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Journal of Environmental Science and Health, Part B
Pesticides, Food Contaminants, and Agricultural Wastes
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lesb20
Removing 2,4-D micropollutant herbicide using
powdered activated carbons: the influence of
different aqueous systems on adsorption process
Lorena Dornelas Marsolla, Gilberto Maia Brito, Jair C. Checon Freitas &
Edumar R. Cabral Coelho
To cite this article: Lorena Dornelas Marsolla, Gilberto Maia Brito, Jair C. Checon Freitas &
Edumar R. Cabral Coelho (2022): Removing 2,4-D micropollutant herbicide using powdered
activated carbons: the influence of different aqueous systems on adsorption process, Journal of
Environmental Science and Health, Part B, DOI: 10.1080/03601234.2022.2084311
To link to this article: https://doi.org/10.1080/03601234.2022.2084311
Published online: 10 Jun 2022.
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Removing 2,4-D micropollutant herbicide using powdered activated carbons: the
influence of different aqueous systems on adsorption process
Lorena Dornelas Marsolla
a
, Gilberto Maia Brito
b
, Jair C. Checon Freitas
c
, and Edumar R. Cabral Coelho
a
a
Departament of Environmental Engineering, Federal University of Esp
ırito Santo, Vit
oria, Brazil;
b
Engineering and Computing Unit, FAESA
University Center, Vit
oria, Brazil;
c
Department of Physics, Federal University of Esp
ırito Santo, Vit
oria, Brazil
ABSTRACT
The presence of microcontaminants in the water supply system offers adverse impacts. This study
analyzed the performance of two powdered activated carbons (PAC1 and PAC2) in the removal of
2,4-D herbicide in ultrapure water (UW) and natural water (NW) to verify the influence of natural
organic matter (NOM) on the adsorptive process. The properties of PAC1 and PAC2 were analyzed
by textural analysis, FTIR, TG, pH, XDR, NMR. The specific surface area of PAC2 was lower than
PAC1 and PAC2 showed better adsorption capacity in UW (37.04mg.g
1
) and in NW (8.06 mg.g
1
).
The results of experiments performed in natural water showed that both activated carbons had
reduced 2,4-D adsorption capacity in the presence of NOM, since it may compete for the same
adsorption sites or block the access of the 2,4-D molecule to the pores of the activated carbon.
PAC2 showed a higher mesopores percentage, decreasing the effects caused by NOM in 2,4-D
adsorption. The use of activated carbons with varying pore sizes for the removal of microcontami-
nants is recommended, especially in NW. This result contributes to the choice of the adsorbent
type to be applied in water treatment plants.
KEYWORD
S: Activated carbon; 2,4-D
herbicide; adsorption;
natural organic matter;
emerging micropollutant;
removing pollutant
Introduction
With the increasing number of human activities and wide-
spread use of pesticides, organic and inorganic pollutants
have been detected in water sources and water supplies
around the world.
[1]
The commercialization and use of pes-
ticides have increased over the years, particularly in Brazil,
currently ranking first in pesticide use; the compound 2,4-
dichlorophenoxyacetic acid is ranked as second in the list of
top ten best-selling active ingredients in the country.
[2]
Commercially known as 2,4-D (Fig. 1), 2,4-dichlorophe-
noxyacetic is an herbicide used to control broadleaf weeds
in various crops such as soybeans, corn, and sugarcane and
is one of the most worldwide used herbicides on account of
its good selectivity, efficiency and low cost.
[3]
2,4-D is
extremely toxic and can cause several effects to human
health such as cancers and cardiovascular problems.
[3,4]
Considered persistent in the environment due to its low bio-
degradability and high water solubility, it can be found in
soils, surface and underground waters, being a potential risk
to the environment and health.
[5]
The presence of microcontaminants in the water supply
system offers adverse impacts and threatens water safety.
[6]
Thus, the World Health Organization recommends
30 mg.L
1
as a tolerable value of 2,4-D
[7]
in water intended
for human consumption. The Brazilian legislation deter-
mines the same limit of 30 mg.L
1
, according to Ordinance
GM/MS n888 of May 4th, 2021.
[8]
Studies show that
conventional water treatment has low efficiency in removing
microcontaminants.
[9,10]
Adsorption by activated carbon has
been used in the removal of contaminants in water treat-
ment and adsorption efficiency is attributed to the activated
carbon properties, target compound and water quality.
[11]
In
water treatment plants (WTP) powdered activated carbon is
commonly used seasonally or sporadically applied to the
water upon arrival at the WTP or in the rapid mix-
ing unit.
[12]
Present in surface water supplies, natural organic matter
(NOM) can adversely affect the adsorption of microcontami-
nants by activated carbon due to the competition for
adsorption sites or pore blocking,
[13]
depending on nature
matter organic like molecular weight and hydrophobicity.
[14]
Newcombe et al.
[15]
observed that low molecular weight
NOM reduced the adsorption of 2-methylisoborneol by
blockage of micropores competition for adsorption sites, but
high molecular weight NOM could not access micropores.
NOM is a complex and heterogeneous mixture of organic
compounds such as humic substances, carbohydrates, hydro-
lytic acids, sugars and others,
[16,17]
with size, molecular
weight and variable adsorptive capacity.
[11]
The influence of
NOM is determined by activated carbon properties, initial
microcontaminant concentration in relation to NOM and
organic matter characteristics.
[16]
Studies show that NOM
from different sources has varied characteristics, which can
show different adsorption behavior by activated carbon in
CONTACT Lorena Dornelas Marsolla lorenamarsolla@gmail.com Departament of Environmental Engineering, Federal University of Esp
ırito Santo, Av.
Fernando Ferrari, 514. Vit
oria, ES –29075-910, Brazil.
ß2022 Taylor & Francis Group, LLC
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART B
https://doi.org/10.1080/03601234.2022.2084311
natural waters.
[6,14]
The microcontaminant can also interact
with NOM throught electrostatic attraction/repulsion, p-p,
or hydrogen bonds.
[14]
Jin et al.
[18]
observed that microcon-
taminant pharmaceuticals were found to be able to interact
with humic acids in an aqueous solution and be adsorbed
onto activated carbon. Adsorption can be greatly affected by
the aqueous solutions different parameters and the NOM
and microcontaminants are components with different func-
tional groups, molecular weights, charges, aromaticity, and
hydrophobicity, which make them behave differently in the
adsorption process. Therefore, the present study aimed at
evaluating the influence of NOM on the adsorptive process
using two commercial activated carbons as adsorbents for
the removal of 2,4-D herbicide in natural water from surface
water sources and in ultrapure water.
Materials and methods
Adsorbents characterization
Two samples of powdered activated carbons (named PAC1
and PAC2) were supplied by different manufacturers and
characterized by the following techniques: (a) Textural ana-
lysis: performed from the adsorption-desorption of N
2
at
77 K in a Quantachrome Autosorb equipment from
Quantachrome Instruments; the specific surface area was
determined by the Brunauer-Emmett-Teller (BET) method.
