Photocatalytic degradation of diphenhydramine in aqueous solution by natural dolomite

Article abstract of DOI:10.1039/d0ra07533g

Natural dolomite, an inexpensive and vastly available natural material, was demonstrated as a potential heterogeneous photocatalyst for the efficient removal of diphenhydramine (DP) from aqueous solution under simulated solar light in this study. About 65

Full text of DOI:10.1039/d0ra07533g

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Photocatalytic degradation of diphenhydramine in
aqueous solution by natural dolomite†
Cite this: RSC Adv., 2020, 10, 38663
Lihong Song, Chunlin Yi, Qingfeng Wu, *a Zhaohui Li, *b Weibin Zhanga
a
a
c
and Hanlie Hong
Natural dolomite, an inexpensive and vastly available natural material, was demonstrated as a potential
heterogeneous photocatalyst for the efficient removal of diphenhydramine (DP) from aqueous solution
under simulated solar light in this study. About 65% DP removal and 14% mineralization were achieved
with dolomite as a catalyst after 75 min irradiation. The electron spin resonance analysis and scavenger
1
2
2ꢀ
experiments verified that O , cOH, and O c produced in the dolomite system were the main reactive
species responsible for DP degradation. Furthermore, first-principle calculations combined with
deoxygenation experiments were employed to elucidate the photocatalytic mechanism. The results
revealed that the dolomite changed from an insulator to a semiconductor after partial substitution of
2+
2+
Mg
by Fe , suggesting that natural dolomite could act as a semiconductor photocatalyst in
photoreactions. Under irradiation, photo-excited electrons and holes separate and migrate to the surface
of dolomite, and subsequently react to form reactive species resulting in the DP degradation. Product
studies demonstrated that the main degradation pathways of DP included hydroxylation of the aromatic
ring as well as hydroxyl radical mediated oxidation of the alkylamine side chain. This work indicated that
natural dolomite could be applied in water and wastewater treatment as a promising photocatalyst.
Received 2nd September 2020
Accepted 8th October 2020
DOI: 10.1039/d0ra07533g
rsc.li/rsc-advances
In recent years, advanced oxidation processes (AOPs), as an
environmental friendly technology based on the oxidation of
1
. Introduction
Pharmaceutically active compounds (PhACs) are a class of contaminants by strong oxidizing radicals, have received great
compounds used to prevent, control, and treat diseases and to attention. Among the AOPs, UV photolysis, UV/H photolysis,
O
2 2
promote human and animal health. Due to widespread Fenton and photo-Fenton oxidation, heterogenous photo-
consumption and incomplete removal in conventional waste- catalysis, and sonolysis have been applied for the removal of DP
water treatment plants, PhACs are constantly introduced into in aqueous solution. About 26% of the initial 5 mM of DP was
ꢀ2
the environment via discharges of wastewater and direct runoff, eliminated under the UV irradiation (1272 mJ cm ), and add-
1
–3
resulting in their occurrence in environmental waters. Prev- ing 0.29 mM H
2
0
O
2
in the photoreaction greatly improved the DP
alence and long-term persistence of trace PhACs in aquatic removal rate. Photocatalytic degradation of DP by TiO ach-
environments can cause potential risks to aquatic organisms ieved 44.8% of DP removal under black blue lamps and 9.0% of
1
2
4
–6
and human health.
Diphenhydramine (DP), an H1-histamine receptor antago- irradiation, and the addition of H
nist, is commonly used to treat allergies, hives, itching and photocatalytic process, obtaining 100% DP degradation and
insomnia, and also used as an analgesic adjuvant in cancer 28.6% total organic carbon (TOC) reduction in UVC system.
pain. Previous reports showed its presence in wastewater Using iron oxide nanoparticles as catalyst via a photo-Fenton
inuent and effluent and surface water. Therefore, to develop process, 100% of DP elimination and 83% of TOC reduction
effective techniques for the removal of DP from aqueous solu- were obtained. Heterogeneous photocatalysis using TiO
mineralization under simulated solar radiation aer 60 min
O
2 2
drastically improved the
11
7
8,9
12
2
and
tion is of great environmental interest.
its modied forms as catalysts also exhibited high efficiency in
13,14
DP degradation and mineralization.
Ultrasonic irradiation
at 640 kHz could effectively degrade DP in aqueous solution,
a
School of Physics and Optoelectronic Engineering, Yangtze University, 1 Nanhuan
and hydroxyl radical produced during cavitation played
Road, Jingzhou, Hubei 434023, China. E-mail: wqfscience@aliyun.com
b
15
a crucial role in DP degradation.
