The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst
Samples of precipitated SnO2 were modified by means of mechanochemical and microwave treatment. Physicochemical properties of all samples were investigated using DTA, XRD, FTIR spectroscopy, nitrogen adsorption-desorption and UV-Vis spectroscopy. Photocatalytic activity was evaluated us...
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V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine
2023
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Catalysis and petrochemistry| _version_ | 1872009059151904768 |
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| author | Samsonenko, Mariia M. Khalameida, Svitlana V. |
| author_facet | Samsonenko, Mariia M. Khalameida, Svitlana V. |
| author_institution_txt_mv | [
{
"author": "Mariia M. Samsonenko",
"institution": "Institute for Sorption and Problems of Endoecology of the National Academy of Sciences of Ukraine, 13 General Naumov Str., Kyiv 03164, Ukraine"
},
{
"author": "Svitlana V. Khalameida",
"institution": "Institute for Sorption and Problems of Endoecology of the National Academy of Sciences of Ukraine, 13 General Naumov Str., Kyiv 03164, Ukraine"
}
] |
| author_sort | Samsonenko, Mariia M. |
| baseUrl_str | https://kataliz.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2024-12-24T10:38:54Z |
| description | Samples of precipitated SnO2 were modified by means of mechanochemical and microwave treatment. Physicochemical properties of all samples were investigated using DTA, XRD, FTIR spectroscopy, nitrogen adsorption-desorption and UV-Vis spectroscopy. Photocatalytic activity was evaluated using the degradation of rhodamine B and safranin T under Vis-irradiation. It was found that the initial precipitated and modified samples correspond to the composition of tin oxyhydroxide - SnO(OH)х. It has been established that as a result of mechanochemical and microwave treatment of tin oxyhydroxide in the wet gel stage, it is possible to obtain photocatalytically active materials with a uniform mesoporous structure and high specific surface values and a band gap of about 3.5-3.6 eV. A peculiarity of the mechanochemical treatment of xerogels in water is the formation of a meso-macroporous structure. Relationship between physicochemical and photocatalytic properties of prepared samples has been discussed. The dependence of the efficiency of photocatalytic degradation of dyes on changes in the porous structure, the presence of defects on the surface of the catalyst, and its electronic characteristics was established. |
| doi_str_mv | 10.15407/kataliz2023.34.073 |
| first_indexed | 2026-03-12T15:50:19Z |
| format | Article |
| fulltext |
Каталіз та нафтохімія, 2023, №34 73
Catalysis and Petrochemistry, 2023, 34
UDC 544.72
https://doi.org/10.15407/kataliz2023.34.073
The influence of mechanochemical and microwave modification
on the properties of SnO2 as photocatalyst
Mariia M. Samsonenko, Svitlana V. Khalameida
Institute for Sorption and Problems of Endoecology of National Academy of Sciences of Ukraine
13 Naumov Str., Kyiv, 03164, Ukraine, e-mail: mashuna.08@gmail.com
Samples of precipitated SnO2 were modified by means of mechanochemical and microwave treatment.
Physicochemical properties of all samples were investigated using DTA, XRD, FTIR spectroscopy, nitrogen
adsorption-desorption and UV-Vis spectroscopy. Photocatalytic activity was evaluated using the degradation of
rhodamine B and safranin T under Vis-irradiation. It was found that the initial precipitated and modified samples
correspond to the composition of tin oxyhydroxide - SnO(OH)х. It has been established that as a result of
mechanochemical and microwave treatment of tin oxyhydroxide in the wet gel stage, it is possible to obtain
photocatalytically active materials with a uniform mesoporous structure and high specific surface area and a band
gap of about 3.5-3.6 eV. A peculiarity of the mechanochemical treatment of xerogels in water is the formation of
a meso-macroporous structure. Relationship between physicochemical and photocatalytic properties of prepared
samples has been discussed. The dependence of the efficiency of photocatalytic degradation of dyes on changes in
the porous structure, the presence of defects on the surface of the catalyst, and its electronic characteristics was
established.
Keywords: SnO2, mechanochemical and microwave treatment, porous structure, photocatalytic activity,
dyes, Vis-irradiation
Introduction
Tin dioxide is one of the wide-gap semiconductor materials with a complex of physicochemical
and functional properties [1-3]. Its characteristics determine the possibility of using SnO2 in adsorption
and catalytic processes aimed at monitoring the condition and protecting the environment. For example,
extraction of ions from wastewater and natural waters, photocatalytic degradation of pollutants in the
aquatic environment and determination of the content of harmful substances in the air, etc. [1-5].
