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Inhibition of stemness and EMT by taxifolin ruthenium-p-cymene complex via downregulating the SOX2 and OCT4 expression on lung cancer
Arabian Journal of Chemistry (2023) 16, 104393
King Saud University
Arabian Journal of Chemistry
www.ksu.edu.sa
www.sciencedirect.com
ORIGINAL ARTICLE
Nonhydrolytic sol-gel in-situ synthesis of high
performance MgAl2O4/C adsorbent materials
Qian Wu a,b,1, Feng Jiang a,1, Guo Feng b,c,*, Sanhai Wang a, Lifeng Miao b,
Weihui Jiang a,b,*, Jian Liang b, Jianmin Liu b
a
Department of Material Science and Engineering, Jingdezhen Ceramic University, Jingdezhen 333000, China
National Engineering Research Center for Domestic & Building Ceramics, Jingdezhen Ceramic University, Jingdezhen 333000,
China
c
Advanced Ceramic Materials Research Institute, Jingdezhen Ceramic University, Jingdezhen 333000, China
b
Received 4 August 2022; accepted 3 November 2022
Available online 9 November 2022
KEYWORDS
Nonhydrolytic sol-gel;
MgAl2O4;
Congo red;
Removal;
Adsorption;
Adsorption capacity
Abstract MgAl2O4/C composite was prepared via a facile low-temperature non-hydrolytic sol-gel
(NHSG) route, using Mg powder, Al wire and isopropanol as raw materials. The influence of types
of magnesium source and heat treatment temperature on the synthesis and adsorption properties
were investigated, and the adsorption mechanism was also studied. The results showed that the
amorphous MgAl2O4 formed at < 600 °C, and it crystallized at 700 °C. No impurity phase
appeared in the samples calcined at 700–1300 °C, which was attributed to MgAl2O4 crystallized
directly from Mg(Al(OiPr)4)2. The uniform-doped carbon in MgAl2O4/C composites came in-situ
from the organic groups in Mg(Al(OiPr)4)2. MgAl2O4/C showed a superior adsorption capacity
for Congo red (CR). The bimetallic alkoxides structure was favorable for high adsorption property,
and the adsorption property of amorphous MgAl2O4/C was significantly superior to that of its crystalline counterpart. The adsorption kinetics data was fitted with the pseudo-second-order model,
while the Langmuir isotherm model could well descript the adsorption isotherm behavior, and
the maximum adsorption capacity for CR was 5690 mg/g. The high adsorption capacity was attributed to the Lewis acid-base reaction and the electrostatic interactions between the anionic dye CR
and MgAl2O4/C surface as well as the in-situ carbon, and amorphous state.
Ó 2022 Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under
the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Abbreviations: NHSG, non-hydrolytic sol-gel; CR, Congo red; HSG, hydrolytic sol-gel method
* Corresponding authors at: National Engineering Research Center for Domestic & Building Ceramics, Jingdezhen Ceramic University,
Jingdezhen 333000, China.
E-mail addresses: guofeng@jci.edu.cn (G. Feng), jiangweihui@jci.edu.cn (W. Jiang).
1
These authors contributed equally to this work and should be considered co-first authors.
Peer review under responsibility of King Saud University.
Production and hosting by Elsevier
https://doi.org/10.1016/j.arabjc.2022.104393
1878-5352 Ó 2022 Published by Elsevier B.V. on behalf of King Saud University.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
2
1. Introduction
Synthetic dyes are widely applied as raw materials in many industries,
e.g., in textile, leather tanning, plastic, papermaking, rubber and printing (Vidhu et al., 2014). They provide rich color for people’s lives and
make important contributions to industrial development and social
progress. However, it should be noticed that synthetic dyes have
caused serious adverse effects on the water environment. Large quantities of dyestuffs are directly discharged into natural water without
meeting the discharging standards. They can change the color of water,
reduce sunlight penetration and affect the growth of animals and
plants in water resource. Worse, most of the dyes are toxic, even carcinogenic and teratogenicity (Hussain et al., 2020), which poses great
threats to human health and other organisms. Therefore, it is an urgent
task to developing efficient techniques to eliminate dyes in wastewater
before releasing to environment. Numerous methods have been used
for the removal of dyes from wastewater, including enzyme degradation (Kaur et al., 2021), adsorption (Ahmad et al., 2020), ion exchange
process (Cseri et al., 2021), Fenton reaction (Jain, 2018) and photocatalytic oxidation (Gao et al., 2022), etc. Among these methods, adsorption method has considered to be a fairly successful separation method
for wastewater purification, because of its excellent ability to remove
almost any type of dyestuff, high removal percentage, easy operation,
require no complex equipment or without posing secondary pollution
generation (Santhoshkumar et al., 2022). It is well-known that the
identity of adsorbent is crucial to the process of alleviating dyestuff
in wastewater. Therefore, developing efficient adsorbents is of great
importance for the removal of dye molecules from aqueous solutions.
So far, several types of adsorbents, including activated carbon (Ma
et al., 2020), waste material or naturally abundant biomass (Dovi
et al., 2021), clay and minerals (Zhou et al., 2021), metal (hydro) oxide
(Kataria et al., 2017), metal-organic frameworks (MOFs) (Guo et al.,
2020), have been investigated for the removal of dyes from polluted
water. The waste materials, such as peanut husk (Dovi et al., 2021),
pineapple peel (Dai et al., 2020), may have lower cost, but adsorbent
prepared by them usually suffer from poor adsorption capacity. The
merits belonging to MOFs are the high BET surface area, abundant
intramolecular pores, thus having attracted much attentions in the
fields of separation and adsorption. But its disadvantages, such as high
preparation cost, complicated process, are remain unsolved.
In recently years, metal oxides have emerged as promising materials in the area of dyes removal, since their low toxicity, abundant Lewis
acid sites and environmentally friendly (Cao et al., 2021, Zhang et al.,
2016b). One of the most attractive metal oxides is MgAl2O4 (Guo
et al., 2018). It is the unique compound in the Al2O3-MgO binary system. Owing to its excellent properties such as high melting point, good
optical properties, high chemical stability and temperature stability
(Ganesh et al., 2013), MgAl2O4 has been extensively used in refractory,
transparent ceramic, organic dye adsorption, catalyst and catalyst support (Ganesh et al., 2004).