The pore volumes, pore size distributions and the average
pore diameter were computed using the Non-Local Density
Functional Theory (NLDFT) approach assuming a model of
slit-shaped pores.
[19]
(b) Fourier transform infrared (FTIR)
spectroscopy: in this analysis, the functional groups were
identified using the Perkin Elmer model 1725X spectropho-
tometer, in the 4.000 to 500 cm
1
regions. (c)
Thermogravimetry (TG): The thermal behavior of the pow-
dered activated carbon samples was studied using the TGA-
50 Shimadzu equipment; the TG curves were recorded with
a heating rate of 10 C.min
1
, using either oxygen gas flow
at 50 mL min
1
with maximum temperatures of 800 C (d)
pH analysis: the pH measurements were conducted follow-
ing the ASTM D3838-05 standard.
[20]
(e) X-ray diffraction
(XRD): the crystalline phases present in the activated car-
bons were analyzed using a Shimadzu equipment, model
XRD 6000, with Cu-Karadiation (k¼1.5418 Å), in the 2h
range from 10 to 80, with speed of 2min
1
and step of
0.02. (f) Solid-state
13
C nuclear magnetic resonance (NMR):
the NMR spectra of the activated carbons were recorded
using a Varian Agilent VNMR 400 MHz spectrometer at
room temperature and at the
13
C NMR frequency of
100.52 MHz (magnetic field of 9.4 T); the powdered samples
were packed into 4 mm diameter zirconia rotors for magic
angle spinning (MAS) experiments at 14 kHz spinning rate;
the spectra were recorded with direct polarization of the
13
C
nuclei, using a pulse sequence designed to avoid probe back-
ground signals, with a p/2 pulse (4.3 ls) immediately fol-
lowed by a pair of ppulses (8.6 ls) and the subsequent
detection of the free induction decay (FID) .
[21]
The spectra
were obtained by Fourier transform of the FIDs, after accu-
mulation of ca. 2000 scans, with a recycle delay of 15 s, a
spectral window of 250 kHz and an acquisition time of
8.192 ms; the chemical shifts were referenced to tetramethyl-
silane (TMS), using hexamethylbenzene as a secondary refer-
ence (signal at 17.3 ppm).
Adsorption experiments
For the adsorption experiments, the PAC1 and PAC2 sam-
ples were used in two water matrices: ultrapure water (UW)
and natural water (NW). UW was obtained by Milli-Q
System Millipore and NW was collected from the Santa
Maria da Vit
oria River, in the state of Esp
ırito Santo, Brazil.
A stock solution of 2,4-D herbicide (97% purity standard,
Sigma - Aldrich) with concentration of 0.5 g.L
1
was pre-
pared in ultrapure water. From the stock solution, working
solutions were made in UW and NW with 2,4-D at a con-
centration of 60 lg.L
1
and pH adjusted to 7.0 with NaOH
and HCl. Volumes of 200 mL of each working solution were
transferred to flasks and samples of the two adsorbents with
mass between 0.25 and 2.00 mg were added. The powdered
activated carbon samples were previously sieved through 325
mesh sieve (0.044 mm). The flasks were shaken at 100 rpm
for 7 days at room temperature (25 ± 2 C). Samples were fil-
tered through a porosity membrane of 0.45 lm. Then, the
solutions were prepared for residual determination of 2,4-D
through Solid Phase Extraction method (SPE) and the herbi-
cide concentration was measured by High Performance
Liquid Chromatography (HPLC), as described below.
Adsorption capacity (q
e
) and removal percentage (R) at
equilibrium were calculated using Eqs. (1) and (2), respect-
ively.
qe¼CoCe
ðÞ
:V
m(1)
R¼CoCe
ðÞ
Co:100 (2)
In these equations, q
e
(mg.g-
1
) corresponds to the
amount of 2,4-D adsorbed per mass unit of the adsorbent at
equilibrium, V (L) is the volume of the solution, m (g) is
the adsorbent mass, C
o
(mg.L
1
) is the initial concentration
of 2,4-D in solution, C
e
(mg.L
1
) is the equilibrium concen-
tration of 2,4-D in solution and R (%) is the percentage of
removal of 2,4-D.
[22]
Figure 1. 2,4-D chemical structure.
2 L. D. MARSOLLA ET AL.
2,4-D Herbicide quantification
Before the chromatographic analysis for quantification of
2,4-D, the SPE technique was performed in aqueous samples
for concentration of 2,4-D below the limit of quantification
(LQ ¼20.00 lg.L
1
) of the chromatographic method, as
proposed by Coelho et al.
[23]
In the SPE process, volumes of
50 mL of each sample were acidified with H
3
PO
4
(0.10%)
and submitted to a vacuum extraction process in C
18
car-
tridges previously conditioned with 10 mL of acetonitrile
(ACN) and 10 mL of ultrapure water (Mili Q-System
Millipore). Then, the cartridges were washed with 5 mL of
ultrapure water and 2,4-D was eluted in 1 mL of ACN and
1 ml of ultrapure water was added for further analysis on
HPLC. The HPLC analysis was performed using a Shimadzu
chromatograph, model CBM-20, mobile phase of ACN and
ammonium formate (NH
4
COOH) in the proportion 47:53
v/v, 1.2 mL.min
1
flow. A C
18
analytical column
(150 4.6 mm, 3.5 lm) was used, with 50 lL injection vol-
ume, temperature of 30 C, detection at 200 nm and 6 min
analysis time. Data were processed using the LC Solutions
software (version 2.1).
[23]
Analysis of the adsorption isotherms
Adsorption data of 2,4-D were fitted to models proposed by
Langmuir
[24]
and Freundlich.
[25]
The Langmuir model
assumes that adsorbent-adsorbate interaction occurs through
the formation of a monolayer, on a homogeneous and ener-
getically uniform surface,
[24]
described by Eq. (3).
qe¼qmbCe
1þbC
e(3)
In this expression, q
e
(mg.g-
1
) is the amount of 2,4-D
adsorbed at equilibrium, q
m
(mg.g
1
) is the monolayer
adsorption capacity, b (L.mg
1
) is the Langmuir constant
and C
e
(mg.L
1
) is the equilibrium concentration of 2,4-D
in solution.
A characteristic of the Langmuir isotherm is the RL separ-
ation factor, defined by Eq. (4). The separation factor indicates
whether the isotherm type is: unfavorable (RL >1), linear (RL
¼1), favorable (0 <RL <1), or irreversible (RL ¼0) .
[23,24]
RL¼1
1þb:Co(4)
The model proposed by Freundlich (Eq. (5)) describes the
adsorption occurring on an inhomogeneous surface and with
non-uniform adsorbate/adsorbent interaction energy.