It appears that heterogeneous photocatalysis is a promising
Department of Geosciences, University of Wisconsin-Parkside, 900 Wood Road,
Kenosha, WI 53144, USA
c
Faculty of Earth Sciences, China University of Geosciences, 388 Lumo Road, Wuhan, technique in water purication and wastewater treatment, with
Hubei 430074, China
potential to achieve complete mineralization of organic pollut-
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/d0ra07533g
ants into CO
2
, water, and inorganic ions under solar irradiation.
1
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Currently, design and utilization of novel photocatalytic mate- Table 1 Elemental compositions of natural dolomite determined by
X-ray fluorescence spectrometer
rials have drawn great attention in the remediation of organic
16–20
micropollutants and clean energy production.
an anhydrous carbonate mineral composed of calcium
magnesium carbonate, with a ideal formula of CaMg(CO
Dolomite is
Composition (%)
3
)
2
.
CO2 MgO Al O3 SiO2
2
P2O5
SO3
K2O
2 3
CaO Fe O
Natural dolomite oen contains a certain amount of iron due to 55.6 23.4
the partial substitution of Mg by Fe in the lattice. As an
industrial mineral, dolomite is widely used in food and phar-
0.103 0.304 0.007 0.026 0.0171 20.5 0.0774
2
+
2+
21
maceutical industries, production of fertilizers, glass and 2.3 Photolysis experiments
building materials, iron and steelmaking, and environmental
Photoreaction was carried out in a PR22-25 photochemical
reactor (PerfectLight, China) equipped with a 300 W xenon light
source (PLS-SXE300UV) and a water-cooling system DC-0506
22
remediation. No studies on photocatalytic degradation of
organic pollutants by natural dolomite and their modied
forms have been reported in a recent literature search by the
authors. As such, the main objectives of the present study were
(HengPing, Shanghai). The spectral range of the xenon light
source is 300–800 nm, and the light power entering the photo-
(1) to examine the possible catalytic effects of dolomite on the
ꢀ2
reactor was about 120 mW cm . During the irradiation, the
photodegradation of DP in aqueous solution, and evaluate its
photocatalytic performance; (2) to identify the byproducts of DP
in the photoreaction and speculate the possible photolytic
pathways; and (3) to elucidate the intrinsic mechanisms for the
photocatalytic activities of natural dolomite.
suspension was stirred continuously with the temperature kept
ꢁ
at 4 C by circulating water to prevent pyrolysis of DP. The
reactor was airtight with a quartz glass plate on the open top of
the vessel. In each experiment, 1.5 g dolomite sample was mixed
ꢀ1
with 200 mL DP solution (40 mg L ) in the 250 mL reactor, and
then magnetically stirred for 30 min, then the suspension was
irradiated under simulated solar light. At the given time intervals,
a 2 mL aliquot of the suspension was collected, ltered through
a 0.22 mm membrane, and analyzed by HPLC and LC-MS. Dark
2
. Experimental
2.1 Materials
The dolomite used in this study was supplied by XBKC Co., Ltd control experiments were conducted in the same manner as the
Shiyan, China). The diphenhydramine hydrochloride with regular experiments except that they were not exposed to light. All
a purity > 98%, superoxide dismutase (SOD), and TiO were experiments were performed in duplicates to check the results.
(
2
provided by Sinopharm Chemical Reagent Co., Ltd (Shanghai,
China). Acetonitrile, acetic acid, triethylamine, 1, 4-diazabicyclo
2
.4 Analytical determination and photoproduct
[2.2.2] octane (DABCO), and isopropanol (IPA) were of high-
identication
performance liquid chromatography (HPLC) grade, and
supplied by J&K Chemical Co., Ltd (Beijing, China). The spin- The concentration of DP in water was determined with a Shi-
trapping reagents 5,5-dimethyl-1-pyrroline N-oxide (DMPO) madzu HPLC (LC-20) equipped with a C18 ODS reversed phase
and 2,2,6,6-tetramethylpiperidine (TEMP) were purchased from column (4.6 mm ꢂ 150 mm, 5 mm) and a SPD20 UV detector.
