Tetracycline Removal Under Solar Illumination Over Ag3VO4/mpg-C3N4 Heterojunction Photocatalysts

Article type

: Research Article

Tetracycline Removal Under Solar Illumination Over

Ag VO /mpg-C N Heterojunction Photocatalysts

3

4

3

4

1

2

Shukun Le , Wenjing Li , Yue Li , Burenbayaer Borjigin , Guangshe Li , Xiaojing

1

Wang*

1

Inner Mongolia Key Laboratory of Chemistry and Physics of Rare Earth Materials, School

of Chemistry and Chemical Engineering, Inner Mongolia University, Huhhot, Inner

Mongolia 010021, P.R. China

2

State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of

Chemistry, Jilin University, Changchun 130012, P.R. China

*

Corresponding author e-mail: wang_xiao_jing@hotmail.com. (Xiaojing Wang)

This article has been accepted for publication and undergone full peer review but has not

been through the copyediting, typesetting, pagination and proofreading process, which may

lead to differences between this version and the Version of Record. Please cite this article as

doi: 10.1111/php.12992

ABSTRACT

Ag

prepared by anchoring tiny Ag

Ag VO /mpg-C heterojunctions were used to removal tetracycline (TC), a kind of

antibiotics widely released into the aquatic environment under solar irradiation. Compared

with pure mpg-C and Ag VO , Ag VO /mpg-C displayed much higher photocatalytic

activity (83.2% removal rate within 90 min under visible-light irradiation). Importantly, no

apparent deactivation was observed for Ag VO /mpg-C -40 after five cycles, inferring a

good reusability. As confirmed by photocurrent measurement and photoluminescence

spectra, the excellent photocatalytic property of Ag VO /mpg-C was credit to the

electron-hole separation enhancement at the formed heterojunction of two semiconductors. In

addition, a possible mechanism and intermediate products for the Ag VO /mpg-C

3

VO

4

/mpg-C

3

N

4

(mesoporous graphitic carbon nitride) heterojunction photocatalysts were

3

VO particles on the nanosheet of mpg-C . The prepared

4

3 4

N

3

4

3 4

N

3

N

4

3

4

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

photocatalysts towards the photodegradation of TC in aqueous solution under artificial sun-

light radiation was proposed based the scavengers trapping test, ESR spectra, and a high

performance liquid chromatograph (HPLC) coupled with mass spectrometer (MS) analysis.

This investigation provides a low cost, green, and easily practical approach to removal the

antibiotics in the aquatic environment.

INTRODUCTION

Tetracycline (TC), a kind of well-known antibiotics, has been widely applied in human

infectious diseases medicines and veterinary medicines. Because of the poor absorption and

metabolism by humans and animals after intake, TC was very undesirable to be released into

the aquatic environment (1). It has been detected in most bodies of water including surface

water, groundwater, and treated wastewater, many of which are used as drinking water

sources (2). Therefore, the pollution of water bodies by the increased presence of TC has

become a threat on the aquatic environment. In addition, it is difficult to remove TC in

aqueous solution by conventional water treatment due to its solubility and biotoxicity.

Consequently, an efficient treatment technology is urgently needed to deal with TC residual

(3). In recent years, on the basis of the general accepted objective to achieve competent

utilization of solar-light radiation to address the aqueous environmental antibiotics pollution,

many trials have been made to develop visible-light-driven (VLD) semiconductor

photocatalysts (4,5). Graphitic carbon nitride (g-C

high chemical and thermal stability, non-toxicity, low-cost, easy preparation and relatively

narrower bandgap (2.7 eV) (6–8). Specifically, the VLD photocatalytic activity of g-C has

been principal interest (6,9). However, g-C has some disadvantages such as the less

3 4

N ) is widely investigated as a result of its

3

N

4

3

N

4

positive oxidative potential and the lower surface area, both of which limited its application

in the photocatalytic oxidation of antibiotics contamination (10). Conceivably, the

construction of heterojunction via combination of two dissimilar semiconductors with

coordinated energy band-gaps is an effective technique to promote redox potential and

quantum efficiency. In two semiconductors, the matched levels of the conduction and valance

band levels may enhance the separation of the photogenerated charges and transfer at

heterojunction interfaces (11). Accordingly, the compounded semiconductor materials would

accomplish with higher photocatalytic activities than their counterparts embracing wide

band-gap semiconductors which show the contribution to the separation of charges. Recently,

various g-C

3

N

4

-based hetero-structured (12) semiconductors such as g-C

(14), g-C /TiO (15), g-C /Ag O (16), g-C /BiOBr (17), and

(18,19) have been reported and demonstrated the improved photocatalytic

3 4 2 4

N /Ag WO (13),

g-C

3

N

4

/MoS

/WO

2

3

N

4

2

3

N

4

2

3 4

N

g-C

3

N

4

3

activities. It should be noted that the photocatalyst particles were well-dispersed into the

3 4

mesoporous g-C N , being special important to transfer the photo-excited charges and inhibit

the aggregation of the photocatalyst particles.

3 4

According to previous report, monoclinic scheelite Ag VO was considered as a good

candidate to composite with g-C

performance and application in visible light catalytic technology, such as cleaving water into

and H under visible-light illumination and resolving organic pollutants (20–25). As a

photocatalyst, Ag VO demonstrated strongly absorption bands in the visible-light region,

which can reduce energy consumption for visible-light catalytic technology. The

photocatalytic performance of Ag VO was well improved by dispersing in g-C (26–28).

For example, Wang et al. synthesized the g-C /Ag VO hybrid photocatalysts with

meaningfully enhanced visible-light photocatalytic activity for triphenylmethane degradation

29). Wu et al. reported the Ag VO /g-C -VN heterojuncted photocatalysts with

remarkable photocatalytic activity under visible light toward the degradation of RhB (30).

Zhu et al. prepared the g-C /Ag VO composites with escalation in photocatalytic

degradation efficiency of dye under visible-light irradiation (31). However, the reusable

unstability of Ag VO composite due to the aggregation of Ag VO particles was still existed.

3 4

N , which has been found exhibiting well photocatalytic

O

2

3

4

3

4

3 4

N

3

N

4

3

4

(

3

4

3 4

N

3

N

4

3

4

3

4

3

4

Recently, mesoporous g-C

templating and hard-templating approaches with an effective surface area (32–35). As a result

of its controllable morphology, higher surface area, and tunable pore diameter, mpg-C has

3 4 3 4

N (mpg-C N ) has been resoundingly prepared through soft-

3

N

4

drastically advantages to uniformly support the suitable metaloxide and it may be expected to

be an effective technique for the advancement of the photocatalytic redox ability and the

charge-carrier generation rate (36,37). Therefore, mirroring the antecedently research (31,38),

we design a new Ag

3

VO

4

3 4

/mpg-C N heterojunction composite by coupling mesoporous g-

C

3

N

4

(mpg-C ) with Ag

3

N

4

3

VO to create high-performance photocatalytic materials for TC

4

removal. The mpg-C

3

N

4

hybridized with Ag

3 4

VO would be possible preventing the

aggregation of Ag

photocatalyst.