[25]
qe¼KfCe1=n(5)
In this expression, K
f
and nare the Freundlich constants;
the parameter K
f
((mg.g
1
) (L.mg
1
)
1/n
) is related to the
adsorption capacity of the adsorbent and nindicates how
favorable the adsorption process is.
Statistical analysis
Linear regression tests and analysis of variance (ANOVA)
using MinitabV
R️19 Statistical software were performed on
the data to analyze the 2,4-D adsorption capacity of PAC1
and PAC2. Variability of the data was expressed as the
standard deviation (STDEV) and a p value of <0.05 was
considered statistically significant.
Results and discussion
Characterization of powdered activated carbons
According to the International Union of Pure and Applied
Chemistry (IUPAC),
[28]
the pores present in activated car-
bons are classified into the following size ranges: micropores
(diameter <20 Å), mesopores (20 Å <diameter <500 Å)
and macropores (diameter >500 Å). Table 1 shows the spe-
cific surface area and pore volumes of PAC1 and PAC2
samples. These data show that PAC1 has higher specific sur-
face area and higher percentage of micropores. The specific
surface area of an activated carbon is usually related to the
micropore volume, i.e., the higher the specific surface area
of an activated carbon, the larger the micropore volume
tends to be.
[19,26]
Predominantly microporous activated car-
bons (with pores smaller than 20 Å) are effective for the
adsorption of small molecules such as 2,4-D herbicide,
which has molecular width 2.074 Å, thus facilitating its dif-
fusion inside the pores.
[27,28]
The results shown in Table 1
highlight then the potential of PAC1 and PAC2 samples for
2,4-D adsorption, as they are both highly microporous acti-
vated carbons.
Table 2 shows pH values and results of proximate ana-
lysis (obtained by TG) of PAC1 and PAC2 samples. PAC2
showed higher moisture content (12%), which is indicative
of adsorbent hydrophilicity and is possibly related to the
existence of oxygen-containing chemical groups on the
adsorbent surface.
[32]
The volatile matter content is associ-
ated with the presence of light compounds in the activated
carbon,
[30]
whose release during the initial thermal decom-
position of the carbonaceous structure (in inert atmosphere)
leads to weight losses of 5 and 6% for PAC1 and PAC2
Table 1. Specific surface area and pore volumes of PAC1 and PAC2 samples.
Sample S
BET
(m
2
.g
-1
)V
micro
(cm
3
.g
-1
)V
meso
(cm
3
.g
-1
)V
total
(cm
3
.g
-1
) Micropore fraction (%)
PAC1 630 0.290 0.095 0.385 75.3
PAC2 568 0.246 0.131 0.377 65.3
S
BET
¼specific surface area (BET method), V
micro
¼micropore volume, V
meso
¼mesopore volume, V
total
¼total pore volume,
Micropore fraction (%) ¼100 V
micro
/V
total
.
Table 2. Results of TG analyses and pH measurements for PAC1 and
PAC2 samples.
Sample Moisture (%) Volatile matter (%) Fixed carbon (%) Ash (%) pH
PAC1 5 5 54 34 8.71 ± 0.03
PAC2 12 6 73 7 5.52 ± 0.01
The pH experiments were conducted in triplicates.
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART B 3
samples, respectively. The fixed carbon content in activated
carbon is an important indicative of quality, as it is related
to the adsorption capacity of the material. As it can
observed in Table 2, PAC2 sample showed a higher fixed
carbon content than PAC1. On the other hand, ash content
interferes negatively in adsorption, as it is related with the
presence of undesirable materials with low porosity, such as
inorganic oxides and salts. PAC1 showed higher ash content
(34%), contributing to the similarly higher pH value of this
sample, which can be attributed to the presence of inorganic
compounds in the adsorbent.
[20,30]
FTIR spectroscopy has been commonly used to identify
functional groups present on activated carbon surface.
[29]
Figure 2 shows the FTIR spectra of PAC1 and PAC2 sam-
ples. Both spectra display similar bands between 2090 and
2330 cm
1
, which can be attributed to C ¼O vibration of
aldehyde, ketone and ester groups.
[29]
The PAC2 spectrum
has a peak at 1572 cm
1
, whereas a similar (albeit weak) sig-
nal is observed at 1564 cm
1
for PAC1 sample; these signals
are attributed to C ¼C vibration of the aromatic ring bond
and their observation is consistent with the aromatic nature
expected for activated carbons.
[31,32]
A low intensity peak at
1160 cm
1
in the PAC2 spectrum may be associated with C-
OH vibrations.
[31,33]
Functional oxygen groups on activated
carbon surface are known to enhance its hydrophilic charac-
ter, which may play a significant role on 2,4-D adsorption
in solution.
[37]
Similar results were also observed in previ-
ous study.
[38]
The XRD patterns obtained for PAC1 and PAC2 samples
are shown in Figure 3. Both patterns contain broad peaks
around 2h¼25 and 42associated with the turbostratic
structure of activated carbons.
[39]
An intense diffraction
peak at 2h¼26is also observed in both cases, indicating
the presence of a quartz form. Furthermore, the XRD pat-
tern of PAC1 sample shows other narrow peaks at 2h¼21;
39;50
,60
and 68. These peaks are associated with the
presence of silicon oxide (SiO
2
) in the quartz form, probably
due to some contamination occurring in the production of
the commercial activated carbon samples.
[35]
Moreover,
many plant materials naturally contain silica in their struc-
ture, which can lead to the observation of silica particles in
activated carbons prepared from natural precursors.
[40]
It is
interesting to note that the significantly higher intensity of
the narrow peaks in the XRD pattern of PAC1 sample is in
complete agreement with the much higher ash content of
this sample in comparison with PAC2 (see Table 2), simi-
larly also to what has been observed in previous investiga-
tions of other activated carbons.
[33]
The solid-state
13
C NMR spectra obtained for the acti-
vated carbons are shown in Figure 4. Both spectra are domi-
nated by a strong and broad signal at 121 ppm, due to
carbon atoms in aromatic domains (sp
2
carbons), as
expected for the turbostratic structure of activated carbons.
There is no observable chemical shift difference in the signal
detected for PAC1 and PAC2 samples, indicating a similar
local chemical environment for the carbon atoms in the aro-
matic domains.
[30,37,38]
Natural water used in the study
Natural water used in this study came from the Santa Maria
da Vit
oria River, in the state of Esp
ırito Santo, Brazil. Water
Figure 2. FTIR spectra of PAC1 and PAC2 samples.
Figure 3. XRD patterns obtained for PAC1 and PAC2 samples.
Figure 4. Solid-state
13
C NMR spectra of PAC1 and PAC2 samples.
4 L. D. MARSOLLA ET AL.
samples were collected upon arrival at the water treatment
plant (WTP) and physicochemical characterization was per-
formed (Table 3).
