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Article

Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen

by
Binara T. Dossumova
1,
Tatyana V. Shakiyeva
1,
Dinara Muktaly
1,
Larissa R. Sassykova
2,*,
Bedelzhan B. Baizhomartov
1 and
Sendilvelan Subramanian
3
1
Al-Farabi Kazakh National University, 71, Al-Farabi Avenue, Almaty 050040, Kazakhstan
2
Faculty of Chemistry and Chemical Technology, Al-Farabi Kazakh National University, 71, Al-Farabi Avenue, Almaty 050040, Kazakhstan
3
Department of Mechanical Engineering, Dr. M.G.R. Educational and Research Institute, Chennai 600095, Tamil Nadu, India
*
Author to whom correspondence should be addressed.
ChemEngineering 2022, 6(5), 68; https://doi.org/10.3390/chemengineering6050068
Submission received: 30 June 2022 / Revised: 24 July 2022 / Accepted: 15 August 2022 / Published: 7 September 2022
Browse Figures
Versions Notes

Abstract

:
The development and improvement of methods for the synthesis of environmentally friendly catalysts based on base metals is currently an urgent and promising task of modern catalysis. Catalysts based on nanoscale magnetite and maghemite have fast adsorption–desorption kinetics and high chemical activity. The purpose of this work is to obtain magnetic composites, determine their physicochemical characteristics and verify their activity in the process of liquid-phase oxidation of phenol with oxygen. Magnetic nanocomposites were obtained by chemical co-deposition of salts of ferrous and trivalent iron. The synthesized magnetic composites were studied by X-ray diffractometry, energy dispersive X-ray fluorescence and Mössbauer spectroscopy, IR-Fourier spectroscopy and elemental analysis. To increase the catalytic activity in oxidative processes, the magnetite surfaces were modified using cobalt nitrate salt. Further, CoFe2O4 was stabilized by adding polyethylenimine (PEI) as a surfactant. Preliminary studies of the oxidation of phenol with oxygen, as the most typical environmental pollutant were carried out on the obtained Fe3O4, CoFe2O4, CoFe2O4/PEI catalysts. The spectrum of the reaction product shows the presence of CH in the aromatic ring and double C=C bonds, stretching vibrations of the C=O groups of carbonyl compounds; the band at 3059 cm−1 corresponds to the presence of double C=C bonds and the band at 3424 cm−1 to hydroquinone compounds. The band at 1678 cm−1 and the intense band at 1646 cm−1 refer to vibrations of the C=O bonds of the carbonyl group of benzoquinone. Peaks at 1366 cm−1 and 1310 cm−1 can be related to the vibrations of C–H and C–C bonds of the quinone ring. Thus, it was demonstrated that produced magnetic composites based on iron oxide are quite effective in the oxidation of phenol with oxygen.