To date, many efforts have been devoted to the preparation of
MgAl2O4 adsorbent. For example, H. Liu et al. (Liu et al., 2022) prepared MgAl2O4 nanoparticles by polyacrylamide gel method with an
adsorption capacity of 89 mg/g for Congo red. J. Tian et al. (Tian
et al., 2015) synthesized MgAl2O4 spinel powders with hierarchical
porous structures via a hard template process with a maximum adsorption capacity (845 mg/g) for Congo red. X. Guo et al. (Guo et al.,
2018) synthesized MgAl2O4 spinel with continuous mesostructured
skeletons and interconnected macropores, which exhibited good
adsorption ability for Congo red (2721 mg/g).
However, the adsorption capacity of the above mentioned MgAl2O4 is poor. Therefore, how to obtain high-efficiency adsorbent for
organic dye removal is in urgent need.
MgAl2O4 is an important oxide that has been fabricated with various methods, including hydrothermal/solvothermal synthesis (Ren
et al., 2015), coprecipitation method (Alvar et al., 2010), sol-gel processing (Milani et al., 2021) and non-hydrolytic sol-gel (NHSG)
Q. Wu et al.
method (Li et al., 2017). Non-hydrolytic sol-gel method (NHSG) is
an attractive wet-chemical method in favor of controlling reaction at
atomic scale. It is proposed by Corriu date back to 19900 s (Corriu
et al., 1992). In contrast to the traditional hydrolytic sol-gel method
(HSG), the sol directly condensed to form the metal-oxide-metal bond
through polycondensation, instead of hydrolyzing to form metal
hydroxides. Hence, there is no need to consider the issue that the
inconsistent hydrolysis rates of different metal alkoxides, which simplifies the process greatly. Moreover, the NHSG method allows reaction
easy to obtain high homogenous mixed gels with different metal ions,
and thus easier to obtain high purity products at lower calcination temperature. Besides, NHSG method is a simple and powerful method to
prepare homogeneous mixed oxide xerogels with mesoporous structure
(Debecker et al., 2013). Whereas only a few researches have synthesized MgAl2O4 by this method. H. Li et al. (Li et al., 2017) prepared
MgAl2O4 nanopowder via NHSG using AlCl3 and MgCl2 as raw materials. MgAl2O4 and MgO coexisted in the as-synthesized sample (calcined at 700–800 °C). The appearance of MgO demonstrated large
number of Mg-O-Mg homogeneous condensation occurred, which
indicating the use of magnesium or aluminum source needed further
optimization.
On the basis of our previous studies (Wu et al., 2022, Jiang et al.,
2021a), MgAl2O4/C adsorbent is prepared via NHSG method in this
work. In NHSG, the sol does not go through metal alkoxide hydrolysis
process but directly turn into gel by the reactants polycondensation.
Therefore, NHSG method allows the heterogeneous polycondensation
products containing carbon instead of hydroxyl (Debecker et al., 2013).
Carbonization of polycondensation products in the heating process is
one of the characteristics of NHSG process. Our previous research
(Zhao et al., 2020b) revealed that the performance of environmental treatment material (Fe2TiO5) was significantly improved by compounding
with in-situ carbon introduced by in situ carbonization of precursors.
There is no similar report in the field of preparing MgAl2O4 adsorption
materials. Therefore, we designed to prepare MgAl2O4/C adsorbent
through the idea that introducing in-situ carbon by NHSG method. To
the best of our knowledge, there is no report about MgAl2O4 adsorbent
or MgAl2O4/C adsorbent for Congo red prepared via NHSG method.
In this work, the influence of types of magnesium source and calcination
temperature on the synthesis and properties of the MgAl2O4/C material
weresystematically investigated. Besides,the presentstudyinvolveda systematically study of the adsorption mechanism. The as-synthesized sampleshowed an ultra-highadsorptioncapacityfor Congored removal from
water. In addition, equilibrium and kinetics studies were performed to
determine the CR adsorption capability of MgAl2O4/C composite adsorbent materials.
2. Experimental
2.1. Chemical reagents
Magnesium fluoride (MgF2, >99.5 %), magnesium chloride
(MgCl2, >99.5 %), aluminum wire (Al, 5 N), isopropanol
(CH3CH(OH)CH3, >99.7 %) were purchased from Sinopharm Chemical Reagent Corporation (Shanghai, China).
Magnesium powder (Mg, 100–200 mesh), iodine (I2,
>99.8 %) and Congo red (C32H22N6Na2O6S2, Ind) was
obtained from Aladdin Industrial Corporation (Shanghai,
China). The above reagents were used without further
purification.
2.2. Samples preparation
The MgAl2O4 sol was prepared by the NHSG method and
MgAl2O4/C adsorbent were obtained by a subsequent calcina-
Nonhydrolytic sol-gel in-situ synthesis
3
tion process. Briefly, 2.160 g aluminum wire and 1.000 g iodine
were carefully added to 100 mL isopropanol, followed by
refluxed under magnetic stirring at 80 °C for 6 h. As the aluminum wire dissolved, a grey transparent solution gradually
formed. Different magnesium source (2.492 g MgF2, 3.818 g
MgCl2 or 0.097 g Mg powder) was added into the solution
above with molar ratio n(Mg)/n(Al) = 1:2 for samples prepared with different magnesium sources, respectively. Keeping
refluxing at 110 °C for 24 h, MgAl2O4 wet gel was obtained. It
was further evaporated to form xerogel and dried at 100 °C for
12 h. Finally, the MgAl2O4/C was achieved after calcining at
different temperatures (200–1300 °C) for 1 h with a 5 °C /
min heating rate. The samples were prepared based on the
steps above, as shown in Fig. 1. Fixing Al wire as aluminum
source, samples of M1, M2, and M3 were obtained by using
MgF2, MgCl2 and Mg powder as magnesium source,
respectively.
solution was measured with UV–vis spectrophotometer
(Lambda 850, PerkinElmer, America). The adsorption capacity (qt, mg/g) of CR adsorption at time t was calculated by
Eq. (1). The isotherm experiments were proceeded in the similar way to the adsorption kinetic experiments. The asprepared adsorbent was placed into CR solution (500–
6000 mg/L), and the adsorbent dosage was kept at 1g/L. Followed by magnetic stirring till reaching the adsorption equilibrium. Subsequently, the mixture was taken out and centrifuged
to determine the residual CR concentration. The equilibrium
adsorption capacity (qe, mg/g) was calculated according to
Eq. (2).
