Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/SnO2-Sb/Er-PbO2 anode

Article abstract of DOI:10.1016/j.cclet.2020.03.073

Electrochemical degradation of sulfamethoxazole (SMX) and its metabolite acetyl-sulfamethoxazole (Ac-SMX) by Ti/SnO₂-Sb/Er-PbO₂ were investigated. Results indicated that the electrochemical degradation of SMX and Ac-SMX followed pseu

Full text of DOI:10.1016/j.cclet.2020.03.073

G Model
CCLET 5571 No. of Pages 5
Chinese Chemical Letters xxx (2019) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Communication
Insights into the electrochemical degradation of sulfamethoxazole and
its metabolite by Ti/SnO2-Sb/Er-PbO2 anode
a
b
Yanping Wanga,b, Chengzhi Zhoub, , Jinhua Wu , Junfeng Niu
*
a
School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
Research Center for Eco-Environmental Engineering, Dongguan University of Technology, Dongguan 523808, China
b
A R T I C L E I N F O
A B S T R A C T
Article history:
Electrochemical degradation of sulfamethoxazole (SMX) and its metabolite acetyl-sulfamethoxazole (Ac-
SMX) by Ti/SnO2-Sb/Er-PbO2 were investigated. Results indicated that the electrochemical degradation of
SMX and Ac-SMX followed pseudo-first-order kinetics. The rate constants of SMX and Ac-SMX were 0.268
and 0.072 min-1 at optimal current density of 10 and 14 mA/cm2, respectively. Transformation products of
SMX and Ac-SMX were identified and the possible degradation pathways, including the cleavage of S-N
bond, opening ring of isoxazole and nitration of amino group, were proposed. Total organic carbon
removal of SMX was nearly 63.2% after 3 h electrochemical degradation. 22.4% nitrogen of SMX was
transformed to NO3-, and 98.8% sulfur of SMX was released as SO42-. According to quantitative structure-
activity relationship model, toxicities of SMX and Ac-SMX to aquatic organisms significantly decreased
after electrochemical degradation. Electric energy consumption for 90% SMX and Ac-SMX degradation
was determined to be 0.58-8.97 and 6.88-44.19 Wh/L at different experimental conditions, respectively.
Compared with parent compound SMX, the metabolite Ac-SMX is more refractory and toxic, which
emphasizes the importance of taking its metabolites into account when investigating the disposal of
pharmaceuticals from wastewater.
Received 21 January 2020
Received in revised form 3 March 2020
Accepted 28 March 2020
Available online xxx
Keywords:
Electrochemical degradation
Sulfamethoxazole and metabolite
Degradation mechanism
Quantitative structure-activity relationship
© 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Antibiotics are now well recognized recalcitrant pollutants
owing to their widespread use in human and animal diseases, poor
reduction in traditional sewage treatment plants and pseudo
persistence in water environment [1,2]. Sulfamethoxazole (SMX) is
one of the mostly used antibiotics for the treatment of urinary tract
infections, respiratory infections, chronic bronchitis and meningi-
tis. This antibiotic is frequently detected in wastewater effluents
(100-2500 ng/L), surface waters (60-150 ng/L) and drinking waters
(12 ng/L) [3,4]. Although SMX is detected with trace concentration,
the relative persistence will lead to its accumulation and result in
ecotoxicological effects, such as drug resistance and carcinogenic
activity [5,6]. In addition, nearly 86% of ingested SMX is excreted as
metabolites, not in its original form. Acetyl-sulfamethoxazole (Ac-
SMX), the primary metabolite of SMX, is reported to be more
persistent than its parent compound SMX. And the concentrations
of Ac-SMX detected in wastewaters and surface waters are
comparable to the parent compound SMX [7–10]. Thus, the
elimination of SMX and its metabolites from wastewater is urgent
and noteworthy.
Advanced oxidation processes (AOPs) have been studied to
degrade SMX, such as ionizing radiation, ozonation, photocatalysis,
photo-Fenton, heat-activated persulfate oxidation and electro-
chemical oxidation [11–15]. For example, the ionizing radiation
and ozonation can effectively degrade SMX, while the mineraliza-
tion of SMX is quite limited. Only 12.4% SMX mineralized after 1.5
kGy irradiation and the complete SMX abatement was achieved
with just 10% of mineralization after 15 min ozonation [16,17].