Sigma-Aldrich (Shanghai, China). All aqueous solutions were The mobile phase consisted of 25 mM acetic acid and acetoni-
prepared with Milli-Q ultrapure water.
trile (60 : 40, v/v), with pH adjusted to 6.0 ꢃ 0.1 using
2.2 Pre-treatment and characterization of natural dolomite
The dolomite was rst sieved to obtain a uniform 40–60 mesh
sized particles. Then, the samples were washed with ultrapure
ꢁ
water for three times, dried at 60 C for 8 h, and stored in
a desiccator for further use. No chemical treatments were made
in order to maintain the natural attributes of dolomite. The
morphology of samples were characterized using eld emission
scanning electron microscope (JEOL, JSM-6700) (Fig. S1†). The
X-ray diffraction (XRD) pattern of the washed dolomite was
ꢁ
ꢁ
recorded at 5 to 90 (2q) using Bruker D8 advanced XRD
instrument equipped with Cu-Ka radiation, and the collected
XRD data were analyzed using MDI Jade 6.5 soware. The
elemental compositions of the dolomite were determined by
a Rigaku-ZSX Primus II X-ray uorescence (XRF) spectrometer.
The results obtained from XRD (Fig. S2†) and XRF (Table 1)
analysis indicate that it is an Fe-containing dolomite. The UV-
vis diffuse reectance spectra (DRS) of the dolomite were
Fig. 1 Photodegradation and mineralization of DP in the presence of
natural dolomite under simulated solar light, as well as the corre-
sponding dark control. The added dolomite sample is 1.5 g per 200 mL
collected using
Shimadzu).
a
UV-vis spectrophotometer (UV2450,
ꢀ1
of DP solution at an initial concentration of 40 mg L
.
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Table 2 Fitted parameters for DP photodegradation under different nm) at ambient temperature. The settings were center eld at
reaction conditions by pseudo-first-order model
3227.67 G; microwave frequency at 9054.62 MHz; and power at
ꢀ
1
2
0.998 mW. To further evaluate the role of these reactive species in
Reaction condition
K
DP (min
)
R
t1/2 (min)
the photodegradation of DP, reactive oxygen species (ROS) scav-
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ2
1
No dolomite
Dolomite
(0.16 ꢃ 0.01) ꢂ 10
(1.29 ꢃ 0.08) ꢂ 10
(2.16 ꢃ 0.05) ꢂ 10
(0.88 ꢃ 0.05) ꢂ 10
(0.82 ꢃ 0.04) ꢂ 10
(1.03 ꢃ 0.04) ꢂ 10
(0.93 ꢃ 0.05) ꢂ 10
0.999
0.982
0.998
0.99
0.986
0.992
0.99
433.1
53.7
32.1
78.7
84.5
67.2
74.5
engers including DABCO ( O
2
scavenger), IPA (cOH scavenger) and
ꢀ
23–25
SOD (O
2
c scavenger) were used for the inhibition experiments.
TiO
2
Dolomite + IPA
Dolomite + SOD
Dolomite + DABCO
2.6 Theoretical calculations
To investigate the photocatalytic mechanism of DP under the
catalysis of dolomite, the rst-principle calculations were per-
formed employing the VASP code (Vienna Ab initio Simulation
Dolomite + N
2
26
Package). The generalized gradient approximation (GGA)
method with the Perdew–Burke–Ernzerhof (PBE) functional was
used for the geometry optimization and electronic band struc-
2
7,28
ture calculations.
The kinetic energy cutoff was set as 500 eV,
29
and a 4 ꢂ 4 ꢂ 1 k-point mesh was applied. Optimization was
performed with a convergence threshold for the maximum
ꢀ
5
energy change of 1.0 ꢂ 10 eV per atom and for the maximum
ꢀ
1
˚
force of 0.01 eV A
.
The experimental lattice constants of dolomite were a ¼ b ¼
ꢀ
ꢀ
ꢁ
30
4
.81 A, c ¼ 16.01 A, and the space group is R3 (NO. 148). The
unit cell of dolomite in our calculations is composed of 6 C
gray), 18 O (red), 3 Mg (blue), and 3 Ca (green) atoms. And
a supercell made of 2 ꢂ 2 ꢂ 1 was applied (Fig. S3(a)†). In order
(
2
+
2+
to simulate the partial substitution of Mg by Fe in natural
2
+
dolomite, the Mg ions in the unit cell are randomly replaced
2
+
2+
by Fe ions (pink), with the Fe number changing from 1 to 9.
2
+
2+
Fig. S3(b)† depicted the substitution of 3 Mg by 3 Fe .
