One-pot synthesis of sulfur doped activated carbon as a superior metal-free catalyst for the adsorption and catalytic oxidation of aqueous organics

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DOI: 10.1039/C7TA09814F

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ARTICLE

One-pot synthesis of sulfur doped activated carbon as a superior

metal-free catalyst for adsorption and catalytic oxidation of

aqueous organics

Received 00th January 20xx,

Accepted 00th January 20xx

a, b

a*

a, b

a**

a

DOI: 10.1039/x0xx00000x

Yaoping Guo , Zequan Zeng , Yongjin Liu , Zhanggen Huang , Yan Cui , and Jieyang Yang

www.rsc.org/

Synthesis of S-doped activated carbon with well developed porous structure and enhanced catalytic activity has been

extensively investigated for their great potential application in various fields. Here, we report a facile one-pot thermal

process for preparation of in-situ S-doped activated carbon by using a potential waste material (Poly(phenylene sulphide)

(PPS)) as precursor, and KOH as activator for adsorptive and oxidative removal of aqueous organics. Experiment results

demonstrated that the as-prepared sample treated at 800 °C (S-AC-800) exhibited both strong adsorption ability and

enhanced persulfate (PS) activity for phenols removal. The effect of adsorption on oxidation was illustrated by

investigating the removal of different phenols organics in their individual solution and mixture solution. It was suggested

that a higher adsorption capacity led to a more rapid degradation process. In the process, the adsorbed organics were

preferentially in-situ degraded, which in turn accelerated the adsorption, then the adsorption and oxidation synergistically

promoted the efficient organics removal. Quenching experiments demonstrated that the activation of PS mainly

proceeded through both surface-bounded radicals and non-radical pathway. The effects of several operate parameters as

well as the influences of various inorganic anions, and background organic matters in water on organic removal were

investigated in detail. In addition, the stability of S-AC-800 and its deactivation reason were also studied. It is expected that

this work could not only provides a promising way to utilize PPS waste, but also provides a facile, economical and effective

method for future development of more efficient sulfur-doped activated carbons for wastewater treatment.

7

8

adsorbents such as zeolites, metal-organic frameworks (MOFs),

9

1

. Introduction

and mesoporous silica because of its low cost, porous structure,

and high special surface area. Also, it is an excellent potential

alternative to the metal-based catalysts for organic catalytic

oxidation due to its non-toxicity, good thermal stability, and easy

Organic pollutants in wastewater with the features of high toxicity

and bad biodegradability have been a big issue in environmental

remediation, which pose great threat to aquatic ecosystems and to

human beings even at low exposure levels. Although diverse

technologies, such as adsorption, microbial degradation, membrane

processes, and advanced oxidation processes (AOPs) (ultrasonic

degradation, chemical oxidation, photocatalytic oxidation, plasma

1

0-15

tunability.

Thus, we suppose that if a porous carbon exhibits

both strong adsorption ability as well as excellent catalytic activity,

it would be an efficient solution to degrade the adsorbed organics

and regenerate the material in-situ, which would be much efficient

and mild for aqueous organics removal in wastewater.

Unfortunately, the generally used carbon materials, such as

activated carbon (AC), carbon nanotubes (CNTs), reduced graphene

oxide (rGO), and nanodiamond (ND) show a weak adsorption ability

1

process), have been proposed to remove the hazardous

2

compounds, the most economical and easiest one is adsorption.

Moreover, the adsorbents can be reused with an appropriate after-

treatment. However, it just move contaminants from one phase to

another phase without destroying them. In terms of destruction,

AOPs are widely acknowledged to be the most efficient method,

1

6-18

and moderate catalytic performance for organic oxidation.

was suggested that physical structure can be easily modified by

It

3

, 19

physical and/or chemical activation.

Therefore, exploring

since it can degrade organics to harmless compounds, CO

2

and

2

O. As well known, porous carbonaceous material is the most

3

preeminent methods for preparing of carbonaceous materials with

high activity is the key for environmental remediation.

H

4

-6

commonly used adsorbent when compared with other designed

Recently, both theoretical calculations and experiments have

proven that tailoring the electron states and creating active sites

within the carbonaceous matrix by heteroatoms (N, B, P, S) doping

a.

State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese

China.

Academy

of

Sciences,

Taiyuan

030001,

P.R.

E-mails:

could be an excellent strategy for producing significantly improved

zengzequan@sxicc.ac.cn (Z. Zeng); zghuang@sxicc.ac.cn (Z. Huang)

University of Chinese Academy of Sciences, Beijing 100049, P.R. China.

. Electronic Supplementary Information (ESI) available: Scheme, XRD patterns,

20-22

b.

materials for numerous applications.

In terms of environmental

†

remediation, many investigations have demonstrated that N atom

is a prominent exotic specie for improving the catalytic activity of

FTIR spectra, TGA curves, SEM images, Tables, XPS spectra, kinetic studies, and

adsorption-oxidation tests. See DOI: 10.1039/x0xx00000x

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rGO (or CNTs, GO, ND) toward persulfate (PS)/peroxymonosulfate promising way to utilize PPS waste, but also provides a new method

1

7, 18, 23

(

PMS) activation for aqueous organics oxidation,

which is an for future development of more efficient sulfur-doped activated

•−

AOP based on sulfate radical (SO4 ) generated from PS/PMS carbons for green remediation, even for applications in other fields.

activation. In addition, S atom, as another important heteroatom,

has also attracted researchers’ much interest. Because the 2. Materials and methods

incorporation of sulfur-containing functional groups into the carbon

2

.1. Chemicals and reagents

matrix would give rise to materials with unique physicochemical

properties (i.e. good electrical conductivity, excellent catalytic

2

4

Polyphenylene sulfide (PPS), phenol (PE, ≥99.0%), p-chlorophenol

activity and superior chemical stability) , which has been applied in

2

5

(PCP, ≥99.0%), 2,4-dichlorophenol (DCP, ≥99.0%) and potassium

persulfate (PS) were obtained from Sigma-Aldrich Inc. (St. Louis,

MO, USA). Methanol (for HPLC analysis) were of HPLC grade and

bought from Aladdin Chemistry Co., Ltd. Other reagents used in this

study were provided by Taiyuan Chemicals Co. (Taiyuan, China). All

chemicals were of analytical grade or higher and used as received

without further purification. Milli-Q water was employed

throughout the experiments.

the storage of hydrogen and carbon dioxide, anode materials in

2

6

lithium batteries, metal-free electrocatalyst for oxygen reduction

2

7

28

reaction in fuel cells, and adsorbents for heavy metals as well as

29

toxic contaminants. However, much less attention has been

focused on S-based catalyst for the heterogeneous catalytic

oxidation of refractory organics in wastewater. Wang et al. reported

that sulfur could act as a promising co-dopant to further improve

the performance of nitrogen doped graphene toward PMS

30

activation, but using of only S-doped as the catalyst for organic

oxidation is rarely reported.

2

.2. Catalyst preparation

In previous studies, we first discovered that in-situ S-doped

activated carbons prepared by chemical activation of polythiophene

derived from 2-thiophenemethanol and thiophene exhibited

outstanding performance in persulfate (PS) activation for catalytic

Chemical activation method using KOH as activating agent was

used to synthesize in-situ S-doped activated carbon (S-AC) from PPS

precursor (Scheme S1). In a typical synthesis, 2 g of PPS and 4 g of

KOH were fully dissolved into 50 mL of mixture solution with 70%

water and 30% ethanol (V:V). After drying in an oven at 110 °C for

3

1-33

oxidation of aqueous organic contaminants.

Compared with

3

4

post-treatment method that sun et al. applied for N-doping, in-

situ process could make sulfur groups homogeneously be

distributed throughout the matrix and permanently fused into the

backbone of the carbon framework. Nevertheless, the catalyst

preparation process involves multiple steps, harsh treatment (such

1

2 h, the mixture was ground and then transferred into a porcelain

crucible for annealing under nitrogen atmosphere at different

−1

temperature for 2 h with a heating rate of 5 °C min . The S-AC

samples were obtained after being washed with 10 wt.% HCl

solution twice (remove any impurities), ultrapure water several

times (until neutral pH), and dried in an oven at 110 °C overnight.