Photo-Fenton technology is limited by the requirement of strong
acidity and generation of large sludge [9]. The SMX degradation
efficiency of heat-activated persulfate oxidation increased with the
increase of persulfate concentration, while this technology
required extra treatment for the produced sulfuric acid wastewater
[18].
Among these AOPs, electrochemical oxidation degradation
appears as an available alternative due to its environmental
compatibility, high energy efficiency and strong oxidation property
[19–21]. The efficiency of electrochemical oxidation is mainly
determined by anode materials, which can produce amounts of
hydroxyl radicals (ꢀOH) [22,23]. PbO2 has been considered as an
excellent anode because of good chemical stability and high
oxygen evolution reaction overpotential [24,25]. Doping rare earth
elements (e.g., Er, Ce, and Gd) into PbO2 coating can significantly
* Corresponding author.
E-mail address: zhoucz@dgut.edu.cn (C. Zhou).
https://doi.org/10.1016/j.cclet.2020.03.073
1001-8417/© 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Y. Wang, et al., Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/
SnO2-Sb/Er-PbO2 anode, Chin. Chem. Lett. (2020), https://doi.org/10.1016/j.cclet.2020.03.073

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Y. Wang et al. / Chinese Chemical Letters xxx (2019) xxx–xxx
improve the efficiency of electrochemical oxidation [26,27]. For
example, the Ti/SnO2-Sb/Er-PbO2 electrode demonstrated the
optimal performance for the oxidation of 4-chlorophenol com-
pared to Ti/SnO2-Sb/Ce-PbO2 electrode, Ti/SnO2-Sb/La-PbO2 elec-
trode and Ti/SnO2-Sb/Gd-PbO2 electrode [24]. However, it is
unknow whether the SMX and Ac-SMX can be degraded by Ti/
SnO2-Sb/Er-PbO2 electrode. The electrochemical degradation
mechanism and toxicity variation of SMX and its metabolite have
not been elucidated. Thus, it is necessary to have insights into the
elimination of sulfamethoxazole and its metabolite by electro-
chemical degradation.
In this study, the electrochemical degradation of SMX and Ac-
SMX was investigated by using Ti/SnO2-Sb/Er-PbO2 electrode.
Affecting factors, such as current density, initial solution pH and
inorganic ions, were investigated to analyze the kinetics and
energy consumption of SMX and Ac-SMX. Degradation intermedi-
ates were identified to propose possible electrochemical degrada-
tion pathways of SMX and Ac-SMX in aqueous solution. Total
organic carbon (TOC) and inorganic ions were measured. Toxicities
of SMX, Ac-SMX and their intermediates were predicted using a
quantitative structure-activity relationship (QSAR) model.
Electrochemical degradation experiments were conducted in
an electrolytic cell. The Ti/SnO2-Sb/Er-PbO2 (anode) and stainless
32.6 and 27.4 min, respectively. Compared to the k values (0.05-
0.50 min-1) of SMX degradation at current density of 10-60 mA/
cm2 using Ti/Ru0.3Ti0.7O2 anode, Ti/SnO2-Sb/Er-PbO2 anode
showed higher degradation efficiency [28]. The degradation
efficiencies of SMX and Ac-SMX were accelerated with the
ꢀ
increasing current density, which may be due to the more OH
production at higher current density [29,30]. It also showed that
the removal rates of SMX and Ac-SMX increased slowly when the
current densities were higher than 10 and 14 mA/cm2, respectively,
which may be owing to the lower rising tendency of ꢀOH
production. Thus, 10 and 14 mA/cm2 were chosen as the optimal
current density for the subsequence experiments of SMX and Ac-
SMX to avoid energy waste. The removal rates of SMX and Ac-SMX
under the optimal current density were 99.6% and 88.5% after
20 min and 30 min electrochemical reaction, respectively. These
results illustrate that the Ac-SMX is more difficult to degrade than
SMX. Therefore, investigating the electrochemical degradation
behavior of Ac-SMX is essential to comprehensively analyze the
risks related with SMX in the water bodies.
