Activated carbons as green and effective catalysts for generation of reactive radicals in degradation of aqueous phenol

Article abstract of DOI:10.1039/c3ra42455c

Several activated carbons (ACs) were used as metal-free catalysts for degradation of a toxic organic compound, phenol, in the presence of different oxidants, H₂O₂, peroxydisulfate (PS) and peroxymonosulfate (PMS). It was found that ACs were effective in heterogeneous activation of PMS to produce sulfate radicals for degradation of phenol, much better than H ₂O₂ and PS. Particle size of AC significantly influenced AC activity, and powder AC was much more effective than granular AC. The complete phenol removal could be achieved in 15 min on powder activated carbon (PAC) under the conditions of [phenol] = 25 mg L^-1, [PAC] = 0.2 g L^-1, [PMS] = 6.5 mmol L^-1, and T = 25 °C. It was also found that phenol degradation was significantly influenced by PMS loading, catalyst loading, phenol concentration and temperature. Surface activation of PMS and phenol adsorption played important roles in phenol degradation. Surface coverage by intermediate adsorption and structural change induced deactivation of AC and catalytic activity could be partially recovered by regeneration using calcination. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra42455c

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PAPER
Activated carbons as green and effective catalysts for
generation of reactive radicals in degradation of
aqueous phenol†
Cite this: RSC Adv., 2013, 3, 21905
a
a
Edy Saputra,ab Syaifullah Muhammad,ac Hongqi Sun and Shaobin Wang
*
Several activated carbons (ACs) were used as metal-free catalysts for degradation of a toxic organic
compound, phenol, in the presence of different oxidants, H2O2, peroxydisulfate (PS) and
peroxymonosulfate (PMS). It was found that ACs were effective in heterogeneous activation of PMS to
produce sulfate radicals for degradation of phenol, much better than H2O2 and PS. Particle size of AC
significantly influenced AC activity, and powder AC was much more effective than granular AC. The
complete phenol removal could be achieved in 15 min on powder activated carbon (PAC) under the
conditions of [phenol] ¼ 25 mg Lꢀ1, [PAC] ¼ 0.2 g Lꢀ1, [PMS] ¼ 6.5 mmol Lꢀ1, and T ¼ 25 ꢁC. It was also
found that phenol degradation was significantly influenced by PMS loading, catalyst loading, phenol
concentration and temperature. Surface activation of PMS and phenol adsorption played important
roles in phenol degradation. Surface coverage by intermediate adsorption and structural change
induced deactivation of AC and catalytic activity could be partially recovered by regeneration using
calcination.
Received 17th May 2013
Accepted 16th September 2013
DOI: 10.1039/c3ra42455c
www.rsc.org/advances
Activated carbons (AC) have been widely used in heteroge-
neous catalysis either as supports or catalysts due to their
Introduction
Conventional wastewater treatments have been proved to be
limited in treating toxic organic compounds. One of the
promising methods for degradation of organic pollutants in
wastewater is an advanced oxidation process (AOP) which can
completely degrade organic compounds into carbon dioxide
and water. AOPs are based on generation and utilization of
reactive species, such as hydroxyl radicals (_OH) and superoxide
radicals (O2ꢀ_) that have a high standard oxidation potential and
react non-selectively.1,2 Among the AOP methods, heteroge-
neous catalytic oxidation systems have attracted much attention
because of economics and easy recovery of catalysts.3 In the
heterogeneous systems, the solid catalysts play an important
role in achieving a highly efficient oxidation process, not
harmful to the environment. Therefore, many studies have
concentrated on developing new and effective catalysts, but
most of them are metal-based systems,4–6 which could induce
secondary pollution to water due to metal leaching.