2.3. Characterization
Where C0 (mg/L) is initial concentration of CR; Ct & Ce
(mg/L) are CR concentration at time t and equilibrium concentrations; V (L) is the volume of the CR solution; m (g) is
mass of the adsorbent.
The phases present in the samples were examined by XRD
analysis (D8 Advance, Bruker, Germany) using copper target
Ka radiation at 30 mA and 40 kV. The sol-gel transition process, along with MgAl2O4/C before and after adsorbed CR
were characterized by Fourier transform infrared (FT-IR)
spectroscopy (Nicolet 5700, Thermo, America) in the
wavenumber range 400–4000 cm1. The 27Al solid-state
NMR spectrum of MgAl2O4/C was analysed (400 M, Bruker,
Switzerland) at a Larmor frequency of 10 KHz. The zeta
potential (f-potential) of MgAl2O4/C before and after
adsorbed CR was studied by a zeta potential analyzer (Zetasizer Nano ZS90, Malvern, England). DTA-TG-MS analysis
was conducted by a DTA-TG (STA449C, Netzsch, Germany)
coupled with a mass spectrometer (GMBH QMS403C, Netzsch, Germany). The element distribution of as-prepared
MgAl2O4/C composite were collected by energy dispersive Xray spectroscopy (Model 500i, IXRF, America). Transmission
electron micrograph (TEM) images were obtained with a
JEOL 2010 microscope operated at 200 kV. The surface chemical state of the as-synthesized MgAl2O4/C adsorbent before
and after adsorption were collected by X-ray photoelectron
spectroscopy (K-Alpha + XPS, Thermo Fisher Scientific,
America) with the Al Ka radiation. All spectra were calibrated
using the binding energy of C 1 s (284.8 eV) to compensate for
the surface charging effects. The avantage software was used to
fit the XPS spectra of each relevant element into subcomponents. The nitrogen adsorption experiments of sample calcined
at different temperature were conducted on a nitrogen adsorption apparatus (ASAP2020M, Micromeritics, America).
2.4. Adsorption performance experiments
The adsorption kinetic experiments of MgAl2O4/C were
obtained on the adsorption of Congo red (CR) in water using
batch experiments. Firstly, the MgAl2O4/C adsorbent was
added into a glass beaker containing CR solution. The dosage
of adsorbent was kept at 1 g/L, and solution pH value was
fixed at 7. The beaker was then magnetically stirred with a
speed of 500 rpm/min. Subsequently, a certain amount of sample (3 mL) was taken from the solution and centrifuged at different time intervals, and the concentration of the supernatant
Adsorption capacity at time t : qt ¼
ðC0 Ct ÞV
m
Equilibrium adsorption capacity : qe ¼
ðC0 Ce ÞV
m
ð1Þ
ð2Þ
3. Results and discussion
3.1. Effects of types of magnesium source on the synthesis of
MgAl2O4
Fig. 2 shows the XRD patterns of samples series M1-M3 calcined at 400–1300 °C to study the effects of magnesium source.
Samples series M1, M2 and M3 shown in Fig. 2(a), (b) and (c)
are samples prepared with MgF2, MgCl2 and Mg powders as
magnesium source calcined at different temperatures,
respectively.
As displayed in Fig. 2(a), most MgF2 has not reacted with
aluminium source or participated in non-hydrolytic polycondensation reaction in the sol-gel process. This is because
MgF2 is dfficult to dissolve in isopropanol, which makes it
can not react with aluminium source. After annealing at
900 °C, a-Al2O3 (JCPDS 10–0173) appears in the sample,
which is due to the decomposition of aluminium isopropoxide
obtained in the reaction between aluminiume and isopropanol
(shown in eq. (4)). MgAl2O4 spinel (JCPDS 21–1152) forms at
1000 °C. a-Al2O3 and MgF2 disappear with the temperature
further increasing to 1300 °C. Correspondingly, the intensity
of the peaks belonging to MgAl2O4 spinel phase increases,
which confirms the MgAl2O4 is produced through the reaction
between a-Al2O3 and MgF2 (shown in eq.(5)). The presence of
diffraction peaks of a-Al2O3 and MgF2 at 900–1200 °C also
demonstrates that pure MgAl2O4 phase can not be synthesized
before 1300 °C. In summary, the formation of MgAl2O4 in M1
sample mainly due to the solid phase reaction between MgF2
and Al2O3 when using MgF2 as magnesium source, instead
of through NHSG route.
I2
2Al þ 6ðCH2 Þ2 CHOH ! 2AlðC3 H7 OÞ3 þ 3H2 "
80 C
ð3Þ
D
ð4Þ
D
ð5Þ
2AlðC3 H7 OÞ3 þ 27O2 ! Al2 O3 þ 21H2 O þ 18CO2 "
2Al2 O3 þ 2MgF2 þ O2 ! 2MgAl2 O4 þ 2F2 "
4
Q. Wu et al.
Fig. 1
Fig. 2
Samples preparation process.
XRD patterns of samples M1(a), M2(b), M3(c) calcined at different temperatures.
When MgCl2 is used as magnesium source, after heattreatment at 700 °C, the diffraction peaks of MgAl2O4 spinel
(JCPDS 21–1152) appear, indicating that the formation of
MgAl2O4 spinel crystalline phase. However, the impurity
phase of MgO (JCPDS 45–0946) is also observed at 500–
1300 °C. The presence of MgO is due to the ionic character
of MgCl2. The electrongativity of magnesium and chlorine element in MgCl2 is 1.2 and 3.0, respectively. According to Eq.
(6), the ionic character percentage of Mg-Cl bond is calculated
to be 55.5 %, which demonstrates that MgCl2 possess relative
ionic character. Consequently, the nonhydrolytic polycondensation reaction is difficult to be adequate (Feng et al., 2018).
Part of MgCl2 exists in solvent isopropanol in the form of
Mg2+ and Cl-, which ultimately lead to the formation of MgO.
Pi ð%Þ ¼ 1 exp½ðXA XB Þ2 =4
ð6Þ
In sharp contrast to the XRD results of M1 and M2, only
one phase of MgAl2O4(JCPDS 21–1152) can be detected in the
sample M3, no impurity peak is observed during the whole
temperatures range.
To further study the NHSG process when using Mg powder
and Al wire as raw material, Fig. 3 presents the FT-IR spectra
of samples of M3 at different reaction stages: (a) isopropanol;
(b) mixtures of Mg powder and Al wire with isopropanol (after
refluxing at 110 °C for 24 h); (c) xerogel; (d) powder calcined at
700 °C for 1 h.