Adsorption isotherms
The removal of 2,4-D by adsorption on PAC1 and PAC2
adsorbents was investigated in ultrapure water (UW) and in
natural water (NW). The adsorption data were fitted using
the Langmuir and Freundlich isotherm models (Figs. 5 and
6); the parameters obtained by these fittings are shown in
Table 4.
The values of the coefficient of determination (R
2
) indi-
cate that Langmuir isotherm fits better to the 2,4-D
adsorption data in UW and NW for activated carbons
(Table 4). Langmuir isotherm assumes that adsorption
occurs in a monolayer, due to the homogeneous active sites
distribution on the surface of the adsorbent.
[24]
Similar find-
ings regarding the ability of the Langmuir model to describe
the 2,4-D adsorption on activated carbons have also been
previously reported in other works.
[24,33,39–41]
The separation
factor values (R
L
), calculated by Eq. (4), show that the 2,4-D
adsorption on PAC1 and PAC2 samples is favorable (0 <R
L
<1) in both UW and NW, as shown in Table 4.
PAC2 sample showed higher adsorption capacity (q
m
)
than PAC1 reaching 36.95 mg.g
1
in UW and 8.68 mg.g
1
Table 3. Physicochemical characteristics of natural water used in this study.
Parameter Value (min. and max.)
pH 6.8 7.2
Temperature (C) 23 25
Turbidity (uT) 49 55
Apparent color (uH) 249 363
Actual color (uH) 105 141
Absorbance –UV
254
(nm) 0,11 0,12
Total organic carbon (mg.L
-1
) 3.03 4.89
2,4-D (mg.L
-1
)LD
LD –below the detection limit of 2,4-D (3.63 lg.L
1
) by the chromatographic
method proposed by Coelho et al.
[18]
Figure 5. Adsorption isotherms of 2,4-D on PAC1 (A) and PAC2 (B) adsorbents
in ultrapure water (UW).
Figure 6. Adsorption isotherms of 2,4-D on PAC1 (A) and PAC2 (B) adsorbents
in natural water (NW).
Table 4. 2,4-D adsorption parameters by PAC1 and PAC2 in UW and NW
obtained by Langmuir and Freundlich models.
Isotherm
Ultrapure Water (UW) Natural Water (NW)
PAC1 PAC2 PAC1 PAC2
Langmuir
q
m
(mg.g
-1
) 23.95 36.95 5.72 8.68
b (L.mg
-1
) 625.46 594.67 746.46 712.47
R
2
0.914 0.853 0.680 0.753
R
L
0.026 0.027 0.021 0.022
Freundlich
K (mg/g).(L/mg)
1/n
55.99 130.76 6.53 11.81
N 4.06 3.01 19.21 9.73
R
2
0.730 0.808 0.507 0.479
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART B 5
in NW. Experiments carried out in natural water showed a
significant reduction in the adsorption capacity of 2,4-D for
the two activated carbons. Reduced adsorption of target
compounds (including 2,4-D) in the presence of NOM has
been reported by different authors.
[6,42–48]
This adsorption
behavior is affected by several properties of the adsorbent
(as porosity), the adsorbate (as molecular weight and size)
and of the medium (such as the concentration of NOM and
of the target compound in solution).
[52]
The reduction of
2,4-D adsorption by PAC1 and PAC2 occurred on account
of the interference of NOM present in natural water, in
which the target compound and NOM are adsorbed simul-
taneously and may compete for the same adsorption sites or
NOM can block the access of 2,4-D to the activated car-
bon pores.
Formed by organic compounds with varying molecular
weights, NOM exhibits different competitive effects on the
adsorption process of the target compound. Reduction in
the adsorptive capacity of 2,4-D is affected by the molecular
weight in NOM, as observed by Newcombe et al.
[15]
The
low molecular weight compounds (<600 g.mol
1
) present in
natural water are the main contributors to target compound
competition; thus, the presence of organic compounds with
low molecular weight in NOM has greater impact on micro-
contaminants adsorption on activated carbon.
[45,49]
NOM can access different pores, such as the micropores
present in activated carbons, making them unavailable for
the adsorption of the smaller target compound.
[46]
On the
other hand, large NOM molecules are easily adsorbed on
the activated carbon mesopores. Newcombe et al.
[15]
state
that the occurrence of larger pores in activated carbons
favors the diffusion of molecules through the porous struc-
ture, so NOM can access the entire structure of a predomin-
antly mesoporous activated carbon. The same authors
conclude that pore blockage and competitive effects associ-
ated with NOM are less important in mesoporous carbons
in comparison with microporous carbons.
The NOM presence also interferes in the target com-
pound internal diffusion through the adsorbent pores, espe-
cially when NOM concentration is high in the aqueous
medium, directly reducing the adsorptive capacity.
[47]
NOM
molecules with no access to the activated carbon micropores
clog the pores due to rapid diffusion on the activated carbon
surface, preventing the access of smaller molecules (such as
2,4-D) to these pores.
[49]
The adsorption process in different waters, such as ultra-
pure water and natural water, explains the water quality
influence on the 2,4-D removal. Thus, the present study sug-
gests that NOM not only blocks the pores, but also com-
petes directly with the micropollutant for the adsorption
sites. Activated carbon with varying pore sizes can decrease
the pore blocking and the competitive effects associated with
NOM regarding the adsorption of micropollutants such as
2,4-D.
[50,51]
The degree of adsorption competition of NOM
depends on the composition of the NOM which varies with
the type of water.
[54,55]
The effect of adsorbent dosage on the removal of 2,4-D
was evaluated by varying the dosage of PAC1 and PAC2
adsorbents from 0.25 to 2.00 g in UW and NW (Fig. 7). As
the adsorbent mass increases, so does the removal of 2,4-D
on account of carbon sites availability for the adsorption
process.
[23,34]
In UW, the 2,4-D removal by PAC1 and
PAC2 became stable after a 0.75 mg dose; to achieve herbi-
cide removal above 90%, 0.75 g of PAC1 and 0.50 g of PAC2
are needed. In NW, removal stability of 2,4-D by PAC1 and
PAC2 was not achieved. 2,4-D removal percentage above
90% in NW was achieved only by PAC2, using a mass of
1.50 mg, three times larger than in UW. PAC1 had a max-
imum 2,4-D removal of 81.84% when using a dosage of
2.00 mg. Therefore, both the presence of NOM in NW and
the adsorbent characteristics can interfere in the 2,4-D
removal by adsorption.
The higher mesopore volume of PAC2 seems to be a
relevant factor in 2,4-D adsorption in NW, since NOM is
more easily adsorbed in larger pores, favoring the target
compound adsorption due to decreased competitiveness.
According to Quinlivan et al.
[53]
activated carbons with
wider pores reduce the NOM impact on the adsorption pro-
cess. Adsorption results mainly depended on the particle
size of the adsorbent.