The as-prepared carbons are labeled as S-AC-x, where x refers to

the annealing temperature. For comparison, a S-AC-800-free sample

was prepared similarly by using PPS as precursor without adding

KOH. In addition, for demonstrating the role of sulphur dopant, a S-

free activated carbon (AC-800) was also synthesized by chemical

activation of polyphenylether (PPO) with KOH as activator at 800 °C.

3

as using FeCl ) and high toxicity as well as high cost of starting

materials. For widespread applications, economical, less toxic

reagents involving and simple synthesis would make such sulfur

doped activated carbon more attractive.

Poly(phenylene sulphide) (PPS), as one of the sulfur-containing

polymers, has been extensively investigated in technological

applications such as molding resins, fibers, and matrices for

thermoplastic composites due to its good mechanical properties,

thermal stability, excellent chemical resistance and electrical

2

.3. Characterization

3

5

properties. Note that the widespread use of PPS would result in a

lot of PPS waste owing to its non-biodegradable property, we

suppose that the conversion of PPS waste into high value-added

carbon materials would be a potential promising way to utilize PPS

waste.

X-ray diffraction (XRD) patterns were obtained on a Bruker D8-

Advanced diffractometer system using Cu-Kα radiation (λ = 1.5418

Å). Thermogravimetric analysis (TGA) was conducted in a Netzsch

−

1

thermal analyzer with a heating rate of 5 °C min in air. Surface

morphologies of the as-prepared S-AC were observed on a scanning

electron microscope (SEM, JSM-7001F, JEOL, Japan) combined with

an energy dispersive X-ray spec-troscopy (EDX) for element

mapping. The specific surface area was calculated by the Brunauer-

Emmett-Teller (BET) equation from nitrogen sorption isotherms at

Herein, a facile one-pot thermal process for preparation of in-situ

S-doped activated carbon (S-AC) by using PPS as precursor, and KOH

as activator was proposed. Results show that the obtained material

annealed at 800 °C (S-AC-800) exhibits high performance for

adsorptive and oxidative removal of phenols organics. The effect of

adsorption on organics degradation and the mechanism of PS

activation were studied. Moreover, the effects of several

operational parameters as well as the influences of various

inorganic anions, and background organic matters in water on

organic degradation in S-AC with PS were investigated in detail. In

addition, the stability of S-AC-800 and its deactivation reason were

also studied. The strong adsorption ability, excellent PS activity,

wide pH usable range, as well as resistant to various anions made us

believe that this work is beneficial since it not only provides a

7

7 K using a Micromeritics TriStar II 3020 apparatus. Prior to

measurement, the samples were degassed at 80 °C for 8 h under

vacuum condition. The total pore volume (V ) was calculated from

t

the volume adsorbed at a relative pressure of 0.99. The micropore

surface area and micropore volume were determined by Dubinin-

Astakhov equation adapted for micro-pore carbon. The pore size

distribution (PSD) was determined by Original Density Functional

Theory (ODFT). All samples were coated with a thin gold film under

vacuum before microscopy. Raman spectra were acquired on a

2

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Horiba (LabRAM HR800) dispersive Raman spectrometer using a standard process with dilution and seeding method on a BOD

TM

5

14 nm argon ion laser. The elemental contents of the carbon analyzer (BOD Trak II, HACH Company).

samples were determined using a Vario EL CUBE elemental analyzer

with the oxygen content calculated by mass difference. X-ray 3. Results and discussion

photoelectron spectroscopy (XPS) was performed on a specs

3

.1. Characterization of S-AC

spectrometer (AXIS ULTRA DLD) using Al Ka X-ray source (1486.6

eV). The binding energies of the XPS spectra were calibrated by

setting C 1s to 284.8 eV. Fourier transform infrared spectra (FTIR)

were recorded on a Bruker Tensor 27 FTIR spectrometer fitted with

a transmission attachment. The pHpzc (point of zero charge) of the

samples were evaluated by dispersing 250 mg of carbon samples

Fig. S1 shows the XRD patterns of the as-made S-AC samples. The

broad diffraction peaks located at about 23.1° (002) and 43.6° (101)

indicated the existence of hexagonal graphitic structure in the S-AC

3

7

samples. Thermogravimetric analysis (TGA) shows that the carbon

samples exhibit high thermal stability (Fig. S2), further

demonstrating the existence of graphitic structure. SEM images of

S-AC are shown in Fig. S3. It can be found that, the surface of the

activated carbon obtained at lower temperature was relatively flat

36

into 4 ml of CO

2

-free water at 25 °C.

2.4. Adsorption experiments

The typical adsorption experiment was carried out in a 250 mL and intact with less porous structures. As the activation

conical flask containing 200 mL of reaction solution with temperature increased, a large amount of pores were generated

−1

predetermined concentration of phenols (20-60 mg L ) and 0.05 g originated from thermal cracking and corrosive effect of KOH.

−1

L

of as-prepared catalyst. The flask was shaken in a constant Remarkably, partially aggregated and crinkled structures can be

temperature shaker (TENSUC Instrument, TS-200B, China) with 280 observed on S-AC-900 due to the excessive enlargement of porous

−1

rad min at 25 °C. At regular time intervals, 1 mL of the solution structures. As a result, the S-AC samples can be tailored with well

was sampled and filtered into a HPLC vial through 0.22 μm PES developed porous structures and high amount of defective edges.

syringe filter. The concentration of residual phenols was detected In addition, the elemental mapping of S-AC-800 suggested that the

immediately by high performance liquid chromatography (HPLC). All distribution of S in the carbon matrix was relatively uniform (Fig.

the experiments were performed in duplicates, and the results S4a-d), which further illustrated that in-situ process could make

showed that the relative errors were less than ±5%.

sulfur groups homogeneously distributed throughout the matrix.

To deeply investigate the textural properties of S-AC, N sorption

2

2.5. Catalytic oxidation experiments

isotherms were carried out. The corresponding results are

concluded in Table 1 and Fig. 1. It can be seen that annealing

The batch catalytic oxidation experiment was conducted in a 250 temperature strongly influenced the formation and the

−

1

mL conical flask containing 200 mL of a 80 mg L phenols solution. development of pore structures during carbonization. With the

The flask was shaken in a constant temperature shaker with 280 rad thermal treatment at 600-800 °C, the specific surface area (S_B_E_T) and

−

1

min at 25 °C. For testing the effect of adsorption on phenols total pore volumes (V ) of S-AC presented a growing trend. At 800

p

degradation, pre-adsorption or not pre-adsorption methods were °C, a sharp and significant orifices extension occurred as revealed by

2

−1

2

−1

put in the degradation experiments. In the pre-adsorption the increased S_B_E_Tfrom 1628 m g for S-AC-700 to 2777 m g for

−1

experiment, unless otherwise specified, 0.1 g L of S-AC was first S-AC-800. It indicates that the alkali metal compounds (KOH and/or

dispersed in the reaction solution and shaken for 60 min to fully K CO ), as chemical activators, strongly modified the carbonization

2

3

achieve the adsorption/desorption equilibrium, followed by adding behavior of PPS at 800 °C (Fig. S5), leading to the significant release

5 mM of PS into the solution to initiate the degradation. In the not of volatile matters and the development of micro- and mesopore

1

pre-adsorption experiment, S-AC and PS were added to the reaction structure. While further increasing of the annealing temperature to

solution simultaneously. At given time intervals, 1 mL of sample was 900 °C would slightly decrease the specific surface area and pore

withdrawn and filtered by 0.22 μm PES syringe filter into a HPLC vial volume attributing to the combination of pores derived from the

38

for analysis. After completion of the reaction, the catalysts were excess enlargement. According to Fig. 1a, it can be seen that

separated and washed with water and ethanol several times, depending on the annealing temperature, the S-AC samples treated

followed by drying in an oven at 110 °C overnight for reuse tests.

at 600-800 °C were predominantly microporous with typical type I

isotherm. While the sample treated at 900 °C belonged to type IV

2.6. Analytic methods

0

with a hysteresis loop above P/P = 0.4, demonstrating the co-

3

9

presence of micropores and mesopores. This can be further

supported by the pore size distribution results (Fig. 1b). It should be

noted that for the cases of S-AC-600, -700, and -800, all of the pores

fell into the size less than 5 nm, and the average pore size was

calculated to be 1.93, 2.01, and 2.09 nm, respectively. While the

thermal treatment at 900 °C imposed a significant enlargement of

the pore size to (~ 8 nm) and resulted in an average pore size of

The concentration of residual phenols was determined by using

an U3000 HPLC system (Thermo Fisher, USA) equipped with a

TM

SunFire C₁₈column (4.6 × 150 mm, 5.0 μm) and a photodiode

array detector (PDA) set at 270 nm for PE, 280 nm for PCP and 288

nm for DCP. The mobile phase was a binary mixture of 70%

−

1

methanol and 30% water at a flow rate of 1 mL min . Chemical

oxygen demand (COD) test was carried out according to the Chinese

national standard method (HJ/T 399-2007) on a COD analyzer (5B-

2

.74 nm.