The efficiency of SnO2 in these processes is determined by a set of physical and chemical properties,
namely its crystalline and porous structure, specific surface area, morphology, surface condition, thermal and
mechanical stability, and the possibility of granulation. The complex of specified characteristics should have
optimal values for the effective use of tin dioxide in adsorption and catalytic processes.
Regulation of the physicochemical characteristics and, as a result, the functional properties of
precipitated tin dioxide can be carried out both at the synthesis stage (traditional deposition, sol-gel
method and template synthesis), and through its following treatment – “post-synthetic modification” [6]
(thermal and hydrothermal treatment). It is known that SnO2 precipitated from aqueous solutions is, as a
rule, an amorphous hydrated oxide with a high specific surface area and a microporous structure, with a
band gap in the range of 4.2-3.6 eV. The use of various methods of synthesizing tin dioxide from
aqueous solutions allows to vary the physicochemical parameters of the obtained samples only to a
certain extent. In particular, it is difficult to obtain a developed mesoporous structure using the sol-gel
method and deposition, but it is possible when using the template method. Also, only the template
method of synthesis allows forming the perfect crystalline structure of cassiterite. In addition, these
methods of synthesis have a number of difficulties and disadvantages in their practical application: the use
74 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
of a significant amount of water for washing samples makes them eco-insensitive, and the use of expensive
templates and precursors, the need for high temperatures for annealing the templates - expensive and
energy-consuming. In turn, thermal and hydrothermal treatments are widely used as methods of modifying
oxide materials, in particular for tin dioxide. These types of processing make it possible to widely vary the
physicochemical parameters of tin dioxide samples processed in the form of gels and xerogels, in
particular textural characteristics [7]. But the use of thermal treatment doesn`t allow reducing the
absorption edge and the width of the band gap of tin dioxide to the dimensions that condition activity in
visible light. At the same time, hydrothermal treatment requires fairly harsh conditions and the use of
special equipment that operates at high temperatures and pressures. Therefore, there is a need to develop
cheaper, environmentally friendly and simple methods of synthesis and modification.
There is a group of simpler and more effective methods of “green chemistry” for the synthesis and
modification of catalysts and sorbents, which use non-convective energy supply to the system [8-11]. They
allow to obtain results close to those for hydrothermal method, but using simpler equipment and lower
temperatures, as well as significantly reduce the duration of the process. In addition, despite a significant
number of publications, research in these areas continues to actively develops. Thus, recently, the rapid
development of mechanochemistry and its prospects for the chemical synthesis and modification of oxide
materials, as well as the conduct of catalytic reactions under MChT, was recently recognized at the level of
the International Union of Theoretical and Applied Chemistry (IUPAC) [12]. Despite the large number of
publications devoted to mechanochemical treatment (MChT) of oxide materials, their number is
insignificant for tin dioxide. The existing works describe only the mechanochemical synthesis of tin (II)
oxide followed by its transformation into tin (IV) oxide during thermal treatment at 350-800 °C. In turn,
microwave treatment (MWT) is a promising method that allows to realize hydrothermal conditions in a
more economical and ecologically beneficial way and to vary the parameters of the crystalline and porous
structure of tin dioxide. However, post-synthetic modification of SnO2 powders and xerogels and the study
of the effect of these treatment methods on the surface structure and parameters of the crystalline, porous,
and electronic structures, as well as the functional properties of tin dioxide, remain almost unexplored.
Thus, the advantages and efficiency of using these methods to modify other oxides and hydroxides make
them interesting and relevant for the search for ways to modify laboratory and commerсial samples of tin
dioxide.
Experiment
Synthesis of SnO2 samples. Two series of tin dioxide samples were obtained by heterogeneous
and homogeneous precipitation from water solutions (Fig. 1).
Modification of SnO2 samples. Wet gels and xerogels were subjected to mechanochemical and
microwave treatments. Mechanochemical treatment was carried out using a planetary ball mill
“Pulverisette-7” (“Fritsch”, Germany) in air and water for 0.5 h at 300 and 500 rpm. High-pressure
reactor “NANO 2000” (“Plazmotronika”, Poland) was used for microwave treatment. It was carried out
at temperatures of 165-235 °C for 0.5-1 hours.