[56,57]
On the other hand, the chemical and physical characteris-
tics of the activated carbon must also be considered in the
adsorption process. The occurrence of oxygen-containing
functional groups on the activated carbon surface has a
strong influence on the 2,4-D adsorption, due to the
molecular interaction between these groups and the hydro-
gen atoms present in the 2,4-D molecule. The ash content
interferes negatively in adsorption too, as it is related with
the presence of inorganic compounds in the adsorbent.
[20,30]
The chemical properties of AC surface have a significant
influence on the adsorption efficiency. The main properties
that influence the removal efficiency are surface charge,
hydrophobicity, and surface functional groups.
[55]
Salom
on
et al.
[30]
observed that the AC has a structure with the pres-
ence of C–H, C ¼O, C–O, and O–H groups, and solution at
lower pH, the 2,4-D is neutral or deprotonated and the sur-
face of AC is positively charged, so this behavior indicates
that the adsorption of 2,4-D onto AC occurs due to
Figure 7. Effect of the dosage of activated carbon (PAC1 and PAC2) on the 2,4-
D removal rate in ultrapure water (UW) and natural water (NW). Error bars rep-
resent the standard deviation.
6 L. D. MARSOLLA ET AL.
hydrogen bond, p–p, or electrostatic interactions. The
increase in ionic strength also produces an enhancement in
the removal of pesticides.
[58]
The p-pinteraction was
reported by Spaltro et al.
[59]
this interaction between ben-
zene ring of 2,4-D and AC layer is an important factor
for adsorption.
Studies of 2,4-D adsorption capacity using different
adsorbents were conducted by other researchers. Table 5
compares the adsorption capacity of different adsorbents
used for 2,4-D removal from distilled water. Coelho et al.
[33]
analyzed the adsorption equilibrium of 2,4-D on a different
type of activated carbon, with a high initial concentration of
herbicide (mg.L
1
), it was much larger compared to our
work (lg.L
1
), frequently the adsorption capacity will
enhance with higher initial concentration. Chingombe, Saha
and Wakeman
[31]
analyzed adsorption on activated carbons
with a larger specific surface area (960 and 790 m
2
.g
1
) and
the adsorptions of 2,4-D were 47.39 and 73.53 mg.g
1
.
Manna et al.
[60]
analyzed 2,4-D onto jute and modified jute
and the authors achieved the lowest adsorption capacity
(16.10 mg.g
1
) and slightly superior to our work
(38.50 mg.g
1
). Trivedi, Kharkar and Mandavgane
[33]
and
also studied 2,4-D adsorption and they achieved only 3.93
and 0.64 mg.g
1
. It is possible to observe that the q
m
values
found in the present work are close to or higher than those
reported in other works, suggesting that PAC1 and PAC2
can be potentially useful adsorbents for 2,4-D removal in
water and the application of these adsorbents can be used
further in water supply unit.
To better compare the adsorption ability of activated car-
bons, according to the outputs of the regression test and
ANOVA, it can be affirmed that the mass of activated carbon
used did not have a significant influence on the removal of 2-
4D (p>0.05). However, PAC2 in ultrapure water proved to
be statically significant since it presented p value (0.048940)
and p (0.000054) respectively. In this way, it is proved that
PAC2 in ultrapure water medium is substantially better.
Conclusion
This work investigated the use of two commercial activated
carbons (PAC1 and PAC2) in the removal of 2,4-D herbicide
in natural water (NW) and in ultrapure water (UW).
Adsorption experiments indicated that PAC2 presented better
2,4-D adsorption capacity in UW (36.95 mg.g
1
)andNW
(8.67 mg.g
1
) compared to that of PAC1 (UW 23.95 mg.g
1
)
and NW (5.72 mg.g
1
). In natural water there was a 76%
reduction in the adsorption capacity of the 2,4-D herbicide by
the two activated carbons. The results of experiments per-
formed in natural water showed that both activated carbons
had reduced 2,4-D adsorption capacity. The reduction in the
activated carbons adsorptive capacity, which may be attributed
to the presence of natural organic matter (NOM) in the water,
since it may compete for the same adsorption sites or block
the access of the 2,4-D molecule to the pores of the activated
carbon. PAC2 showed higher mesopores percentage and,
decreasing the effects caused by NOM in 2,4-D adsorption.
The chemical properties of PAC2 surface have an influence on
the adsorption efficiency as well, like functional oxygen groups
on activated carbon surface. Thus, the use of activated carbons
with varying pore sizes for the removal of microcontaminants
is recommended, especially in aqueous medium when NOM is
present, a result that contributes to the choice of the adsorbent
type to be applied in water treatment plants for microcontami-
nants removal.
Acknowledgements
The support of Dr. Daniel F. Cipriano during the NMR and XDR anal-
yses is also gratefully acknowledged and the support of Renata Estevam
for statistical analysis.
Funding
The authors are thankful to the Brazilian funding agencies CNPq,
CAPES and FAPES.
ORCID
Lorena Dornelas Marsolla http://orcid.org/0000-0002-0925-2250
Gilberto Maia Brito http://orcid.org/0000-0001-6205-0511
Jair C. Checon Freitas http://orcid.org/0000-0002-4474-2474
Data availability statement
The data that support the findings of this study are available from the
corresponding author, [Marsolla, L.D.], upon reasonable request.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
References
[1] Mojiri, A.; Zhou, J. L.; Robinson, B.; Ohashi, A.; Ozaki, N.;
Kindaichi, T.; Farraji, H.; Vakili, M. Pesticides in Aquatic
Environments and Their Removal by Adsorption Methods.
Chemosphere 2020,253, 126646–126646. DOI: 10.1016/j.chemo-
sphere.2020.126646.
Table 5. Comparison of adsorption capacity (q
m
) of 2,4-D by different adsorb-
ents in distilled water.
Adsorbent q
m
(mg.g
-1
) Refs.
Granular activated carbon 181.82
[44]
Powdered activated carbon (PAC2) 116.28
[33]
Powdered activated carbon (PAC3) 102.04
[33]
Granular activated carbon (GAC) 92.59
[33]
Powdered activated carbon (PAC1) 91.74
[33]
Modified activated carbon (F400AN) 73.53
[31]
Activated carbon (F400) 47.39
[31]
Modified jute (NJ) 38.50
[61]
PAC2 36.95 This work
Activated carbon (SSAC) 36.16
[62]
PAC1 23.73 This work
Jute (UJ) 16.10
[61]
Clay mineral (OP1CEC) 12.24
[60]
Clay mineral (DP1CEC) 9.14
[60]
Cotton plant char (CPC) 3.93
[36]
Cotton plant ash (CPA) 0.64
[36]
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART B 7
[2] IBAMA (Brazilian Institute of Environment). The 10 Best-
Selling Active Ingredients - 2017 - 302 Consolidation of Data
Provided by the Registrants of 303 Technical, Pesticide and
Related Products, Art. 41 of Decree No. DOI:4.074/2002. 2018.