1. Introduction

The processes of liquid-phase oxidation of phenols are comprehensively studied by various scientists [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. As oxidants, depending on which phenol oxidation product should be obtained, it is proposed to use a number of compounds of both organic and inorganic nature. Recently, heterogeneous catalytic oxidation of phenols with air oxygen is widespread, which has a number of advantages over other methods of destructive oxidation of phenolic compounds. The direction of the oxidation reaction depends on the conditions of the process and the catalyst used. In the processes of destructive oxidation of phenol in the liquid phase, the most popular are persulfates, peroxides and ozone [1,2,3,4,5,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]. These oxidizers can be introduced into the liquid-phase system from the outside or obtained directly in the reaction volume in situ. It is possible to intensify the oxidation process by adding various catalytic systems. The use of oxygen as an environmentally friendly and cheap oxidizer for phenol and phenyl-substituted compounds depends on the specificity of the action of catalysts with respect to oxygen. To date, there is a large number of works studying the possibility of deep catalytic oxidation of highly toxic organic compounds, including phenol and phenol-substituted compounds using metallic and metal oxide Pd, Pt, Ru, Rh, Fe, Ni, Si, Co, Mn, as well as deposited catalysts with an active metal content of 0.05–30.0% [10,20,21,22,23,24,25,26,27,28].
The development and improvement of methods for the synthesis of environmentally friendly materials and catalysts based on base metal nanoparticles is currently an urgent and promising problem of modern industry and catalysis [32,33,34,35]. Among such catalytic systems, catalysts containing iron nanoparticles and/or iron oxides are of particular interest. This is due to the fact that iron is characterized by low cost, it is widely distributed in soils, non-toxic and it has unique magnetic properties. Among the oxides of variable metals, iron oxides and their composites are used with great success [36,37,38,39,40,41,42,43]. They are used, not only in the field of electronics, medicine, protection and purification of the environment from various pollutants, such as phenol and its derivatives, but also due to their cheapness, good thermal stability and high specific surface area as heterogeneous catalysts in complete and partial oxidation reactions. Catalysts based on nanoscale magnetite and maghemite have a high degree of extraction, fast adsorption–desorption kinetics and high chemical activity [36,37,38,44,45,46,47,48,49,50,51].
The purpose of this work was to obtain magnetic composites, determine their physico-chemical characteristics and test their activity in the process of liquid-phase oxidation of phenol with oxygen.

2. Materials and Methods

2.1. Preparation of Magnetic Nanocomposites

Magnetic nanocomposites were obtained by chemical co-deposition of salts of ferrous and trivalent iron. The main advantage of the process of co-deposition of iron salts is that a large number of nanoparticles can be synthesized in this way. The process of co–deposition occurs in two stages: the first is the nucleation of crystals when the concentration reaches a critical supersaturation, and then there is a slow growth of embryos by diffusion of dissolved substances to the crystal surface. To obtain iron oxide nanoparticles, these two stages must be separated, i.e., the nucleation of crystals during the growth period should be avoided [48,49,50,51,52,53,54,55].
Composites were obtained in a mini glass reactor with a capacity of 50 mL, equipped with a mini stirrer with a rotation speed controller up to 1500 rpm. An aqueous solution of iron (II) sulfate FeSO4∙7H2O and iron (III) chloride FeCl3∙6H2O was prepared by stirring at 180 rpm and slowly heated to a temperature of 80 °C. Next, a 25% ammonia solution was added dropwise to the prepared solution of iron salts with vigorous stirring (600 rpm), while controlling the temperature and pH of the solution, until a pH of at least 10 was obtained, and the mixture was stirred for another 30 min. The resulting black precipitate of magnetite was washed by decanting with bidistilled water until a pH value of 7–8 was reached, then the magnetic dispersion was centrifuged in a CM-6M centrifuge at 2000 rpm for 10 min.
The chemical reaction of the formation of Fe3O4 can be written as:
Fe2+ + 2Fe3+ + 8OH− = Fe3O4 + 4H2O
In order to increase the catalytic activity in oxidative processes, magnetite surfaces were modified using cobalt nitrate salt, since among spinel ferrites with the general formula is MeFe2O4, where “Me” is some divalent cation (Fe2+, Co2+, Ni2+, Cu2+) cobalt ferrite (CoFe2O4) has a stronger cubic magnetocrystalline anisotropy.
To obtain CoFe2O4, a mixture of aqueous solutions of FeCl3∙6H2O and Co(NO3)2∙6H2O at 180 rpm was slowly heated to a temperature of 80 °C. Then, a 25% ammonia solution was added drop-by-drop to the prepared solution with intensive stirring (600 rpm), controlling the pH of the solution, the temperature and stirring for another 40 min.
At the same time, an instantaneous formation of a dark brown suspension was observed. The reaction was carried out at a temperature of 80 °C ± 5 °C: the temperature was kept constant in the process with the need to obtain nanodisperse ferrite composites. The resulting precipitates were washed by decantation in a rotary evaporator and dried at a temperature of 90–100 °C.
The chemical reaction of CoFe2O4 formation can be written as:
Co2+ + 2Fe3+ + 8OH− = CoFe2O4 + 4H2O
Further, CoFe2O4 was stabilized by adding polyethylenimine as a surfactant, hybrid materials based on cobalt ferrite and polyethylenimine (PEI) which were obtained by mixing an aqueous suspension of cobalt ferrite and an aqueous solution of PEI at the same temperature (80 °C) at which cobalt ferrite synthesis was carried out, and mixed at the specified temperature for 1.5 h. The resulting composites were then dried at 25 °C in air. As a result, samples of hybrid materials CoFe2O4 and CoFe2O/PEI were obtained.