Physicochemical studies of modified samples. The physicochemical properties of the modified
samples were investigated by the following methods. Differential thermal analysis (DTA-TG) was
carried out using the Derivatograph-C device in the temperature range of 20-800 °С and heating rate of
10°С/min. XRD analysis was performed on a Philips PW1830 diffractometer with CuKα radiation
(λ = 0.15406 nm). The crystallite sizes L were calculated using the Debye-Scherrer equation (1):
Каталіз та нафтохімія, 2023, №34 75
Catalysis and Petrochemistry, 2023, 34
cos*
*89.0
L , (1)
where 0.89 is a constant, λ = 0.154 nm is the wavelength, nm, β is the width at half height of the peaks,
measured from the diffractogram, degrees, Ɵ is the Bragg angle from the diffractogram.
Fig. 1. The scheme for obtaining wet gels and xerogels of SnO2 by hetero- and homogeneous precipitation
FTIR spectra were recorded using spectrophotometer “Spectrum-One” (Perkin-Elmer Instruments) in
the range of 4000-400cm−1 in reflection mode. The adsorption-desorption isotherms of nitrogen were
recorded using analyzer ASAP 2405N (Micromeritics Instrument Corp). The specific surface areas S,
sorption pore volume Vs, micropores Vmi and mesopores volume Vme were calculated from isotherms using
the BET, t- and the BJH methods. The total pore volume VƩ was determined by ethanol impregnation of the
samples granules dried at 150 °C. The volume of macropores Vma was calculated as the difference between
VΣ and VS. The diameter of the mesopores dme was calculated from the pore size distribution curves (PSD) by
the BJH method. UV-Vis spectra of the initial and modified samples SnO2 in the wavelength range of
200-800 nm were obtained using a Lambda 35 UV - Vis spectrophotometer with Labsphere RSA-PE-20
attachment (Perkin-Elmer Instruments). The value of the band gap Eg was calculated according to Planck’s
formula (2):
5.1239
gE , (2)
where λ is the absorption edge, nm.
Photocatalytic studies of modified samples. The study of the photocatalytic activity of all
samples was carried out by the degradation of dyes (rhodamine B, safranin T) under the action of visible
light in an aqueous medium (1·10–5 mol/l). Below are the structural formulas of the dyes used:
Rhodamine B Safranin T
76 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
At first, to achieve adsorption equilibrium, the dye solution (80 ml) and the catalyst (80 mg) were
stirred for 30 minutes in a glass reactor without irradiation. In the future, irradiation was carried out with
a Philips LED Cool daylight LED lamp with a power of 100W for 10 hours. Sampling of irradiated
solutions was carried out at certain time intervals. Catalysts were separated from the solution by
centrifugation. A spectrophotometer UV-2450 (Shimadzu) was used to determine the dye concentration
in these solutions. Photodegradation rate constants Kd were obtained by analyzing the change in optical
density of the substrates solution at 553 and 520 nm for RhB and ST, respectively using the first-order
kinetic equation. The degree of discoloration of solutions as criterium of substrates degradation was
determined using spectrophotometric data. The degree of pollutants mineralization was calculated as
decrease in the total organic carbon TOC [13, 14] using a TOC analyzer 5050A (Shimadzu).
Results and Discussion
Physicochemical properties. It was found that the initial precipitated and modified samples
correspond to the composition of tin oxyhydroxide - Sn3O4(OH)4. On the DTA-TG curves for the initial
sample of the precipitated xerogel of tin oxyhydroxide (Fig. 2 a), it is possible to observe a mass loss of
Δmexp of 5.7 wt. % when the temperature is increased to 800 °С, which corresponds to the value of
x = 1.15. Similar DTA-TG results were obtained when SnO2 powder forms were obtained from
hydroxides [15]. During mechanochemical treatment (MChT), partial removal of OH groups occurs,
which is evidenced by a decrease in the value of the calculated coefficient x (Table 1). Microwave
treatment (MWT), like MChT, but to a greater extent, helps to reduce the number of OH groups. A ratio
of the number of structural OH groups to Sn for the modified sample is 0.53 (Table 1). However, in the
latter case, the composition of the sample is closer to SnO2. The obtained results are confirmed by IR
spectroscopy.