As shown in Fig. S1 (Supporting information), the effect of
initial pH ranging from 3-11 on the electrochemical degradation
efficiencies of SMX and Ac-SMX was investigated. For SMX, the k
values increased from 0.183 to 0.457 min-1 with the pH decreasing
from 11 to 3, and the corresponding removal rates increased from
97.8% to 99.9%. For Ac-SMX, the k values were 0.074, 0.078, 0.079,
0.087 and 0.094 min-1 at the pH of 11, 9, 7, 5 and 3, respectively. The
corresponding removal rates slightly increased from 88.0% to
94.1%. Obviously, SMX and Ac-SMX were favorable to degrade
under acidic condition. The species and hydration of target
compound molecules are affected by the pH of solution [31].
Based on pKa of SMX (pKa1 = 1.8, pKa2 = 5.8) and Ac-SMX (pKa1 < 2,
pKa2 = 5.1) [7], the molecular forms of SMX and Ac-SMX were
dominant under acidic condition and the negatively charged forms
were dominant under alkaline condition. The mass transfer
coefficient of molecular form was higher than negatively charged
form [32–34]. Thus, mass transfer efficiency under acidic condition
was higher than that under alkaline condition, which resulted in
higher k values at lower pH. In addition, concentration of ꢀOH
decreased at alkaline condition due to its reaction with OHÀ, which
also led to lower degradation efficiency [35,36].
steel
(cathode)
were
with
the
same
dimension
(50 mm  50 mm  1 mm), and the electrode distance was 1 cm.
The life time of this anode was more than 1000 h and the electrode
preparation is described in Supporting information. Initial con-
centrations of SMX (prepared with deionized water) and Ac-SMX
(prepared with 1% acetonitrile cosolvent) were both 10 mg/L.
Volume of electrolyte solution was 120 mL with 20 mmol/L Na2SO4
as supporting electrolyte. Five variables including current densities
(4-18 mA/cm2), initial pH (3-11), Cl- concentrations (1-10 mmol/L),
-
-
HCO3 concentrations (1-10 mmol/L) and NO3 concentrations (1-
10 mmol/L) were investigated during the electrochemical degra-
dation experiments. Degradation rate constants (k), half-lives (t1/2
)
and removal rates are illustrated in Tables S1 and S2 (Supporting
information).
Fig. 1 exhibits the electrochemical degradation efficiencies of
SMX and Ac-SMX under different current density. The k values of
SMX were measured to be 0.058, 0.083, 0.139, 0.268 and 0.299 min-
at the current density of 4, 6, 8, 10 and 12 mA/cm2, and the
Fig. 2 illustrates the electrochemical degradation efficiencies of
1
-
corresponding t1/2 values were 40.4, 28.6, 17.7, 10.4 and 9.2 min,
respectively. The k values of Ac-SMX were 0.030, 0.043, 0.072,
0.073 and 0.090 min-1 at the current density of 10, 12, 14, 16 and
18 mA/cm2, and the corresponding t1/2 values were 77.2, 53.5, 34.0,
SMX and Ac-SMX under different concentrations of HCO3-, NO3
and Cl-. With the concentration of HCO3 increasing from 0 to
-
10 mmol/L, the k values of SMX and Ac-SMX were measured to be
0.244–0.277
and
0.064–0.069 min-1,
respectively.
The
Fig. 1. Effect of applied current density on the electrochemical degradation of SMX and Ac-SMX. Initial concentration: 10 mg/L, Na2SO4: 20 mmol/L, electrode distance: 1 cm,
pH: unadjusted.
Please cite this article in press as: Y. Wang, et al., Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/
SnO2-Sb/Er-PbO2 anode, Chin. Chem. Lett. (2020), https://doi.org/10.1016/j.cclet.2020.03.073

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Fig. 2. Degradation rate constants (k) of SMX and Ac-SMX at different anion concentrations. Applied current density: 10 mA/cm2 for SMX and 14 mA/cm2 for Ac-SMX, initial
concentration: 10 mg/L, Na2SO4: 20 mmol/L, electrode distance: 2 cm, pH: unadjusted. Noting that the removal rate of SMX reached 99.0% in two minutes with the addition of
6 and 10 mmol/L Cl-, so the rate constants were not calculated.
