polyacrylonitrile and diethanolamine attached to it [24].
3.4. Elemental analyses of VT-PANDEA sorbent. During SEM scanning of VT-PANDEA sorbent, analysis of chemical elements was obtained from the sorbent surface area. Spectra of chemical element analysis of VK-PANDEA sorbent were obtained together with 10 pm magnification and 100 pm SEM images.
Fig. 7. SEM analysis of diethanolamine-modified polyacrylonitrile and vermiculite composite ionite (VT-PANDEA): 100 pm magnified image (taken from four different focuses).
Fig. 8. Element analysis analysis of VT-PANDEA a)10pm b)100pm.
We can see that the difference between the amount of elements in chemical element analysis is not very big (Fig. 8). According to the analysis, the highest mass fractions are C; and O; which belong to Si. It seems that the highest percentage of the substance belongs to element C. It is known that this is due to polyacrylonitrile in the investigated sorbent, maleic anhydride inserted as a polymer binder between it and vermiculite, and diethanolamine included in the composition to attach the amine group. The O element, which made up more than 29% of the mass of the substance, corresponded to O in oxides, OH groups, and maleic anhydride and OH groups in diethanolamine in vermiculite. In several areas,
the metals contained in vermiculite, namely Mg; No; We can see peaks corresponding to metals such as K, Al, Fe+3; Fe+2. Cl, which is more than 2% in the composition of the sorbent, belongs to the residues of Cl in the activation of vermiculite [25]. Quantitative proportions of elements in the sorbent are presented in Table 4.
From the analysis of the results, it can be seen that the porosity of the polyacrylonitrile and vermiculite composite ionite (VT-PANDEA) modified with diethanolamine is high, that is, the starting materials are completely connected. It can be seen that the elements are connected and that there are no additives in the composition of the substances. Also, in the elemental analysis of ionite, it was
shown that the percentages of elements have almost the same index [26]. presented in the 10 pm and 100 pm SEM images
Table 4.1 he results of t he analysis of e lements in the VK-PANDEA ionite (in percentages)
Elements C O Si N Mg Fe K Al Cl Ti S Na
Weight. % 100дт 33,1 29,14 11,63 7,85 3,95 3,81 3,45 3,19 2,38 0,81 0,42 0,32
Weight. % 10am 31,4 29,9 11,63 9,42 3,46 3,76 3,00 2,90 2,40 0,71 0,51 0,36
Sigma Weight. % 100am 0,60 0,40 0,10 0,60 0,10 0,30 0,10 0,10 0,10 0,10 0,01 0,01
Sigma Weight % 10am 1,30 0,70 0,26 0,90 0,10 0,40 0,10 0,10 0,10 0,13 0,06 0,05
3.5. X-ray phase analysis of VK-PANDEA sorbent. From the X-ray diffraction (XRD) of VT-PANDEA composite sorbent, we can observe that the vibrational peaks of the formed compounds moved along a line and gave clear
peaks. To obtain diffractograms in XRD, CuKa 1=1.5406 A, CuKa 2=1.54443A; CuKb =1.39225 A in the radiation mode and the current mode was set to 40 mA and tube voltage 45 kV, respectively.
Fig. 9. Graphic analysis view of X-ray phase analysis of vermiculite-based VT-PANDEA composite ionite modified with polyacrylonitrile and diethanolamine
Fig. 10. X-ray phase analysis of VT-PANDEA sorbent: main graph and donut diagram analysis
view
Scanning was applied with a K-A2 / K-A1 ratio of 0.50000, a detector step of 0.020 for 96.3900 c at a constant rotation rate of 4 deg/min (overlap ro/29), and the scan angle was varied from 00 to 900. A rotating camera was used to record the experiments, and its rotation speed was 30 rpm. The analysis was carried out on a continuous-type goniometer with a radius of
240 mm and a divergence crack radius of 100 mm, with a divergence crack size of °0.4354, with the participation of 10 mm samples [27]. Graphs of the spectra resulting from scanning to determine the X-ray phase composition of VT-PANDEA sorbent are presented in Figures 9-11. The results and calculations of the spectrum peaks in these graphs are shown in Table 4.