The FT-IR spectrum of (a) isopropanol shows absorption
peaks at 817 & 952 & 1129 &1162 cm1, 1310 & 1378 &
1467 cm1, 2886 & 2973 cm1, 663 & 3382 cm1, correspond-
Nonhydrolytic sol-gel in-situ synthesis
5
ing to the stretching vibration of CAO bond, the asymmetric
stretching vibration of CAH, the asymmetry stretching mode
of CH3 groups, the bending vibration and stretching vibration
of OAH bond in the isopropanol, respectively (Ermini et al.,
2000). These demonstrate a characteristic FT-IR spectrum of
isopropanol.
In FT-IR spectrum of (b)mixture of Mg + Al+(CH3)2CHOH (after refluxing at 110 °C for 24 h), the bending vibration at 663 cm1 ascribing to OAH bond of isopropanol
disappears, and the broad bond at 3382 cm1 assigned to
OAH bond becomes weaker. It can be concluded that isopropanol has already reacted. In addition, it is worth mention
that the absorption peak located at 817 cm1 which associated
to the CAO stretching vibration belonging to isopropanol shift
to a lower wavenumber of 813 cm1 and became weaker.
These indicate the formation of C-(O-Mg) bond
(Thanabodeekij et al., 2003). Furthermore, the absorption
peaks of 457 and 613 cm1 are related to the stretching vibration of AlAO and CA(OAAl) (Alinejad et al., 2008). The peak
at 613 cm1 is significantly broader than that of the typical CA
(OAAl) bonds (Li et al., 2017), which indicates the existence of
AlAO and MgAOAAl bond. Based on the analysis above, the
chemical reaction between Mg, Al and isopropanol is displayed in Eq. (7) (Liu et al., 2013):
ð7Þ
Fig. 3(c) illustrates the FT-IR spectrum of xerogel, it can be
seen that the bond associated with the C-(O-Al) at 613 cm1
become stronger, whereas the peak at 457 cm1 (Al-O) disappears, demonstrating the further reaction of Al-O bond to
form Mg-O-Al bond. It is mainly due to the polycondensation
reaction happens between MgAl2(OiPr)8, which further
increases the Mg-O-Al bond. The reaction is shown in Eq.
(8) (Wu et al., 2022, Turova et al., 2002).
Fig. 3 FT-IR spectra of (a) (CH3)2CHOH, (b) precursors
mixture, (c) xerogel, (d) powder calcined at 700 °C.
located at 66, 37, and 8 ppm can be associated to Al3+ ions
in tetrahedral [AlO4], hexahedral [AlO5] and octahedral
[AlO6] coordination, respectively (Düvel et al., 2011). These
coordination unsaturated Al-species (AlO4 and AlO5) are
derived from polycondensation reaction between MgAl2(OiPr)8. It is generally believed that the coordination unsaturated
Al-species exhibit high activity (Sarou et al., 2013). Notably,
the coordinatively unsaturated Al-species accounted for a large
proportion in the MgAl2O4/C composite adsorbent.
Fig. 5 shows the effect of contact time on the adsorption
process of sample M1, M2 and M3 calcined at 300 °C. The initial concentration of CR is 1000 mg/L. The samples obtained
at 300 °C are labeled as M1-300, M2-300 and M3-300, respectively. Fig. 6 shows the schematic diagram of the products of
gel powder prepared from three magnesium sources after heat
treatment at 300 ℃.
It can be seen from Fig. 5 that the adsorbents obtained
from the three different magnesium sources exhibit distinct dif-
ð8Þ
After calcination at 700 °C (Fig. 3(d)), two broad absorption bands appear at 528 and 707 cm1, corresponding to
the vibration of Mg-O-Al network in the MgAl2O4 (Sanjabi
et al., 2015). These indicate the formation of MgAl2O4 spinel.
The high-resolution 27Al solid state NMR spectrum of sample M3 obtained at 300 °C is shown in Fig. 4. The peaks
ferent adsorption performance for CR solution. Among them,
the MgAl2O4 sample prepared with magnesium powder as
magnesium source shows the highest adsorption capacity
(98.89 mg/g) for CR, followed by the MgCl2 (543.95 mg/g)
and the MgF2 (19.51 mg/g). Therefore, it can be speculated
that the sample M3 which possesses the bimetallic alkoxides
6
Q. Wu et al.
ture can effectively adsorb CR, while amorphous aluminium
isopropoxide and MgCl2 cannot. Therefore, the adsorption
performance of M2-300 is at the value between M1-300 and
M3-300.
3.2. Effect of calcination temperature on the adsorption
performance
Fig. 4
27
Al NMR of M3-300 adsorbent.
Fig. 5 Adsorption capacity of the sample M1-300, M2-300 and
M3-300 for CR removal with the change of contact time.
structure is favorable for the adsorption of CR solution. XRD
patterns shown in Fig. 2 demonstrate that the three different
magnesium sources have different phase transition process.
These correspond to the different proceed degree of nonhydrolytic heterogeneous polycondensation reaction, and ultimately lead to their difference in adsorption performance.
Sample M1-300 is composed of amorphous aluminium isopropoxide and MgF2, because MgF2 cannot dissolve in isopropoxide. The saturated Al3+ and Mg2+ ions in aluminium
isopropoxide and MgF2 lead to poor adsorption performance.
However, when using Mg powder as magnesium source, tetracolecular association structure (Wu et al., 2022, Turova et al.,
2002) shown in the right part of equation (8) formed in sample
M3-300 through the polycondensation between MgAl2(OiPr)8.
The Al3+ and Mg2+ irons in tetracolecular association structure are mostly unsaturated, which guarantees the excellent
adsorption performances of M3-300. Sample M2-300 contains
tetracolecular association structure, amorphous aluminium
isopropoxide and MgCl2. The tetracolecular association struc-
Fig. 7(a) illustrates the relationship between adsorption capacity and initial concentration when using sample M3 prepared
at different temperatures as adsorbents. The maximal adsorption capacities variation with calcination temperature are
shown in Fig. 7(b). The samples calcined at 200–900 °C are
labelled as M3-200, M3-300, M3-400, M3-500, M3-600, M3200, M3-800 and M3-900, respectively.
The results reveal that calcination temperature has a significant influence on the adsorption capacity toward CR solution.