Fig. 2 Photocatalytic efficiency for the natural dolomite in the cycling
experiments. The irradiation time is 75 min.
3
. Results and discussion
triethylamine. Isocratic elution was performed at a ow rate 0.8 3.1 Photodegradation and mineralization of DP in the
ꢀ1
mL min . The injection volume was 20 mL. Oven temperature presence of natural dolomite
ꢁ
was kept at 30 C and the detector wavelength was 220 nm.
Thermo Scientic Q Exactive mass spectrometer paired with
the Ultimate 3000 LC system was used for the product studies.
The analytical column was Agilent Zorbax XDB-C18 (2.1 mm ꢂ
Fig. 1 illustrates the photodegradation of DP as a function of
irradiation time in the presence and absence of natural dolo-
mite, as well as the corresponding dark controls. For the dark
control without dolomite, almost negligible loss of DP within
5
0 mm, 1.8 mm). A mobile phase made of solvent A (0.1% formic
acid in acetonitrile) and solvent B (0.1% formic acid in water)
was used to elute the column with a ow rate 0.2 mL min and
the optimized gradient program 0–8 min, from 5% to 90% A; 8–
0 min, 90% A. The column temperature was 30 C. An injection
volume of 5 mL was used for analytical samples. For MS detec-
tion, the operating parameters were as follows: spray voltage,
200 V; capillary temperature, 300 C; sheath gas pressure, 40
75 min indicated that the degradation by hydrolysis or thermal
degradation could be neglected. While for the dark control with
dolomite, approximately 4% of DP loss was detected, which
could be attributed to physical adsorption to the surface of
dolomite. When exposed to simulated solar light, DP in
aqueous solution in the absence of dolomite was gradually
decomposed with the irradiation time, and about 12% of DP
removal was achieved aer 75 min irradiation. A recent study
reported DP removal of 32.5, 2.5, and 1.4% aer 60 min irra-
diation under UVC, simulated solar light, and solar irradiation,
ꢀ
1
ꢁ
1
ꢁ
3
arb; aux gas pressure, 15 arb; S-lens RF, 50 V.
11
respectively. With the addition of dolomite into the solution,
the DP removal increased to 62%, and the rate constant (KDP
estimated from the pseudo-rst order kinetic model increased
2
.5 Determination of reactive species during photocatalytic
)
degradation
ꢀ2
ꢀ2
ꢀ1
In order to determine the reactive species in the photoreactions, from 0.16 ꢂ 10 to 1.29 ꢂ 10 min (Table 2). Obviously, the
electron spin resonance (ESR) signals for singlet oxygen, presence of the natural dolomite greatly promoted the photo-
superoxide anions, and hydroxyl radicals trapped by TEMP and degradation of DP, exhibiting remarkable photocatalytic
DMPO were obtained on a Bruker model ESP300E electron activity. The TOC reduction, an indication of mineralization,
paramagnetic resonance spectrometer equipped with a Quanta- follows a similar trend as observed for DP degradation, about
Ray Nd: YAG laser system as the irradiation light source (l ¼ 355 14% of TOC elimination aer 75 min irradiation indicated that
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1
2
2ꢀ
Fig. 3 ESR spectral changes of the TEMP– O (a), DMPO–cOH (b), and DMPO–O c (c) adducts generated in the natural dolomite system under
simulated solar light irradiation.
2
that by TiO , it could still be considered as a promising pho-
tocatalyst in the eld of water treatment due to its much lower
material cost, vast reserves, and environmental-friendly char-
acters. Moreover, the recyclability and stability of the dolomite
were evaluated through cycling experiments. As shown in Fig. 2,
the degradation rate of DP was about 63% in the rst cycle, and
signicantly decreased to 30% in the second cycle. Aer 4
cycles, the dolomite almost completely lost its photocatalytic
activity. This result suggested that deactivation of the dolomite
could occurred aer several applications.