[3] Islam, F.; Wang, J.; Farooq, M. A.; Khan, M. S. S.; Xu, L.; Zhu,
J.; Zhao, M.; Mu~
nos, S.; Li, Q. X.; Zhou, W. Potential Impact of
the Herbicide 2,4-Dichlorophenoxyacetic Acid on Human and
Ecosystems. Environ. Int. 2018,111, 332–351. DOI: 10.1016/j.
envint.2017.10.020.
[4] USEPA (United States Environmental Protection Agency).
Prevention, Pesticides, and Toxic Substances. Reregistration
Eligibility Decision for 2,4-D,2005. Available at https://archive.
epa.gov/pesticides/reregistration/web/pdf/24d_red.pdf
[5] Hameed, B. H.; Salman, J. M.; Ahmad, A. L. Adsorption
Isotherm and Kinetic Modeling of 2,4-D Pesticide on Activated
Carbon Derived from Date Stones. J. Hazard. Mater. 2009,163,
121–126. DOI: 10.1016/j.jhazmat.2008.06.069.
[6] Zhang, J.; Shi, B.; Li, T.; Wang, D. Adsorption of Methyl
Parathion on PAC from Natural Waters: The Effect of NOM
on Adsorption Capacity and Kinetics. Adsorption 2013,19,
91–99. DOI: 10.1007/s10450-012-9422-2.
[7] WHO (World Health Organization). Guidelines for Drinking-
Water Quality, 4th ed. 2017. Available at https://www.who.int/
publications/i/item/9789241549950
[8] Ministry of Health. Ordinance GM/MS n
o
888, May 4th, 2021.
Brazil, 2021.
[9] Trivedi, N. S.; Mandavgane, S. A. Fundamentals of 2,4
Dichlorophenoxyacetic Acid Removal from Aqueous Solutions.
Sep. Purif. Rev. 2018,47, 337–354. DOI: 10.1080/15422119.
2018.1450765.
[10] Rathi, B. S.; Kumar, P. S.; Show, P. L. A Review on Effective
Removal of Emerging Contaminants from Aquatic Systems:
Current Trends and Scope for Further Research. J. Hazard.
Mater. 2021,409, 124413–124413. DOI: 10.1016/j.jhazmat.2020.
124413.
[11] Bunmahotama, W.; Hung, W. N.; Lin, T. F. Prediction of the
Adsorption Capacities for Four Typical Organic Pollutants on
Activated Carbons in Natural Waters. Water Res. 2017,111,
28–40. DOI: 10.1016/j.watres.2016.12.033.
[12] Howe, K. J.; Hand, D. W.; Crittenden, J. C.; Trussell, R. R.;
Tchobanoglous, G. Principles of Water Treatment; Wiley:
Hoboken, NJ, 2012.
[13] Jeirani, Z.; Niu, C. H.; Soltan, J. Adsorption of Emerging
Pollutants on Activated Carbon. Rev. Chem. Eng. 2017,33,
491–522. DOI: 10.1515/revce-2016-0027.
[14] Guillossou, R.; Le Roux, J.; Mailler, R.; Pereira-Derome, C. S.;
Varrault, G.; Bressy, A.; Vulliet, E.; Morlay, C.; Nauleau, F.;
Rocher, V.; Gasperi, J. Influence of Dissolved Organic Matter
on the Removal of 12 Organic Micropollutants from
Wastewater Effluent by Powdered Activated Carbon
Adsorption. Water Res. 2020,172, 115487. DOI: 10.1016/j.
watres.2020.115487.
[15] Newcombe, G.; Morrison, J.; Hepplewhite, C.; Knappe, D. R. U.
Simultaneous Adsorption of MIB and NOM onto Activated
Carbon II. Competitive Effects. Carbon 2002,40, 2147–2156.
DOI: 10.1016/S0008-6223(02)00098-2.
[16] Qi, S.; Schideman, L. C. An Overall Isotherm for Activated
Carbon Adsorption of Dissolved Natural Organic Matter in
Water. Water Res. 2008,42, 3353–3360. DOI: 10.1016/j.watres.
2008.04.016.
[17] Bhatnagar, A.; Sillanp€
a€
a, M. Removal of Natural Organic
Matter (NOM) and Its Constituents from Water by Adsorption
- A review. Chemosphere 2017,166, 497–510. DOI: 10.1016/j.
chemosphere.2016.09.098.
[18] Jin, J.; Feng, T.; Gao, R.; Ma, Y.; Wang, W.; Zhou, Q.; Li, A.
Ultrahigh Selective Adsorption of Zwitterionic PPCPs Both in
the Absence and Presence of Humic Acid: Performance and
Mechanism. J. Hazard. Mater. 2018,348, 117–124. DOI: 10.
1016/j.jhazmat.2018.01.036.
[19] Lowell, S.; Shields, J. E.; Thomas, M. A.; Thommes, M.
Characterization of Porous Solids and Powders: Surface Area.
In Pore Size and Density; Springer Science & Business Media:
New York, 2004. DOI: 10.1007/978-1-4020-2303-3.
[20] ASTM D3838-05. Standard Test Method for pH of Activated
Carbon. ASTM Internation: West Conshohocken, PA, 2017.
DOI: 10.1520/D3838-05R17.
[21] Cory, D. G.; Ritchey, W. M. Suppression of Signals from the
Probe in Bloch Decay Spectra. J. Magn. Reson. 1988,80,
128–132. DOI: 10.1016/0022-2364(88)90064-9.
[22] Brito, G. M.; Roldi, L. L.; Schetino, Jr., Freitas, J. C. C.; Coelho,
E. R. C. High-Performance of Activated Biocarbon Based on
Agricultural Biomass Waste Applied for 2,4-D Herbicide
Removing from Water: Adsorption, Kinetic and
Thermodynamic Assessments. J. Environ. Sci. Heal. Part B
2020,55, 769–782. DOI: 10.1080/03601234.2020.1783178.
[23] Coelho, E. R. C.; Leal, W. P.; de Souza, K. B.; do Roz
ario, A.;
Antunes, P. W. P. Development and Validation of Analytical
Method for Analysis of 2,4-D, 2,4-DCP and 2,4,5-T for
Monitoring of Public Water Supply. Eng. Sanit. Ambient 2018,
23, 1043–1051. DOI: 10.1590/s1413-41522018161536.
[24] Langmuir, I. The Adsorption of Gases on Plane Surfaces of
Glass, Mica and Platinum. J. Am. Chem. Soc. 1918,40,
1361–1403. DOI: 10.1021/ja02242a004.
[25] Freundlich, H. M. F. €
Uber Die Adsorption in L€
osungen. J.
Phys. Chem. 1906,57, 385–470.