Fig. 2. The DTA–TG curves for tin oxyhydroxide: initial xerogel (a),that after MChT in air (b) and that
after MWT gel
Каталіз та нафтохімія, 2023, №34 77
Catalysis and Petrochemistry, 2023, 34
Table 1. Mass losses Δmеxp and coefficient x for initial and modified samples of SnO(OH)х
Samples x Δmеxp, %
SnO(OH)х
xerogel initial 1.15 5.7
xerogel MChT air 600 rpm 1.13 5.6
xerogel MChT H2O 600 rpm 1.12 5.6
gel МChT 600 rpm. 0.91 4.5
gel MWT 235 °C 1 h 0.53 2.6
In FTIR spectra (Fig. 3) of the initial and modified samples SnO(OH)2, absorption bands are
observed in the area of vibrations of the frame and vibrations of OH groups. Thus, several absorption
bands can be distinguished in the region of vibrations of the tin dioxide framework (700-400 cm–1): at
660 and 579 cm–1, which relate to the vibrations of bridging bonds in O-Sn-O and the Sn-O(H) terminal
group, respectively [16-19]. Their position after MChT of heterogeneously and homogeneously
precipitated samples changes by approximately 5-10 cm–1, which indicates a certain disorganization of
the structure of tin dioxide. As a result of the modification, the intensity of the absorption bands at 930
and 1245 cm–1, which are related to the deformation vibrations of different types of OH-groups [20, 21],
decreases. Similarly, the intensity of absorption bands decreases in the region of valence vibrations of
OH groups (3000-3500 cm–1). Thus, the greatest loss of OH groups occurs during MChT of gels. It
should be noted that treatment speed contributes to this process. Similar results were obtained for SnO2
powders after MChT [22]. Absorption bands at 1635 and 2430 cm–1 correspond to oscillation of С=О
and residual CO2 from the atmosphere, respectively [23].
Fig. 3. FTIR-spectra of samples of the tin oxyhydroxide samples: initial (1) as well as those after MChT
of xerogel in water (2), in air (3) and MChT of gel (4)
XRD analysis indicates that the initial sample has an imperfect crystal structure corresponding to
the tetragonal modification of cassiterite (JCPDS (No. 41-1445)) (Fig. 4). During mechanochemical
treatment, the phase composition of the samples does not change. Diffraction peaks (110), (101), and
(211) at 2θ = 26.5°, 33.8°, and 51.9°, respectively, are observed both with dry MChT and with MChT in
water. But at the same time, all modified samples are characterized by a slight increase in the intensity of
reflexes, compared to the initial SnO(OH)2 (Fig. 4, Table 2). This is probably related to the dispersion
processes and changes in the structure of primary particles that occur during MChT. For example, the
intensity of the reflex for the (110) plane (2θ = 26.5°) for sample after dry MChT increases by 1.8 times
78 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
compared to the initial SnO(OH)2, and after MChT in water – by 1.4 times. In turn, the size of the
crystallites increases when calculated in the direction of the (110) plane (Table 2).
Table 2. Crystallite sizes L and interplanar distances d for modified SnO(ОН)2 samples calculated by
the Debye-Scherrer and Wolff-Bragg equations from XRD data
Samples hkl L*, nm β**, degree d***, nm
S
nO
(O
H
) 2
initial
(110) 2.02 4.04 0.334
(101) 3.14 2.64 0.265
(211) 2.09 4.22 0.176
MChT air 600 rpm
(110) 2.29 3.56 0.336
(101) 3.22 2.58 0.265
(211) 2.08 4.24 0.176
MChT H2O 600 rpm
(110) 2.05 3.97 0.329
(101) 3.53 2.35 0.265
(211) 2.03 4.35 0.176
MWT xerogel 165 °C 0.5h
(110) 3.07 2.7 0.336
(101) 2.55 3.2 0.264
(211) 3.76 2.3 0.177
MWT gel 185 °C 0.5h
(110) 2.20 3.7 0.333
(101) 2.06 4.0 0.264
(211) 2.51 3.5 0.176
MWT gel 235 °C 1h
(110) 1.95 4.2 0.336
(101) 1.85 4.5 0.265
(211) 2.24 3.9 0.176
MWT 270 °C
(110) 2.25 3.6 0.336
(101) 1.98 4.2 0.265
(211) 2.53 3.5 0.177
* L - crystallite size, nm; **β - width at half height of the peak, degree; ***d - interplanar distance, nm
Fig. 4. XRD for samples tin oxyhydroxide: initial (1) and that after MChT in air (2), MChT in water
(3), MWT of gel at 185 °C (4) and MWT of xerogel at 165 °C (5)
Каталіз та нафтохімія, 2023, №34 79
Catalysis and Petrochemistry, 2023, 34
For samples of tin oxyhydroxide after MWT, with an increase in the treatment time and
temperature, an increase in the intensity of reflexes I and the size of crystallites L is observed (Table 2),
which correlates with the results of DTA-TG and indicates the processes of transformation of an
amorphous crystalline structure into a more crystalline one, close to crystalline SnO2. [24]. For example,
the intensity of I reflexes for a sample after MWT in the gel stage at 185 °C for 0.5 h increases by
1.5 times, and at 235 °C and 95 atm for 1 h – by almost 3 times, compared to the initial sample. At the
same time, the size of L crystallites increases by 2 times (Table 2). Similar processes occur during
hydrothermal treatment, but at higher temperatures and during longer treatment [25].