It can be seen from Fig. 7(b) that the maximal adsorption
capacity is calculated to be 5723.15, 5710.12, and 5612.12,
5564.51 mg/g for M3-300, M3-400, M3-500 and M3-600,
respectively. Thereby, M3-300 adsorbent displays the optimum
adsorption efficiency among all these samples, which is slightly
higher than the adsorption capacity of M3-400, M3-500 and
M3-600. Taking M3-300 adsorbent as an example, it can be
seen from Fig. 7 (a) that the adsorption capacities qe increase
linearly with the increase of initial concentration C0 (at the
range of 600–5000 mg/L), the linear growth of adsorption
capacities qe is retarded under further increase of initial concentration, and then the adsorption capacities qe gradually
become a fixed value (at the range of 5000–6500 mg/L). It
reveals that sample M3-300 exhibits excellent adsorption
capacity toward CR solution.
However, the maximum adsorption capacity of M3-700,
M3-800 and M3-900 decrease significantly with the elevating
of temperature. Samples M3-700, M3-800 and M3-900 only
have the adsorption capacities of 934.72, 611.99 and
425.76 mg/g. This significant decreasing of adsorption capacities of M3-700, M3-800 and M3-900 is mainly due to the crystallization of MgAl2O4 spinel at 700 °C. There are abundant
coordinative-unsaturated Al3+ and Mg2+ in the tetracolecular
association structure at the temperatures below 700 °C. In the
process of MgAl2O4 crystallization, the unsaturated Al3+ and
Mg2+ irons transfer to the saturated Al3+ and Mg2+ in
MgAl2O4, which leads to the reduction of adsorption
performance.
Meanwhile, it should also be noted that sample M3-200,
which is also amorphous, exhibits a lower adsorption capacity
than M3-300. In order determine the reason for causing this
difference, Fig. 8 shows the DTA-TG-MS curves of the xerogel
of M3. There are three stages for the decomposition of xerogel
in the air atmosphere. The first stage locates in the temperature
ranges from room temperature to 126 °C, which corresponds
to a weight loss of 4.79 %. This endothermic peak centered
at 76 °C is associated with the further removal of solvent isopropanol and polycondensation by-product isopropyl ether.
The second stage involves a wide-broad endothermic peak
accompanied by a mass loss of 31.42 %, and the endothermic
peak is in the range of 160–600 °C centered at 227 °C. This
endothermic peak can be ascribed to the carbonization of
the skeleton of residual organic groups in the xerogel and
Nonhydrolytic sol-gel in-situ synthesis
Fig. 6
7
Schematic diagram for the effect of magnesium source on the CR adsorption.
Fig. 7 (a) adsorption capacity of the sample M3 calcined at different temperatures for CR removal with the change of initial
concentration, (b) maximal adsorption capacity of sample M3 calcined different temperatures.
the emission with burning of residual organic groups. After the
temperature of 600 °C, the third weight loss stage in the thermogravimetric curve is observed, and it is attributed to the
slowly oxide of the carbon-containing group, which lays the
foundation for the preparation of MgAl2O4/C composite.
These are the reasons that sample M3-300 with the carbonization exhibits the higher adsorption capacity than that of sample M3-200. Besides, thermogravimetry (TG) curve
of > 300 °C is shown in Fig. 8(b). The total weight loss varies
in the range of 74.34–54.88 wt%. According to the mass of the
sample tested and the final weight loss in the test process (Zhao
et al., 2020b), the carbon-containing residual content of M3300 is calculated to be 26.15 wt%.
In addition, the emissions of the MS curves of xerogel
shown in Fig. 8(c)(d) present high concentration emissions
and low concentration emissions, respectively. These emissions
+
include C3H+ (225 °C), C3H+
2 (225 °C), C3H3 (225 °C),
+
+
+
C3H4 (225 °C),C3H5 (225 °C), C3H6 (225 °C), H2O+
(260 °C), OH–(252 °C）and CO+
(188 °C & 301 °C &
2
455 °C), respectivelyH2O+ (260 °C) shows the strongest emission in the temperature ranges from 120 to 600 °C, and OH–
(252 °C) also exhibit a high emission in the range of 120–
500 °C. These two points suggest that a great number of O
8
Q. Wu et al.
Fig. 8 (a) DTA-TG curves of the xerogel, (b) TG curve of the xerogel from 300 °C to 1100 °C, (c-d)MS curves of various products
during thermal decompositon.
and H originated from residual organic group releasing during
the heat treatment of the xerogel, which ensures in situ C residue to form MgAl2O4/C composite material.
The formation mechanism of OH– from the residual
organic group can be explained as follows. In contrast to
MgAl2O4 crystal phase, M3 sample calcined at the
temperatures < 600 °C has an amorphous structure, the amorphous MgAl2O4 are composed of abundant coordinativeunsaturated Mg2+ and Al3+. Both Mg2+ and Al3+ are strong
Lewis acid, they can coordinate strongly with oxygencontaining groups. This process makes oxygen-containing
groups undergo strong polarization during calcination and
decompose into various free radicals or radical association
compounds (Martra et al., 2000, Suh et al., 1992). The emission of H2O+ can be attributed to the H contained in isopropyl combined with OH–, then ultimately caused the
carbonization of residual organic group. In addition, as can
be seen from Fig. 8(c), the group of C3H+
7 emission occurs
at 189 °C. It is worth mention that a series group of C3H+,
+
+
+
+
C3H+
2 , C3H3 , C3H4 , C3H5 and C3H6 emit at 225 °C, which
are the isopropyl group (-C3H7) that have lost hydrogen with a
higher emitting concentration. These are the specific reasons
ensure the residual of carbon in the system.
As presented in Fig. 8(d), the continuous escape of C3H+
4
after 300 °C demonstrated that in-situ carbon in the MgAl2O4/
C may exist in the form of C3H+
4 . During the adsorption process, the existence of C3H+
4 in the MgAl2O4 adsorbent is benefit to improve the wetting process between organic pollutants
and adsorbent, leading to the promoting of the adsorption,
and carbon itself is also a commonly used adsorbent. Based
on the analysis above, the groups emission-carbonization process in the heating process of xerogel is shown in Fig. 9.
3.3. Adsorption kinetics
The contact time dependence of the adsorption capacity at different initial concentrations is shown in Fig. 10. The adsorbent
shows a very fast adsorption rate, when the initial concentration of CR solution is 500, 1000 and 2000 mg/L. Its time
required is only 20, 120 and 270 min, respectively. The quick
adsorption is ascribed to the abundant sorption sites on the
surface of MgAl2O4/C adsorbent material.