3 4

VO particles and thus worth to try as a well reusable and high active

3 4 3 4

In this study, at room temperature the Ag VO /mpg-C N heterojunction photocatalysts

were designed by making tiny Ag VO nanoparticles charging on surface of the mpg-C N .

3

4

3 4

The photocatalytic performance and reusable stability were assessed by degrading TC

underneath visible-light. Furthermore, the photocatalytic possible mechanism of

3 4 3 4

Ag VO /mpg-C N heterojunctions was proposed on the basis of the scavengers trapping test,

ESR spectra, photoluminescence emission, and the transient photocurrent response

experiment.

MATERIALS AND METHODS

Materials. The chemicals utilized in the work, silver nitrate, melamine, tetraethyl orthosilicate,

sodium orthovanadate, sulfuric acid, hydrochloric acid, were bought from the Medicines Group.

The copolymers P123 was commercially available from Aldrich Company. The tetracycline was

purchased from Aladdin Industrial Corporation.

Synthesis of mpg-C

according to our previous publication (39).

Synthesis of Ag VO /mpg-C . The typical routine was as follows: mpg-C

dispersed in 50 mL of double-distilled water and sonicated for 30 min. Then, 2 g of AgNO

was added. The mixture was magnetically stirred for 30 min. Subsequently, 40 mL containing

g Na VO ·12H O aqueous solution was gradually dropped and reacted with stirring for 6 h.

3 4 3 4

N . The hard-template SBA-15 and mpg-C N were synthesized

3

4

3

N

4

3 4

N was

3

2

3

4

2

Next, the sample was three times water-washed with double-distilled water. Dried for 8 h

0

with the oven temperature at 60 C. Eventually, the powder was received. A new series of

Ag

mpg-C

percent. For corresponding study, the Ag

Ag VO

Catalyst characterization. X-ray powder diffractometer was investigated using XRD-

100Lab X-ray diffractometer (Japan Shimadzu). Fourier transform near-infrared spectra

FT-IR) were investigated using BRUKER FT-IR spectrometer. The microstructures and

3

VO

4

/mpg-C

for austerity, where x displayed in the heterojunctions, the mpg-C

VO were prepared by similar method, denoted as

3

N

4

materials were traced as Ag

3

VO

4

/mpg-C

3

N

4

-x with different contents of

3

N

4

3 4

N

weight

3

4

3

4

.

6

(

morphologies were recorded on scanning electron microscopy (JEOL JSM-6700F). The

morphology was observed on transmission electron microscopy (Japan JEOL JEM-2010F).

USA Quantachrome NOVA2000e instrument was used to measure the Barrett-Joyner-

Halenda (BJH) and Brunauer-Emmett-Teller (BET). An X-ray photoelectron spectrum was

used with an Al-Kα X-ray source in Thermo ESCALAB 250. The UV–visible reflectance

spectra were obtained using UV-vis-NIR spectrometer (PerkinElmer Lambda). The

photoluminescence spectra (PL) of the samples were investigated using Varian Cary Eclipse

spectrometer. Electrochemical analyzer (CHI660B, Shanghai, China) was used to measure

the photocurrent. Total organic carbon analyses (TOC) were obtained using vario TOC

selects (Elementar, Germany). The ESR signals were determined on a JES FA200

spectrometer. Tetracycline (TC) and possible intermediates were analyzed employing a high

performance liquid chromatograph coupled with mass spectrometer (HPLC–MS/MS).

Photocatalytic activity. Photocatalytic degradation of TC under visible-light was determined over

3 4 3 4

the Ag VO /mpg-C N samples. In every experiment, 15 mg of photocatalyst was added into 35

mg/L TC solution of 30 mL. First, in the dark stirring 60 min to assure the equalization of

adsorption-desorption. And a Xenon lamp (500 W) with a cutoff filter (λ>420 nm) was utilized as

the visible-light provenience. At intervals of 15 min, a 4 mL solution was sampled and

centrifugated to take away the photocatalyst particles. Then, the absorbance of photocatalysts

was measured using a UV-Vis spectrometer. To measure the photostability, after one

experimental run, the photocatalyst was recovered via centrifugation, and then washed and dried

by double-distilled water.

RESULTS AND DISCUSSION

Characterization of photocatalysts

Structural information

The Ag

depicts the XRD patterns of mpg-C

mpg-C , two characteristic peaks were observed at 13.1º and 27.4º, which correspond to

the in-planar structural packing motif and typical (002) interlayer, respectively (40). Clearly,

the pure Ag VO sample elucidated series of sharp and narrow diffraction peaks, which are

completely in accordance with its monoclinal phase (JCPDS No. 43-0542) (41). To

Ag VO /mpg-C samples, the main characteristic diffraction peaks of mpg-C can be

markedly identified Ag VO /mpg-C samples (the content of mpg-C >40%). The

diffraction peak of mpg-C could be detected with the increasing of mpg-C content.

Based on the XRD results, the co-existence of mpg-C and Ag VO in the Ag VO /mpg-

heterojunction materials (the content of mpg-C >40%) was successfully verified.

The components of the as-prepared Ag VO /mpg-C heterojunction were further

elucidated by the Fourier transform infrared (FT-IR) spectroscopy. As indicated in Figure 1b,

the mpg-C and additionally Ag VO /mpg-C -40 samples reveal the main characteristic

3

VO

4

/mpg-C

3

N

4

samples phase structure was obtained by XRD analysis. Figure 1a

3

N

4

, Ag VO , and the Ag VO /mpg-C samples. For

3

4

3

4

3 4

N

3

N

4

3

4

3

4

3

N

4

3 4

N

3

4

3

N

4

3 4

N

3

N

4

3 4

N

3

N

4

3

4

3

4

C

3

N

4

3 4

N

3

4

3 4

N

3

N

4

3

4

3 4

N

-1

peaks of g-carbon nitride. The several absorbance peaks ranging from 1100 to 1650 cm can

be attributed to the typical C=N and C–N heterocycles stretching oscillation modes. The

-1

other peak at about 811 cm is originated from the s-triazine units of characteristic breathing

-1

mode. The wide absorption peaks at around 2900-3400 cm correspond to the extending

oscillation of N–H bonds, linked with uncondensed amino groups (40,42). Additionally, main

diffraction peaks of pure Ag

3

VO

4

also could be clearly seen in the Ag

, the characteristic peaks of mpg-C

and mpg-C in the heterojunction, which further

3

VO

4

/mpg-C

3

N

4

-40

composites. For Ag VO /mpg-C

3

4

3

N

4

3

N

4

and Ag

3

VO

4

reveal the co-existence of Ag

testified the XRD results.