Nitrogen adsorption-desorption isotherms and pore size distribution curves for the initial and
modified samples SnO(OH)2 are shown in Fig. 5 a, b. The isotherms of the initial tin oxyhydroxide
samples belong to type I. For samples after dry MChT and MChT in water, they are close to type I. In
turn, the isotherms of samples after MChT gels are similar to the initial ones, but a sharp rise is observed
in the region of high values of P/P0 > 0.9. The parameters of the porous structure of initial and modified
samples SnO(OH)2, calculated from the nitrogen adsorption-desorption isotherms, are given in Table 3.
Fig. 5. N2 adsorption-desorption isotherms and pore size distribution (BJH method) (inset) for
SnO(OH)2 samples (a): initial (1), after MChT air at 300 rpm (2), after MChT H2O at 300 rpm (3), after
MChT gel at 300 rpm (4); (b): initial (1), after MWT xerogel at 165 °C (2), after MWT gel at 235 °C (3)
The initial samples have high specific surface area and a high content of micropores [25-27]. Dry
MChT leads to a decrease in the specific surface area S and volume of micropores Vmi. At the same time,
with MChT in water, there is an increase in VΣ and a slight decrease in S. A feature of MChT of dry
xerogel in water is the formation of secondary porosity represented by macropores, which is indicated by
the excess of VƩ values over the values of the sorption volume of VS pores (Table 3). This effect of
MChT on the porous structure corresponds to previously obtained results for other oxides and
hydroxides [20, 28]. It should be noted that the parameters of the porous structure of the samples after
MChT gels remain almost unchanged compared to the initial samples. A slight increase in the specific
surface area and sorption volume is observed, as well as a slight decrease in the volume of mesopores
and the size of primary particles.
The isotherms of the samples SnO(OH)2 after MWT (Fig. 5 b) belong to different types. Thus,
the isotherm of the sample after MWT at the wet gel stage at 185 °C for 0.5 h is close to type I. At the
same time, the isotherms of other modified samples belong to type IV and have clearly defined
80 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
hysteresis loops close to types H2 and H3. This indicates that the mesoporous structure of tin dioxide is
formed during MWT. Moreover, when SnO(OH)2 is modified in the form of xerogels, a change in the
type of isotherms is observed already after 0.5 h of treatment and at lower temperatures, compared to
samples of tin oxyhydroxide modified at the gel stage. Similar trends are characteristic of SnO2 after
hydrothermal treatment [25, 29, 30]. The parameters of the porous structure calculated from the
isotherms are given in Table 3. In the case of MWT of tin oxyhydroxide xerogel, the specific surface
area S and volume of micropores Vmi decrease, the total VΣ and sorption volume VS of pores, the volume
Vме and diameter d мe of mesopores increase. In turn, during the MWT gel of tin oxyhydroxide, a certain
increase in the specific surface area S, an increase in the VΣ and sorption volume VS volume of pores, and
the formation of meso- and macropores are observed within 0.5 h. During further processing for 1 hour,
the specific surface area S decreases and the volume Vме and diameter d мe of mesopores increase.
Table 3. Influence of mechanochemical and microwave treatment on the parameters of the porous
structure of initial and modified SnO(ОН)2 samples
Samples
S,
m2 /g
VƩ,
cm3/g
VS,
cm3/g
Vmiі ,
cm3/g
Vme ,
cm3/g
Vma ,
cm3/g
d me,
nm
SnO(ОН)2
initial 178 0.10 0.05 0.08 0.02 - 2.3
MChT air 300 rpm 138 0.08 0.08 0.04 0.03 - 4.1
MChT air 600 rpm 135 0.16 0.07 0.04 0.02 0.09 5.4
MChT H2O 300 rpm 163 0.33 0.10 0.04 0.05 0.23 4.3
MChT H2O 600 rpm 159 0.27 0.08 0.04 0.03 0.19 3.8
MChT gel 300 rpm 180 0.17 0.09 0.04 0.04 0.08 2.4
MChT gel 600 rpm 183 0.13 0.08 0.04 0.03 0.04 3.7
MWT xerogel 165 °C 0.5 h 166 0.17 0.17 0.00 0.17 - 3.7
MWT xerogel 175 °C 1 h 92 0.14 0.12 0.00 0.12 0.02 5.8
MWT gel 185 °C 0.5 h 183 0.31 0.11 0.00 0.11 0.20 2.7
MWT gel 235 °C 1 h 156 0.25 0.25 0.00 0.25 - 4.3
In the electronic spectra in the Kubelka-Munk coordinates (Fig. 6) for the initial and modified
samples SnO(OH)2, there are absorption bands that are characteristic of tin dioxide (260-290 nm) [20, 31-
32] After MChT SnO(OH)2, a bathochromic shift of the absorption edge is observed from 302 nm to 312
nm for the initial sample and after MChT in water, respectively (Table 4). This contributes to a decrease in
the value of the band gap from 4.1 to 3.9 eV and an increase in light absorption from 14 to 19 % (Table 4).