Nonhydrolytic sol-gel in-situ synthesis
Fig. 9
9
Schematic illustration of the whole transition process of xerogel during heating process.
To further analyze the adsorption mechanism, the kinetics
of CR adsorption on the MgAl2O4/C composite were investigated by pseudo-first-order (PFO) and pseudo-second-order
(PSO) kinetics models. The corresponding linear equations of
the two kinetic models are shown in Eq. (9) and (10), respectively. Fig. 11 illustrates the fitted straight lines, and Table 1
displays the values of kinetic parameters calculated according
to the two equations.
ln ðqe qt Þ ¼ ln qe k1 t
ð9Þ
t
t
1
¼ þ
qt qe k2 q2e
ð10Þ
Where k1 (min1) and k2 (g/mgmin) are rate constants of
pseudo-first and second-order models, respectively.
As observed, the straight lines in Fig. 11(b) show a better
match with the experimental data points compared with those
in Fig. 11(a). According to Table 1, it can be seen that experimental results agree well with the PSO kinetic model. Because
the R2 (correlation coefficients) values for this model are closer
to 1 (0.993–0.997), and the R2 calculated from PFO model is
much lower (0.728–0.821). In addition, the as-measured experimental adsorption capacity data [qe(exp)] can match better to
the calculated adsorption capacity values [qe(cal)] obtained by
PSO model than that from PFO kinetic model. Therefore, it
can be seen that the adsorption process of MgAl2O4/C fitted
better with the PSO model, and it is reasonable to conclude
that chemical adsorption is probably-one of the rate-limiting
steps.
3.4. Adsorption isotherms
The adsorption isotherms were used to reveal the relationship
between the amount of CR adsorbed and the constant equilib-
10
Q. Wu et al.
1
Lnqe ¼ LnKF þ LnCe
n
ð12Þ
Where KL (L/mg) is the Langmuir adsorption constant, KF
is the Freundlich constant, and n is the adsorption intensity
factor.
Fig. 13 illustrates the fitted results using isotherm equations, and the determined parameters of both isotherm models
are presented in Table 2. As shown in Fig. 13 and Table 2, the
Langmuir model fitted better to the adsorption data. Because
the Langmuir model gave higher correlation coefficients
(R2 = 0.9996) than that of the Freundlich equations
(R2 = 8057), so the CR is adsorbed on the surface of MgAl2O4/C composite in a monolayer coverage.
The as-prepared MgAl2O4/C with outstanding adsorption
capability is superior to other previously reported magnesium
oxide based and alumina based metal (hydro)oxides adsorbents shown in Table 3.
Fig. 10 Contact time dependence of the adsorption capacity at
different initial concentrations.
rium concentration of CR in the liquid phase. The adsorption
isotherms of MgAl2O4/C composite are shown in Fig. 12. The
equilibrium adsorption quantity increases with the increase of
equilibrium concentrations and then reaches adsorption
saturation.
To attain profound information about the adsorption
behavior and mechanism, two well-known adsorption isotherms have been selected to analyze the experimental adsorption results. They are Langmuir and Freundlich isotherm
models. The linearized forms of the two models can be
expressed by Eqs. (11) and (12), respectively. The Langmuir
model is used to described monolayer adsorption, and it
assumes the adsorption occurs on the homogenous surface of
adsorbent. The Freundlich model stands for the heterogeneous
adsorption and multilayer adsorption patterns.
1
1
1
1
¼
þ
qe KL qmax Ce qmax
ð11Þ
3.5. Adsorption mechanisms analysis
FT-IR was used to further investigate the interaction between
MgAl2O4/C composite adsorbent and CR in the adsorption
process. The spectra of MgAl2O4/C, CR and CR-adsorbed
MgAl2O4/C are performed and displayed in Fig. 14. For
MgAl2O4/C before adsorption (curve (a) in Fig. 14), two
strong vibration bonds centered at around 528 and 707 cm1
appear. These bonds correspond to the characteristic bond
of Al-O-Mg vibrations from MgAl2O4/C (Dash et al., 2017).
In the IR spectrum of CR (curve (c) in Fig. 14), the adsorption peak appears at 3459 cm1 is ascribed to the stretching
vibration of NAH bond (Cao et al., 2021). The peak at
1548 cm1 can be attributed to the stretching vibration of
azo group (AN‚NA) (Cao et al., 2021). The peak at
1616 cm1 is associated with C‚C stretching vibration in benzene (Wang et al., 2013), and the peaks at 1226, 1178 and
1062 cm1 are ascribed to the stretching vibration of S‚O
in sulfonate group (ASO23 ) (Cao et al., 2021). In comparison
with the FT-IR spectrum of the pure MgAl2O4/C and CR, it
is noticed that several obvious changes appear after adsorption. The ANH2 group peak (at 3459 cm1) shifts to a lower
Fig. 11 (a)linearly fitted kinetic curves for CR adsorption according to the linear equations for pseudo-first-order, (b) pseudo-secondorder kinetics.
Nonhydrolytic sol-gel in-situ synthesis
Table 1
C0/mg/L
500
1000
2000
11
Parameters for adsorption kinetics of MgAl2O4/C (sample M3-600).
qe (exp) / mg/g
499.63
998.84
1997.65
Pseudo-first order
Pseudo-second order
qe cal
k1*10-2
R2
qe cal
K2*10-2
R2
138.15
1284.55
2497.78
5.67
7.78
2.25
0.728
0.765
0.821
510.20
1137.76
2375.21
0.066
0.0033
0.0007
0.997
0.993
0.997
Fig. 12 Equilibrium isotherms of MgAl2O4/C for CR adsorption. (Initial CR concentration = 2000–6000 mg/L, adsorbent
dose = 1 g/L, T = 30 °C).
position (3425 cm1). It merges with the OH stretching vibration bond of the MgAl2O4/C (3384 cm1). It can be explained
by the Lewis acid-base interaction between Mg2+ and Al3+ on
the MgAl2O4 and ANH2 on CR molecules. According to Pearson‘ s hard-soft acid-base (HSAB) principle, Mg2+ and Al3+
are both hard Lewis acid site, and ANH2 is belong to a hard
Lewis base site. They tend to combine with each other to form
Fig. 13
more stable bonds (Wang et al., 2020). Furthermore, after
adsorption on the MgAl2O4/C, it is evident that the sharp
bond at 1062 cm1 which relate to S‚O stretching vibration
occurs at a lower wavenumber of 1048 cm1. The shift of
S‚O bond, which ascribe to the characteristic peak of sulfonate group (ASO23 ) in CR molecules, indicates that the stability of S‚O bond on CR decreases. The results above verify
that Congo red molecules have successfully adsorbed onto the
surface of MgAl2O4/C.