Fig. 11. X-ray phase analysis of VT-PANDEA sorbent: analysis results obtained in a Cu anode
goniometer with a voltage of 45 keV
Table 5. Resu ts of VT-PANDEA X-ray spectra analysis
Pos. [°20] Height [cts] FWHM Left [°20] d-spacing [Al Rel. Int. [%]
9.1057 15029.73 0.2494 9.70409 100.00
19.6480 206.23 0.0825 4.51464 1.37
24.6300 381.03 1.7070 3.61157 2.54
26.9628 13155.16 0.1640 3.30417 87.53
28.6795 498.21 0.4359 3.11016 3.31
30.9617 272.20 0.3583 2.88592 1.81
33.3619 54.69 0.1677 2.68357 0.36
34.5303 1160.99 0.1977 2.59540 7.72
36.0949 1303.72 0.2027 2.48640 8.67
37.2388 587.96 0.1965 2.41261 3.91
40.0960 103.46 0.0942 2.24703 0.69
41.8705 879.69 0.2458 2.15581 5.85
45.4995 1789.37 0.2730 1.99195 11.91
47.9537 306.49 0.0746 1.89557 2.04
52.7637 125.32 0.3014 1.73354 0.83
55.1802 1690.30 0.2621 1.66320 11.25
60.5226 1393.79 0.3166 1.52854 9.27
62.5045 137.98 2.5941 1.48475 0.92
65.4266 285.67 1.5593 1.42533 1.90
69.2279 933.23 0.4356 1.35605 6.21
71.3319 187.34 0.7295 1.32114 1.25
72.5146 218.14 1.0774 1.30247 1.45
75.9630 195.41 1.4466 1.25169 1.30
78.8649 130.85 2.6229 1.21275 0.87
86.1379 128.77 0.2878 1.12802 0.86
From the X-ray diffractograms of the sorbent samples, we can see that the peak output of the X-ray spectrum was observed at °29 = 5.0131°, the end of the spectrum was 29 = 89.9811°.
According to the data obtained as a result of X-ray phase scanning of the sorbent, the compounds present in the sample and their information are presented in Table 6.
Table 6. X-ray phase analysis data of compounds in polyacrylonitrile-modified vermiculite and _______________________________diethanolamine composite ionite_________________________________
Ref.Code Score Compound Name Displ.f°201 Scale Fac. Chem. Formula
03-065-7994 59 Titanium Carbide 0.197 0.078 Ti C
01-089-7213 24 Carbon 0.509 0.331 C
01-088-2324 31 Iron -0.306 0.096 Fe
01-076-2729 14 Calcium Silicide -0.342 0.027 Ca2 Si
01-073-1148 25 Aluminum Magnesium 0.092 0.029 Al12 Mg17
01-080-4429 20 Magnesium Hydride 0.438 0.041 Mg H2
01-076-0884 51 Potassium Sodium Iron Magnesium Aluminum Titanium Silicate Hydroxide 0.275 0.472 K.78 Na.22 Mg1.63 Fe.85 Ti.33 Al1.35 Si2.84 O11 (OH)
01-078-1257 17 Silicon Oxide -0.162 0.219 SiO2
01-077-7981 41 Iron oxide -0.272 0.045 Fe O
01-073-3990 14 Sodium Aluminum Silicate 0.062 0.084 NaAlSi3O8
01-089-3615 10 Sodium Chloride 0.141 0.075 NaCl
01-071-5127 11 Calcium Chloride -0.230 0.014 CaCl2
3.6. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of VK-PANDEA composite ionite. The thermal stability of VT-PANDEA composite sorbent is an important indicator reflecting its efficiency. Through this TGA analysis, the onset and termination temperatures of mass loss effects of polyacrylonitrile-based vermiculite were determined. The TGA and DTA parameters of the sorbent were calculated using the combined
curves of peaks reflecting temperature changes [28]. Results of a thermogravimetric experiment for polyacrylonitrile-modified vermiculite The results of the thermogravimetric experiment for vermiculite-based polyacrylonitrile and
diethanolamine-modified composite ionite 4.88 mg sample was studied in an argon
environment, in the temperature range of 20-800 °C (Fig. 12).
Fig. 12. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of polyacrylonitrile-modified vermiculite and diethanolamine composite ionite (VT-PANDEA).