Fig. 6. UV- Vis spectra for SnO2 samples: initial (1); after MChT in air (2), after MChT in H2O (3),
after MChT of gel (4), after MWT of xerogel (4) and gel (6)
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Catalysis and Petrochemistry, 2023, 34
After MWT, as after MChT, there is a shift of the absorption edge λ to the long-wave region
from 302 nm to 335 nm for initial sample and the sample after MWT at the xerogel stage at 165 °С for
0.5 h, respectively. Due to this, there is a narrowing of the band gap to 3.56 eV (Table 4), and the
absorption of visible light A increases by two times, compared to the initial sample. Such changes in
electronic characteristics can be associated with the transformation of oxyhydroxide into tin dioxide, as
well as the formation of structural defects [32].
Таble 4. The effect of mechanochemical and microwave treatment on the electronic properties of initial
and modified tin oxyhydroxide samples
Samples λ *, nm Еg **, eV A***,%
S
nO
(O
H
) 2
initial 302 4.2 14
MChT air 300 rpm 311 3.98 18
MChT H2O 300 rpm 312 3.97 19
MChT gel 300 rpm 309 4.01 10
MWT xerogel 165 °C 0.5 h 373 3.32 11
MWT gel 185 °C 0.5 h 370 3.35 7
* λ - absorption edge, nm; ** Eg - band gap width, eV; ***A - light absorption at 550 nm, %
Photocatalytic activity. The previously described changes in the physicochemical characteristics
of modified tin oxyhydroxide samples contributed to changes in their photocatalytic activity. Studies of
the photocatalytic activity of the initial and modified samples show that the initial precipitated samples
SnO(OH)2 are inactive in the photodegradation processes of safranin T and methyl orange under the
influence of visible light. Also, they have low photocatalytic activity in relation to rhodamine B, only
partial deethylation of rhodamine B occurs. The degradation constants of rhodamine B are about 2*10–5s–1,
and the degree of decolorization in 2 h is 16-22 % (Table 5).
Таble 5. Photocatalytic activity of modified tin oxyhydroxide samples
Samples
Rhodamine B Safranin T
Kd×105, s–1
Degree of
discoloration, %
Kd×105, s–1
Degree of
discoloration, %
Initial 2.9 16 n.a. n.а.
MChT air 300 rpm 93.2 96 1.5 78
MChT H2O 300 rpm 101.0 95 3.3 86
МChT gel 300 rpm 49.6 98 1.6 60
MWT xerogel 165 °C 0.5 h - - 3.1 76
MWT xerogel 175 °C 1 h - - 3.2 71
MWT gel 185 °C 0.5 h - - 3.3 85
MWT gel 235 °C 1 h - - 3.3 83
* n.а. – non active
Modification of precipitated tin oxyhydroxide by MChT and MWT leads to an increase in
photocatalytic activity under Vis-irradiation. This is confirmed by changes in the electronic absorption
spectra of the solutions of the dyes used. It can be seen that stepwise deethylation of rhodamine B and
degradation of rhodamine 110 at different rates are observed for samples of precipitated SnO(OH)2 after
МChT and МWT (Fig. 7). SnO(OH)2 modified by MChT and MWT also acquires photocatalytic
activity in the process of safranin T degradation under visible light (Fig. 8). Indicators of photocatalytic
activity, namely: constants of photocatalytic degradation of rhodamine B and safranin T under visible
82 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
light and the degree of discoloration are given in Table 5.1. For example, the degradation rate constant
Kd of rhodamine B increases from 0.2 to 10.1×10–4 s–1 (Table 5), and the degradation rate constant of
safranin T reaches (1.5-3.4)×10–5 s–1 (Fig. 5). In turn, the degree of decolorization of dye solutions when
using modified samples reaches 86-98 %.