3A, Lian-hua Tech. Co., Ltd., Lanzhou, China). Biochemical oxygen

demand after 5 days (BOD ) was determined according to the Hach

5

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Table 1 Textural properties of the carbon samples

2

-1

2

-1

3

-1

3

-1

Sample

S

BET/m g

S

micro/m g

V

p

/cm g

V

micro/cm g

Average pore size (nm)

1.93

S-AC-600

S-AC-700

S-AC-800

S-AC-900

1585

1628

2777

1912

1131

1126

1816

1292

0.77

0.82

1.45

1.31

0.46

0.76

0.55

2.01

2.09

2.74

of superabundant oxygen/sulfur-containing groups would also

release the defect edges occupied by the excess oxygen/sulfur

1

0

groups.

To detect the elemental composition and the surface chemistry

of the as-prepared samples, FTIR spectra (Fig. S6) and XPS

spectroscopic technique was performed. As shown in the XPS

survey spectra for the S-AC samples (Fig. 3a), characteristic peaks of

C 1s, O 1s, and S 2p were observed at ~285, ~532, and ~164 eV,

respectively. According to the XPS data, it can be noted that the S

content was gradually decreased with an increase in the annealing

temperature, and then underwent a slight increase at 900 °C. In

view of this, elemental analysis was also performed and a similar

trend of 10.85, 7.57, 4.05, and 5.31 wt.% was obtained for S-AC-

6

00, -700, -800, and -900, respectively (Table S1). This may be

attributed to the more intense reaction between carbon matrix and

KOH at 900 °C, leading to a reduction of carbon content, and then

the sulfur and oxygen contents were relatively increased.

The high resolution XPS C 1s spectra was shown in Fig. S7. It can

be found that the C 1s spectra can be deconvoluted into five

components. The main peak at 284.5 eV is assigned to carbon

2

atoms with sp hybridization, suggesting that most of the C atoms

3

0

were in the conjugated honeycomb lattice. The asymmetric and

broadened C 1s peak of sp2 carbon toward the high binding energy

side indicated that the samples contained a relatively high amount

4

1

of functional groups. The three broad peaks located at 285.8,

2

87.2, and 289.2 eV could be attributed to sp carbon bonded with

heteroatoms such as C–O and/or C–S, C=O species (carbonyl or

quinine), and O=C–O (carboxyl or ester), respectively, which are

30

consist with the FTIR results. The band on the high binding energy

side located at

Fig. 1 (a) N sorption isotherms, and (b) pore size distributions of

2

the S-AC samples.

Raman spectroscopy has been proved to be a powerful,

40

structural probe for carbonaceous materials. Hence, Raman

spectroscopic investigation was further conducted as shown in Fig.

2

. It can be seen that the Raman spectra of the samples contained a

−1

G band at 1594 cm related to in-plane vibrations of sp2 carbon in

−1

S-AC, and a D band at 1341 cm arised from disorder (structurally

1

3

disordered carbon, defects, and edges). The intensity ratio of D

band versus G band (I /I ) could reflect the defect and disorder

level of the samples. A notable observation is that the I /I ratio

D

G

D

G

gradually increased from 1.01 to 1.21 as the annealing temperature

increased from 600 to 900 °C, suggesting that an increased amount

of defect sites was obtained at an elevated temperature. This may

be originated from the severe etch of alkali metal compounds at

higher temperature, as characterized by SEM combined with N

sorption isotherms. In addition, it was suggested that the removal

2

Fig. 2 Raman spectra of the carbon samples.

4

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2

91.2 eV is possibly assigned to the π-π* transition due to

4

2

conjugation.

The high resolution XPS S 2p spectra (Fig. 3c) can be decomposed

into four components. The two peaks centered at 164.0 eV and

1

65.2 eV are corresponded to the S 2p₃_/₂and S 2p₁_/₂of thiophene

sulfur (–C–S–C–) and/or –C–S–C– sulphide bridges, and the other

two peaks located at 168.7 eV and 169.9 eV can be attributed to

4

3, 44

oxygen-containing S groups (–C–SO –C–, x=2, 3, 4).

It is worth

x

noting that with the increase of annealing temperature, the

thiophene sulfur species became dominant as shown in Fig. 3b.

Remarkably, the percentage of –C–S–C– in overall S dopants can

reach 65.3% for the sample treated at 800 °C, indicating that a

better reductive degree was obtained on S-AC-800. This point can

also be confirmed by the fact that the sample was characterized as

a weak acidic material with the highest pHPZC of 4.6 (Table S1). This

may be favorable because activated carbon with basic character is

45

presumed to be beneficial for the catalytic oxidation process.

Fig. 3 (a) XPS survey spectra for the S-AC samples, (b) contents of

different sulfur species, and (c) the high resolution XPS S 2p spectra

of the S-AC samples.

3

.2. Adsorption kinetics and isotherms of phenols on S-AC

The roles of KOH activation and sulfur doping in the adsorption

performance of carbon samples are shown in Fig. S8. It can be

found that almost no PCP was adsorbed by S-AC-800-free with a

−1

4

17 mg g , respectively. From the obtained results, we can

conclude that the adsorptive performance of S-AC was significantly

improved by increasing annealing temperature and then declined

upon treatment at 900 °C. Associated with the BET analysis of S-AC

samples, it is noted that the adsorption capacities were closely

related with their SBET order. In addition, the removal of oxidized

sulfur groups at elevated temperature would also enhance the

2

-1

small SBET of 6.8 m g (Fig. S9). While both S-AC-800 and AC-800

show an excellent adsorption performance, suggesting that KOH

could strongly modify the carbonization behavior of PPS and lead to

the significant development of pore structures, hereby endowing

the carbon samples with strong adsorption ability. However, it is

worthy noting that AC-800 shows a superior adsorption ability

adsorption performance of S-AC. Compared with commercial

2

-1

(

50.9%) with a lower SBET (2182 m g , Fig. S9) when compared with

−1

m

activated carbon AC (q = 88 mg g ), and our previously prepared

S-AC-800 (46.0%). It indicates that sulfur doping is detrimental for

the adsorption capacity enhancement, since the oxidized sulfur

groups with acid character were not beneficial for the adsorption of

acidic PCP molecules.

−1

sulfur doped activated carbon ACS-800 (q

m

= 481 mg g ) and SDAC-

−1

8

00 (q = 394 mg g ) (Fig. S12-14 and Table S2), S-AC-800 sample

m

presented extremely high adsorption ability, which may be

attributed to the ultrahigh SBET of S-AC-800. It was well established

that the following aspects including π-π interaction, hydrogen

bonding, covalent and electrostatic attraction may contribute to the

To evaluate the effect of carbonization temperature on the

adsorption performance of S-AC, the adsorption behavior of several

phenols on S-AC was investigated in detail. Fig. 4 shows the

isothermal adsorption of PCP on S-AC. It can be seen that the

adsorption process was quite rapid initially, then slowly increased

until attaining adsorption/desorption equilibrium at about 20 min.

Based on the experimental data, the adsorption kinetics of S-AC

samples were evaluated. Results show that the data were well

fitted with the pseudo-second-order model (Fig. S10), suggesting

that the adsorption of PCP onto S-AC was dominated by chemical

48, 49

adsorption of organics on carbonaceous materials surface.

Since S-AC-800 possessed the largest SBET, more reaction space and

active sites can be exposed for PCP contact, hereby enhancing the

aforementioned interactions and resulting in a high adsorption

capacity.

Furthermore, PE and DCP were also employed as model

pollutants to investigate the role of –Cl substitution in the

adsorption of phenols on S-AC-800, considering that chlorophenols

4

6, 47

adsorption.

50,

(

51

CPs) are common pollutants in both surface and ground waters.