2.2. Tests of Synthesized Catalysts in the Process of Oxidation of Phenol with Oxygen

Preliminary studies of the oxidation of phenol with oxygen, as the most typical environmental pollutant, were carried out on the obtained Fe3O4, CoFe2O4 and CoFe2O4/PEI catalysts.
The oxidation reactions of phenol with oxygen were carried out in a non-flowing glass gradient-free thermostatic reactor of “the duck” type (Figure 1), equipped with a potentiometric device. The kinetic regime was provided by intensive shaking of the reactor (300–400 swings per minute) and the volume of the liquid phase was no more than 40 cm3, with a total reactor volume of 180 cm3. The reaction rate was monitored by oxygen absorption from a thermostatic burette connected to the reactor.
The components of the system were introduced in the following order: solutions of substances were poured into the reactor, the interactions between which are limited by equilibrium processes in the liquid phase, or the speed of which can be neglected compared to the speed of the reaction under study. Then, a given oxygen atmosphere was created in the reactor. The reactor was shaken until a constant volume of the gas phase was established within the experimental error, after which the remaining components of the system were quickly introduced through a glass faucet. This moment was taken as the beginning of the reaction. The temperature was maintained with an accuracy of 0.5 °C using a thermostat.
When the oxygen absorption rate became below 0.1 mL/min, the reaction was considered complete. Samples were taken at certain intervals, which were analyzed for the content of phenol and benzoquinone by UV and IR spectroscopy.
The reactions were carried out under optimal conditions established during the studies of phenol transformation in the presence of the obtained catalysts. The initial concentration of phenol was 0.003 mol/L.

2.3. Conducting an Analysis

The obtained magnetic composites were studied by X-ray diffractometry, energy dispersive X-ray fluorescence spectroscopy, Mössbauer and IR-Fourier spectroscopy. Mössbauer spectroscopy was used to study the magnetic structure and phase analysis. The source was 57Co in a rhodium matrix with an activity of 100 mCi. The spectra were processed on a PC using “the least squares” method. The values of isomeric shifts (Is) are given relative to α-Fe. The temperature of taking spectra is 20 °C. Shooting mode is “in transmission”. Spectrometer MS 1104Em was applied. ΔIS = ±0.03 mm/s; ΔQS = ±0.03 mm/s; ΔS = ±2.0%.
Elemental analysis was performed using energy-dispersive X-ray fluorescence spectroscopy on an INCA Energy 450 energy-dispersive microanalysis system mounted on a JSM 6610 LV Scanning Electron Microscope, JEOL, Musashino, Akishima, Tokyo, Japan. Determination error was ±0.01%.
X-ray diffractometry was performed using a Dron-4M X-ray diffractometer (Russia, “Burevestnik”, St. Petersburg) with a tube with a cobalt anode. Shooting mode had a sweep speed of 2 degrees/min, and the operating parameters of the tube were 30 kV, 20 mA.
IR spectra were recorded and processed on a VERTEX 70 IR-Fourier spectrometer in the frequency range from 4000 to 500 cm−1 and using a PIKE MIRacle ATR single frustrated internal total reflection (ATR) attachment with a germanium crystal. The results were processed using the OPUS 7.2.139.1294 software of the Bruker.
The absorption spectra were measured using a Shimadzu UV-1240 spectrophotometer, with a spectrum measurement range from 190 to 1100 nm.