3

VO

4

3 4

N

XPS measurements were used to analyze the interaction of mpg-C

the surface chemical composition and the bonding modality in the midst of the atoms of the

Ag VO /mpg-C -40. Figure 2a demonstrated the survey scan XPS spectra of the Ag VO

mpg-C and Ag VO /mpg-C -40, which elucidate the co-existence elements of N, C, Ag,

O, and V in the Ag VO /mpg-C composite, compared with pure Ag VO and mpg-C

3 4 3 4

N with Ag VO ,

3

4

3

N

4

3

4

,

3

N

4

3

4

3 4

N

3

4

3

N

4

3

4

3 4

N .

Pursuant to the high resolution XPS spectrum of C 1s (Figure 2b), the C 1s components in the

powder binding energies at 288.1 eV and284.7 eV were manifested as the external carbon

atoms and the coordination between three nitrogen atoms and carbon atoms, respectively

(

43,44). The N 1s peak of Ag

3

VO

4

/mpg-C

3

N

4

-40 was observed at 397.7 eV and 399.8 eV in

2

Figure 2c. The first peak is ascribed to the sp hybridized from C−N=C group. The second

peak might be originated from (C)

2

−N−H or N−(C)

/Ag VO

3

coordination (45). The Ag 3d peaks at

+

3

67.4 eV and 373.4 eV in mpg-C

3

N

4

3

4

-40 elucidate the presence of Ag , which is

corresponding to the binding energies of Ag 3d3/2 and Ag 3d5/2 (Figure 2d). No peaks of

0

metallic Ag were found, inferred a stability of Ag

3

VO

(46). A similar phenomenon was occurred in the V 2p

also. Figure 2e showed the peaks at523.1 eV and 515.3 eV in Ag VO /mpg-C -40, in

which the suiting to binding energies of V 2p1/2 and V 2p3/2 demonstrate the existence of V

4

in this composite. Besides, the peaks

3 4

are approximate to the pure Ag VO

3

4

3 4

N

5

+

(

46). As shown in Figure 2f, the binding energy 527.8 eV and 531.0 eV belong to O 1s for

2

−

3 4 3 4

Ag VO /mpg-C N -40. The important peak located at 527.8 eV is linked with the O ions in

2

−

the V−O bonding of the Ag

3

VO

structure (29). Such analyses showed the existence of chemical bonds

and Ag VO , rather than a primitive physical mixture.

4

. And another peak is assigned to the O in the

Ag

3

VO

4

/mpg-C

3

N

4

between mpg-C

3

N

4

3

4

Morphology

The morphology and structure of Ag

observed by scanning electron microscopy (SEM) and transmission electron microscopy

TEM) were certified in Figure 3. The TEM image of mpg-C (Figure 3a) clearly shows

that typical stacked nano-plates lamellar structure about several hundred nanometers, with

some pores in it. It is evident that the pure Ag VO sample (Figure 3b) consists of spherical

particles with super small sizes. As shown in Figure 3c, a lot of floc-like mpg-C and some

of the fine spherical Ag VO particles with diameters range from 10 to 30 nm are appeared in

the TEM images. Also, the Ag VO /mpg-C is still retained the pure mpg-C structure

and morphology of the SBA-15 template. The Ag VO /mpg-C sample of SEM images

Figure 3d) further indicate that the small spherical Ag VO particles have attached to the

surface of mpg-C , identifying the interfacial interaction between Ag

It was clearly evident that the mpg-C not only prevents the agglomeration of Ag

3 4 3 4 3 4 3 4

VO , mpg-C N and Ag VO /mpg-C N photocatalysts

(

3 4

N

3

4

3

N

4

3

4

3

4

3

N

4

3 4

N

3

4

3 4

N

(

3

4

3

N

4

3

VO

4

and mpg-C

3

N

4

.

3

N

4

3

VO

4

3 4

particles, but also forms the heterojunction with Ag VO in the sample.

Textural property

The nitrogen adsorption-desorption isotherms and porosity of the Ag

3

VO

4

/mpg-C

3

N -40

4

sample, significant essential that affects the photocatalysts activity, were further researched.

As can be seen in Figure 4, the isotherms corresponding to Ag VO /mpg-C -40 is a type

3

4

3 4

N

IV isotherm with a type H3 hysteresis loop (30), reflecting the existence of the slit-like pores

and mesoporous in the size range of 3-20 nm. It is noted that the hysteresis loop

3 4 3 4

corresponding to Ag VO /mpg-C N is meaningfully left-shifted up to 0.4, meaning the

mesoporous size distribution, which is authorized by the matching pore size assignment in

3 4 3 4

the inset in Figure 4. The ordinary pore sizes of the Ag VO /mpg-C N distributed in an

average of 5 nm, which is consistent with the size of the SBA-15 template (47). The textural

parameters of particular surface area of the samples are also demonstrated in Table S1, where

behold that the BET surface area of the Ag

content of mpg-C . Owing to the mpg-C

Ag VO in the Ag VO /mpg-C samples, the particular surface area of Ag

is larger than the Ag VO (18.0 m g ). In addition, after loading Ag

mpg-C , the particular surface area decreased from 38.2 (mpg-C

Ag VO /mpg-C -10). It can be ascribed to the Ag VO

, which can block part of the space of mpg-C

3

VO

possess the agglomerated particles of the

VO /mpg-C

particles on the

4 3 4

/mpg-C N increased with the increased

3

N

4

3 4

N

3

4

3

4

3

N

4

3

4

3 4

N

2

-1

3

4

3

VO

4

2

-1

3

N

4

3

N

4

) to 22.6 m g

(

3

4

3

N

4

3

4

particles in the inner layers, pores

and on the surface of mpg-C

3

N

4

3

N

4

.

Optical absorption property

The optical absorption of Ag

was tested by UV-vis diffuse reflectance spectroscopy (DRS), and the results were shown in

Figure 5. The pure mpg-C at about 493 nm has an absorption edge, nevertheless the pure

Ag VO has a wide absorption with an absorption edge at about 581 nm. And the band-gap

energy is close to 2.6 eV and 2.2 eV, respectively. Apparently, with the increased quantity of

Ag VO in the Ag VO /mpg-C composites, the absorption of Ag VO /mpg-C modify

expressively at 500-800 nm visible light region (30), presenting evident absorption red shift.

3 4 3 4 3 4 3 4

VO , mpg-C N , and various Ag VO /mpg-C N composites

3

N

4

3

4

3

4

3

4

3

N

4

3

4

3 4

N

Therefore, it confirms that the Ag

3

VO

4

particles are charged up on the surface of mpg-C

3

N

4

,

emerging the hetero-structure. The results from DSR show that the intervention of mpg-C

affects the property of the composites, which enhance visible-light photocatalytic activity.