porous structure, high specic surface area and pore volume,
inexpensiveness and environmentally friendliness.7–10
A
number of studies have shown that activated carbons are active
in the degradation of some dissolved organic pollutants such as
4-chlorophenol, trichlorophenol, trichloroethane, methyl tert-
butyl ether, methylamines and dimethylamines in the presence
of H2O2.11–13 It was shown that AC can promote hydrogen
peroxide decomposition through the formation of hydroxyl
radicals as shown in the following equations:
AC + H2O2 / AC+ + OHꢀ + _OH
AC+ + H2O2 / AC + H+ + HO2_
(1)
(2)
Reactions (eqn (1) and (2)) are commonly known as elec-
tron-transfer catalysis similar to the Haber–Weiss mechanism,
following the Fenton reaction mechanism involving the
oxidized (AC+) and reduced (AC) catalyst states.14 However, AC
exhibits much low activity in such a reaction. Recently, sulfate
radicals (SO4ꢀ_) have been proposed as an alternative to
hydroxyl radicals for organic degradation due to the higher
oxidizing potential (1.82 V) than that of H2O2 (1.76 V). Sulfate
radicals can be produced from persulfate (PS) or perox-
ymonosulfate (PMS). Up to now, activation of PS or PMS was
only achieved by metal ions, heat and light, which either
requires high energy input or produces metal toxicity.15–17
However, few investigations have been reported using
aDepartment of Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA
6845, Australia. E-mail: shaobin.wang@curtin.edu.au; Fax: +61 8 92662681; Tel: +61
8 92663776
bDepartment of Chemical Engineering, Riau University, Pekanbaru 28293, Indonesia
cDepartment of Chemical Engineering, Syiah Kuala University, Banda Aceh, Indonesia
† Electronic supplementary information (ESI) available: XRD, TGA of powder
activated carbon, effect of phenol concentration and effect of catalyst loading
and rate constant. See DOI: 10.1039/c3ra42455c
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carbonaceous materials for production of sulfate radicals.18 phenolic solutions, which was attached to a stand and dipped in
We recently found that graphene could be a good catalyst for a water bath with a temperature controller. The reaction
PMS activation.19 However, graphene is expensive material. mixture was stirred constantly at 400 rpm to maintain a
Activated carbon is widely available and cheap carbon. Using homogenous solution. A xed amount of PMS was added into
activated carbon as an alternative to graphene and metal- the solution and allowed to dissolve completely before reaction.
based catalysts would be not only economic but also envi- Further, a xed amount of catalysts was added into the reactor
ronmental benign. In this paper, we report that AC powder can to start the oxidation reaction of phenol. The reaction was
be a green catalyst in effective activation of PMS, showing an carried on for 90 minutes and at a xed interval time, 0.5 mL of
excellent capability of phenol degradation. We investigated solution sample was taken out from the mixture using a syringe
the performance of different carbon samples in PMS activation lter of 0.45 mm and then mixed with 0.5 mL methanol to
and compared the activity of powder activated carbon in quench the reaction. A few other tests were carried out with
activation of different oxidants, H2O2, PS and PMS. Several different oxidants, hydrogen peroxide and peroxydisulfate (PDS)
factors inuencing the phenol degradation with PMS at the same concentration as PMS. Concentration of phenol was
oxidation were also studied at varying phenol concentrations, analyzed using a HPLC with a UV detector set at l ¼ 270 nm.
AC and PMS loadings and temperatures. The regeneration of The column used was C-18 with mobile phase of 30% CH3CN
AC was also investigated.
and 70% water.
For recycled catalyst tests, two regeneration methods were
used. One is simple washing treatment and the other is high-
temperature calcination. In general, all the carbon samples
were collected by ltration aer reaction, washing with water
and drying at 80 ꢁC overnight for reuse test. Some dried samples
Experimental section
Samples and chemicals
Two activated carbons produced from coconut shells were
obtained in powder and granule from Pancasari Puspa
Company, Indonesia. Powder activated carbon (PAC) was used
without further treatment. The average particle size was deter-
mined to be 30 mm by a particle analyzer (Hydro 2000S, Mal-
vern). Granular activated carbon (GAC) was crushed into small
particles and separated according to their sizes into two
sections: 60–90 mm (GAC-1) and 90–120 mm (GAC-2). The
oxidant, peroxymonosulfate (KHSO5ꢀ, PMS) derived from the
triple salt, Oxone (2KHSO5$KHSO4$K2SO4), was supplied by
Sigma-Aldrich, Australia. Phenol solution of the required
concentrations (i.e. 25, 50, 75 and 100 mg Lꢀ1) were prepared
from phenic acid (C6H5OH, 99% purity, Sigma-Aldrich) by
mixing with ultrapure water. Methanol as a quenching reagent
(CH3OH, 100% purity) for HPLC analysis was purchased from
Perth Scientic, Australia. Sodium nitrite for quenching the
reaction for the total organic carbon (TOC) analysis was
purchased from Sigma-Aldrich. H2O2 (30 wt%) and peroxy-
disulfate (PDS) were also obtained from Sigma-Aldrich.
