A hybrid Zr/amine-modified mesoporous silica for adsorption and preconcentration of as before its FI HG AAS determination in water

Microporous and Mesoporous Materials 328 (2021) 111484

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Microporous and Mesoporous Materials
journal homepage: www.elsevier.com/locate/micromeso

A hybrid Zr/amine-modified mesoporous silica for adsorption and
preconcentration of as before its FI HG AAS determination in water
´ ska a, *, Rafał Olchowski a, Emil Zięba b, Ryszard Dobrowolski a
Joanna Dobrzyn
a

Department of Analytical Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie Skłodowska University in Lublin, Poland
Centre for Interdisciplinary Research, Faculty of Biotechnology and Environmental Sciences, The John Paul II Catholic University of Lublin, Ul. Konstantyn´
ow 1”J”, 20708, Lublin, Poland

b

A R T I C L E I N F O

A B S T R A C T

Keywords:
Arsenic adsorption
Zr modified silica
Preconcentration
SBA-15
Hydride generation atomic absorption
spectrometry

A hybrid Zr/amine-modified mesoporous silica sorbent (SBA/TMPED/Zr-0.5) was proposed to preconcentrate
traces of inorganic As from drinking water before its flow injection hydride generation atomic absorption
spectrometry (FI HG AAS) determination. In order to select the sorbent suitable for As traces preconcentration a
series of six hybrid Zr modified and Zr/amine modified SBA-15 materials were synthesized, characterized (SEM,
XRD, XPS, nitrogen adsorption/desorption), and compared in terms of As(V) adsorption properties. It was stated
that the introduction of Zr to the SBA-15 structure results in a slight decrease of the sorbent surface area, the
deterioration of hexagonal ordering, and changes in materials morphology. The introduction of amine groups
into Zr/silica results in the extension of the pH range of effective As(V) adsorption and the increase of the
adsorption capacity from 8 to 14 mg g− 1 for SBA/Zr-0.5 and SBA/Zr-1 to 24 and 32 mg g− 1 for SBA/TMPED/Zr0.5 and SBA/TMPED/Zr-1, respectively. Taking into account fast adsorption and the possibility of quantitative
desorption of As from sorbent surface SBA/TMPED/Zr-0.5 was chosen for arsenic traces preconcentration from
drinking waters. In order to preconcentrate the total inorganic As, As(III) was initially oxidized to As(V) by
KMnO4. Before FI HG AAS measurements preconcentrated arsenic was desorbed from SBA/TMPED/Zr-0.5 by
using 10 mol L− 1 hydrochloric acid. The linearity of the calibration plot ranges from 2 to 40 μg L− 1. The detection
and quantification limits were 0.025 μg L− 1 and 0.086 μg L− 1, respectively. The recoveries from spiked water
samples range between 95 and 105%.

1. Introduction
The entering of arsenic into the body through a food chain can lead to
serious health consequences. Inorganic arsenic species are considered as
much more toxic than organic ones. Both As(V) and As(III) are known as
class 1 carcinogens which significantly increase the risk of liver, skin,
kidney, and lung cancer [1]. Apart from cancer, inorganic arsenic may
also cause respiratory and hematological diseases, diabetes, diarrhea,
vomiting, and severe nervous system disorders. In this respect, 10 μg
L− 1 has been fixed by World Health Organization as a guideline value for
As concentration in drinking water [2]. The significant exceeding of this
limit occurs in West Bengal, where from 29 million to 40 million people
are exposed to drinking water containing over 50 μg L− 1 of As [3], which
is naturally found in water in two oxidation states: arsenite (AsO33− ) and
arsenate (AsO43− ) [4]. However, a trivalent form, which is more toxic