Three important isothermal models, including Langmuir,

Freundlich, and Temkin isotherms, were applied to analyze the

adsorption isotherms of PCP on S-AC. The experiment results and

the parameters of isothermal models are shown in Fig. S11 and in

Table S2, respectively. It can be seen that the adsorption data were

well fitted with the Langmuir model, indicating that the adsorption

of PCP on S-AC was a monolayer adsorption process. From the

Langmuir parameters summarized in Table S2, we can find that the

Their adsorption kinetics and isotherms were discussed similarly.

Results (Fig. S15-16) show that the adsorption behaviour of PE and

DCP on S-AC-800 is similar to PCP. It can be seen from Table S3 that

the maximum monolayer adsorption capacities were evaluated to

−1

be 295, and 813 mg g for PE and DCP, respectively. It indicates

that the adsorption capacities significantly increased with increasing

the number of –Cl substitutions on phenols. Two possible solute-

sorbent interactions may be responsible for the enhancement: (1)

hydrophobic effect (their hydrophobicity increased sharply from PE

−

1

maximum monolayer adsorption capacities (q_m_,mg g ) of PCP on S-

AC-600, -700, -800, and -900 were estimated as 292, 385, 526, and

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Fig. 4 The kinetic data for PCP adsorption on S-AC at different PCP

concentration. Reaction conditions: [PCP] = 20, 30, 40, 50, 60 mg Fig. 5 The removal of PCP on S-AC samples with PS in pre-

0

−1

L , catalyst = 0.05 g L , and temperature = 25 °C.

0

adsorption system. Reaction conditions: [PCP] = 80 mg L , catalyst

−

1

=

0.1 g L , [PS] = 15 mM, and temperature = 25 °C.

5

2

to PCP and then to DCP, since –Cl is a hydrophobic group); (2) –Cl

substitution enhanced π-π interactions between the phenols and PCP removal were observed in the cases of S-AC-600, and S-AC-700

49

the S-AC surface.

in 170 min, respectively. It indicates that pre-adsorption was

beneficial for the PCP degradation enhancement, which can be also

confirmed by the fact that PCP cannot be adsorbed by S-AC-800-free

,

3

.3. Adsorption and catalytic oxidation of phenols on S-AC

and accordingly cannot be degraded (Fig. S18). As for the S-AC-800

and S-AC-900 samples, no decrease of PCP removal was observed,

which may be attributed to the high catalytic activity of the two

samples.

The catalytic activity of the as-prepared S-AC samples toward PS

activation was initially evaluated by degrading PCP with PS. No PCP

degradation was attained at the control test with PS alone (Fig. 5).

In the pre-adsorption experiments, before the time of zero, around

Although experiments confirmed that pre-adsorption played an

positive role in PCP degradation process, the definite relationship

between the adsorption and the oxidative degradation was still

unclear.

2

9.4%, 34.0%, 46.0%, and 35.5% of PCP was removed attributing to

adsorption on S-AC-600, -700, -800, and -900, respectively. After PS

was rapidly introduced into the above systems, the PCP degradation

process was significantly enhanced for all the S-AC/PS systems. To

be specific, about 69.7% and 76.7% of PCP was removed on S-AC-

Here, we designed a set of experiments following the method

2

previously reported to make clear the effect of adsorption on the

degradation processes. In the tests, PE, PCP and DCP were

employed as probes since sorption affinity of these compounds by

S-AC-800 was obviously different as demonstrated in section 3.2.

6

00 and S-AC-700 in 170 min, respectively. Remarkably, S-AC-800

presented the best performance with 100% PCP removal within 45

min, and the residual PCP in solution can be fully degraded by S-AC-

−1

Fig. 7a shows that the adsorption capacity (qes, mg g ) on S-AC-800

9

00/PS within 170 min.

The toxicity of initial PCP and its oxidation products produced

after a 170 min reaction (Fig. S17) in S-AC/PS systems was

evaluated by measuring the biodegradability index (the ratio of

BOD

5

versus COD). To eliminate the toxicity of PS to microorganism,

SO to

the reaction solution was initially treated with excessive Na

2

3

5

3

convert all the residual PS to innocuous sulfate ions. It is reported

that the ratio less than 0.2 means a toxic aqua and greater than 0.4

means a good biocompatibility aqua. Results show that the values

of BOD

.30, 0.52, 0.87, and 0.85 after treated by S-AC-600, -700, -800, and

900 with PS for 170 min, respectively. It indicates that the

5

/COD sharply increased from 0.06 of initial PCP solution to

0

-

biodegradability of PCP can be significantly improved by the S-

AC/PS systems, which might be applied as the pretreatment

approach for the biological treatment of phenolic wastewater.

To test the role of adsorption on the catalytic oxidation process,

the degradation experiments without pre-adsorption were also

carried out as shown in Fig. 6. It can be seen that, compared with Fig. 6 The comparison of PCP removal on S-AC samples with PS in

the pre-adsorption experiments, 6.9% and 4.1% decline in the total

pre-adsorption and non pre-adsorption systems. Reaction

−1

0

conditions: [PCP] = 80 mg L , catalyst = 0.1 g L , [PS] = 15 mM, and

temperature = 25 °C.

6

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Fig. 7 (a) The removal of phenols on S-AC-800 with PS in single-pollutant systems; (b) fitting of pseudo-first-order kinetic model for phenols

degradation, and the correlation between the adsorption capacity (qes) and the apparent degradation rate constant ( ) for phenols in their

k

s

individual single-pollutant solution (inset). (c) The removal of phenols on S-AC-800 with PS in mixture-pollutant system; and (d) fitting of

pseudo-first-order kinetic model for phenols degradation in the first 5 min, and the correlation between the adsorption capacity (qem) and

the apparent degradation rate constant (

k

m

) for phenols in the mixture-pollutant solution (inset). Reaction conditions: [PE]

0 0

, [PCP] , and

−1

[

DCP] = 80 mg L , catalyst = 0.1 g L , [PS] = 15 mM, and temperature = 25 °C.

0

−

1

was 589 mg g for DCP, being about 1.54 times that of PCP (368, mixture solution. By plotting

m

k against qem, a good linear

−1

mg g ), and 2.98 times that of PE (197, mg g ). After PS was rapidly relationship was also observed in the mixture solution (inset in

added, all the phenols could achieve a complete removal with an Fig.7d). Accordingly, from the results we have obtained, one can

−1

apparent rate constant (

k

s

) of 0.31 min for DCP, 0.12 min for speculate that the adsorbed phenols molecules may be in-situ

PCP, and 0.04 min for PE (Fig. 7b). In qes and , the subscript s preferentially degraded by the reactive species derived from the

represents the single solution. By plotting against qes, we found activation of PS, which in turn results in more adsorption of phenols

−1

k

s

k

s

that the two parameters showed a good linear relationship (inset in on the S-AC-800 surface. Then, the adsorption and degradation

Fig. 7b), indicating that a higher adsorption capacity leads to a more facilitated on each other, synergistically promoted the efficient

rapid degradation process. In the mixture of DCP, PCP, and PE, their phenols removal. Interestingly, the AC-800 sample possessed a

adsorption capacities and degradation efficiencies were both higher adsorption ability (50.9%), but showed an inferior catalytic

decreased due to the competitive effect among the coexisting performance with 86.5% of PCP removal in 45 min when compared

−1

phenols. As shown in Fig. 7c, the adsorption capacities (qem, mg g )

with S-AC-800 (100%) (Fig. S18), suggesting that sulfur doping plays

of DCP, PCP, and PE were declined to 438, 187, and 34 mg g , an important role in improving the catalytic activity of S-AC-800.

respectively. After PS was introduced, their corresponding apparent Based on the obtained results, we suppose that the excellent

rate constants ( ) in the first 5 min were estimated as 0.09, 0.04, catalytic activity of S-AC-800 can be explained in several aspects.

−

1

k

m

−1

and 0.01 min (Fig. 7d). Here, the subscript m represents the

Firstly, its large adsorption capacity originated from its high SBET is

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Table 2 The removal of phenols over different catalysts with PS

Journal Name

−

1

−1

Catalysts (g L )

Organics (mg L )

PS

(mM)

T

( C)

t

Efficiency

(%)

Entry

o

Ref.