corresponding t1/2 values of SMX and Ac-SMX were determined to
40.6, 38.3, 16.4 and 12.2 min. ꢀOH may be main oxidant for the Cl-
concentration of 1 and 3 mmol/L, so the consumption of OH via
ꢀ
be 10.0-10.9 and 32.6-36.5 min, respectively. These results
demonstrated that the addition of HCO3 had slight effect on the
reaction with Cl- led to an inhibitory effect. For the Cl-
concentration of 6 and 10 mmol/L, the active chlorine species
played a major role and showed a facilitation effect [16]. The
different effects of SMX and Ac-SMX toward active chlorine species
may be related with the phenylamino group as well as the
reactivity and concentration of oxidants [46].
-
-
electrochemical degradation of SMX and Ac-SMX. HCO3 can
significantly accelerate the degradation of oxcarbazepine, per-
fluorooctanoic acids and oxytetracycline, which may be due to the
ꢀ
ꢀ
-
production of CO3 via the reaction with OH [36–38]. While the
-
HCO3 restrained the degradation efficiency of ciprofloxacin [33],
norfloxacin [34] and abacavir [37] as the quencher of OH. These
ꢀ
Electrochemical degradation products of SMX and Ac-SMX
were determined by UPLC-MS/MS in the positive mode. Five major
transformation products (TP286, TP270, TP112, TP110 and TP98)
were identified for SMX and six transformation products (TP283,
TP267, TP215, TP142, TP112 and TP98) were identified for Ac-SMX.
Detailed information of these transformation products was shown
in Table S3 (Supporting information). TP286 and TP270 were
hydroxylated products of SMX. TP283 and TP267 were oxidation
products of Ac-SMX. TP215, TP112 and TP98 were the products by
the cleavage of S-N bond. TP100 was isoxazole ring-cleavage
product.
In accordance with the discussions above, the possible
degradation pathways of SMX (red line) and Ac-SMX (blue line)
are proposed in Fig. 3. SMX was attacked by ꢀOH to form TP270, and
further hydroxylated toTP286 [31]. Meanwhile, SMX generated the
TP98 and S173 after the cleavage of S-N bond via the attack of ꢀOH.
Then the amino of TP98 was oxidized to form the nitroso derivative
TP112 and further oxidized to the nitro product S128 [47].
Meanwhile, the isoxazol ring of TP98 was attacked by ꢀOH to
generate the ring-opening product TP100. Similar degradation
different effects were inferred that the transition between
promotion and inhibition for the degradation was determined
ꢀ
-
by the rate constant of CO3 toward compound, and the value of
carbonate rate constant for this transition was somewhere around
108 L mol-1 s-1 [39,40].
For the concentration of NO3- of 0, 1, 3, 6 and 10 mmol/L, the k
values of SMX were 0.254, 0.137, 0.108, 0.096 and 0.092 min-1,
respectively. At the same NO3- concentration gradient, the k values
of Ac-SMX were 0.072, 0.045, 0.045, 0.034 and 0.030 min-1,
respectively. Compared to the sample without NO3-, the k value
of SMX decreased by 63.8% and that of Ac-SMX decreased by 58.3%
-
for the NO3 concentration of 10 mmol/L. The corresponding t1/2
values of SMX and Ac-SMX were 11.2-24.8 and 34.0-73.3 min,
respectively. The removal rates of SMX decreased from 99.5% to
84.4% with the NO3- concentration increasing from 0 to 10 mmol/L,
and those of Ac-SMX decreased from 88.5% to 62.5% as well. It was
-
clearly that NO3 exerted an inhibitory performance on the
-
degradation of SMX and Ac-SMX. This inhibitory effect of NO3
was also found in the electrochemical degradation of other organic
pollutants, such as stavudine [41], lamivudine [42] and enroflox-
-
acin [43]. The reason for the inhibition may be that NH3+ and NO2
ꢀ
(generated by the reduction of NO3-) can easily react with OH,
which decreases the concentration of ꢀOH and results in the
suppression phenomenon [30,33,44].
As for the effect of Cl-, the k values of SMX increased from 0.254
to 1.261 min-1 with the concentration of Cl- increasing from 0 to
3 mmol/L. The corresponding t1/2 values of SMX were 1.6-11.2 min.