than a pentavalent one, predominates in groundwaters. Although, in
most water reservoirs the arsenic content is lower than the mentioned
value, as a result of prolonged exposure it may accumulate in edible
plants and enter into the food chain [5].
Due to the high toxicity of arsenic and its low concentrations in
environmental samples, many highly advanced and sensitive analytical
methods like atomic fluorescence spectroscopy (AFS) [6], graphite
furnace atomic absorption (GFAAS), hydride generation atomic ab­
sorption (HGAAS) [7], and inductively coupled plasma-mass spec­
trometry (ICP-MS) [8,9] are employed for its concentration monitoring.
However, when the concentration of arsenic is lower than the limit of
quantification of the chosen analytical technique, the preconcentration
of an analyte is necessary. Besides the lowering of the detection limit,
the preconcentration often leads to the elimination of matrix in­
terferences. It may be accomplished by liquid-liquid extraction

* Corresponding author.Department of Analytical Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie Skłodowska University in Lublin,
Poland, M. C. Sklodowska Sq. 3, 20-031, Lublin, Poland.
E-mail address: (J. Dobrzy´
nska).
/>Received 30 June 2021; Received in revised form 13 September 2021; Accepted 5 October 2021
Available online 9 October 2021
1387-1811/© 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license ( />

J. Dobrzy´
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Microporous and Mesoporous Materials 328 (2021) 111484

techniques such as cloud point extraction (CPE) [10], dispersive
liquid-liquid microextraction [11,12] or various types of solid-phase
extraction [13].
Among the numerous preconcentration techniques solvent-free
solid-phase extraction based on the partitioning of the analyte be­
tween solid sorbent and liquid sample, due to its simplicity, high pre­
concentration factors, and time-saving, seems to be the most appropriate
choice. The analyte-loaded sorbent can be analyzed directly, or analyte
elution may be required, depending on the employed determination
technique. With regard to preconcentration and removal of inorganic
arsenic a number of materials have been proposed, including activated
carbon [14], titanium dioxide [15], iron oxide [16], graphene oxide
[17], and silicas [18,19]. Hexagonal mesoporous SBA-15 material,
modified by ligating groups due to its large surface area, large pore
volume, and high hydrothermal stability, seems to be particularly
attractive for this purpose [20]. However, as presented in [20], the
application of amine-functionalized SBA-15 does not ensure the quan­
titative removal of As(V) ions from the solution, which is crucial for the
accurate determination of preconcentrated ion. To synthesize the ma­
terial ensuring the quantitative elimination of As(V) from solution, the
simultaneous modification of SBA-15 by ZrOCl2 [21,22] and
amine-containing monomer was proposed by us. The influence of
experimental parameters such as pH of aqueous solution, contact time,
presence of chosen anions, initial As(V) ions concentration on their
adsorption
onto
N-[3-(trimethoxysilyl)propyl]-ethylenediamine
(TMPED) and ZrOCl2 modified SBA-15 materials were investigated and
discussed. The hybrid material was successfully applied for the pre­
concentration of As(V) from water samples before flow injection hydride

generation atomic absorption spectrometry (FI HG AAS) determination.

Table 1
Structural parameters of synthesized materials.
Material

Reaction mixture
TEOS/TMPED/
ZrOCl2 [mmol/
mmol/mmol]

Total BET
surface area,
SBET [m2
g− 1]a

Pore
volume
[cm3 g− 1]b

Pore
diameter,
dBJH [nm]b

SBA
SBA/Zr0.5
SBA/Zr-1
SBA/
TMPED
SBA/

TMPED/
Zr-0.5
SBA/
TMPED/
Zr-1

20/0/0
20/0/0.5

760 ± 5
637 ± 7

1.29
1.14

5.9
8.1

20/0/1
20/2/0

626 ± 6
738 ± 3

1.23
1.30

8.8
6.5

20/2/0.5

613 ± 8

1.17

8.1

20/2/1

550 ± 4

0.88

7.3

a
b

from BET desorption method.
from BJH desorption method.