3.2 Study of reactive oxygen species
1
Photo-induced ROS, such as singlet oxygen ( O
2
), superoxide
ꢀ
anion radical (O
2
c), and hydroxyl radical (cOH) were oen
considered as the main reactive species in photocatalytic
processes. Therefore, it could be speculated that the enhanced
DP degradation might also be due to the ROS produced in the
dolomite system under irradiation. The EPR spin-trapping
Fig. 4 Suppressed photodegradation of DP in the presence of natural
dolomite by the radical scavengers. The initial concentration of IPA,
ꢀ1
DABCO, and SOD were 50, 50 mM, and 75 kU L , respectively.
technique was deployed to examine the ROS generated in the
1
photocatalytic process. The characteristic peaks of TEMP– O
2
,
ꢀ
DMPO–O
2
c, and DMPO–cOH adducts are observed in the
the dolomite photocatalytic process could effectively lead to the dolomite system aer irradiation, and the intensity of the peaks
mineralization of DP (Fig. 1).
increased gradually with the irradiation time, while no signal
To further evaluate the photocatalytic performance of dolo- was detected in the dark (Fig. 3). These evidences veried the
1
ꢀ
mite, photocatalytic degradation of DP by dolomite was generation of O , O c, and cOH in the photocatalytic system.
2
2
compared to that by TiO
2
under the same conditions. Although
In order to quantitatively evaluate the role of ROS in the
the photocatalytic performance of dolomite was 19% lower than present system, scavenger experiments were performed. In the
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2+
Fig. 5 Band structure for dolomite supercell with 0 (a), 3 (b), 6 (c), and 9 (d) Fe -substitution. The Fermi level is set to 0.
2ꢀ
presence of SOD (O c scavenger) and IPA (cOH scavenger), DP dolomite. The calculated band gap of the pristine dolomite is
photodegradation was signicantly suppressed (Fig. 4), indi- 5.02 eV, consistent with a previous report of 5.035 eV
ꢀ
32
2+
cating the dominant role of the O2 c and cOH in the photo- (Fig. 5(a)). With 3 Fe substitution, two new bands appear in
1
degradation of DP. In contrast, the addition of DABCO ( O
2
the band structures, resulting in forbidden band gap being
scavenger) showed a slight inhibition, which might be due to divided into three parts (Fig. 5(b)). Among them, the maximum
2
+
weak reactions between the amine drugs (including DP) and band gap is 2.04 eV. With the increase of Fe content, more
1
31
O
2
.
Combining the EPR analyses and the radical scavenger energy levels appear in the forbidden band gap, and the new
ꢀ
1
experiments, it could be concluded that the O c, O , and cOH bands become wider, leading to reduction of the band gap. Aer
were the main reactive species responsible for the enhanced DP 9 Fe substitution, the maximum band gap decreased to
degradation in the presence of dolomite, and the O2 c and cOH 1.63 eV (Fig. 5(d)), close to the band gap calculated from the UV-
2 2
2
+
ꢀ
played the dominant role.
vis reectance spectra (1.33 eV) of dolomite (Fig. S4†). The
change in band gap of dolomite from 5.02 to 1.63 eV implies
that the dolomite changes from an insulator to a semiconductor
3.3 Mechanisms for photocatalytic activity of dolomite
2
+
2+
In order to further elucidate the photocatalytic mechanism, with partial substitution of Mg by Fe .
density functional theory (DFT) was employed to calculate the
The DOS calculation indicated that the states near the
electronic band structure and density of states (DOS) for valence band maximum (VBM) are contributed by the hybrid
2+
Fig. 6 Density of state for pure (a) and 3 Fe -substituted (b) dolomite. The Fermi level is set to 0.
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between O 2p and Mg 3p orbitals, and the states near the
conduction band maximum (CBM) mainly originate from C 2p
and Ca 3d orbitals for the pristine dolomite (Fig. 6(a)). Two
additional doping states appear in the forbidden band gap aer
2
+
3
3
Fe substitution, which is attributed to the hybrid between Fe
2
+
d and Ca 3d orbitals (Fig. 6(b)). With the increase of Fe
contents, the two doping states become wider, thereby resulting
in gradual decrease of the band gap.
Overall, the theoretical calculation results indicate that the
dolomite exhibits the characters of semiconductors aer the
2
+
2+
substitution of Mg by Fe , suggesting that dolomite could act
as a semiconductor photocatalyst under the irradiation of solar
light. To verify the role of O
deoxygenation experiments were performed and the DP degra-
dation was suppressed by N purging (Fig. 7). The generation of
ROS in the dolomite system was related to the dissolved oxygen
DO) in solution. N purging causes a decrease of DO concen-
2
during the photocatalytic process,
2
(
2
Fig. 7 The photodegradation of DP in the presence of natural dolo-
tration, thus inhibiting the formation of reactive oxygen
species.
mite in the deoxygenated solution.