Photocatalytic performances of the heterojunction materials

Visible-light photocatalytic activity

3

N

4

3 4 3 4

Among the heterojunction composites, Ag VO /mpg-C N -40 presents the highest visible-

light photocatalytic activity, with 85.3% of MO decolorized within 120 min (Figure S1). To

further inquire into the outcomes of the heterojunction on the escalation of photocatalytic

activity, a series of TC photocatalytic degradation trials with the mpg-C , Ag VO , and

Ag VO /mpg-C as the photocatalysts were carried out and the parabole of photocatalytic

activity is demonstrated in Figure 6. The adsorption equalization is quickly gained after 15

min of touch, and no further TC adsorption on Ag VO /mpg-C is observed after 30 min

Figure 6a). In photocatalytic experiments in existence of 15 mg photocatalysts, a maximum

degradation was obtained under visible light illumination. It can be shown in Figure 6b that

Ag VO /mpg-C heterojunction photocatalysts exhibit higher photocatalytic activities than

mpg-C and Ag VO . For pure mpg-C and Ag VO , the photocatalytic activity was low

and the degradation of TC is 16.8% and 38.8% for 90 min of visible-light irradiation,

respectively. In contrast, 83.2% of TC is degraded by the Ag VO /mpg-C -40 under visible

3

N

4

3

4

3

4

3 4

N

3

4

3 4

N

(

3

4

3 4

N

3

N

4

3

4

3

N

4

3

4

3

4

3 4

N

light irradiation. This is expected owing to higher charge carrier mobility which leads to

faster electron-hole separation rate and hence higher photocatalytic activity. In addition,

Figure 6c showed the kinetic curves of the miscellaneous samples, reflecting that the TC

photodegradation follows the pseudo-first-order kinetics. The transparent rate constants are

−1

resolved as 0.00801, 0.00167, 0.00151, 0.00339, 0.00624, 0.01966, and 0.01185min for

mpg-C , Ag VO , Ag VO /mpg-C -10, Ag VO /mpg-C -20, Ag VO /mpg-C -30,

Ag VO /mpg-C -40 and Ag VO /mpg-C -50, respectively. For comparison, the

photocatalytic activity of the standard TiO Degussa P-25 (P25) was evaluated under the

same conditions (Fig. 6d). Obviously, P25 presents the poor degradation for TC (only about

0%). Therefore, our samples possess a well superiority in photocatalytic oxidation of TC in

3

N

4

3

4

3

4

3

N

4

3

4

3

N

4

3

4

3 4

N

3

4

3

N

4

3

4

3 4

N

2

contrast to traditional photocatalyst of P25.

TOC analysis

To determine the photocatalytic properties of the as prepared samples in solution in time of

the photocatalytic process, the TOC analysis was compared with the degradation of TC. It

can be seen in Figure S2, topical mineralization occurs during TC photocatalytic reactions.

Even, TOC depletion was observed under visible light sources, reaching 33.2% removal after

9

0 min. On the other hand, the removal rate of TOC is lower than the degradation rate within

0 min toward TC degradation. Even though TC is promptly degraded, absolute

mineralization is hardly observed after irradiation period with the solarium apparatus.

Besides mineralized TC into CO and H O in the solution during illumination, many small

intermediate products could be generated by destroying the organic group of TC molecules.

2

These results suggest that the as-prepared Ag

potential for environmental applications.

Mass spectral analysis

3 4 3 4

VO /mpg-C N -40 photocatalysts should have

The probable intermediates formed in the TC photodegradation process were identified by

the Mass spectrometry (MS). The matching analysis of the adsorption for 1 h in the dark, the

degradation for 30 min and 90 min of TC were shown in Figure 7a-c. The protonated TC

molecular ions are spotted at the important oxidative species with m/z 445.10. Intermediate

products were observed, which is analyzed over collision-induced dissociation. Figure 7d

illustrates the proposed degradation products and the simple degradation pathway of TC

during the different reactive period. It can be seen that TC proceeds an intermediate

(m/z=318) by peeling off the outer ring and then an intermediate (m/z=277) by losing an

aldehyde group. Also the MS results confirmed the TOC analysis. In addition, hydroxyl

radical, superoxide radical species and singlet oxygen could directly oxidize TC. All above

analysis shown that the TC molecules and intermediate products are possibly degraded to

2 2

H O, CO and other small molecules.

Regeneration and reusability

The stability of the photocatalysts is another significant factor for pragmatic application. The

reconstruction and reusability of the as-synthesized Ag

photocatalyst was learnt by several recycle tests. The cyclic runs toward the photocatalytic

degradation of TC were performed five times on Ag VO /mpg-C -40 under the same

conditions. For every recycling run, the Ag VO /mpg-C -40 photocatalyst was collected

by centrifugation, then washed three times with ethanol and dried. As shown in Figure 8a, no

apparent deactivation of the Ag VO /mpg-C -40 photocatalyst was observed after five

cycles. To further research the stability of photocatalysts, the Ag VO /mpg-C -40 of XRD

analysis before and after five coherent experiments for degradation of TC is represented in

Figure 8b. From the XRD patterns of the Ag VO /mpg-C -40, the main characteristic

diffraction peaks are in same positon, which recommend the crystal structure is unchanged

after five cycling tests. Therefore, as-prepared Ag VO /mpg-C heterojunction

3 4 3 4

VO /mpg-C N heterojunction

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

3

4

3 4

N

photocatalysts shows remarkable catalytic stability, staging as positive heterogeneous VLD

photocatalysts to break down aqueous organic pollutants efficiently.

Mechanism of the enhanced photocatalytic activity

Photoluminescence measurements

The photoluminescence spectra of the photocatalysts were recorded to conclude the higher

3 4 3 4

photocatalytic activity of the Ag VO /mpg-C N heterojunction (Figure 9a). It is well-known

that the recombination and transfer process of photo-generated electron-hole pairs may

liberate energy in the form of PL emission. In short, the lower fluorescence intensity presents

lower reorganization of electron-hole pairs, leading to higher photocatalytic activity. It is

distinct that the PL spectrum of the pure mpg-C

strong emission peak. At similar emission position, the emission intensity of pure Ag

extremely lower than that of pure mpg-C . From Figure 9a, it shown that the PL intensities

3

N

4

photocatalyst at around 470 nm has a

3

VO is

4

3

N

4

of Ag

and Ag

pure mpg-C

formation of a heterojunction between mpg-C

electron-hole pairs on the mpg-C surface is prohibited.