The removal rates of SMX reached 99.0% in two minutes with the
addition of 6 and 10 mmol/L Cl-, so the rate constants were not
calculated. The degradation efficiency of SMX was significantly
accelerated with the addition of Cl-, which may be due to the
generation of active chlorine species (e.g., Cl2, ClO-, ClO2-, Cl- and
Clꢀ) via the reaction with ꢀOH or direct oxidation [45]. For Ac-SMX,
the k values of Ac-SMX were 0.073, 0.057, 0.059, 0.154 and
0.204 min-1 in the presence of 0, 1, 3, 6 and 10 mmol/L Cl-,
respectively. The corresponding t1/2 values of Ac-SMX were 31.4,
Fig. 3. Proposed degradation pathways of SMX (red line) and Ac-SMX (blue line).
Degradation products in dotted rectangle (marked “S”) were not actually detected.
Please cite this article in press as: Y. Wang, et al., Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/
SnO2-Sb/Er-PbO2 anode, Chin. Chem. Lett. (2020), https://doi.org/10.1016/j.cclet.2020.03.073

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Y. Wang et al. / Chinese Chemical Letters xxx (2019) xxx–xxx
pathway of Ac-SMX, including the cleavage of S-N bond and the
transformation of TP98 were also indicated. Afterwards, product
TP215 of Ac-SMX was transformed to the 4-amino benzene
sulphinic acid S173 via the break of amide bond. Subsequently, the
amino group and an oxygen atom of S173 were removed to
generate TP142. Otherwise, the amide bond of Ac-SMX was broken,
and further oxidized to nitroso derivative TP267 and nitro
derivative TP283 [48]. Finally, these intermediates of SMX and
Ac-SMX were mineralized to CO2, H2O and inorganic ions.
worth noting that the chronic toxicities of TP100 and TP98 to
daphnia were higher than those of SMX and Ac-SMX, which
indicated that assessing the potential risks to aquatic organisms
was essential in view of some toxic intermediates.
The economic feasibility of SMX and Ac-SMX degradation was
valuated through electrical energy per order (EEO), and the
calculation of EEO values is illustrated in Supporting information
[49]. As exhibited in Table S5 (Supporting information), the EEO
values of SMX were between 0.58 and 8.97 Wh/L, and those of Ac-
SMX ranged from 6.88 Wh/L to 44.19 Wh/L. When the current
density of SMX increased from 4 mA/cm2 to 12 mA/cm2, the lowest
EEO value occurred at the current density of 10 mA/cm2 and
determined to be 4.12 Wh/L. For Ac-SMX, the lowest EEO value
occurred at the current density of 14 mA/cm2 and determined to be
21.15 Wh/L. These results were consistent with the choice of
optimal current density of 10 mA/cm2 and 14 mA/cm2 for SMX and
Ac-SMX, respectively. Notably, the EEO values significantly de-
As aforementioned introduction, many techniques have been
used to degrade SMX, such as ozonation and ionizing radiation.
However, various organic intermediates were produced and
complete mineralization was difficult during the degradation of
SMX. Thus, it is significant to determine the mineralization of SMX
by electrochemical degradation. As shown in Fig. S2 (Supporting
information), the TOC removal of SMX was nearly 63.2% with 3 h
electrochemical degradation. 22.4% nitrogen of SMX was trans-
formed to NO3 and 98.8% sulfur was released as SO42-. Although
creased in the presence of high concentration of Cl-, while the
-
-
the removal rate of SMX reached 99.6% within 20 min at 10 mA/
cm2 current density, only 54.2% sulfur of SMX was recovered as
SO42- and 14.9% nitrogen was transformed to NO3-, which implying
that the total mineralization required longer reaction time or
enhancing current density, which might be explained to the
generation of refractory intermediates via the electrochemical
degradation. However, compared with the TOC of SMX by
electrochemical degradation using other anodes, Ti/SnO2-Sb/Er-
PbO2 anode was still competitive. For example, the TOC removal of
SMX was 28.6% after 2 h electrochemical degradation using Ti/
Ru0.3Ti0.7O2 anode [28]. TOC and inorganic ions of Ac-SMX were
not measured because it was dissolved with acetonitrile cosolvent.