Species

Loading

0.1

Species

PCP

DCP

PE

Concentration

(min)

2

+

1

2

3

4

5

6

7

8

9

Co

ZVI

80

5

80

4

15

1.85

15

3

25

170

60

1.8%

90

－

0.1

+

Ag

0.1

10

100

92.3

100

94.8

100

5

3

4

1

3

SDBC

1

0.1

100

130

90

ACS-800

SDAC-800

S-AC-800

0.1

0.056

0.1

45

15

30

This work

0

55

Pre-Fe

1

5

3

6

3

0.5%~Fe/S-CNTs

SDAC-800

5

0.031

15

6.5

15

1

0

1

2

3

0.1

80

20

80

60

15

S-AC-800

This work

5

7

AND-1000

S-AC-800

0.2

45

0.1

PE

120

This work

enable to expedite the in-situ degradation process. Also, its high same reaction condition. It indicates that PPS could act as an

BET enable more active sites to be exposed for PS activation and excellent and efficient sulfur precursor for preparation of S-doped

S

organic oxidation. The other aspects are concerned with the surface porous carbons through a more facile process.

chemistry of the catalyst, especially the species and concentration

of sulfur-containing groups, which can be investigated by the XPS

analysis (Table S4). To begin with, its high concentration of sp2

hybridized structure, O=C groups, and defect sites (that are widely

accepted to be the active sites for PS/PMS activation) would endow

S-AC-800 with high catalytic activity toward PS activation. In

addition, the significant removal of oxidized sulfur groups is able to

increase the reductive degree of S-AC-800 and promote the

electron transport from carbon to PS. More importantly, the

incorporation of sulfur atom into carbon framework would

redistribute the spin density of carbon atoms and create more

active sites, and hereby disrupting the chemical inertness of carbon

and facilitating electron transfer. In conclusion, the synergistic

effect exerted by the aforementioned aspects contributed to the

best catalytic activity of S-AC-800 toward PS activation.

3

.4. Catalytic mechanism of PS activation on S-AC

Based on the achievements above, we speculated that the

degradation of PCP is mainly occurred on the catalyst surface,

where the adsorbed PCP would be in-situ degraded by the activated

PS. To further shed light on this point, the removal of PCP in the S-

AC-800/PS system was conducted in the presence of radical

−

scavengers. Halide (Br : in the form of KBr) was applied as the

•−

•

58

scavenger for SO

4

free and HO free produced in aqueous solution,

1

11

and l-histidine was used as singlet-oxygen ( O

2

) scavenger. Fig. 8a

−

shows that, the introduction of minor amount of Br would

−

decrease the PCP degradation rate from 0.12 (0 mM Br ) to 0.11 (5

−

−1

−

mM Br ) and to 0.10 min (10 mM Br ). Then the value gradually

−1

−

increased to 0.21 min when 30 mM Br was presented. This is

In addition, we also investigated the removal of PCP in the

−

because that the hydrophilic Br can react with the free radicals

2

+

classical homogeneous Co /PS, Ag /PS, and zero-valent iron

produced in aqueous solution to form less reactive and more

2

+

(

ZVI)/PS systems, and found that Co showed negligible

•

•−

selective halogen radicals (Br and Br

2

, that are more prone to

degradation. In the other two systems, 100% and 90% of PCP

59

reacting with electron-rich target pollutant) (Eqs 1-3). Thus, the

+

removal can be achieved on Ag and ZVI within 10 min and 60 min,

−

presence of low level Br would shield the highly reactive radicals,

respectively. It indicates that the S-AC-800 samples can be

comparable or superior to the most popular transition metal

catalysis without involving any metal ions to the water body.

Moreover, the catalytic performance of S-AC-800 was also

compared with the advanced catalysts developed in recent years

for the removal of phenols with PS. As listed in Table 2, complete

PCP and DCP removal can be achieved in S-AC-800/PS system with

less catalyst dosage and higher contaminant concentration in a

shorter time when compared with advanced metal-free catalyst

such as SDBC derived from sludge, and metal-based catalysts such

and then slow down the reaction rate. While the generation of

•

•−

−

excess Br and Br

2

from high concentration of Br could facilitate

the mineralization of electron-rich PCP and its intermediates such

as benzoquinone and 4-chlororesorcinol, hereby improving the PCP

degradation rate. Nevertheless, the slight effect of halide on PCP

removal allows us to conclude that only a minimal amount of

•−

•

SO

4

free and HO free was generated in solution. Fig. 8b shows that

the introduction of excess amount of l-histidine (30 and 60 mM)

was able to compete the adsorptive sites with PCP, resulting in a

decrease in the PCP adsorption efficiency, which in turn presented a

0

as Pre-magnetized Fe0 (Pre-Fe ) and Fe/S modified carbon

minor inhibitory effect on PCP degradation. The quenching

nanotubes (Fe/S-CNTs). Most importantly, compared with our

previously prepared S-doped activated carbons derived from 2-

thiophenemethanol (ACS-800) and thiophene (SDAC-800), the time

for PCP completely removal can be shorten from 130 min for ACS-

1

experiments by using l-histidine as scavenger suggested that O

2

is

not the major reactive species responsible for PCP degradation.

From the obtained results, one can conclude that the particle-

surface interaction plays a dominant role in PS activation and PCP

oxidation.

800 to 90 min for SDAC-800 and to 45 min for S-AC-800 under the

8

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−

Fig. 8 Effects of (a) Br , (b) l-histidine, and (c) ethanol on PCP degradation in S-AC-800/PS system; and (d) the comparison of PCP

−1

degradation on S-AC-800/PS in initial pH 10.7 and in ethanol/PS of 100 systems . Reaction conditions: [PCP] = 80 mg L , catalyst = 0.1 g L ,

0

[

PS] = 15 mM, and temperature = 25 °C.

SO^∙ꢂ Br^ꢁ→ Br ∙ ꢂSO^ꢃ_ꢀ^ꢁ, k_ꢄ_ꢅ _ꢆ∙ ꢇ

ꢁ

_ꢈ_ꢉ_ꢊꢇ

ꢋ 3.5 ꢌ 10 M^ꢁ^ꢎs^ꢁ^ꢎꢏꢏ

ꢍ

(1) bounded radicals were generated in the S-AC-800/PS system, the

ꢀ

_H_O_∙_ꢂ_B_rꢁ _→_B_r_O_H∙ꢁ, k_ꢐ_ꢅ_∙_ꢈ_ꢉ_ꢊ

_ꢋ₁_.₁_ꢌ₁₀ꢎꢑ_Mꢁꢎ_sꢁꢎ

PCP degradation rate would also slow down in the presence of

ꢇ

(2)

ethanol. Therefore, it is difficult to clearly differentiate the negative

BrOH^∙^ꢁꢂ Br^ꢁ^→^B^rꢃ^∙^ꢁꢂ OH^ꢁ

(3)

effects of the two aspects on PCP oxidation. Here we qualitatively

analyze them in virtue of the effect of pH on PCP removal. As shown

in Fig. 8d, the PCP adsorption efficiency in the system of initial

solution pH 10.7 was comparable to the system with a certain

amount of ethanol (ethanol : PS = 100 : 1). In addition, the system

of pH 10.7 with PS alone suggested that the degradation of PCP

attributed to base activation was not significant in the initial stage.

It was well established that, in terms of particle-surface

interaction, two additional mechanisms including surface-bounded

radical pathway and non-radical pathway were proposed for PS

5

7, 60

activation.

on S-AC-800, ethanol was used as a probe to shield the total

radicals generated in the PS activation process (k = (1.6-

Thus, to deeply investigate the PS activation process

ethanol/SO4•

−1 −1 60

−

7

−1 −1

9

Accordingly, if no surface-bounded radicals were generated in the

S-AC-800/PS system, the degradation of PCP in the two systems

were almost the same. However, Fig. 8d shows that after a 5 min

reaction, PCP removal decreased from 65.3% with initial pH 10.7 to

7

.8) × 10 M s , k

= (1.2-2.8) × 10 M s ). Fig. 8c

ethanol/HO•

shows that ethanol had a significant inhibiting effect on PCP

adsorption and total removal in S-AC-800/PS system. We suppose

that the high solubility of PCP in organic solvent led to the decrease

in PCP adsorption. Remarkably, when the molar ratio of ethanol : PS

elevated to 1000 : 1, only 3.5% of PCP was adsorbed. As discussed

above, a higher adsorption capacity leads to a more rapid

degradation process. Thus the decline in PCP adsorption originated

from the addition of ethanol would in turn decrease the PCP

degradation efficiency. In addition, if large amount of surface-

5

1.1% with the presence of ethanol in the S-AC-800/PS system,

demonstrating the generation of surface-bounded radicals.