3. Results

3.1. Characterization of Magnetic Composites

Figure 2 shows an X-ray diffractogram of a magnetic composite. The X-ray image of synthesized iron oxide nanoparticles agrees well with the literature data for magnetite [47,48,49,55,56,57,58]. The peaks at 2θ values 35°, 43°, 57°, 63° and 74° correspond to the lattice planes’ (311), (400), (422), (511) and (440), respectively, characteristic of iron oxide, indicating its crystal structure. However, the positions of the diffraction peaks of magnetite and maghemite are very much the same, and they have a common crystal lattice structure.
The structure of maghemite is a defective structure of magnetite, a cation-deficient form of spinel. Mössbauer spectroscopy allows us to solve the problem of phase analysis in magnetic composites; therefore, using Mössbauer spectroscopy, we studied the structure and phase composition of magnetic composites.
Figure 3 shows the Mössbauer spectrum of a composite obtained at room temperature belonging to iron oxides in a magnetically ordered state.
The Mössbauer spectrum has a relaxation character, as indicated by the parabolic shape of the background line. The magnetic hyperfine splitting of resonance lines indicates the magnetically ordered states of iron ions at room temperature. A satisfactory fit of the calculated spectrum to the experimental one was obtained by decomposing the latter into four magnetically ordered components (phases) with a distribution of effective magnetic fields (Heffective) from 485 to 397 keV.
The spectrum can be considered as two sextets similar in their parameters, corresponding to trivalent iron ions and with slightly less splitting from divalent iron ions. The values of isomeric shifts (Is) and quadrupole cleavages (Qs) indicate the simultaneous presence of phases of magnetite Fe3O4 and maghemite γ-Fe2O3, which completely coincide with the tabular values. The values of the isomeric shift and the effective ultrathin magnetic field obtained from the experimental Mössbauer spectra correspond to 57Fe nuclei occupying tetrahedral and octahedral positions. The low values of the effective magnetic fields can be explained by the high dispersion of the sample particles. This possibility is indicated by the relaxation nature of the spectrum. In this case, the size of the studied particles is close to 10 nm [55,56,57,58,59,60,61].
To determine the chemical composition of magnetic composites, an elemental analysis was carried out. Figure 4 and Figure 5 show the results of the SEM (scanning electron microscopy) with the corresponding spectra of energy dispersion analysis.
The elemental analysis of the magnetic composite is shown in Table 1. Parameters of processing: all elements were analyzed (normalized).
The IR spectrum of the composite (Figure 6) contains wide bands of valence vibrations with an absorption maximum of 3380 cm−1 and deformation vibrations of 1637 cm−1, indicating the presence of hydroxyl groups. In the IR spectrum of the magnetic composite, an absorption band is observed at 1111 cm−1 and a shoulder at 1051 cm−1, according to the literature data [62,63,64,65], which can be identified as deformation vibrations of Fe–O–H bonds in the spinel structure. Valence fluctuations of the Fe–O bond in oxides are manifested in the region of 800–600 cm−1 at 783.649 cm−1.