Fig. 7. Temporal spectral changes of RhB in the presence of SnO(OH)2 sample after MChT of gel at 300 rpm
Fig. 8. Temporal spectral changes of safranin T in the presence of SnO(OH)2 sample after MWT of the
xerogel at 165 °C for 0.5 h
It was also shown that in the process of photodegradation of dyes, not only discoloration of
solutions occurs, but also mineralization. The degree of mineralization is calculated by the decrease in
the content of total organic carbon (TOC) and shows the degree of transformation of organic substances
into less harmful inorganic ones. For modified samples of tin dioxide, the degree of mineralization of the
studied dyes is 60-80 %. Probably, the increase in photocatalytic activity as a result of mechanochemical
and microwave modification of the precipitated tin oxyhydroxide can be associated with the preservation
of a high specific surface area, the formation and expansion of mesopores (from 2.3 to 5.4 nm), as well
as the introduction of defects into the structure of the modified samples SnO(OH)2 (Urbach tail). The
latter causes an additional increase in dye adsorption on the surface of the photocatalyst and absorption
of visible light by the photocatalyst. It is worth noting that the amount of adsorption of dyes increases
monotonically with increasing intensity of tin oxyhydroxide treatments, and the band gap width Eg
Каталіз та нафтохімія, 2023, №34 83
Catalysis and Petrochemistry, 2023, 34
decreases into varying degrees. An increase in the photocatalytic activity of the modified samples may
indicate that visible light is absorbed by the dye, as a result of which the dye molecules are excited,
followed by electron injection into the conduction zone of the photocatalyst, which is characteristic of
the photosensitization process [33].
Conclusions
The work studied the modification of precipitated tin oxyhydroxide using mechanochemical and
microwave treatments under various conditions and established the possibility of regulating its
physicochemical characteristics. It was found that the application of mechanochemical and microwave
treatment of tin oxyhydroxide at the wet gel stage leads to the formation of a homogeneous mesoporous
structure with high values of specific surface area (178-183 m2/g), pore volume (0.11-0.25 cm3/g) and
mesopore diameter (2.4-5.4 nm). In turn, mechanochemical treatment of xerogels in water allows to
form a meso-macroporous structure. At the same time, microwave treatment contributes to the formation
of a more perfect structure of the samples. Both types of modification help reduce the band gap of tin
dioxide from 4.19 to 3.56 eV and increase the absorption of visible light by 2 times, due to the presence
of structural defects (i.e., Urbach energy). As a result, the photocatalytic activity of modified samples of
tin oxyhydroxide increases under the action of visible light.
Acknowledgements
The authors are grateful to the junior scientific researcher L. Kotynska (Institute for Sorption and
Problems of Endoecology NAS of Ukraine, Kyiv, Ukraine) and doctor hab J. Skubiszewska-Zięba (Maria Curie-
Skłodowska University, Lublin, Poland) for their help and support in the experiment.
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Надійшла до редакції 31.07.2023
Каталіз та нафтохімія, 2023, №34 85
Catalysis and Petrochemistry, 2023, 34
Вплив механохімічного та мікрохвильового модифікування на властивості
SnO2 як фотокаталізатора
Mарія М. Самсоненко, Світлана В. Халамейда
Інститут сорбції та проблем ендоекології Національної академії наук України
вул. Генерала Наумова, 13, Київ, 03164, Україна, mashuna.08@gmail.com
Зразки осадженого SnO2 модифікували за допомогою механохімічної та мікрохвильової обробки.
Фізико-хімічні властивості всіх зразків були досліджені за допомогою ДТА, РФА, FTIR-спектроскопії,
адсорбції-десорбції азоту та UV-Vis спектроскопії. Фотокаталітичну активність під дією видимого світла
оцінювали за допомогою розкладу родаміну Б і сафраніну Т у водному середовищі. Показано, що вихідні
осаджені та модифіковані зразки відповідають складу оксигідроксиду олова – SnO(OH)х. Встановлено, що
в результаті механохімічної та мікрохвильової обробки оксигідроксиду олова на стадії вологого гелю
можна отримати фотокаталітично активні матеріали з однорідною мезопоруватою структурою та
високими значеннями питомої поверхні та шириною забороненої зони близько 3.5-3.6 еВ. Особливістю
механохімічної обробки ксерогелів у воді є утворення мезо-макропоруватої структури. Обговорено
зв’язок між фізико-хімічними та фотокаталітичними властивостями модифікованих зразків. Встановлено
залежність ефективності фотокаталітичної деградації барвників від зміни поруватої структури, наявності
дефектів на поверхні фотокаталізатора та його електронних характеристик.