Moreover, it is worth noting that even though a large amount of

ethanol (ethanol : PS = 1000 : 1) was added, 35.3% of PCP could still

be removed in 170 min, unlike the classic radical-based oxidation

process originated from PS activation on zero-valent iron (ZVI) (Fig.

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S19), suggesting that not only surface-bounded radicals but also

non-radical oxidation process played an important role in PCP

degradation in S-AC-800/PS system.

3

.5. Effects of several parameters on PCP removal

Since S-AC-800 exhibited the best catalytic activity among all of

the as-prepared S-AC samples, it was chosen for the subsequent

studies. The effects of catalyst dosage and initial PCP concentration

on PCP adsorption and oxidation were shown in Fig. S20 and S21.

Fig. 9 depicted the influence of PS concentration on PCP

degradation with different dosage of S-AC-800. It can be seen that

the increase of PS concentration shows a marginal effect on PCP

−

1

−1

removal with a higher (0.1 g L ) or a lower (0.025 g L ) S-AC-800

−1

loading. While at catalyst dosage of 0.05 g L , the removal of PCP

increased as the PS concentration increased from 3 to 13 mM and

then declined with the continuous increase of PS concentration. As

discussed above, the PS activation and PCP oxidation is a surface

phenomenon, in which the formation of reactive species from PS

activation as well as the adsorption-desorption of PCP and its

Fig. 10 Effect of initial pH on PCP degradation in S-AC-800/PS

−1

system. Reaction conditions: [PCP]

PS] = 15 mM, initial pH = 2.6, 4.2, 6.8, 8.6, 10.7, and 11.3, and

temperature = 25 °C.

0

= 80 mg L , catalyst = 0.1 g L ,

[

controlling step, leading to the insignificant role of PS

concentration. Whereas under lower catalyst dosage, the limited

reactive site was not available to active overdose PS. At this point,

the activation of PS became the bottleneck, and the degradation of

PCP was little influenced by the PS concentration. When an

appropriate amount of catalyst was added, the two steps

synergistically contributed to the PCP degradation.

5

3

intermediates are diffusion- and equilibrium-driven processes. We

suppose that under higher catalyst dosage, larger surface area and

more active sites were served for PCP adsorption and PS activation,

where a relative large amount of intermediates can be produced

instantly. In this case, the desorption of intermediates was the rate

The effect of initial pH (pH 2.6–11.3) on PCP removal was also

−

1

−1

2 4

investigated by adding 0.1 mol L of H SO or 0.1 mol L of NaOH.

Fig. 10 shows that for the pH investigation range, both the

adsorption and the oxidation efficiencies of PCP on S-AC-800 were

little influenced by solution pH except for pH 10.7 and pH 11.3. The

pHpzc of the S-AC-800 sample was estimated as pH 4.6 (Table S1),

suggesting that the surface charge of the carbon was dominated by

the negatively charged sites under a highly basic condition (pH

1

1.3). The p

a a

K of PCP is 9.38, which implies that when pH > pK (pH

0.7–11.3), the PCP species was mainly in its anionic forms. Thus,

the electrostatic repulsion between the two aspects results in the

decrease in PCP adsorption, and consequently decreases the PCP

oxidation efficiency. In addition, the generation of hydroxyl radical

•

•−

61

(

HO ) under strong alkaline conditions from SO

4

(Eq 4), with a

•−

62

lower redox potential (1.8 V) compared to SO

4

(2.5–3.1 V), could

also reduce the PCP oxidation efficiency. These results suggest that

S-AC-800 exhibits a high catalytic activity within a wide pH range,

which can be applied in various aqueous environments since most

of real wastewater matrix are usually not strong alkaline solution.

SO^∙ꢂ OH^ꢁ→ SO^ꢃ_ꢀ^ꢁꢂ HO ∙, k ꢋ ꢒ6.5 ꢓ 1.0ꢔ ꢌ 10 M^ꢁ^ꢎs^ꢁ^ꢎ(4)

ꢁ

ꢕ

ꢀ

Further kinetic studies were performed to investigate the effect

of reaction temperature on PCP oxidation over S-AC-800 (Fig. S22).

Results show that the degradation of PCP with S-AC-800/PS obeyed

pseudo-first-order kinetics and the reaction rate constant was

Fig. 9 Effect of PS concentration on PCP degradation with (a) 0.1 g

−1

L , (b) 0.05 g L , and (c) 0.025 g L of S-AC-800. Reaction

−

1

conditions: [PCP]

0

= 80 mg L , [PS] = 3, 6, 13, 26 mM, and

−1

estimated as 0.12, 0.14, and 0.16 min at the reaction temperature

temperature = 25 °C.

of 25, 45, and 55 °C, respectively. Based on the Arrhenius equation,

−

1

the apparent activation energy was estimated to be 13.16 kJ mol ,

which was much lower than that on the reduced graphene oxide

1

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−

2−

3

Fig. 11 The influences of (a) HCO

3

, (b) HPO

4

, (c) CO

, and (d) HA on PCP removal in S-AC-800/PS system. Reaction conditions: [PCP]

0

= 80

−1

mg L , catalyst = 0.1 g L , [PS] = 15 mM, and temperature = 25 °C.

−

1

−1

∙ꢁ

ꢀ

ꢂ HCO^ꢁ

→ HCO^∙

ꢃꢁ

ꢀ

(

rGO) (33.40 kJ mol ), AC (65.69 kJ mol ), and our previously

SO

ꢜ

ꢂ SO

,

−1

prepared ACS-800 (22.53 kJ mol ), and SDAC-800 (13.53 kJ mol )

Fig. S23), indicating the excellent catalytic activity of S-AC-800.

ꢋ 2.8 ꢞ 9.1 ꢌ 10 M_ꢁ_ꢎ_sꢁꢎ

ꢛ

ꢏk_ꢄ_ꢅ _ꢆ∙ ꢇ_ꢈ_ꢐ_ꢗ_ꢅ_ꢝ

ꢇ

(7)

(8)

(

SO^∙ꢂ CO_ꢜ^ꢃ^ꢁ→ CO^∙_ꢜ^ꢁ ꢂ SO_ꢀ^ꢃ^ꢁ,ꢏ

ꢁ

ꢀ

ꢄꢅ∙ꢇꢈꢗꢅꢖ_ꢝ ꢇ ꢋ 6.1 ꢞ 410 ꢌ 10 M^ꢁ^ꢎs^ꢁ^ꢎ

ꢛ

3

.7. Effects of anions and natural organic matters on PCP removal

k

ꢆ

NOM ꢂ SO^∙^ꢁ→ products, k_ꢄ_ꢅ∙_ꢆꢇ

ꢋ 2.35 ꢌ 10 M_ꢗs^ꢁ^ꢎ(9)

ꢕ

ꢁꢎ

ꢀ

ꢈꢟꢅꢠ

As well known, even trace amount of ions and natural organic

Herein, the influences of several anions were taken into account

in the PCP removal in S-AC-800 with PS. It is indicated from Fig. 11a

matters (NOMs) existed in real wastewater matrix would have

•

−

potential influences on AOPs. Especially when SO

4

is the dominant

−

^t^h^a^t^t^h^e^p^r^e^s^eⁿ^c^e^o^f^H^C^O3 at concentrations ranging from 10-30

reactive radical responsible for the organics oxidation. The anions

−

2−

4

−

2−

mM exhibited a negligible effect on PCP adsorption but decreased

its oxidation efficiency. A similar trend was also observed in the

such as Cl , HPO

, HCO

3 3

, and CO , as well as the NOMs could

•

−

63, 64

react with SO

4

through Eqs. 5-9 to form less reactive radicals,

2

−

presence of HPO

4

(Fig. 11b). The reason for these may be that the

resulting in the decrease of contaminants degradation efficiency.

Besides, some anions have significant effects on the acidic/basic of

wastewater, and hereby influencing the AOPs.