In the DTA analysis of vermiculite-based sorbent modified with polyacrylonitrile and diethanolamine, the mass loss occurred in three stages, and one exothermic and one endothermic process occurred. The first mass loss started at 25.85°C and continued to 136.7°C in 12.04 minutes [29]. A mass loss of 0.301 mg or 6.157% was observed. At this stage, the release of hygroscopic water vapor was observed. The second stage lasted until 49.40 minutes of temperature increase, i.e. up to 505.52°C, and the mass loss during this interval was 1.197 mg,
i.e. 24.484%. Carbon (II) oxide was released as a result of the decomposition of carboxyl groups in this range of temperatures. The third stage is the main decomposition stage, starting at 440.31°C and ending at 877.7°C, 4.648 mg, 43.458% mass loss was observed. In this case, from the decomposition of organic compounds, the decomposition of oxides from the amino group of nitrogen and some other organic
compounds was observed. In the DTA analysis of the synthesized product, it can be seen that 2.751 mg or 25.725% of residual substances remained at 802.34°C in the endothermic process. At this stage, it can be observed that the remains of metal salts remain.
3.7. Analysis of adsorption isotherms and pore sizes of VT-PANDEA sorbent. Textural properties of VT-PANDEA sorbent samples were studied by benzene vapor adsorption using an Mc-Ben-Bakra sensitive quartz spiral setup [30]. The benzene was first stripped under vacuum, cooled until its vapor pressure reached the vapor pressure given in the table for pure benzene, and degassed. Before measuring the adsorption of benzene vapor on adsorbents, each adsorption system was vacuumed until the residual pressure was 1.33 10-3 Pa and heated at 473 K for 6 hours, then adsorption isotherms were obtained (10-12 figures).
Fig. 13. Benzene vapor adsorption isotherm in VT-PANDEA ionite
It was calculated that the adsorption of vermiculite and diethanolamine composite ionite modified with polyacrylonitrile to benzene vapor is high. According to the amount of benzene adsorbed on ionite increases sharply from zero relative pressure to P/Ps =0.1 and
approaches full saturation at P/Ps =1 (Fig. 13). The obtained isotherm belongs to the type I according to the IYUPAK classification, and 70-75% of the sorbent consists of micropores [31-32].
Tab
e 7. VT-PANDEA composite ionite adsorption isotherm calculations
P/Ps a 1-P/Ps a*(1-P/Ps) (P/Ps)/a*(1-P/Ps)
0 0 0
0,1 0,174 0,9 0,1563212 0,639708333
0,2 0,239 0,8 0,1910593 1,046795455
0,3 0,282 0,7 0,1975727 1,518428571
0,4 0,326 0,6 0,1954016 2,047066667
G=2.04496; A=0.0558
Fig. 15. Benzene vapor adsorption isotherm in VT-PANDEA ionite
Table 8. VT-PANDEA composite ionite adsorption isotherm
P/Ps a log(a) PS/P LOG(Ps/P) (logPs/P)2
0.1 0.1737 -0.760224518 10 1 1 -0.760224518
0.2 0.2388 -0.621921819 5 0.698970004 0.488559067 -0.621921819
0.3 0.2822 -0.549371152 3.333333333 0.522878745 0.273402182 -0.549371152
0.4 0.3257 -0.487223246 2.5 0.397940009 0.158356251 -0.487223246
0.6 0.3799 -0.420276456 1.666666667 0.22184875 0.049216868 -0.420276456
0.8 0.4451 -0.351560644 1.25 0.096910013 0.009391551 -0.351560644
1 0.5319 -0.27414842 1 0 0 -0.27414842
Table 9. Sizes of VT-PANDEA composite ionite adsorbed
benzene
Mr density max mol/kg Substance density A G B lga a Vm
78 0,88 0.532 40 0.0558 2.04496 5.1124 -0.3735 0.42315551 0.088636
The density of VT-PANDEA composite ionite in water (Mr-18g/mol; r=1 g/m3) is 10.8 g/m3 and in benzene (Mr=78g/mol; r=0.88g/m3)
it is 40 g/m3 was founded. The following results can be noted during the study of the mentioned adsorption isotherms and calculations (Fig. 14,
15). Porous and benzene sorption parameters of VT-PANDEA ionite are presented in Table 10.
Table 10. Sizes
representing porosity properties of VT-PANDEA composite sorbent
a (monolayer capacity) S (comparative surface) Micropore Wo Saturation volume Vs Mesa poreWme Pore radius
0.193mol/kg 46.59m2/g 0.037507 0.0471545 0.01 20.2 A 2.02nm
4. Conclusions
The following results were obtained from the results of the research conducted based on Tebinbulok mine vermiculite in this research work:
I. The chemical composition of
Tebinbulok mine vermiculite was studied by the elemental analysis method. The natural
vermiculite was heated in an incinerator to expel the bound water, thus increasing the volume and porosity of the vermiculite several times. To increase the surface area of vermiculite and its activity, it was activated with 7% hydrochloric acid.