Figure 7 and Figure 8 show the X-ray diffraction patterns of CoFe2O4 and CoFe2O4/PEI composites, respectively. In the diffraction pattern of CoFe2O4 (Figure 7), along with peaks related to iron oxide, a cobalt peak appears in the region of angles 2θ = 50–55° and an indistinguishable shoulder in the region 2θ = 40–45°. When stabilized with polyethyleneimine, the reflex diffraction patterns revealed several phases of iron oxides—γ-Fe2O3, α-Fe2O3, ε-Fe2O3, which are confirmed by Mössbauer spectroscopy data (Figure 9 and Figure 10, Table 2). The diffraction peaks for cobalt oxide correspond to spinel Co3O4 [40,41,45,60,61,66].
Diffraction peaks: 2.96; 2.53; 2.09; 1.71; 1.61; 1.48; 1.32; 1.27 Å—correspond to γ-Fe2O3 (ASTM 5-637).
Diffraction peaks: 2.70; 2.53; 1.84; 1.48; 1.45; 1.30; 1.18 Å—correspond to α-Fe2O3 (ASTM 13-534).
Diffraction peaks: 2.98; 2.73; 1.38 Å—correspond to ε-Fe2O3 (ASTM 16-653).
Diffraction peaks: 4.29; 2.87; 2.73; 2.65; 2.38; 2.36; 2.04; 1.43; 1.23 Å—correspond to Co3O4 (ASTM 80-1535).
Figure 9 and Figure 10, as well as Table 2, show the Mössbauer spectrum of composites obtained at room temperature belonging to iron oxides in a magnetically ordered state.
The substitution of the Fe atom for the Co atom leads to an increase in the hyperfine magnetic field at the 57Fe nucleus. The Mössbauer spectroscopy data confirm the results of X-ray phase analysis. We assume that during the process, the decrease in the values of Heffective (keV) in CoFe2O4/PEI compared to CoFe2O4 is associated with a high dispersion of sample particles during the addition of PEI. The values of the shifts observed in the spectra make it possible to identify them as partial spectra of the Fe2+ and Fe3+ cations in the paramagnetic state.
The chemical composition of CoFe2O4 was also determined.
Figure 11 and Figure 12 show the results of SEM with the corresponding energy dispersive analysis spectra.
Elemental analysis is presented in Table 3. Parameters of processing: all elements were analyzed (normalized).
The IR spectrum of CoFe2O4 (Figure 13) contains wide bands of valence oscillations with an absorption maximum of 3388 cm−1 and deformation oscillations of 1607 cm−1, indicating the presence of hydroxyl groups. The absorption band is observed at 1031 cm−1 and 678–663 cm−1, according to the literature data [67,68,69], which can be identified as valence oscillations of the Co-O-H and Co–O bonds, respectively. Deformation fluctuations of Fe-O-H bonds in the spinel structure are manifested at 1355, 1219 cm−1. Valence vibrations of the Fe-O bond in oxides manifest themselves in the region of 800–600 cm−1 in the form of several bands at 735, 663, 649, 626 cm−1.
Figure 14 and Table 4 show the XRF of the CoFe2O4/PEI samples with the corresponding energy dispersive analysis and elemental analysis spectra.
When identifying the IR spectra of CoFe2O4/PEI, in addition to the absorption bands Co-O and Fe-O, Fe-O-H absorption bands in the region of 1105 and 1048 cm−1 corresponding to the valence oscillations of C–N and CH2, respectively, are observed. The shift of the absorption bands with respect to the PEI spectrum is observed, as well as the shift of the bands’ characteristic of the bonds of the NH group in the region of 1649 cm−1. The complexity of the spectra in this area did not allow us to find out the participation of PEI in the formation of complexes with metal ions [54,66,67,68,69,70,71,72].