−

2−

quenching effects of HCO

3

and HPO

4

on the surface-bounded

radicals interfered with the catalytic oxidation process, leading to

the decrease of PCP degradation. However, it should be noted that

_S_O∙ _ꢂ_C_lꢁ → Cl ꢂ SO_ꢀ, k_ꢄ_ꢅꢖꢇ

ꢁ

∙

ꢃꢁ

ꢋ 3.0 ꢌ 10 M_ꢁ_ꢎ_sꢁꢎ

ꢙ

a steady and consistent PCP removal was observed with the

_ꢈ_ꢗ_ꢘꢇ

(5)

ꢀ

ꢆ

2−

increased HPO

4

2 4

concentration. As Na HPO is a well-known

SO^∙^ꢂ^H^P^O ^ꢃꢀ^ꢁ^→^H^P^O ^∙ꢀ^ꢁ^ꢂ^S^O ^ꢃꢀ^ꢁ

ꢁ

,

ꢀ

alkaline agent, which would change the solution pH from 6.8 to 9.2

2

−

ꢏk_ꢄ_ꢅ∙_ꢆꢇ_ꢈ_ꢐ_ꢚ_ꢅ _ꢆꢖ ꢇ ꢋ 1.2 ꢌ 10 M^ꢁ^ꢎs^ꢁ^ꢎ

ꢛ

(6) when 30 mM of HPO

4

was presented in the PCP solution. We

speculate that the basic environment facilitated the activation of

J. Name., 2013, 00, 1-3 | 11

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ARTICLE

Journal Name

2

−

PS, which could be further confirmed by the fact that HPO

4

(30 synthesized through a one-pot thermal process by using a potential

mM) with PS alone contributed to 13.5% PCP removal. The waste material (Poly(phenylene sulphide) (PPS)) as precursor, and

2

−

influence of CO

introduction of alkaline CO

adsorption efficiency from 47.8% (0 mM CO

strong electrostatic repulsion under highly basic environment (pH = organics in their individual solution and mixture solution suggested

3

is depicted in Fig. 11c. As observed, the KOH as activator. Experiments demonstrated that the obtained

2

−

3

significantly decreased the PCP materials were extremely efficient for adsorptive and oxidative

2

−

3

) to 18.5% due to the removal of phenols organics. The degradation of different phenols

2−

1

1.1, 11.3, and 11.4 at a CO

3

concentration of 10, 20, 30 mM, that a higher adsorption capacity leads to a more rapid degradation

respectively), as revealed by the effect of initial pH on PCP removal process, which in turn accelerates the adsorption, then the

(

Fig. 10). As such, it is noted that, the presence of a minor amount adsorption and degradation synergistically promotes the efficient

2

−

of CO

3

would impede the PCP removal process, but an elevated organics removal. Quenching experiments indicated that both

amount could facilitate the catalytic oxidation process surface-bounded radicals and non-radical pathway played

attributed to base activation (48.8% PCP removal was obtained in dominant role in PS activation. The high adsorption ability, excellent

2

−

CO

3

a

2

−

59

PS with 30 mM CO

3

). In addition, Ma et al. reported that the PS activity, wide pH usable range, as well as resistant to various

was more selective, which may be also contributed to the anions and HA make it a promising candidate as an metal-free

enhanced PCP degradation. catalyst for wastewater purification and environmental remediation.

•−

CO

3

The influence of humic acid (HA), a typical natural organic matter, The successfully fabrication of sulfur-doped activated carbons

is depicted in Fig. 11d. It was suggested that the presence of HA derived from PPS make us believe that this work not only provides a

would decrease the removal efficiency toward target contaminant potential promising way to utilize PPS waste, but also opens a new

in AOPs via the competitive adsorption on catalyst surface and the way to synthesis other sulfur-doped activated carbon with both

1

0

competitive reaction with reactive species. However, in the S-AC- enhanced adsorption performance and catalytic activity via a facile,

−

1

8

00/PS system, HA at a concentration of 10-30 mg L presented a economical and efficient method for environmental remediation.

negligible effect on both PCP adsorption and oxidation. We suppose

that the predominant micro-pore characteristic of S-AC-800 limited

the adsorption of HA macromolecular structure, giving rise to the

negligible influence on PCP adsorption, and hereby leading to a

minor effect on PCP degradation.

Conflicts of interest

There are no conflicts to declare

Acknowledgements

3.8. Stability and reusability of the S-AC-800 sample

The authors gratefully acknowledge the ﬁnancial support from the

National Natural Science Foundation of China (21507140), and the

Youth Scientific and Technological Foundation of Shanxi Province

The stability and reusability of the S-AC-800 sample was

examined through three successive runs. Results show that both

the adsorption and the oxidation efficiencies of PCP were

significantly reduced over three cycles (Fig. S24). Characterization

results indicated that the deactivation of catalyst can be attributed

two aspects: 1) the change of porous structure due to the

adsorption of PCP and PCP oxidation products, as confirmed by the

(

201701D221232).

References

N

2

sorption isotherms that its SBET and pore volume significantly

1. H. Zhou and D. W. Smith, J. Environ. Eng. Sci., 2002, 1, 247-264.

2

3

4

5

6

. X. Wang, Y. Qin, L. Zhu and H. Tang, Environ. Sci. Technol., 2015,

, 6855-6864.

. W. Peng, S. Liu, H. Sun, Y. Yao, L. Zhi and S. Wang, J. Mater.

Chem. A, 2013, , 5854.

. A. Dhaouadi, L. Monser and N. Adhoum, J. Hazard. Mater.,

010, 181, 692-699.

. J. Gong, J. Liu, X. Chen, Z. Jiang, X. Wen, E. Mijowska and T.

Tang, J. Mater. Chem. A, 2015, , 341-351.

decreased after the first use (Table S5 and Fig. S25); and 2) the

change of surface chemistry under the highly oxidative

environment, as confirmed by the XPS S 2p spectra that the

4

9

1

x

percentage of –C–SO –C– in overall S dopants increased from 34.7%

to 65.8% after the first use (Fig. S26), which was suggested to be

detrimental for the electron transport from carbon to persulfate.

However, it is worth noting that the adsorption performance and

2

3

st

catalytic activity of S-AC-800 after 1 cycle can be greatly recovered

. K. Okawa, K. Suzuki, T. Takeshita and K. Nakano, Water Res.,

2007, 41, 1045-1051.

after being annealed at 450 °C in N

removal of the adsorbed organics and recovery of the surface

chemistry, as illustrated by the N sorption isotherms (Table S5 and

2

for 2 h due to the partially

7. W. A. Cabrera-Lafaurie, F. R. Román and A. J. Hernández-

Maldonado, J. Environ. Chem. Eng., 2014, , 899-906.

. N. A. Khan, Z. Hasan and S. H. Jhung, J. Hazard. Mater., 2013,

44-245, 444-456.

. T. X. Bui and H. Choi, Chemosphere, 2010, 80, 681-686.

2

8

9

Fig. S25) and XPS analysis (Fig. S26). Nevertheless, further efforts

should be made to enhance the stability of the carbon material in

future studies.

2

1

0. X. Duan, Z. Ao, L. Zhou, H. Sun, G. Wang and S. Wang, Appl.

Catal. B, 2016, 188, 98-105.

1. H. Lee, H. I. Kim, S. Weon, W. Choi, Y. S. Hwang, J. Seo, C. Lee

and J. H. Kim, Environ. Sci. Technol., 2016, 50, 10134-10142.

4

. Conclusions

In summary, in-situ sulfur doped activated carbon with both 12. Y. Wang, Y. Xie, H. Sun, J. Xiao, H. Cao and S. Wang, ACS Appl.

strong adsorption ability and enhanced PS activity was successfully

Mater. Inter., 2016, , 9710-9720.

8

1

2 | J. Name., 2012, 00, 1-3

Please do not adjust margins

Page 13 of 14

Jou a f Materials Ch i A

Pl er na s el od o not adjust me ma r gs ti nr ys

View Article Online

DOI: 10.1039/C7TA09814F

Journal Name

ARTICLE

1

3. S. Indrawirawan, H. Sun, X. Duan and S. Wang, J. Mter. Chem. A, 44. M. Sevilla and A. B. Fuertes, Micropor. Mesopor. Mat., 2012,

58, 318-323.

1

2

015,

4. P. Wang, P. Xiao, S. Zhong, J. Chen, H. Lin and X.-L. Wu, J. Mater.

Chem. A, 2016, , 15450-15456.