XPS measurement was performed to further study the surface chemical states and surface composition of MgAl2O4/C
adsorbent before and after adsorption of CR. The XPS test
results are shown in Fig. 15. The XPS survey profile of MgAl2O4/C reveals four major sets of peaks corresponding to Mg 1 s,
Al 2p, O 1 s and C 1 s. In addition, no other impurity peaks are
detected. The carbon peak is attributed to the residual carbon
in the sample and hydrocarbons from the XPS instrument
(Ansari et al., 2019).
As shown in Fig. 15, CR-adsorbed MgAl2O4/C exhibits
obvious Na, N and S peaks besides to MgAl2O4/C relative
peaks. This confirms the existence of CR onto MgAl2O4/C.
No other significant changes are observed in the spectra after
CR adsorption, which suggests that no secondary pollutant
is generated during the adsorption process (Beheshti et al.,
2018).
For more specific insight comparisons before and after CR
adsorption, high-resolution XPS spectra of Mg 1 s, Al 2p, N
1 s and S 2p, collected from adsorbents, pure CR powders
and CR-adsorbed adsorbent were carefully recorded. The
results are shown in Fig. 16. As shown in Fig. 16(a), for the
Corresponding linearly fitted isotherms: Langmuir isotherm (a) and Freundlich isotherm (b).
12
Table 2
Q. Wu et al.
Parameters in linearized Langmuir and Freundlich isotherms for CR adsorption.
Langmuir isotherm
Freundlich isotherm
KL (L/mg)
qm (mg/g)
R2
KF (L/mg)
n
R2
0.1085
5690.19
0.9996
1777.41
4.5149
0.8057
Table 3 The maximum adsorption capacity for Congo red by
different adsorbents for comparison.
Adsorbent type
Adsorption
capacity
(mg/g)
Reference
MgAl2O4/C
MgO nanofiber
20 % MgO-SiO2
MgO hollow microspheres
MgAl2O4
MgO nanoparticles
MgO sphere
Porous MgO
Mesoporous cAl2O3 nanofibers
Flower-like Mg/Fe-LDO
Fe2O3Al2O3 composite
porous MgAl2O4
Al2O3@ZnO
MgO/GO
c-Al2O3/ZnFe2O4
g-Al2O3
Mg–Al-LDH
MgAl2O4 nanoparticles
5690
4802
4000
3022
2721
2375
1928
1638
1323
this work
Yu et al., 2018
Hu et al., 2018
Dai et al., 2018
Guo et al., 2018
Zhang et al., 2019
Ahmad et al., 2019
Zhao et al., 2020a
Li et al., 2021
1250
941
845
714
684
413
370
305
89
Mubarak, 2021
Jiang et al., 2021b
Tian et al., 2015
Zheng et al., 2019
Guo et al., 2021
Sun et al., 2018
AlSalihi et al., 2022
Sriram et al., 2020
Liu et al., 2022
Mg 1 s and Al 2p spectra, the peaks located at 1303.73 eV and
74.43 eV are shown in the MgAl2O4/C, and both of them shift
to higher binding energy positions (1304.38 eV and 74.73 eV)
after CR adsorption, indicating some charge transfer to the
Mg and Al during the process of adsorption (Carley et al.,
1996).The N 1s peak of CR can be divided into two peaks,
and they are 399.45 eV (C‚N) and 401.88 eV (ANH2)
(Xiong et al., 2021).After the adsorption of CR onto MgAl2O4/C, the peak position of-NH2 shifts to a higher binding
energy position, suggesting that the N containing groups are
responsible for strong chemical bonding which can lead to
electron density change (Aoopngan et al., 2019).
Furthermore, S 2p spectra of CR (Fig. 16d) can be divided
into two peaks. Peaks of S1 (168.45 eV) and S2(169.74 eV) are
related to S 2p1/2 and S 2p3/2 of sulfonic group (-SO23 ) of CR
molecules. After CR adsorption onto the surface of MgAl2O4/
C, the S 2p peaks shift to lower binding energies (168.34 and
169.60 eV) slightly, further suggesting that electrostatic attraction occurs via the -SO23 groups of Congo red (Aoopngan
et al., 2019).
Here zeta potential analysis is applied to study the surface
charge of the adsorbent in aqueous solution at pH = 7.
Fig. 17 illustrates the change of zeta potential value before
and after CR adsorption. It is clear that the adsorbent
obtained at 700 °C possesses electropositive surface, with the
zeta potential values of 7.62 mV. After adsorption of CR,
the zeta potential of MgAl2O4/C adsorbent changed from positive to negative. As known, Congo red is polar molecules, it
Fig. 14 (a)FT-IR spectra of MgAl2O4/C, (b) MgAl2O4/C after
CR adsorption and (c) pure CR.
Fig. 15
XPS spectra of samples.
exists in the form of anions and cations in both alkaline and
acidic aqueous. Its isoelectronic point is about 3. Therefore,
when adsorbent MgAl2O4/C is dispersed in CR aqueous at
pH = 7, the negatively charged CR can be adsorbed by the
positive charged MgAl2O4/C due to the electrostatic
attraction.
The N2 adsorption–desorption isotherms of samples calcined at different temperatures are presented in Fig. 18. Table 4
Nonhydrolytic sol-gel in-situ synthesis
13
Fig. 16 XPS spectra of (a) Mg 1s, (b) Al 2p on the surface of MgAl2O4/C before and after removal of CR, (c) N 1s, and (d) S 2p on the
surface of CR and MgAl2O4/C after CR adsorption.
Fig. 17 Zeta potentials of sample prepared at 600 °C before
(black) and after CR adsorption (red).
lists corresponding characterized data. The samples prepared
at 200, 300, 600 and 700 °C are M3-200, M3-300, M3-600
and M3-700, respectively.