Photo-electrochemical experiments

3

VO

4

/mpg-C

, which reveals that a lower recombination rate of electrons and holes than the

and Ag VO under visible-light (30). The PL results indicate that after the

and Ag VO , the reorganization of the

3 4 3 4

N heterojunction photocatalysts are lower than that of pure mpg-C N

3

VO

4

3

N

4

3

4

3

N

4

3

4

3

N

4

The detachment of photo-induced electrons and holes could be demonstrated by the

photocurrent regarded as the most competent proof. The photocurrent value is proportional to

the charge separation efficiency for the visible-light photocatalytic reaction. The

photocurrent-time measurement of pure mpg-C

was used to investigate the photo-induced charge transfer dynamics of the Ag

heterojunction photocatalysts. Also the promotion of photocatalytic activity of Ag

heterojunction composites was elucidated. Figure 9b showed the photocurrent−time (I–t)

curves of mpg-C , Ag VO and Ag VO /mpg-C -40 composite with six on−off cycles of

3

N

4

, pure Ag

3

VO

4

and Ag

3

VO

4

/mpg-C

VO /mpg-

3 4

N -40

3

VO

4

3 4

N

3

4

3 4

C N

3

N

4

3

4

3

4

3 4

N

desultory irradiation. It can be clearly seen that the increased photocurrent responses occur

for all tested working electrodes ever the irradiation is implemented, and the generated

photocurrents are stable and reproducible during six cycles. The Ag

3

VO

4

/mpg-C

3

N

4

-40

composite sample presents a higher photocurrent than that of mpg-C

3

N

4

and Ag

3

VO

4

,

proposing longer life time and more competent separation of photo-induced electron-hole

pairs (48,49). This result could be attributed to the inhibition of the charge recombination

3 4 3 4

process in the Ag VO /mpg-C N -40 heterojunction, as certified by the PL analysis.

Reactive species scavenging experiments

As well-known that dyes are broken down by photocatalysts under visible-light, which is

+

−

2

basically owing to generate reactive species such as hole (h ), superoxide radical (•O ) and

the hydroxyl radical (•OH). To further inquire into the photocatalytic mechanism of the

3 4 3 4

Ag VO /mpg-C N heterojunction in specific and the role of the three reactive species over

the photocatalytic degradation reaction, the consequence of scavengers on the degradation of

TC was checked to show the remarkable reactive species in the photocatalytic system. In our

experiment, the hydroxyl radical scavenger is t-BuOH, the holes scavenger is EDTA, and the

superoxide radical scavenger is 1, 4-benzoquinone (BQ) (49). As is clear from Figure 10a,

3 4 3 4

contrapositive with the degradation of TC over Ag VO /mpg-C N -40 without adding

possessory active species scavenger, the TC degradation rate is suppressed after the addition

of three scavenger t-BuOH (1 mM), EDTA (1 mM) and BQ (1 mM). According to these

results, the above three active species are entire generated over the photocatalytic degradation

course of TC under irradiation. The repression degree follows the order t-BuOH > EDTA >

+

BQ, which also suggests that the photo-generated h and •OH radical is the main reactive

−

species in the photocatalytic reaction meanwhile the •O

specie for TC degradation.

2

radical is other important reactive

ESR behavior analysis

To research the generation of reactive oxygen species (ROS) during the photocatalysis

approach and ascertain the mechanism potential photolysis of TC, electron spin resonance

−

(

ESR) experiments are implemented to explore 1O

2

, •O

2

and •OH radicals (22). TEMP (4-

oxo-2,2,6,6-tetramethyl) and DMPO (5,5-diamethyl-1-pyrroline N-oxide) are utilized as the

−

explore molecules for 1O

2

and •O

2

/•OH, respectively. The ESR signal shown in Figure 10b

−

indicates that •OH is generated upon visible-light irradiation. There is obvious DMPO-•O

2

appeared in the spectra after irradiation (Figure 10c), indicating that during the system of

photodegradation the photo-generated electrons in the semiconductors conduction band could

−

be innovated into •O

2

radicals. Meanwhile, TEMP-1O is shown in Figure 10d. A strong

intensity for the TEMP-1O

2

signals was produced when the visible light added, collating with

the ESR signal in dark. What is more, the singlet oxygen (1O

2

) is generated between

−

+

electrons and holes from the reaction, can also being produced by •O

2

and h reacted under

light irradiation (51). Consequently, according to the above analysis, it could be concluded

−

that the •OH, h+, •O

2

and 1O

2

are the photocatalytic active species in the degradation of TC

under visible-light, which is consistent with the consequence of the species scavenging proof.

Discussion

Based on all of the above information, the photocatalytic mechanism of the TC photo-

degradation over Ag

and schematically clarified in Figure 11. The heightened photocatalytic activity could be

attributed to the structure of heterojunction between mpg-C and Ag VO . Both mpg-C

and Ag VO could be simultaneously excited to form electron-hole pairs under visible light

illustration as convinced in UV-vis spectra.

3 4 3 4

VO /mpg-C N heterojunction under visible-light was briefly arranged

3

N

4

3

4

3 4

N

3

4

The conduction band-edge energy of semiconductors is theoretically calculated by

Mulliken electronegativity theory: ECB = Χ – Ec − 0.5Eg. The Χ is the Mulliken

electronegativity of the component atoms. Ec is the free electrons energy in the hydrogen

scale. Eg is the semiconductor band-gap energy. The valence band-edge energy could be

procured by EVB = ECB + Eg. The VB and CB energy of Ag

and 2.07 eV (vs NHE), while the mpg-C are computed to be −1.08 eV and 1.52 eV (vs

NHE). The positions of the VB and CB of mpg-C match properly with those of Ag VO

Consequently, it is obviously that the charge transfer appears in the Ag VO /mpg-C

heterojunction. As the mpg-C CB edge potential is furthermore negative than Ag VO

electrons in CB of mpg-C will transfer and inject into the Ag VO CB. And holes in VB

of Ag VO will transfer to the VB of mpg-C as a result of its more positive potential

compared to that of mpg-C . Thus, photo-generated electrons will tend to be accumulated

in the Ag VO CB and holes in the mpg-C VB, which effectively separated the electron-

hole pairs on the heterojunction formed between mpg-C and Ag VO as well as led to the

3 4

VO are computed to be 0.22 eV

3

N

4

3

N

4

3

4

.

3

4

3 4

N

3

N

4

3

4

,

3

N

4

3

4

3

4

3 4

N

3

N

4

3

4

3 4

N

3

N

4

3

4

high photocatalytic activity. Such carriers transfer route is supported by ESR testing.

−

Generally, the photoexcited electrons in the CB of Ag

3

VO

4

cannot reduce O

2

to generate •O

2

−

because the CB edge potential of Ag VO is more positive than that of the O

3

4

2

/•O

2

potential

(

−0.046 V). Moreover, the formation of hydroxyl radicals is also prohibited because the VB

−

potential of mpg-C

a heterojunction of Ag

could respond with O

could react with O

3

N

4

is more negative than the OH /•OH potential. However, after forming

3

VO

4

/mpg-C

3

N

4

3 4

, the accumulated electrons on the CB of Ag VO

−

2

to organize •O

2

radical. Meanwhile, the photo-generated electrons

+

2

and H to create •OH radicals (29). And the h located on the mpg-C

3

N

4

VB would react with TC straight. Both the ESR analysis and trapping experiment suggest

−

+

that •OH, •O

Ag VO /mpg-C

that •OH and •O

Ag VO /mpg-C

2

, and h are the active species during the photo-degradation of TC by the

3

4

3

N

4

photocatalyst. Both the ESR analysis and trapping experiment suggest

are the active species during the photo-degradation of TC by the

−

2

3

4

3 4

N photocatalyst. The process is described as follows:

−

+

−

+

Ag

VO

3

VO

4

/mpg-C

3

N

4

→ Ag

3

VO

4

(e + h ) / mpg-C

3

N

4

(e + h )

−

+

−

+

−

+

Ag

3

4

(e + h ) / mpg-C

3

N

4

(e + h ) → Ag

3

VO

4

(e ) / mpg-C N (h )

3 4

−

2 2

O + e → •O

−

+

−

•O

2

+ 2H + 2e → H

→ 2•OH

/•OH / h + TC → degradation products

2 2

O

2 2

H O

−

+

•O

2

Based on the above discussions, the heterojunction of Ag

efficiently enhance the detachment of photo-generated electron-hole pairs under visible light.