[26] Mom
cilovi
c, M. Z.; Rand
-elovi
c, M. S.; Zarubica, A. R.; Onjia,
A. E.; Kokune
soski, M.; Matovi
c, B. Z. SBA-15 Templated
Mesoporous Carbons for 2,4-Dichlorophenoxyacetic Acid
Removal. Chem. Eng. J. 2013,220, 276–283. DOI: 10.1016/j.cej.
2012.12.024.
[27] Shaarani, F. W.; Hameed, B. H. Batch Adsorption of 2,4-
Dichlorophenol onto Activated Carbon Derived from
Agricultural Waste. Desalination 2010,255, 159–164. DOI.
DOI: 10.1016/j.desal.2009.12.029.
[28] Thommes, M.; Kaneko, K.; Neimark, A. V.; Olivier, J. P.;
Rodriguez-Reinoso, F.; Rouquerol, J.; Sing, K. S. W.
Physisorption of Gases, with Special Reference to the
Evaluation of Surface Area and Pore Size Distribution (IUPAC
Technical Report). Pure Appl. Chem. 2015,87, 1051–1069. DOI:
10.1515/pac-2014-1117.
[29] Pallar
es, J.; Gonz
alez-Cencerrado, A.; Arauzo, I. Arauzo, I.
Production and Characterization of Activated Carbon from
Barley Straw by Physical Activation with Carbon Dioxide and
Steam. Biomass Bioenergy 2018,115,64–73. DOI: 10.1016/j.bio-
mbioe.2018.04.015.
[30] Salom
on, Y. L. D. O.; Georgin, J.; Franco, D. S. P.; Netto, M. S.;
Piccilli, D. G. A.; Foletto, E. L.; Oliveira, L. F. S.; Dotto, G. L.
High-Performance Removal of 2,4-Dichlorophenoxyacetic Acid
Herbicide in Water Using Activated Carbon Derived from
Queen Palm Fruit Endocarp (Syagrus Romanzoffiana). J.
Environ. Chem. Eng. 2021,9, 104911–104911. DOI: 10.1016/j.
jece.2020.104911.
[31] Chingombe, P.; Saha, B.; Wakeman, R. J. Effect of Surface
Modification of an Engineered Activated Carbon on the
Sorption of 2,4-Dichlorophenoxy Acetic Acid and Benazolin
from Water. J. Colloid Interface Sci. 2006,297, 434–442. DOI:
10.1016/j.jcis.2005.10.054.
[32] Lagorsse, S.; Campo, M. C.; Magalh~
aes, F. D.; Mendes, A.
Water Adsorption on Carbon Molecular Sieve Membranes:
Experimental Data and Isotherm Model. Carbon 2005,43,
2769–2779. DOI: 10.1016/j.carbon.2005.05.042.
[33] Coelho, E. R. C.; Brito, G. M.; Frasson, L. L.; Schetino, M. A.;
Jr,.; Freitas, J. C. C. 2,4-Dichlorophenoxyacetic Acid (2,4-D)
Micropollutant Herbicide Removing from Water Using
Granular and Powdered Activated Carbons: A Comparison
Applied for Water Treatment and Health Safety. J. Environ. Sci.
Heal. Part B 2019,4, 361–375. DOI: 10.1080/03601234.2019.
1705113.
8 L. D. MARSOLLA ET AL.
[34] Salman, J. M.; Njoku, V. O.; Hameed, B. H. Batch and Fixed-
Bed Adsorption of 2,4-Dichlorophenoxyacetic Acid onto Oil
Palm Frond Activated Carbon. Chem. Eng. J. 2011,174,33–40.
DOI: 10.1016/j.cej.2011.08.024.
[35] Brito, G. M.; Cipriano, D. F.; Schettino, M. A.; Jr., Cunha,
A. G.; Coelho, E. R. C.; Freitas, J. C. One-Step Methodology for
Preparing Physically Activated Biocarbons from Agricultural
Biomass Waste. J. Environ. Chem. Eng. 2019,7, 103113–103113.
DOI: 10.1016/j.jece.2019.103113.
[36] Trivedi, N. S.; Kharkar, R. A.; Mandavgane, S. A. Utilization of
Cotton Plant Ash and Char for Removal of 2, 4-
Dichlorophenoxyacetic Acid. Resour. Technol. 2016,2, S39–S46.
DOI: 10.1016/j.reffit.2016.11.001.
[37] Bahrami, M.; Amiri, M. J.; Beigzadeh, B. Adsorption of 2,4-
Dichlorophenoxyacetic Acid Using Rice Husk Biochar,
Granular Activated Carbon, and Multi-Walled Carbon
Nanotubes in a Fixed Bed Column System. Water Sci Technol.
2018,78, 1812–1821. DOI: 10.2166/wst.2018.467.
[38] Legnoverde, M. S.; Simonetti, S.; Basaldella, E. I. Influence of
pH on Cephalexin Adsorption onto SBA-15 Mesoporous Silica:
Theoretical and Experimental Study. Appl. Surf. Sci. 2014,300,
37–42. DOI: 10.1016/j.apsusc.2014.01.198.
[39] Li, Z. Q.; Lu, C. J.; Xia, Z. P.; Zhou, Y.; Luo, Z. X-Ray
Diffraction Patterns of Graphite and Turbostratic Carbon.
Carbon 2007,45, 1686–1695. DOI: 10.1016/j.carbon.2007.03.
038.
[40] Yapuchura, E. R.; Tartaglia, R. S.; Cunha, A. G.; Freitas,
J. C. C.; Emmerich, F. G. Observation of the Transformation of
Silica Phytoliths into SiC and SiO
2
Particles in Biomass-Derived
Carbons. by Using SEM/EDS, Raman Spectroscopy, and XRD.
J. Mater. Sci.2019, 54, 3761–3777. DOI: 10.1007/s10853-018-
3130-6.
[41] Lopes, T. R.; Cipriano, D. F.; Gonc¸alves, G. R.; Honorato,
H. A.; Schettino, M. A.; Jr, Cunha, A. G.; Emmerich, F. G.;
Freitas, J. C. C. Multinuclear Magnetic Resonance Study on the
Occurrence of Phosphorus in Activated Carbons Prepared by
Chemical Activation of Lignocellulosic Residues from the
Babassu Production. J. Environ. Chem. Eng. 2017,5, 6016–6029.
DOI: 10.1016/j.jece.2017.11.028.
[42] Freitas, J. C. C.; Bonagamba, T. J.; Emmerich, F. G.
Investigation of Biomass- and Polymer-Based Carbon Materials
Using
13
C High-Resolution Solid-State NMR. Carbon 2001,39,
535–545. DOI: 10.1016/S0008-6223(00)00169-X.
[43] Salman, J. M.; Al-saad, K. A. Adsorption of 2,4-
Dichlorophenoxyacetic Acid onto Date Seeds Activates Carbon:
Equilibrium, Kinetic and Thermodynamic Studies. Int. J. Chem.