Ключові слова: SnO2, механохімічна та мікрохвильова обробка, порувата структура,
фотокаталітична активність, барвники, видиме світло
|
| id | oai:katalizorgua:article-94 |
| institution | Catalysis and petrochemistry |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-03-12T15:50:19Z |
| publishDate | 2023 |
| publisher | V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | katalizorgua/00/86a784ec6653d207da384446a738b800.pdf |
| spelling | oai:katalizorgua:article-942024-12-24T10:38:54Z The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst Samsonenko, Mariia M. Khalameida, Svitlana V. SnO2, mechanochemical and microwave treatment, porous structure, photocatalytic activity, dyes, Vis-irradiation SnO2, mechanochemical and microwave treatment, porous structure, photocatalytic activity, dyes, Vis-irradiation Samples of precipitated SnO2 were modified by means of mechanochemical and microwave treatment. Physicochemical properties of all samples were investigated using DTA, XRD, FTIR spectroscopy, nitrogen adsorption-desorption and UV-Vis spectroscopy. Photocatalytic activity was evaluated using the degradation of rhodamine B and safranin T under Vis-irradiation. It was found that the initial precipitated and modified samples correspond to the composition of tin oxyhydroxide - SnO(OH)х. It has been established that as a result of mechanochemical and microwave treatment of tin oxyhydroxide in the wet gel stage, it is possible to obtain photocatalytically active materials with a uniform mesoporous structure and high specific surface values and a band gap of about 3.5-3.6 eV. A peculiarity of the mechanochemical treatment of xerogels in water is the formation of a meso-macroporous structure. Relationship between physicochemical and photocatalytic properties of prepared samples has been discussed. The dependence of the efficiency of photocatalytic degradation of dyes on changes in the porous structure, the presence of defects on the surface of the catalyst, and its electronic characteristics was established. Зразки осадженого SnO2 модифікували за допомогою механохімічної та мікрохвильової обробки. Фізико-хімічні властивості всіх зразків були досліджені за допомогою ДТА, РФА, FTIR-спектроскопії, адсорбції-десорбції азоту та UV-Vis спектроскопії. Фотокаталітичну активність під дією видимого світла оцінювали за допомогою розкладу родаміну Б і сафраніну Т у водному середовищі. Показано, що вихідні осаджені та модифіковані зразки відповідають складу оксигідроксиду олова – SnO(OH)х. Встановлено, що в результаті механохімічної та мікрохвильової обробки оксигідроксиду олова на стадії вологого гелю можна отримати фотокаталітично активні матеріали з однорідною мезопоруватою структурою та високими значеннями питомої поверхні та шириною забороненої зони близько 3.5-3.6 еВ. Особливістю механохімічної обробки ксерогелів у воді є утворення мезо-макропоруватої структури. Обговорено зв’язок між фізико-хімічними та фотокаталітичними властивостями модифікованих зразків. Встановлено залежність ефективності фотокаталітичної деградації барвників від зміни поруватої структури, наявності дефектів на поверхні фотокаталізатора та його електронних характеристик. V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine 2023-09-07 Article Article application/pdf https://kataliz.org.ua/index.php/journal/article/view/94 10.15407/kataliz2023.34.073 Catalysis and petrochemistry; No. 34 (2023): Catalysis and petrochemistry; 73-85 Каталіз та нафтохімія; № 34 (2023): Каталіз та нафтохімія; 73-85 2707-5796 2412-4176 10.15407/kataliz2023.34 en https://kataliz.org.ua/index.php/journal/article/view/94/86 Copyright (c) 2023 Catalysis and petrochemistry |
| spellingShingle | SnO2 mechanochemical and microwave treatment porous structure photocatalytic activity dyes Vis-irradiation Samsonenko, Mariia M. Khalameida, Svitlana V. The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_alt | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_full | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_fullStr | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_full_unstemmed | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_short | The influence of mechanochemical and microwave modification on the properties of SnO2 as photocatalyst |
| title_sort | influence of mechanochemical and microwave modification on the properties of sno2 as photocatalyst |
| topic | SnO2 mechanochemical and microwave treatment porous structure photocatalytic activity dyes Vis-irradiation |
| topic_facet | SnO2 mechanochemical and microwave treatment porous structure photocatalytic activity dyes Vis-irradiation SnO2 mechanochemical and microwave treatment porous structure photocatalytic activity dyes Vis-irradiation |
| url | https://kataliz.org.ua/index.php/journal/article/view/94 |
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