As a result, the photocatalytic activity of Ag VO /mpg-C heterojunction composites over

VO and mpg-C

3 4 3 4

VO /mpg-C N could

3

4

3 4

N

the visible-light catalytic reactions is extremely higher than blank Ag

3

4

3 4

N .

CONCLUSION

Focused on the refractory TC residual in aquatic environment, we assembled the

heterojunction photocatalyst Ag

mesoporous g-C templet. The prepared composite exhibited remarkable photocatalytic

activity towards the TC degradation under visible-light, much higher than the pure Ag VO

and mpg-C . It is showed that an optimized Ag VO /mpg-C -40 sample had the most

3 4 3 4 3 4

VO /mpg-C N via dispersing tiny Ag VO particles into a

3

N

4

3

4

3

N

4

3

4

3 4

N

efficient TC removal of 83.2% under 90 mins solar light illuminating. No apparent

deactivation was observed after five cycles, inferring a good recycle usage. The optical and

3 4 3 4

morphological studies reveal that the formation of the Ag VO /mpg-C N heterojunction

performs on a pivotal role on the competent separation of carriers for the enhancement of

photocatalytic activity as committed by photoluminescence spectra and photocurrent

measurement. Moreover, the mechanism of TC removal was proved to be mainly an

+

oxidation process through the reactive species of •OH and h based on the scavengers

trapping test, ESR spectra, and mass spectrum analysis. This investigation proposed the

3 4 3 4

Ag VO /mpg-C N heterojunction might be a valuable material for the removal of antibiotics

residual with the merits of low cost, green, and easy to be industrialized as well.

ACKNOWLEDGEMENTS: This work is financially supported by National Natural

Science Foundation of China (Grants 21777078 and 21567017), the Project of Research and

Development of the Applied Technology for Inner Mongolia (201702112), the Postgraduate

Scientific Research Innovation Foundation of Inner Mongolia (No. 10000-16010109-52).

SUPPORTING INFORMATION

Additional Supporting Information may be found in the online version of this article:

Figure S1. Effect of various photocatalysts including pure Ag

Ag VO /mpg-C nanocomposites on degradation efficiency of MO under visible light.

Figure S2. TOC profiles under the visible-light irradiation in the presence of Ag VO /mpg-

-40 for 90 min.

3 4 3 4

VO , mpg-C N and

3

4

3 4

N

3

4

3 4

C N

Table S1. BET areas of the different samples.

REFERENCES

1

2

. Wang, H., X. Yuan, Y. Wu, G. Zeng, H. Dong, X. Chen, L. Leng, Z. Wu and L. Peng

2016) In situ synthesis of In @MIL-125(Ti) core–shell microparticle for the removal

(

2 3

S

of tetracycline from wastewater by integrated adsorption and visible-light-driven

photocatalysis. Appl. Cataly., B. 186, 19–29.

. Chen F., Q. Yang, X. Li, G. Zeng, D. Wang, C. Niu, J. Zhao, H. An, T. Xie and Y. Deng

3 4 4

(2017) Hierarchical assembly of graphene-bridged Ag PO /Ag/BiVO (040) Z-scheme

photocatalyst: An efficient, sustainable and heterogeneous catalyst with enhanced

visible-light photoactivity towards tetracycline degradation under visible light irradiation.

Appl. Cataly., B. 200, 330–342.

3

. Pang S., J. Huang, Y. Su, B. Geng, S. Lei, Y. Huang, C. Lyu and X. Liu (2016) Synthesis

2

and modification of Zn-doped TiO nanoparticles for the photocatalytic degradation of

tetracycline. Photochem. Photobiol. 92, 651–657.

4

5

. Chen X. B., S. H. Shen, L. J. Guo and S. S. Mao (2010) Semiconductorbased

photocatalytic hydrogen generation. Chem. Rev. 110, 6503−6570.

. Sun J., S. Sun, M. Fan, H. Guo, Y. Lee and R. Sun (2008) Oxidative decomposition of p-

nitroaniline in water by solar photo-Fenton advanced oxidation process. J. Hazard. Mater.

1

53, 187−193.

6

. Wang X. C., K. Maeda, A. Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K. Domen and

M. Antonietti (2009) A metal-free polymeric photocatalyst for hydrogen production from

water under visible light. Nat. Mater. 8, 76–80.

7

8

. Hu J., W. Cheng, S. Huang, D. Wu and Z. Xie (2006) First-principles modeling of

nonlinear optical properties of C

. Ge L., C. C. Han, J. Liu and Y. F. Li (2011) Enhanced visible light photocatalytic activity

of novel polymeric g-C loaded with Ag nanoparticles. Appl. Catal. A. 409-410, 215–

22.

. Xiang Q. J., J. G. Yu and M. Jaroniec (2011) Preparation and enhanced visible-light

photocatalytic H -production activity of graphene/C composites. J. Phys. Chem. C.

15, 7355–7363.

3 4

N polymorphs. Appl. Phys. Lett. 89, 841–53.

3

N

4

2

9

1

2

3 4

N

1

0. Zheng Y., J. Liu, J. Liang, M. Jaroniec and S. Z. Qiao (2012) Graphitic carbon nitride

materials: Controllable synthesis and applications in fuel cells and photocatalysis.

Energy Environ. Sci. 5, 6717−6731.

3 4

1. Zhao X., L. Song and S. Zhang (2018) Synthesis of AgCl/Ag PO composite

photocatalysts and study on photodegradation activity based on a continuous reactor.

Photochem. Photobiol. 94, 484–490.

1

2. Fu J., J. Yu, C. Jiang, and B. Cheng (2018) g-C

photocatalysts. Adv. Energy Mater. 8, 17015031–170150331.

3. Zhu B., P. Xia, Y. Li, W. Ho and J. Yu (2017) Fabrication and photocatalytic activity

enhanced mechanism of direct Z-scheme g-C /Ag WO photocatalyst. Appl. Surf. Sci.

91, 175–183.

4. Fu Y., Z. Li, Q. Liu, X. Yang and H. Tang (2017) Construction of carbon nitride and

MoS quantum dot 2D/0D hybrid photocatalyst: Direct Z-scheme mechanism for

improved photocatalytic activity. Chin. J. Catal. 38, 2160–2170.