Although the degradation intermediates of SMX were identified
in other studies, the toxicities of SMX, metabolite Ac-SMX and their
intermediates have received little scrutiny to date. In this study, the
toxicities of SMX, Ac-SMX and their intermediates were predicted
based on QSAR model. The detailed values of toxicity are shown in
Table S4 (Supporting information). As shown in Fig. 4, the chronic
toxicity of metabolite Ac-SMX to fish, daphnia and green algae was
higher than that of parent compound SMX, which indicated that it
was noteworthy to investigate the treatment of Ac-SMX. The
toxicities of SMX and Ac-SMX decreased after electrochemical
degradation process. The toxicities of products with large
molecular mass were higher than that of low molecular mass.
TP142 possessed the lowest toxicity, and its lethal concentration
(LC50), effective concentration (EC50) and chronic value (ChV) were
hundreds of times higher than those of SMX and Ac-SMX. It was
highest EEO values occurred in the presence of 10 mmol/L NO3
.
These phenomena were mainly due to the different degradation
rates of SMX and Ac-SMX under various conditions. It also
indicated that inorganic ions ubiquitous in water environments
were crucial for the practical application of electrochemical
degradation process.
It was worth noting that the EEO values of metabolite Ac-SMX
were higher than those of parent compound SMX, which can be
explained by the lower degradation efficiency of Ac-SMX. This
phenomenon further indicated that the metabolite Ac-SMX was
more refractory than SMX. Compared with energy consumption
values of other compounds, such as 0.87-2.29 Wh/L for stavudine
[41], 0.099-2.988 Wh/L for naproxen [50], 3.3-62.1 Wh/L for
benzophenone-3 [49] and 41.7-71.6 Wh/L for perfluorodecanoic
acid [51], those of SMX and Ac-SMX were close to naproxen and
benzophenone-3, but lower than that of perfluorodecanoic acid.
The high energy consumption of perfluorodecanoic acid was
ascribed to low degradation efficiency caused by the refractory C–F
bond. As we known, energy consumption is affected by electrode
activity, pollutant structure and reaction conditions, implying that
optimizing reaction condition and improving electrode perfor-
mance are effective way to reduce energy consumption in practical
applications.
In conclusion, SMX and its metabolite Ac-SMX can be efficiently
degraded by the Ti/SnO2-Sb/Er-PbO2 anode. The degradation of
SMX and Ac-SMX is significantly accelerated in the presence of
high concentration of Cl-, while NO3- exerts an inhibitory effect on
Fig. 4. Toxicity assessments for SMX, Ac-SMX and their intermediates. Very toxicity: LC50/EC50/ChV < 10ꢁ, toxicity: 101 > LC50/EC50/ChV > 10ꢁ, harmful: 102 > LC50/EC50/ChV >
101, not harmful: LC50/EC50/ChV > 102 [37].
Please cite this article in press as: Y. Wang, et al., Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/
SnO2-Sb/Er-PbO2 anode, Chin. Chem. Lett. (2020), https://doi.org/10.1016/j.cclet.2020.03.073

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Y. Wang et al. / Chinese Chemical Letters xxx (2019) xxx–xxx
5
the degradation of SMX and Ac-SMX. The degradation pathways of
SMX and Ac-SMX mainly involve the cleavage of S–N bond,
opening ring of isoxazole and nitration of amino group. The
toxicities of SMX and Ac-SMX significantly decrease after
electrochemical degradation. The metabolite Ac-SMX is more
refractory and toxic compared with SMX, implying that dispose of
metabolites should be taken into account when removing parent
pharmaceuticals from wastewater. The process also demonstrates
an effective removal of SMX and its metabolites from the hospital
effluent.
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Declaration of completing interests
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgments
This study was financially supported by the National Science
Fund for Distinguished Young Scholars (No. 51625801), the
Guangdong Innovation Team Project for Colleges and Universities
(No. 2016KCXTD023), and Guangdong Province Universities and
Colleges Pearl River Scholar Funded Scheme (2017), the China
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Please cite this article in press as: Y. Wang, et al., Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/
SnO2-Sb/Er-PbO2 anode, Chin. Chem. Lett. (2020), https://doi.org/10.1016/j.cclet.2020.03.073