ꢁ
were further calcined at 500 C in N2 for 1 h.
In order to evaluate the possible effect of inorganic metal
components in AC on catalytic activity, powder AC was calcined
in air at 500 ꢁC for 2 h to obtain ash and the ash was tested for
phenol degradation at the above similar conditions.
Results and discussion
Characterization of the activated carbons
The BET surface area, pore volume and pore radius for the
carbons are shown in Table 1. It can be observed that there is a
signicant difference in the surface area and pore volume.
PAC has higher surface area (824.7 m2 gꢀ1), pore volume
(0.470 cm3 gꢀ1), and pore radius (22.8 A) than others. For both
˚
granular AC particles (GAC-1 and GAC-2), GAC-1 has slightly
higher surface area, pore volume and pore radius due to smaller
particle size. XRD indicates amorphous structure of PAC
without other crystallites (Fig. S1†) and a thermogravimetric
analysis (TGA) shows PAC contains 93% of carbon (Fig. S2†).
The AC surface area and pore size measurements were carried
out by N2 adsorption using Autosorb-1, Quantachrome (USA). The
AC samples were degassed at 100 ꢁC for 24 h prior to adsorption
analysis. The surface area and pore size distribution were
obtained by the Brunauer–Emmett–Teller (BET) and the Barrett–
Joyner–Halenda (BJH) methods respectively. Fourier transform
infrared spectra (FTIR) were acquired from a Bruker instrument
using an ATR mode. X-ray diffraction (XRD) patterns were
obtained on a Bruker D8-Advanecd X-ray diffractometer with Cu
Preliminary study of phenol oxidation using AC catalysts
Fig. 1 shows the preliminary tests of adsorption and catalytic
oxidation of phenol using different AC samples. It is generally
accepted that AC has a good adsorption capacity. As can be
seen, all ACs were able to adsorb phenol with different capac-
ities. Both GAC-1 and GAC-2 showed low adsorption of phenol
at less than 20% in 90 min. While PAC presented double phenol
adsorption efficiency in 90 min at 50%, which can be ascribed to
˚
Ka radiation (l ¼ 1.5418 A), at accelerating voltage and current of
40 kV and 40 mA, respectively. Thermogravimetric analysis (TGꢀA1)
was conducted in air atmosphere at a heating rate of 10 ꢁC min
on a Perkin-Elmer Diamond TG/DTA thermal analyzer.
Table 1 Surface area, pore volume and pore radius of activated carbons
Catalyst SBET (m2 gꢀ1
)
V (cm3 gꢀ1
)
Pore radius (A) Conv./SBET
˚
Catalytic evaluation of PMS activation for phenol degradation
PAC
GAC-1
824.7
586.9
560.9
0.470
0.250
0.236
22.8
17.0
16.9
0.103
0.051
0.052
The catalytic oxidation of phenol was carried out in a 1 L glass
beaker containing 500 mL at 25, 50, 75 and 100 mg Lꢀ1 of GAC-2
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Fig.
1
Preliminary study of phenol at different size of catalyst. Reaction
condition: [phenol] ¼ 50 mg Lꢀ1, catalyst ¼ 0.2 g Lꢀ1, PMS ¼ 6.5 mmol Lꢀ1, and
Fig. 2 Phenol transformation by the interaction of PAC and three different
oxidants. Reaction condition: [phenol] ¼ 25 mg Lꢀ1, catalyst ¼ 0.2 g Lꢀ1, oxidant ¼
6.5 mmol Lꢀ1, and T ¼ 25 ꢁC.
T ¼ 25 ꢁC.
higher surface area of PAC. Inset of Fig. 1 displayed oxidation of
phenol by PMS without AC and negligible change in phenol
concentration was observed. Less than 3% in phenol concen-
tration reduction was found aer 90 min, suggesting that PMS
itself could not produce sulfate radical to induce signicant
oxidation of phenol. In oxidation tests, PAC with PMS in the
heterogeneous system could degrade phenol up to 85% in
90 min. Meanwhile, GAC-1 and GAC-2 could only reach around
30 and 25% phenol removal, respectively, at the same period.