5. X. Wang and Y. Li, J. Mater. Chem. A, 2016,

6. H. Sun, S. Liu, G. Zhou, H. M. Ang, M. O. Tade and S. Wang, ACS

Appl. Mater. Inter., 2012, , 5466-5471.

3, 3432-3440.

4

5. R. S. Ribeiro, N. A. Fathy, A. A. Attia, A. M. T. Silva, J. L. Faria and

H. T. Gomes, Chem. Eng. J., 2012, 195-196, 112-121.

4

6. Y. Liu, M. Chen and H. Yongmei, Chem. Eng. J., 2013, 218, 46-54.

7. Y. Zhang, C. Liu, B. Xu, F. Qi and W. Chu, Appl. Catal. B, 2016,

1

4, 5247-5257.

1

99, 447-457.

8. S. Wang, H. Sun, H. M. Ang and M. O. Tadé, Chem. Eng. J., 2013,

26, 336-347.

9. D. Lin and B. Xing, Environ. Sci. Technol., 2008, 42, 7254-7259.

0. M. Pera-Titus, V. Garcıa-Molina, M. A. Baños, J. Giménez and S.

4

1

2

7. H. Sun, C. Kwan, A. Suvorova, H. M. Ang, M. O. Tadé and S.

2

Wang, Appl. Catal. B, 2014, 154-155, 134-141.

4

5

8. X. Duan, Z. Ao, D. Li, H. Sun, L. Zhou, A. Suvorova, M. Saunders,

G. Wang and S. Wang, Carbon, 2016, 103, 404-411.

9. S. Liu, W. Peng, H. Sun and S. Wang, Nanoscale, 2014,

71.

0. J. Gong, H. Lin, M. Antonietti and J. Yuan, J. Mater. Chem. A,

016, , 7313-7321.

1. F. Yang, X. Fan, C. Wang, W. Yang, L. Hou, X. Xu, A. Feng, S. Dong,

K. Chen, Y. Wang and Y. Li, Carbon, 2017, 121, 443-451.

2. W. Yang, X. Xu, L. Hou, X. Ma, F. Yang, Y. Wang and Y. Li, J.

́

Esplugas, Appl. Catal. B, 2004, 47, 219-256.

1. T. G. Danis, T. A. Albanis, D. E. Petrakis and P. J. Pomonis, Water

Res., 1998, 32, 295-302.

6, 766-

5

6

7

2. S. Wang, C. W. Ng, W. Wang, Q. Li and Z. Hao, Chem. Eng. J.,

2

4

2

012, 197, 34-40.

3. W.-D. Oh, S.-K. Lua, Z. Dong and T.-T. Lim, J. Mater. Chem. A,

014, , 15836-15845.

2

4. J. Wang, Z. Liao, J. Ifthikar, L. Shi, Y. Du, J. Zhu, S. Xi, Z. Chen and

Z. Chen, Chemosphere, 2017, 185, 754-763.

5. X. Li, M. Zhou, Y. Pan and L. Xu, Chem. Eng. J., 2017, 307, 1092-

Mater. Chem. A, 2017, 5, 5952-5960.

3. D. Li, X. Duan, H. Sun, J. Kang, H. Zhang, M.O. Tade and S. Wang,

Carbon, 2017, 115, 649-658.

4. W. Kiciński, M. Szala and M. Bystrzejewski, Carbon, 2014, 68, 1-

1

104.

6. X. Cheng, H. Guo, Y. Zhang, Y. Liu, H. Liu and Y. Yang, J. Colloid

Interf. Sci., 2016, 469, 277-286.

7. X. Duan, C. Su, L. Zhou, H. Sun, A. Suvorova, T. Odedairo, Z. Zhu,

Z. Shao and S. Wang, Appl. Catal. B, 2016, 194, 7-15.

8. X.-Y. Xu, G.-M. Zeng, Y.-R. Peng and Z. Zeng, Chem. Eng. J., 2012,

3

2.

25. Y. Xia, Y. Zhu and Y. Tang, Carbon, 2012, 50, 5543-5553.

26. L. Yue, H. Zhong, D. Tang and L. Zhang, J. Solid State Electr., 2012,

17, 961-968.

2

3

7. S. Inamdar, H.-S. Choi, P. Wang, M. Y. Song and J.-S. Yu,

2

00-202, 25-31.

Electrochem. Commun., 2013, 30, 9-12.

9. Y. Yang, J. J. Pignatello, J. Ma and W. A. Mitch, Environ. Sci.

Technol., 2014, 48, 2344-2351.

0. X. Duan, H. Sun, Y. Wang, J. Kang and S. Wang, ACS Catal., 2015,

8. C. Petit, G. W. Peterson, J. Mahle and T. J. Bandosz, Carbon,

2

010, 48, 1779-1787.

9. M. Seredych and T. J. Bandosz, Appl. Catal. B, 2011, 106, 133-

41.

0. X. Duan, K. O'Donnell, H. Sun, Y. Wang and S. Wang, Small, 2015,

, 3036-3044.

1. Y. Guo, Z. Zeng, Y. Li, Z. Huang and J. Yang, Sep. Purif. Technol.,

017, 179, 257-264.

2. Y. Guo, Z. Zeng, Y. Li, Z. Huang and Y. Cui, Catal. Today, 2017,

DOI: 10.1016/j.cattod.2017.05.080.

3. Y. Guo, Z. Zeng, Y. Zhu, Z. Huang, Y. Cui and J. Yang, Appl. Catal.

B, 2018, 220, 635-644.

5

, 553-559.

1. C. Liang, Z. S. Wang and C. J. Bruell, Chemosphere, 2007, 66

06-113.

1

,

1

2. B-T Zhang, Y. Zhang, Y. Teng and M. Fan, Crit. Rev. Env. Sci. Tec.,

2015, 45, 1756-1800.

63. W.-D. Oh, Z. Dong and T.-T. Lim, Appl. Catal. B, 2016, 194, 169-

201.

2

64. P. Xie, J. Ma, W. Liu, J. Zou, S. Yue, X. Li, M. R. Wiesner and J.

Fang, Water Res., 2015, 69, 223-233.

4. X. Duan, Z. Ao, H. Sun, S. Indrawirawan, Y. Wang, J. Kang, F.

Liang, Z. H. Zhu and S. Wang, ACS Appl. Mater. Inter., 2015,

169-4178.

5. H. Wayne Hill, Jr. and D. G. Brady, Polym. Eng. Sci., 1976, 16

31-835.

6. S. Morales-Torres, A. M. T. Silva, F. J. Maldonado-Hódar, B. F.

Machado, A. F. Pérez-Cadenas, J. L. Faria, J. L. Figueiredo and F.

Carrasco-Marín, Appl. Catal. B, 2011, 105, 86-94.

7

,

4

3

,

8

37. W. Tian, H. Zhang, X. Duan, H. Sun, M. O. Tade, H. M. Ang and S.

Wang, ACS Appl. Mater. Inter., 2016, 8, 7184-7193.

38. J. Hayashi, A. Kazehaya, K. Muroyama and A. P. Watkinson,

Carbon, 2000, 38, 1873-1878.

3

4

9. W. Kiciński and A. Dziura, Carbon, 2014, 75, 56-67.

0. D. Geng, Y. Chen, Y. Chen, Y. Li, R. Li, X. Sun, S. Ye and S. Knights,

Energ. Environ. Sci., 2011,

1. Z. Yang, Z. Yao, G. Li, G. Fang, H. Nie, Z. Liu, X. Zhou, X. Chen and

S. Huang, ACS Nano, 2012, , 205-211 .

2. J. E. Park, Y. J. Jang, Y. J. Kim, M. S. Song, S. Yoon, D. H. Kim and

S. J. Kim, Phys. Chem. Chem. Phys., 2014, 16, 103-109.

3. H. Liu, P. Sun, M. Feng, H. Liu, S. Yang, L. Wang and Z. Wang,

Appl. Catal. B, 2016, 187, 1-10.

4, 760.

4

6

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Sulfur doped activated carbon with strong adsorption ability and excellent catalytic activity is

successfully synthesized through a one-pot process.

Article Doi

One-pot synthesis of sulfur doped activated carbon as a superior metal-free catalyst for the adsorption and catalytic oxidation of aqueous organics

DOI: 10.1039/c7ta09814f

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Full text of DOI:10.1039/c7ta09814f

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