3.2. Results of Testing the Synthesized Catalysts in the Oxidation of Phenol with Oxygen

The obtained Fe3O4, CoFe2O4 and CoFe2O4/PEI were investigated as catalysts in the oxidation of phenol as the most typical environmental pollutant. The initial concentration of phenol was 0.003 mol/L.
Figure 15 shows that the most effective oxidation of phenol occurs at CoFe2O4/PEI.
When phenol is oxidized to CoFe2O4 stabilized with polyethylenimine, the concentration of phenol decreases from 0.03 to 0.001 mol/L in 120 min. On Fe3O4, CoFe2O4 catalytic systems, phenol oxidation occurs with a decrease in the concentration of phenol from 0.03 to 0.0025 mol/L in 150 min. With an increase in temperature from 30 °C to 80 °C, the maximum degree of transformation of C6H5H is observed at 80 °C.
In the UV spectrum of the initial solution of phenol, absorption bands are observed in the region of 193, and 210.8 and 270 nm (Figure 16a) characteristic of phenol. Depending on the oxidation time in the UV spectra, a shoulder in the region of 207 nm (Figure 16b) and a plateau in the region of 275 nm are similarly observed.
The ratio of intensities and spectral characteristics of the absorption bands of phenol with a shift to the long-wavelength region from absorption measurements in the wavelength range 190–320 nm allows us to estimate the concentration of phenol in the sample and to give a primary qualitative assessment of the oxidation of phenol.
The IR spectra of phenol and reaction products are shown in Figure 17. In the IR spectra of phenols, the characteristic absorption bands of valence vibrations of the OH group lie in the frequency range 3390–3600 cm−1 and valence vibrations of the C–O group are observed at 1230 cm−1. In the UV spectra, the absorption bands of phenol are as follows: 210 (ε = 6200 L/mol·cm) and 270 nm (ε = 1450 L/mol·cm).
In the IR spectrum of the phenol solution, characteristic absorption bands of the OH group valence oscillations in the region of 3394 cm−1 are observed, and the band in the region of 1242 cm−1 refers to the valence vibrations of the C−O groups of phenol (Figure 17a).
A qualitative comparison of the obtained spectra of the reaction product shows the presence of CH in the aromatic ring and double C=C bonds, as well as valence vibrations of C=O groups of carbonyl compounds. The band 3059 cm−1 corresponds to the presence of double C=C bonds, and the band 3424 cm−1 may refer to vibrations of hydroxyl groups of the intermediate compound hydroquinone. The band in the region of 1678 cm−1 and the intense band in the region of 1646 cm−1 refers to fluctuations in the bonds of the C=O carbonyl group of benzoquinone [43,44,45,46,47,66,70,71,72]. The peaks of 1366 cm−1 and 1310 cm−1 may relate to fluctuations in the C-H and C-C bonds of the quinone ring (Figure 17b).
Thus, according to the data of UV and IR spectroscopy, magnetic composites based on iron oxide show their good effectiveness in the oxidation of phenol with oxygen.
The research will be continued.

4. Conclusions

The work aimed at creating magnetic nanocomposites for the oxidation of the organic pollutant phenol and its derivatives. Magnetic nanocomposites were obtained by chemical co-precipitation of ferrous and trivalent iron salts. The co-precipitation process consisted of two stages: the nucleation of crystals, when the concentration reaches a critical supersaturation, and the slow growth of nuclei by diffusion of solutes to the crystal surface. Magnetite surfaces were modified with cobalt nitrate salt. Next, polyethyleneimine (PEI) was added to CoFe2O4 as a surfactant. The composition and structure of the catalysts were characterized using modern physicochemical methods. The study of the characteristics of magnetically active nanocomposites was carried out using electron microscopy, and Mössbauer and IR-Fourier spectroscopy. The developed nanomagnetic composites were tested in the process of phenol oxidation in aqueous solutions. UV and IR spectroscopy data confirm that magnetic composites based on iron oxide are active and efficient in the oxidation of phenol with oxygen.

Author Contributions

Conceptualization, D.M. and T.V.S.; methodology, B.T.D. and T.V.S.; software, B.B.B. and L.R.S.; validation, T.V.S., L.R.S. and S.S.; formal analysis, D.M. and L.R.S.; investigation, B.T.D., B.B.B. and T.V.S.; resources, T.V.S. and B.T.D.; data curation, T.V.S. and B.T.D.; writing—original draft preparation, B.T.D., T.V.S. and L.R.S.; writing—review and editing, L.R.S. and B.T.D.; visualization, L.R.S., S.S. and B.B.B.; supervision, B.T.D., T.V.S., D.M. and L.R.S.; project administration, T.V.S.; funding acquisition, B.T.D., T.V.S. and D.M. All authors have read and agreed to the published version of the manuscript.