The experimental results showed that surface area of ACs
inuenced signicantly phenol degradation. Based on surface
area, phenol conversions for three ACs were normalized
(Table 1) and it is seen that PAC presented higher activity than
GACs. This suggests particle size also affect the catalytic activity.
Characterization shows that the three AC samples have
different particle sizes and surface areas. PAC has the highest
surface area and lowest particle size. Phenol removal iꢀs
the active catalyst. The reaction mechanism for heterogeneous
phenol oxidation can be proposed as follows.
ꢀ
ꢀ
_
AC + HSO5 / AC+ + OHꢀ + SO4
(3)
(4)
(5)
(6)
AC+ + HSO5 / AC + H+ + SO5
_
ꢀ
ꢀ
SO4ꢀ_ + H2O / SO4 + _OH + H+
2ꢀ
SO4ꢀ_ + C6H5OH / several steps / CO2 + H2O + SO4
2ꢀ
Several investigations have been reported in activated carbon
catalysts for organic decomposition using different oxidants.
Santos et al.23 studied the modied activated carbon (100–
300 mm) for heterogeneous activation of H2O2 to generate
hydroxyl radicals targeting at the decolorization of reactive red
241. Modied activated carbon could achieve 65% color removal
at reactive red 241 concentration of 50 mg Lꢀ1 within 150 min.
They also found that the catalytic activity was inuenced
signicantly by pH. Yao et al.24 used reduced graphene oxide
(rGO) nanoparticle with peroxymonosulfate for phenol degra-
dation at 20 mg Lꢀ1. rGO could achieve 20% phenol degradation
within 60 min. Shukla et al.8 studied activated carbon with per-
oxymonosulfate for phenol degradation at 25 mg Lꢀ1. The acti-
vated carbon could achieve 48% phenol degradation within
60 min. Therefore, it is seen that PAC with peroxymonosulfate in
this investigation presented higher activity in phenol degrada-
tion than other activated carbons and rGO.
dependent on adsorption and produced sulfate radicals (SO4
and SO5ꢀ_). At the same concentration of PMS, sulfate radical
concentration produced will depend on active sites on surface
area and edges of carbon catalysts. Thus, the catalysts with a
high surface area can provide more active sites for adsorption
and more sulfate radicals, resulting in high phenol degradation.
Meanwhile, small particle size of AC provides more edges,
making the contact more frequently between AC and reactant,
thus enhancing reaction rate or efficiency. In addition, TOC
removal in PAC/PMS system was also examined and the result
showed that about 75% phenol removal was obtained within
90 min.
_
Previously, Anipsitakis and Dionysiou20 have tested several
metal ions, Ag(I), Ce(III), Co(II), Fe(II), Fe(III), Mn(II), Ni(II), Ru(III),
and V(III), for homogeneous activation of PMS and found that
Effect of reaction parameters on phenol degradation
Co(II), Ru(III), and Fe(II) interact with PMS to produce freely Fig. 2 shows a comparison of phenol oxidation in PAC with
diffusible sulfate radicals for reaction. In this investigation, PAC different oxidants (PMS, PDS, and H2O2). As can be seen, PAC
was calcined to obtain its ash component and then tested under could activate all three oxidants although the removal efficien-
the same conditions in PMS activation for phenol degradation. cies of phenol were different. PAC with peroxymonosulfate
As shown in Fig. 2, the ash did not produce strong phenol resulted in complete degradation of phenol in less than 20 min.
degradation with only 4% phenol removal in 90 min. Some PAC with PDS could achieve 100% removal of phenol in 90 min
other investigations have shown that solid metal oxides, TiO2, while PAC with H2O2 could achieve only 50% phenol removal in
SiO2, Al2O3, zeolites, y ash and red mud could not activate 90 min. The experimental results indicate that the catalytic
PMS.15,21,22 Thus, the inorganic impurities as metal oxides in activity strongly depends on the oxidation potential of oxidants.
activated carbon can not induce PMS activation and carbon is The catalytic activity shows an order of PAC/H2O2 < PAC/PDS
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< PAC/PMS in phenol degradation. Anipsitakis and Dionysiou20
studied homogeneous activation of PMS, PDS and H2O2 with
some transition metal ions for 2,4-DCP oxidation. It was
reported that M2+/PMS showed the highest 2,4-DCP removal,
followed by M2+/PDS and M2+/H2O2. Thus, it would be expected
a similar reaction rate for heterogeneous systems in this
investigation.