Sci. 2012,10, 677–690.
[44] Salman, J. M.; Hameed, B. H. Adsorption of 2,4-
Dichlorophenoxyacetic Acid and Carbofuran Pesticides onto
Granular Activated Carbon. Desalination 2010,256, 129–135.
DOI: 10.1016/j.desal.2010.02.002.
[45] Doczekalska, B.; Ku
smierek, K.;
Swia˛tkowski, A.; Bartkowiak,
M. Adsorption of 2,4-Dichlorophenoxyacetic Acid and 4-
Chloro-2-Metylphenoxyacetic Acid onto Activated Carbons
Derived from Various Lignocellulosic Materials. J. Environ. Sci.
Health B 2018,53, 290–297. DOI: 10.1080/03601234.2017.
1421840.
[46] Pelekani, C.; Snoeyink, V. L. Competitive Adsorption in
Natural Water: Role of Activated Carbon Pore Size. Water Res.
1999,33, 1209–1219. DOI: 10.1016/S0043-1354(98)00329-7.
[47] Matsui, Y.; Fukuda, Y.; Inoue, T.; Matsushita, T. Effect of
Natural Organic Matter on Powdered Activated Carbon
Adsorption of Trace Contaminants: Characteristics and
Mechanism of Competitive Adsorption. Water Res. 2003,37,
4413–4424. DOI: 10.1016/S0043-1354(03)00423-8.
[48] Dudamel, W.; de Cazeaudmec, Y.; Wolbert, D.; Laplanche, A.
Reducci
on de los Pesticidas del Agua en Presencia De Materia
Org
anica Modelado de la Adsorci
on Sobre Carb
on Activado.
Ing. Qu
ım. 2004,410, 161–175.
[49] Humbert, H.; Gallard, H.; Suty, H.; Crou
e, J. P. Natural
Organic Matter (NOM) and Pesticides Removal Using a
Combination of Ion Exchange Resin and Powdered Activated
Carbon (PAC). Water Res. 2008,42, 1635–1643. DOI: 10.1016/
j.watres.2007.10.012.
[50] Koner, S.; Pal, A.; Adak, A. Use of Surface Modified Silica Gel
Factory Waste for Removal of 2,4-D Pesticide from Agricultural
Wastewater: A Case Study. Int. J. Environ. Res. 2012,6,
995–1006. DOI: 10.22059/ijer.2012.570.
[51] Li, Q.; Snoeyink, V. L.; Mari~
aas, B. J.; Campos, C. Elucidating
Competitive Adsorption Mechanisms of Atrazine and NOM
Using Model Compounds. Water Res. 2003,37, 773–784. DOI:
10.1016/S0043-1354(02)00390-1.
[52] Bajracharya, A.; Liu, Y. L.; Lenhart, J. J. The Influence of
Natural Organic Matter on the Adsorption of Microcystin-LR
by Powdered Activated Carbon. Environ. Sci.: Water Res.
Technol. 2019,5, 256–267. DOI: 10.1039/C8EW00582F.
[53] Quinlivan, P. A.; Li, L.; Knappe, D. R. U. Effects of Activated
Carbon Characteristics on the Simultaneous Adsorption of
Aqueous Organic Micropollutants and Natural Organic Matter.
Water Res. 2005,39, 1663–1673. DOI: 10.1016/j.watres.2005.01.
029.
[54] Ebie, K.; Li, F.; Azuma, Y.; Yuasa, A.; Hagishita, T. Pore
Distribution Effect of Activated Carbon in Adsorbing Organic
Micropollutants from Natural Water. Water Res. 2001,35,
167–179. DOI: 10.1016/S0043-1354(00)00257-8.
[55] Loganathan, P.; Kandasamy, J.; Jamil, S.; Ratnaweera, H.;
Vigneswaran, S. Ozonation/adsorption hybrid treatment system
for improved removal of natural organic matter and organic
micropollutants from water - A mini review and future per-
spectives . Chemosphere 2022,296, 133961. DOI: 10.1016/j.che-
mosphere.2022.133961.
[56] Mardones, L. E.; Legnoverde, M. S.; Simonetti, S.; Basaldella,
E. I. Theoretical and Experimental Study of Isothiazolinone
Adsorption onto Ordered Mesoporous Silica. Appl. Surf. Sci.
2016,389, 790–796. DOI: 10.1016/j.apsusc.2016.07.113.
[57] Spaltro, A.; Pila, M. N.; Colasurdo, D. D.; Noseda Grau, E.;
Rom
an, G.; Simonetti, S.; Ruiz, D. L. Removal of Paracetamol
from Aqueous Solution by Activated Carbon and Silica.
Experimental and Computational Study. J. Contam. Hydrol.
2021,236, 103739. DOI: 10.1016/j.jconhyd.2020.103739.
[58] Spaltro, A.; Simonetti, S.; Laurella, S.; Ruiz, D.; Compa~
ny,
A. D.; Juan, A.; Allegretti, P. Adsorption of Bentazone and
Imazapyc from Water by Using Functionalized Silica:
Experimental and Computational Analysis. J. Contam. Hydrol.
2019,227, 103542. DOI: 10.1016/j.jconhyd.2019.103542.
[59] Spaltro, A.; Pila, M.; Simonetti, S.;
Alvarez-Torrellas, S.;
Rodr
ıguez, J. G.; Ruiz, D.; Compa~
ny, A. D.; Juan, A.; Allegretti,
P. Adsorption and Removal of Phenoxy Acetic Herbicides from
Water by Using Commercial Activated Carbons: Experimental
and Computational Studies. J. Contam. Hydrol. 2018,218,
84–93. DOI: 10.1016/j.jconhyd.2018.10.003.
[60] Xi, Y.; Mallavarapu, M.; Naidu, R. Adsorption of the Herbicide
2,4-D on Organo-Palygorskite. Appl. Clay Sci. 2010,49,
255–261. DOI: 10.1016/j.clay.2010.05.015.
[61] Manna, S.; Saha, P.; Roy, D.; Sen, R.; Adhikari, B. Removal of
2,4-Dichlorophenoxyacetic Acid from Aqueous Medium Using
Modified Jute. J. Taiwan Inst. Chem. Eng. 2016,67, 292–299.
DOI: 10.1016/j.jtice.2016.07.034.
[62] Kırbıyık, C¸.; P€
ut€
un, A. E.; P€
ut€
un, E. Equilibrium, Kinetic, and
Thermodynamic Studies of the Adsorption of Fe(III) Metal
Ions and 2,4-Dichlorophenoxyacetic Acid onto Biomass-Based
Activated Carbon by ZnCl
2
Activation. Surf. Interfaces 2017,8,
182–192. DOI: 10.1016/j.surfin.2017.03.011.
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH, PART B 9