Funding

The research is funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan Grant No. AP09260687 “Technology for the recovery and disposal of toxic compounds from industrial wastewater”.

Conflicts of Interest

The authors declare no conflict of interest.

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Chemengineering 06 00068 g001 550
Figure 1. Laboratory installation for oxidation of phenol with oxygen: 1, reactor; 2, electrode; 3, funnel for reagent input; 4, potentiometer; 5, thermostat; 6, measuring burette; 7, gasometer; 8, transition valve; 9, taps.
Figure 1. Laboratory installation for oxidation of phenol with oxygen: 1, reactor; 2, electrode; 3, funnel for reagent input; 4, potentiometer; 5, thermostat; 6, measuring burette; 7, gasometer; 8, transition valve; 9, taps.
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Figure 2. X-ray diffractogram of synthesized iron oxide, magnetic composite.
Figure 2. X-ray diffractogram of synthesized iron oxide, magnetic composite.
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Figure 3. Mössbauer spectrum of a magnetic composite at 20 °C.
Figure 3. Mössbauer spectrum of a magnetic composite at 20 °C.
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Figure 4. SEM image of magnetic composite.
Figure 4. SEM image of magnetic composite.
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Figure 5. X-ray fluorescence spectrum of magnetic composite. The full scale of 51,979 pulses. The cursor is 3569 (1230 pulses).
Figure 5. X-ray fluorescence spectrum of magnetic composite. The full scale of 51,979 pulses. The cursor is 3569 (1230 pulses).
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Figure 6. The IR spectrum of magnetic composite.
Figure 6. The IR spectrum of magnetic composite.
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Figure 7. X-ray diffraction pattern of CoFe2O4 composite.
Figure 7. X-ray diffraction pattern of CoFe2O4 composite.
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Figure 8. X-ray diffraction pattern of CoFe2O4/PEI composite.
Figure 8. X-ray diffraction pattern of CoFe2O4/PEI composite.
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Figure 9. Mössbauer spectrum of CoFe2O4.
Figure 9. Mössbauer spectrum of CoFe2O4.
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Figure 10. Mössbauer spectrum of CoFe2O4/PEI.
Figure 10. Mössbauer spectrum of CoFe2O4/PEI.
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Figure 11. X-ray fluorescence spectrum of CoFe2O4. The full scale of 39,700 pulses. The cursor is 0.118 (427 pulses).
Figure 11. X-ray fluorescence spectrum of CoFe2O4. The full scale of 39,700 pulses. The cursor is 0.118 (427 pulses).
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Figure 12. SEM image of CoFe2O4.
Figure 12. SEM image of CoFe2O4.
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Figure 13. The IR spectrum of CoFe2O4.
Figure 13. The IR spectrum of CoFe2O4.
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Figure 14. X-ray fluorescence spectrum of CoFe2O4/PEI. The full scale of 32,642 pulses. The cursor is 0.257 (3640 pulses).
Figure 14. X-ray fluorescence spectrum of CoFe2O4/PEI. The full scale of 32,642 pulses. The cursor is 0.257 (3640 pulses).
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Figure 15. Dependence of phenol concentration on oxidation time: (a) in the presence of 1, Fe3O4; 2, CoFe2O4; 3, CoFe2O4/PEI; (b) in the presence of CoFe2O4/PEI: 1, 30 °C; 2, 40 °C; 3, 50 °C; 4, 60 °C; 5, 80 °C.