Fig. 3 presents the variation of normalized phenol concen-
tration as a function of PMS concentration in the solution. As
can be seen, the degradation of phenol by PAC/PMS depended
on initial concentration of PMS. Higher concentration of PMS
resulted in higher removal efficiency of phenol. The complete
phenol degradation could be achieved at 6.5 mmol PMS loading
in 15 min, while in the same duration at PMS concentrations of
5.5, 2.6, and 1.3 mmol, phenol removal efficiency were obtained
at 98, 94, and 87%, respectively.
Fig. 4 Effect of temperature on phenol removal. Reaction condition: [phenol] ¼
50 mg Lꢀ1, catalyst ¼ 0.2 g Lꢀ1, and PMS ¼ 6.5 mmol Lꢀ1
.
The effect of PAC loading in solution on phenol degradation
is shown in Fig. S4.† An increase in PAC amount in the solution
A general pseudo rst order kinetics for phenol degradation
was employed to estimate the kinetic rates, as shown in equa-
tion below:
increased the phenol degradation efficiency.
A complete
removal of phenol could be reached within 15 min at 0.2 g Lꢀ1
PAC loading. Whereas 70.5% and 40% removals could be
reached at PAC loading of 0.1 and 0.06 g Lꢀ1, respectively. For
phenol degradation, increased catalyst loading would enhance
adsorption and provided additional sites for generation of
active sulfate radicals, thus enhancing phenol degradation.
Furthermore, temperature is also a variable inuencing
catalyst activity and phenol degradation. Fig. 4 shows the
reduction of phenol concentration versus time at various
ln(C/C0) ¼ ꢀk ꢂ t
(7)
where k is the apparent rst order rate constant of phenol
removal, C is the concentration of phenol at various time (t). C0
is the initial phenol concentration. Using this model, ln(C/C0)
versus time (t) produced straight lines as shown in Fig. 3 (inset).
The rate constants at varying PMS concentrations are shown in
Table S1.† As seen, rate constant will decrease as the concen-
tration of PMS decreases.
ꢁ
temperatures of 25–45 C. As can be seen that the rate of reac-
tion would increase with increased temperature. At temperꢀat1ure
of 25 ꢁC, phenol removal would reach 85% at 50 mg L in
90 min. While in the same duration and phenol concentration
at temperatures of 35 and 45 ꢁC, phenol removal efficiency were
obtained at 91 and 95%, respectively. Using the rst order
kinetic rate constant, the activation energy for this heteroge-
neous phenol decomposition was found to be 17.6 kJ molꢀ1. It
should be noted that phenol degradation in PAC/PMS system
would be ascribed to adsorption and oxidation. In this study, it
would be difficult to distinguish the contribution of each part
(adsorption and oxidation). Thus, the activation energy value
obtained would refer to the combined processes. Previously, we
have investigated several heterogeneous carbon supported Co
and Ru catalysts, such as Co/AC, Co/CX (carbon-xerogel) and
RuO2/AC, in activation of PMS for phenol degradation and the
activation energies obtained are presented in Table 2. As can be
It is believed that phenol degradation efficiency also
depended on initial concentration of phenol in solution.
Fig. S3† shows phenol degradation at various concentrations
between 25 and 100 mg Lꢀ1. At high phenol concentration,
removal efficiency tended to decrease. At 25 mg Lꢀ1, phenol
removal was very fast and achieved 100% degradation within
15 min, whereas at phenol concentrations of 50, 75 and 100 mg
Lꢀ1, the degradation rate was slower and phenol removal would
achieve at only 85, 62, and 42%, respectively, in 90 min.
Table 2 Activation of heterogeneous catalysts with PMS for phenol degradation
Activation energy
Catalyst
(kJ molꢀ1
)
Reference
Co/AC
Co/CX-1
Co/CX-G
RuO2/AC
Co/rGO
rGO
59.7
48.3
62.9
61.4
26.5
84.9
17.6
8
25
25
26
27
19
Fig. 3 Effect of PMS concentration on phenol removal. Reaction condition:
[phenol] ¼ 25 mg Lꢀ1, catalyst ¼ 0.2 g Lꢀ1 and T ¼ 25 ꢁC.