II. Porous and activated vermiculite was
modified using polyacrylonitrile and
diethanolamine. Reaction conditions and optimal temperatures of the synthesized composite were studied. The static exchange capacity of the sorbent was calculated following the requirements of GOST 20255.1-8. Sorption was carried out against Cu(II) and Zn(II) ions. The experiment conducted at a temperature of 338 K was found to be the most optimal temperature, and the reaction yield was 95.5%. The SAS value of Cu(II) is 10 mmol/g and that of Zn(II) is 6.5 mmol/g.
III. Roman spectrum analyzes of the composite sorbent and Cu(II) ion absorbing state were obtained. In the novel spectroscopy analysis, the highest and broadest peak was recorded for intensively bonded -OH bonds in the vibrational region of 1376.49 cm-1 and Men(CO) in the vibrational region of 1932.51 cm-1 and 1864.96 cm-1 We were able to observe metal ions with m valence vibrations, intensively bound, sorbed to VT-PANDEA and the bonds of the complex formed between ionite.
IV. Using scanning electron microscope (SEM) and elemental analysis, the images of the surface morphology of polyacrylonitrile and
vermiculite composite modified with diethanolamine at sizes of 10pm, 50pm, and 100 pm were studied. In the scanner images magnified by 10 pm and 50 pm, it was found that the remains of the initial substances were not visible on the surface of the composite and pores were noticeable. Scan images of the composite sorbent were taken at 100 pm magnification from four different focal points. Analysis of these images confirmed the descriptions given to the specimen.
V. During SEM scanning of VT-PANDEA sorbent, analysis of chemical elements was obtained from the sorbent surface area. Spectra of chemical element analysis of VT-PANDEA sorbent were obtained together with 10 pm magnification and 100 pm SEM images. From this analysis, the amount of elements in the composite sorbent corresponds to theoretical calculations. It turned out that the only foreign element in the composition is Cl, and it is a residue left in the composition during the activation of vermiculite. Quantitative proportions and б masses of the elements in the sorbent were given.
VI. X-ray phase analyses of the compounds formed were obtained from X-ray diffraction (XRD) of polyacrylonitrile and vermiculite composite ionite (VTPAN-DEA) modified with diethanolamine. From the X-ray diffractograms of the sorbent samples, the spectra related to the TiC compound, i.e., the peak output of the X-ray spectrum was observed at °29 = 5.0131°, and the end of the spectrum was 29 = 89.9811° (Figures 9-11). The results of the VK-PANDEA X-ray spectra analysis and the indicators of compounds in the sample are given in the tables.
VII. To determine the thermal stability of
VT-PANDEA composite ionite,
thermogravimetric and differential thermal
analyses were conducted. The starting and ending temperatures of mass loss effects of vermiculite modified based on polyacrylonitrile were determined. The TGA and DTA indicators of ionite were calculated using the combined curves of peaks reflecting temperature changes. During the analysis, there was a mass loss in three stages one exothermic and one endothermic process.
VIII. Textural properties of VT-PANDEA sorbent samples were studied by benzene vapor adsorption using an Mc-Ben-Bakra sensitive quartz spiral setup. The sample was heated at 473 K for 6 h, then adsorption isotherms were obtained. Based on adsorption isotherms, parameters such as monolayer capacity, specific surface area, saturation volume, micropore, mesopore level, and pore radii of the sorbent were calculated.
IX. A method of synthesizing a new sorbent based on vermiculite modified with polyacrylonitrile and diethanolamine was developed and a new organic-inorganic sorbent was synthesized. The reaction conditions of the obtained sorbent were studied. Experiments on the sorption of Cu(II) and Zn(II) ions by the sorbent were conducted. The amount of these ions adsorbed on the surface of the sorbent was calculated and the SAS value was calculated. This amount represented a high sorption capacity. The thermal stability of the sorbent was determined based on DTA and TGA analyses. Adsorption isotherms and physical properties of such a sorbent were obtained using the Mac-Ben-Bakra apparatus. It can be concluded that the sorbent has sufficient surface area based on the porosity level and pore radii.
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