Figure 15. Dependence of phenol concentration on oxidation time: (a) in the presence of 1, Fe3O4; 2, CoFe2O4; 3, CoFe2O4/PEI; (b) in the presence of CoFe2O4/PEI: 1, 30 °C; 2, 40 °C; 3, 50 °C; 4, 60 °C; 5, 80 °C.
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Figure 16. Absorption spectra of the initial aqueous solution of phenol (a) and oxidation time (b) 1 h (c) 2.0 h.
Figure 16. Absorption spectra of the initial aqueous solution of phenol (a) and oxidation time (b) 1 h (c) 2.0 h.
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Figure 17. IR spectra of the initial aqueous solution of phenol before (a) and after (b) reactions.
Figure 17. IR spectra of the initial aqueous solution of phenol before (a) and after (b) reactions.
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Table
Table 1. Data of elemental analysis of magnetic composite (in wt.%).
Table 1. Data of elemental analysis of magnetic composite (in wt.%).
AreaElements
OAlSiSClCrMnFeTotal
Area 126.510.150.131.131.270.470.4069.94100.00
Area 226.520.120.130.871.340.500.3070.22100.00
Area 326.210.150.111.001.330.470.3370.38100.00
Average26.420.140.121.001.310.480.3470.18100.00
Table
Table 2. Results of Mössbauer spectra of CoFe2O4, CoFe2O4/PEI composites.
Table 2. Results of Mössbauer spectra of CoFe2O4, CoFe2O4/PEI composites.
SampleIS
(mm·s−1)		QS
(mm·s−1)		Heffective (keV)S (%)
Composite CoFe2O40.37−0.2251892
0.310.54-8.0
Composite CoFe2O4/PEI0.37−0.1852020.0
0.28−0.0149534.0
0.41−0.0942317.0
0.39−0.0746921.0
0.420.76-2.0
1.152.42-3.0
0.340.53-3.0
Table
Table 3. Data of elemental analysis of CoFe2O4 (in wt.%).
Table 3. Data of elemental analysis of CoFe2O4 (in wt.%).
AreaElements
OAlSiClCaCrMnFeCoTotal
Area 121.160.170.1214.680.030.190.2243.2820.15100.00
Area 221.290.140.1113.760.050.220.1442.4821.80100.00
Area 320.690.150.1314.810.180.270.2442.5620.98100.00
Average21.050.150.1214.420.090.230.2042.7720.98100.00
Table
Table 4. Data of elemental analysis of CoFe2O4/PEI (in wt.%). Parameters of processing: all elements were analyzed (normalized).
Table 4. Data of elemental analysis of CoFe2O4/PEI (in wt.%). Parameters of processing: all elements were analyzed (normalized).
AreaElements
OAlNaSiClCaCrMnFeCoTotal
Area 123.080.180.710.131.060.140.410.3340.3233.63100.00
Area 224.450.200.720.161.140.120.620.3247.3824.89100.00
Area 323.610.180.770.291.170.120.520.3640.9032.06100.00
Average23.710.190.730.191.120.130.520.3442.8730.19100.00
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Dossumova, B.T.; Shakiyeva, T.V.; Muktaly, D.; Sassykova, L.R.; Baizhomartov, B.B.; Subramanian, S. Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen. ChemEngineering 2022, 6, 68. https://doi.org/10.3390/chemengineering6050068

AMA Style

Dossumova BT, Shakiyeva TV, Muktaly D, Sassykova LR, Baizhomartov BB, Subramanian S. Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen. ChemEngineering. 2022; 6(5):68. https://doi.org/10.3390/chemengineering6050068

Chicago/Turabian Style

Dossumova, Binara T., Tatyana V. Shakiyeva, Dinara Muktaly, Larissa R. Sassykova, Bedelzhan B. Baizhomartov, and Sendilvelan Subramanian. 2022. "Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen" ChemEngineering 6, no. 5: 68. https://doi.org/10.3390/chemengineering6050068

APA Style

Dossumova, B. T., Shakiyeva, T. V., Muktaly, D., Sassykova, L. R., Baizhomartov, B. B., & Subramanian, S. (2022). Synthesis, Characterization of Magnetic Composites and Testing of Their Activity in Liquid-Phase Oxidation of Phenol with Oxygen. ChemEngineering, 6(5), 68. https://doi.org/10.3390/chemengineering6050068

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