3 4

N -Based heterostructured

3

N

4

2

4

3

1

2

1

2

5. Sridharan K., E. Jang and T. J. Park (2013) Novel visible light active graphitic C

3 4

N -

TiO composite photocatalyst: Synergistic synthesis, growth and photocatalytic treatment

2

of hazardous pollutants. Appl. Cataly., B. 142-143, 718−728.

3 4 2

6. Xu M., L. Han and S. J. Dong (2013) Facile fabrication of highly efficient g-C N /Ag O

heterostructured photocatalysts with enhanced visible-light photocatalytic activity. ACS

Appl. Mater. Interfaces. 5, 12533−12540.

7. Fu J., Y. L. Tian, B. B. Chang, F. Xi and X. Dong (2012) BiOBr-carbon nitride

heterojunctions: synthesis, enhanced activity and photocatalytic mechanism. J. Mater.

Chem. 22, 21159−21166.

8. Katsumata K., R. Motoyoshi, N. Matsushita and K. Okada (2013) Preparation of

3 4 3

graphitic carbon nitride (g-C N )/WO composites and enhanced visible-light-driven

photodegradation of acetaldehyde gas. J. Hazard. Mater. 260, 475−482.

9. Yu W., J. Chen, T. Shang, L. Chen, L. Gu and T. Peng (2017) Direct Z-scheme g-

C

3

N

4

3 2

/WO photocatalyst with atomically defined junction for H production. Appl.

Cataly., B. 219, 693–704.

0. Konta R., H. Kato, H. Kobayashi and A. Kudo (2003) Photophysical properties and

photocatalytic activities under visible light irradiation of silver vanadates. Phys. Chem.

Chem. Phys. 5, 3061–3065.

2

1. Hu X. X. and C. Hu (2007) Preparation and visible-light photocatalytic activity of

3 4

Ag VO powders. J. Solid State Chem. 180, 725–732.

2. Huang C. M., K. W. Cheng, G. T. Pan, W. S. Chang and T. K. Yang (2010) CTAB-

assisted hydrothermal synthesis of silver vanadates and their photocatalytic

characterization. Chem. Eng. Sci. 65, 148–152.

2

3. Chen S. F., W. Zhao, W. Liu, H. Y. Zhang, X. L. Yu and Y. H. Chen (2009) Preparation,

2 4

characterization and activity evaluation of p–n junction photocatalyst p-CaFe O /n-

Ag

3 4

VO under visible light irradiation. J. Hazard. Mater. 172, 1415–1423.

2

4. Zhang L., Y. M. He, P. Ye, W. H. Qin, Y. Wu and T. H. Wu (2013) Enhanced

3 4 3 4

photodegradation activity of Rhodamine B by Co O /Ag VO under visible light

irriadiation. Mater. Sci. Eng. B. 178, 45–52.

5. Das D. P., A. Samal, J. Das, A. Dash and H. Gupta (2013) One-pot fabrication of RGO–

Ag VO nanocomposites by in situ photoreduction using different sacrificial agents: high

selectivity toward catechol synthesis and photodegradation ability. Photochem. Photobiol.

0, 57–65.

6. She X., J. Yi, Y. Xu, Y. Song, L. Huang, H. Ji, H. Xu and H. Li (2017) Designing Z-

scheme 2D-C /Ag VO hybrid structures for improved photocatalysis and

3

4

9

2

3

N

4

3

4

photocatalytic mechanism insight. Phys. Status Solid A 214, 16009461–16009468.

7. Wu J., X. Shen, X. Miao, Z. Ji, J. Wang, T. Wang and M. Liu (2017) An all-Solid-State

3 4 3 4

Z-scheme g-C N /Ag/Ag VO photocatalyst with enhanced visible-light photocatalytic

performance. Eur. J. Inorg. Chem. 21, 2845–2853.

8. Barzegar J., A. Habibi-Yangjeh, A. Akhundi and S. Vadivel (2018) Novel ternary g-

3 4 3 4

C N /Ag VO /AgBr nanocomposites with excellent visible-light-driven photocatalytic

performance for environmental applications. Solid State Sci. 78, 133–143.

9. Wang S., D. Li, C. Sun, S. Yang, Y. Guan and H. He (2014) Synthesis and

characterization of g-C

photocatalytic activity for triphenylmethane dye degradation. Appl. Catal. B. 144,

85−892.

0. Wu S. Z., K. Li and W. D. Zhang (2015) On the heterostructured photocatalysts

Ag VO /g-C with enhanced visible light photocatalytic activity. Appl. Surf. Sci. 324,

24−331.

1. Zhu T. T., Y. H. Song, H. Y. Ji, Y. G. Xu, Y. X. Song, J. X. Xia, S. Yin, Y. Li, H. Xu, Q.

3 4 3 4

N /Ag VO composites with significantly enhanced visible-light

8

3

4

3 4

N

3

3 4 3 4

Zhang and H. Li (2015) Synthesis of g-C N /Ag VO composites with enhanced

photocatalytic activity under visible light irradiation. Chem. Eng. J. 271, 96−105.

2. Lee E. Z., Y. S. Jun, W. H. Hong, A. Thomas and M. M. Jin (2010) Cubic mesoporous

graphitic carbon(IV) nitride: an all-in-one chemosensor for selective optical sensing of

metal ions. Angew. Chem. Int. Ed. 49, 9706−9710.

3

3. Liang J., Y. Zheng, J. Chen, J. Liu, D. H. Jurcakova, M. Jaroniec and S. Z. Qiao (2012)

Facile oxygen reduction on a three-dimensionally ordered macroporous graphitic

C

3

N

4

/carbon composite electrocatalyst. Angew. Chem. 51, 3892−3896.

4. Cui Y. J., J. S. Zhang, G. G. Zhang, J. H. Huang, P. Liu, M. Antonietti and X. C. Wang

2011) Synthesis of bulk and nanoporous carbon nitride polymers from ammonium

(

thiocyanate for photocatalytic hydrogen evolution. J. Mater. Chem. 21, 13032−13039.

5. Vinu A. (2008) Two-dimensional hexagonally-ordered mesoporous carbon nitrides with

tunable pore diameter, surface area and nitrogen content. Adv. Funct. Mater. 18, 816−827.

6. Wang X. C., K. Maeda, X. F. Chen, K. Takanabe, K. Domen, Y. D. Hou, X. Z. Fu and M.

Antonietti (2009) Polymer semiconductors for artificial photosynthesis: hydrogen

evolution by mesoporous graphitic carbon nitride with visible light. J. Am. Chem. Soc.

3

1

31, 1680−1681.

3

7. Takanabe K., Kamata K., Wang X. C., Antonietti M., Kubotaa J., Domen K., 2010.

Photocatalytic hydrogen evolution on dye-sensitized mesoporous carbon nitride

photocatalyst with magnesium phthalocyanine. PCCP. 12, 13020−13025.