As shown in Fig. 18(a), sample M3-200 has the smallest
amount of adsorption of N2, which is about 2 cm3/g, and
the BET of M3-200 is only 0.79 m2/g. However, in Fig. 18(b-d), the amount of N2 adsorption and BET specific surface
area of M3-300, M3-600 and M3-700 are evidently higher than
M3-200. Besides, all the three isotherms (Fig. 18b-d) show the
hysteresis loop when the P/P0 in the range of 0.3–0.8. Based on
the IUPAC classification (Zhang et al., 2016a), this kind of isotherms could be classified as the type IV curve, suggesting the
presence of mesopores in their structure. Moreover, the hysteresis loop obtained in M3-300 and M3-600 are evidently
broader than M3-700 within the range of P/P0 = 0.3–0.8. It
is well-known that the phenomenon of capillary condensation
will occur in the middle-pressure sections (P/P0 = 0.3–0.8)
when the sample has a mesoporous structure, and this is the
root cause for the hysteresis of N2 desorption curve. Therefore,
it can be concluded that higher quantity of mesoporous exist in
M3-300 and M3-600 than M3-700. Besides, it can be seen in
Fig. 18(d) that M3-700 has large amount of adsorption in
14
Fig. 18
Q. Wu et al.
N2 adsorption–desorption isotherms of samples calcined at different temperatures: (a) 200 °C (b) 300 °C (c) 600 °C (d) 700 °C.
Table 4 The surface area, pore volume, and pore diameter of
the samples prepared at different temperatures.
temperatures
BET specific surface area
(m2g1)
Pore
volume
(cm3g1)
Pore
diameter
(nm)
200
300
600
700
0.79
84
79
70
0.001
0.05
0.11
0.12
26.8
3.7
6.2
7.5
the high-pressure sections (0.8–1.0), which is nearly 30 cm3/g.
Essentially, the quantity of N2 adsorption belong to M3-600
shows a flatlining growth, which is only 11 cm3/g. This flatlining growth indicates that less large pores exist in the sample
calcined at 600 °C. These results indicate that the sample
M3-300 and M3-600 shows a mesoporous structure, which is
favorite to the adsorption of CR solution.
Fig. 19 illustrates the TEM images of M3-600. It is clearly
seen that numerous mesopores distributed in the sample.
Fig. 19 (b) show the pore diameter is about 6.56 nm, which
Fig. 19
(a)(b) TEM images of sample M3-600.
is in good agreement with the result determined via BarrettJoyner-Halenda (BJH) method shown in Table.4.
Fig. 20 shows the SEM (a) and EDS mapping (b-e) of
adsorbent M3-300. The images displayed in Fig. 20 demonstrated that the signal of C is appeared, verifying the existence
of C in the adsorbent. Moreover, the C element distributes
homogeneously, and matches with the dispersion of Mg, Al
Nonhydrolytic sol-gel in-situ synthesis
Fig. 20
15
SEM image of (a) MgAl2O4/C adsorbent, EDS mapping of (b-e) Al, Mg, O and C.
Fig. 21
Schematic illustration of the CR adsorption process on to MgAl2O4/C.
and O elements. These findings indicate that the in-situ
carbon-containing composite can be prepared by the NHSG
method, through forming a carbon-containing precursor.
The element composition of M3-300 was studies by EDS as
shown in Fig.S1, the atomic fractions of C is 13.496 %.
Based on the MgAl2O4/C before and after adsorbing CR
identified by FT-IR spectra, XPS spectra, zeta potential,
TEM and N2 adsorption–desorption results, along with the
adsorption kinetics and isotherms, a possible adsorption mechanism of MgAl2O4/C composite to CR is proposed and shown
in Fig. 21.
According to the zeta potential analysis, electrostatic
attraction involves in the adsorption process. The negatively
charged sulfate group (-SO23 ) on CR molecules are attracted
by the unsaturated Mg2+ and Al3+ on the MgAl2O4/C composite surfaces. Furthermore, according to the pseudo-
16
second-order kinetics evaluation, chemical adsorption dominates the adsorption process. It is confirmed that such chemical adsorption is Lewis acid-base interaction between
unsaturated Mg2+/Al3+ on the MgAl2O4/C nanocomposite
as the hard Lewis acid site and ANH2 on CR as the hard Lewis
base site (Ansari et al., 2019). Meanwhile, the presence of insitu carbon is benefit to improve the wetting process between
organic pollutants and adsorbent, leading to the promoting
of the adsorption. Besides, the adsorption process is also driven by the pore filling, this was confirmed by the mesoporous
structure of as-prepared MgAl2O4/C nanocomposite observed
from TEM and N2 adsorption–desorption analysis.
Overall, these mechanisms might take effect synergistically
to endow the MgAl2O4/C composite with such a high adsorption capacity. Specifically, it is the uniformly dispersed
microstructure, electrostatic attractions, mesoporous structure, homogenous mixing of unsaturated Mg, Al and C elements, and more exposure of Lewis acid sites (Guo et al.,
2020) that have enabled such high adsorption properties.
4. Conclusions
The MgAl2O4/C composite adsorbent was prepared by the NHSG
method. The MgAl2O4/C composite with pure MgAl2O4 phase and
without impurity phase could be obtained only when using magnesium
powder as magnesium source. The in-situ C came from the organic
groups in Mg(Al(OiPr)4)2, which was formed in the xerogel reacted
from the precursors of Mg powder, Al wire and isopropanol. The
uniform-dispersed C was originated from residual organic groups
–
+
+
+
through removal of C3H+, C3H+
2 , C3H3 , C3H5 , C3H6 , OH ,
H2O+, CO+
2 at 225 °C, 260 °C and 188 °C &301 °C &455 °C. The
adsorption kinetics and isotherms studies for MgAl2O4/C composites
followed the pseudo-second-order and Langmuir model. The MgAl2O4/C composite adsorbent prepared at 300 °C exhibited a maximum
adsorption capacity for CR was up to 5690 mg/g. This was due to
abundant coordinatively unsaturated Mg and Al irons in amorphous
MgAl2O4, the electrostatic interactions between the anionic dye CR
and MgAl2O4/C surface, in-situ formed C as well as pore filling.
Acknowledgments
This work was supported by the National Natural Science
Foundation of China [grant numbers 52072162, 51962014,];
Jiangxi Provincial Natural Science Foundation, China, [grant
numbers 20202ACBL214006, 20202BABL214013]; the Jingdezhen
ceramics
major
special
project,
China,
(2021ZDGG001); the Jingdezhen science and technology planning project, China, (2020GYZD013-09); the Science Foundation of Jiangxi Provincial Department of Education, China,
(GJJ211315).
Appendix A. Supplementary material
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.arabjc.2022.104393.
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