PAC
This work
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more strong absorption bands could be observed. One is at
1192 cmꢀ1, which is corresponding to S–O stretching vibration28,29
and the other is carboxylic C]O absorption at 1720 cmꢀ1. In
addition, the band at 3200–3400 cmꢀ1 became stronger, which is
due to OH stretching of HSO4 group. These changes in FT-IR
suggest the activation of PMS by carbon for sulfate radical
generation. Aer reaction with PMS and phenol, FT-IR showed all
the absorption bands related to phenol adsorption and PMS
activation. However, the band for C–O was shied to 1080 cmꢀ1
,
due to the decomposition of phenol and weaker adsorption. In
addition, the peak at 1720 cmꢀ1 is much weaker, due to the
consumption of sulfate radical in phenol oxidation.
During catalytic oxidation of toxic organics, powder activated
carbon primarily acted as an adsorbent for phenol, as shown in
Fig. 1. This may increase the probability of a reaction between
peroxymonosulfate and phenol. Meanwhile, powder activated
carbon catalyzes the decomposition of peroxymonosulfate into
free radicals, such as sulfate radicals. These sulfate radicals are
very active in oxidation reactions on carbon surface and in the
aqueous phase. Then, sulfate radicals and phenol can react on
the catalyst surface to produce simple molecular compounds
including CO2 and H2O (eqn (3)–(6)). Although the perox-
ymonosulfate decomposition mechanism is not completely
understood, the electron transfer from the surface of powder
activated carbon have been suggested to take place during the
reaction. According to the mechanism, the reaction might be
initiated by a reducing site transferring an electron to perox-
ymonosulfate to produce sulfate radicals (eqn (3)). Moreno-
Castilla et al.30 investigated activated carbon cloth with H2O2 for
the removal of amitrole from aqueous solution. The studies
have suggested that basic sites on carbon surface promote H2O2
decomposition into hydroxyl and perhydroxyl radicals, thereby
enhancing the oxidation of organic compounds in liquid. They
also found that the surface sites may be delocalized p electrons
from the graphene layers (C-p), which transferring electron
according to the mechanism as follows:
Fig. 5 Phenol removal in tests of recycled PAC catalyst. Reaction condition:
[phenol] ¼ 25 mg Lꢀ1, catalyst ¼ 0.2 g Lꢀ1, and PMS ¼ 6.5 mmol Lꢀ1
.
seen, PAC presented lower activation energy than AC supported
Co and Ru catalysts.
Reactivity of spent PAC catalyst and reusability
Fig. 5 shows the catalytic activity of recycled PAC for phenol
degradation. As can be seen, the catalytic activity signicantly
reduced in the second use, suggesting deactivation of the catalyst.
In the second use, phenol removal was 34% at 15 min compared
with 100% in the rst use.ꢁFurthermore, in PAC second use aer
thermal treatment at 500 C for 1 h, it appears that the catalyst
activity increased again although not as the same as the rst use
and 62% phenol degradation could be achieved at 15 min.
Role of powder activated carbon catalyst in phenol
degradation
Fig. 6 shows FT-IR spectra of fresh PAC, aer adsorption of
phenol and PMS as well as aer reaction. For fresh PAC, two
strong absorption bands were observed at 1120 and 1560 cmꢀ1
,
respectively, which are corresponding to C–O and C]O func-
tional groups, respectively. Aer phenol adsorption, the absorp-
tion band at 1120 cmꢀ1 was shied to 1065 cmꢀ1, due to the
strong interaction of adsorbed phenol with carbon. Meanwhile,
C-p + H2O2 / C-p+ + OHꢀ + _OH
C-p+ + H2O2 / C-p + H+ + HO2_
(8)
(9)
two weak absorption peaks were appeared at 2895 and 2980 cmꢀ1
,
which are referred to C–H vibration. For PAC–PMS system, two
Thus, the current study using peroxymonosulfate as an
oxidant will be in similar consequences. The reaction initiated
by the activation of peroxymonosulfate by a reducing site in a
Fenton like reaction to produce a SO4ꢀ_ radical. This sulfate
radical can then react with phenol as shown in Scheme 1.
Scheme 1 Mechanism for phenol removal during powder activated carbon
Fig. 6 FT-IR spectra of PAC before and after adsorption and reaction.
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(PAC) activation of peroxymonosulfate.
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PAC can be a cheap, green and effective catalyst in activation of
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phenol degradation. PAC exhibited higher activity than GAC
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21910 | RSC Adv., 2013, 3, 21905–21910
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