8. Le S., T. Jiang, Y. Li, Q. Zhao, Y. Li, W. Fang and M. Gong (2017) Highly efficient

visible-light-driven mesoporous graphitic carbon nitride/ZnO nanocomposite

photocatalysts. Appl. Catal. B. 200, 601–610.

9. Le S. K., T. S. Jiang, Q. Zhao, X. F. Liu, Y. Y. Li, B. W. Fang and M. Gong (2016) Cu-

doped mesoporous graphitic carbon nitride for enhanced visible-light driven

photocatalysis. Rsc. Adv. 6, 38811−38819.

4

0. Liu J. H., T. Zhang, Z. C. Wang, G. Dawsona and W. Chen (2011) Simple pyrolysis of

urea into graphitic carbon nitride with recyclable adsorption and photocatalytic activity. J.

Mater. Chem. 21, 14398−14401.

4

1. Tao X. C., Q. H, T. Z. Xu and F. Liao (2014) Highly efficient photocatalytic performance

3 4

of graphene-Ag VO composites. J. Mater. Sci.-Mater. Electron. 25, 3480-3485.

2. Niu P., G. Liu and H. M. Cheng (2012) Nitrogen vacancy-promoted photocatalytic

activity of graphitic carbon nitride. J. Phys. Chem. C. 116, 11013−11018.

3. Yan H. J. (2012) Soft-templating synthesis of mesoporous graphitic carbon nitride with

enhanced photocatalytic H

430−3432.

4. Chai B., T. Y. Peng, J. Mao, K. Li and L. Zan (2012) Graphitic carbon nitride (g-C

Pt-TiO nanocomposite as an efficient photocatalyst for hydrogen production under

visible light irradiation. PCCP. 14, 16745−16752.

5. Xiang Q. J., J. G. Yu and M. Jaroniec (2011) Preparation and enhanced vsible-light

photocatalytic H -production activity of graphene/C composites. J. Phys. Chem. C.

15, 7355−7363.

6. Zhang L., Y. He, P. Ye, W. Qin, Y. Wu and T. Wu (2013) Enhanced photodegradation

2

evolution under visible light. Chem. Commun. 48,

3

4

3 4

N )-

2

3 4

N

1

3 4 3 4

activity of Rhodamine B by Co O /Ag VO under visible light irradiation. Mater. Sci.

Eng., B. 178, 45−52.

7. Zhang Y. F., X. J. Bo, A. Nsabimana, C. Luhana, G. Wang, H. Wang, M. Li and L. Guo

2014) Fabrication of 2D ordered mesoporous carbon nitride and its use as

(

2 2

electrochemical sensing platform for H O , nitrobenzene, and NADH detection. Biosens.

Bioelectron. 53, 250−256.

4

8. Yu J. G. and B. Wang (2010) Effect of calcination temperature on morphology and

photoelectrochemical properties of anodized titanium dioxide nanotube arrays. Appl.

Catal., B. 94, 295−302.

4

5

9. Bu Y. Y., Z. Y. Chen and W. B. Li (2014) Using electrochemical methods to study the

promotion mechanism of the photoelectric conversion performance of Ag-modified

3 4

mesoporous g-C N heterojunction material. Appl. Catal., B. 144, 622−630.

0. Wang T., F. Zhang, G. Xiao, S. Zhong and C. Lu (2015) Synthesis of Bi

2

6 2 3

WO /Bi O

composite with enhanced photocatalytic activity by a facile one-step hydrothermal

synthesis route. Photochem. Photobiol. 91, 291–297.

1. Parangusan H., D. Ponnamma, M. A. A. Al-Maadeed and A. Marimuthu (2018)

Nanoflower-like yttrium-doped ZnO photocatalyst for the degradation of methylene blue

dye. Photochem. Photobiol. 94, 237–246.

FIGURE CAPTIONS

3 4 3 4

Figure 1. XRD patterns (a) and FT-IR spectra (b) of mpg-C N , Ag VO , and the synthesized

Ag

Figure 2. XPS spectra of the synthesized Ag

Ag VO , mpg-C and Ag VO /mpg-C samples; (b) C 1s; (C) N ls; (d) Ag 3d; (e) V 2p;

f) O 1s.

Figure 3. TEM images of mpg-C

images of Ag VO /mpg-C (d).

3 4 3 4

VO /mpg-C N nanocomposites.

3

4 3 4

VO /mpg-C N -40 sample: (a) Survey of the

3

4

3

N

4

3

4

3 4

N

(

3

4 3 4 3 4 3 4

N (a), Ag VO (b) and Ag VO /mpg-C N (c), and SEM

3

4

3 4

N

3 4 3 4

Figure 4. Nitrogen adsorption-desorption isotherms of Ag VO /mpg-C N materials. The

inset is the corresponding pore-size distribution.

3 4 3 4

Figure 5. UV-Vis absorbance spectra of mpg-C N , Ag VO , and the synthesized

Ag VO /mpg-C nanocomposites.

3

4

3 4

N

Figure 6. (a) Adsorption envelopes of the different samples for TC in the dark; (b) Effect of

various photocatalysts on degradation efficiency of TC under visible light; (c) first-order

kinetics of TC degradation in the presence of the different samples; (d) The degraded rate of

TC with P25, Ag

3

VO

4

/mpg-C

3

N

4

-40, and without any catalyst.

4 3 4

VO /mpg-C N -40 composite in

Figure 7. Mass spectra of degraded tetracycline over Ag

3

dark (a) , 45 min (b) and 90 min (c) visible-light irradiation,(d) the possible intermediate

products and reaction pathway for TC degradation under visible light.

Figure 8. (a) Recycling experiments of visible-light photocatalytic degradation of TC over

the Ag

photocatalytic degradation of TC for the fifth cycle.

Figure 9. Photoluminescence emission spectra (a) and transient photocurrent response (b) of

mpg-C , Ag VO , and Ag VO /mpg-C -40.

Figure 10. Influence of various scavengers on the visible-light photocatalytic activity of

Ag VO /mpg-C -40 toward the degradation of TC (a); ESR spectra of the radical adducts

trapped by DMPO and TEMP with Ag

3 4 3 4 3 4 3 4

VO /mpg-C N -40; (b) XRD patterns of Ag VO /mpg-C N -40 before and after

3

N

4

3

4

3

4

3 4

N

3

4

3 4

N

3

VO

4

/mpg-C

3

N

4

-40 in the dark and under visible light

−

irradiation for 70 s at ambient temperature for DMPO-•OH (b), DMPO-•O

2

(c), and TEMP-

1O

2

(d).

3 4 3 4

Figure 11. A possible visible-light photocatalytic degradation diagram of Ag VO /mpg-C N

nanocomposite.

Article Doi

Tetracycline Removal Under Solar Illumination Over Ag3VO4/mpg-C3N4 Heterojunction Photocatalysts

DOI: 10.1111/php.12992

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Authors:

Article abstract of DOI:10.1111/php.12992

Full text of DOI:10.1111/php.12992

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