Table 3 Retention time, mass spectra, and structure of the identified photoproducts
Retention time
m/z
(min)
Elemental composition
Proposed structure
1
67
83
7.1
C
13
H
11
1
8.0
C
13
H O
11 2
2
56
5.8
17
C H22NO
2
72
6.0
17 2
C H22NO
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Fig. 8 Proposed degradation pathways of DP in the presence of natural dolomite.
According to the theoretical calculations, the results from of cOH in the dolomite system, it is logical to expect the addition
ESR analysis, and the deoxygenation experiments, we proposed of cOH to the aromatic ring in DP molecules, leading to the
a mechanism for the photocatalysis of dolomite. Under irradi- formation of m/z 272. As for the products of m/z 183 and 167,
ation, photo-excited electrons and holes migrate to the surface their formation might result from the hydroxyl radical mediated
3
2,33
of the dolomite (eqn (1)). Subsequently, further reactions oxidation of the alkylamine side chain (Fig. 8).
ꢀ
1
according to eqn (2)–(6) yield cOH and O2 c. As for O , its
In summary, from the intermediates determined it appears
2
generation might be due to the energy transfer between dolo- that the oxidation process occurs mainly through the hydroxyl
mite and DO.
radicals. However, the results from the scavenger experiments
indicated that the superoxide anions also play an important
role. Thus, it seems that the superoxide anions generated were
converted to hydroxyl radicals via further reaction, reinforcing
the role of hydroxyl radicals.
+
ꢀ
Dolomite + hn / h + e
(1)
(2)
(3)
(4)
+
+
H O + h / cOH + H
2
ꢀ
2ꢀ
c
O
2
+ e / O
4. Conclusions
2ꢀ
+
2
c
O
c + H / HO
For the rst time, dolomite, an inexpensive and easily available
2
HO c / H O + O
(5) mineral, was used for photocatalytic degradation of DP in
2
2
2
2
aqueous solution. The results demonstrated that the presence
of dolomite greatly promoted the degradation of DP, exhibiting
2ꢀ
ꢀ
2
H
2
O
2
+ O c / cOH + OH + O
(6)
signicant photocatalytic activity. The ESR analysis and scav-
1
ꢀ
2 2
, O c, and cOH were
enger experiments demonstrated that O
produced in the dolomite system aer irradiation, and
3.4 Identication of degradation products and pathways
To obtain a further insight into the photolytic mechanism and contributed to the enhanced DP photodegradation. Based on
the photochemical fate of the DP, the main degradation prod- the rst-principles calculations, it was proposed that the
ucts of DP in the reaction were identied using HR LC-MS, process of dolomite photocatalysis mainly involved in two steps:
respectively (Fig. S5†). As shown in Table 3, the photocatalytic rst, the dolomite with semiconductor properties produces
process leads to the formation of m/z 183, m/z 272, and m/z 167, photo-generated electrons and holes under irradiation, which
15,31,33
which were also detected in the previous studies.
subsequently react to form reactive species. Second, the reactive
Among the observed products, m/z of 272 could be attributed species such as hydroxyl radicals caused the oxidation of DP. The
to the hydroxylation of DP (m/z 256) (Fig. 8). Hydroxyl radical is product studies indicated, on the one hand, that the hydroxyl-
a strong electrophilic species, and readily adds to aromatic ation of aromatic rings and oxidation of the alkylamine side
rings. Thus, hydroxyl radical addition to the aromatic ring chain are the main degradation pathways of DP; while, on the
accompanied by dehydrogenation is a common reaction other hand, the hydroxyl radicals are produced in the photo-
15
pathway for aromatic compounds. Considering the generation catalytic process and play an important role in DP degradation.
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1
1 N. L ´o pez, P. Marco, J. Gim ´e nez and S. Esplugas,
Photocatalytic diphenhydramine degradation under
different radiation sources: kinetic studies and energetic
comparison, Appl. Catal., B, 2018, 220, 497–505.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
´
1
2 L. M. Pastrana-Martınez, N. Pereira, R. Lima, J. L. Faria,
H. T. Gomes and A. M. T. Silva, Degradation of
diphenhydramine by photo-Fenton using magnetically
recoverable iron oxide nanoparticles as catalyst, Chem. Eng.
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This work was supported by the National Natural Science
Foundation of China (Grant 41403083), the Key Project of
Science and Technology of Hubei Provincial Department of
Education (Grant D20141305) and Natural Science of Founda-
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