with a surface area analyzer ASAP 2405 N (Micromeritics). The specific
surface area and pore volume were calculated using the BET and BJH
methods, respectively.
Powder X-ray diffraction (XRD) patterns were collected with Seifert
RTG DRON-3 diffractometer (Cu Kα radiation) with 0.02◦ size step and
10 s time step covering a range of 0.5◦ < 2θ < 5.0◦ at RT.
The scanning electron microscopy (Carl Zeiss Ultra Plus (Germany))
was adopted to observe the morphologies of synthesized materials. All

experiments were carried out under 20-kV acceleration voltage and 5nA probe current.
XPS spectra were collected with Multi-Chamber Analytical System
(Prevac, Poland) equipped with a monochromated Kα-Al radiation
source (1486.6 eV) (Gammadata Scienta, Sweden) and the X-ray power
of 450 W C1s = 284.7 eV line was used for binding energy scaling. The
vacuum in the analysis chamber was better than 1.5 × 10− 7 Pa.

2. Experimental
2.1. Materials and reagents
The following compounds were used: tetraethoxysilane (TEOS, 99%,
ABCR), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TMPED, 97%,
ABCR), Pluronic P123 (P123, Sigma-Aldrich), ZrOCl2⋅8H2O (Merck),
HCl (Suprapure, 36%, POCH), HNO3 (Suprapure, 60%, Merck), standard
solution of As(V) (1000 mg L− 1) (Merck), sodium arsenite (Merck),
NaOH (POCH), ethanol (EtOH, 99.8%, POCH), sodium chloride (POCH),
potassium nitrate (POCH). All reagents were used as received, without
further purification. Ultrapure water prepared by a Millipore purifica­
tion system with a resistivity of 18.2 MΩ cm was used throughout. The
water samples were taken from Lublin’s water supply.

2.4. Adsorption experiments
Adsorption experiments were carried out in a water batch regime.
Each measuring point was obtained at 25 ◦ C for the suspension con­
sisting of 5 mg of modified SBA-15 and 5 mL of the As(V) solution. The
solid sorbent was separated from the solution by centrifugation. The
initial and equilibrium concentrations of As(V) in the liquid phase were
measured by the AAS method. The adsorption value was calculated
according to the equation:

2.2. Synthesis of sorbents

a=

Six SBA-15 type sorbents applied for As(V) preconcentration were
synthesized by the one-pot route via co-condensation of TEOS with
TMPED in the presence of ZrOCl2. The typical synthesis was as follows:
Firstly, 2 g of P123 was added to 72 mL of 1.6 mol L− 1 HCl and dissolved
at 40 ◦ C under vigorous stirring. Then, powdered ZrOCl2⋅8H2O, TEOS,
and functionalizing monomer were added in this order. Wherein,
TMPED was dropped about 2 h after TEOS. The mixture was kept under
stirring at 40 ◦ C for 24 h. Afterwards, the reaction mixture was heated at
100 ◦ C for 48 h without stirring. Finally, the suspension was filtered and
P123 was removed by triple 6-h extraction with acidified ethanol carried
out at 78 ◦ C. The obtained solid material was washed with deionized
water and dried at 100 ◦ C for 2 h. Six materials of various amounts of
zirconyl chloride and TMPED were synthesized. The names of the sor­
bents and the composition of the reaction mixture used for their syn­
thesis are shown in Table 1.

(ci − c) × V
m

(1)

where: ci and c are the initial and equilibrium As(V) concentration (mg
L− 1), respectively, V is the volume of the As(V) ions solution (L) and m is
the mass of modified SBA-15 (g).
The determination of arsenic concentrations in the solutions pre­
pared for adsorption and in residual solutions separated from adsorption
systems was carried out using the FI HG AAS technique. FI HG AAS

determination of arsenic was realized by using atomic absorption
spectrometer Spectr AA800 (Varian) equipped with an electrically
heated quartz atomizer. Arsine generation was performed with a
laboratory-modified commercially available flow analysis VGA-77
Vapor Generation Accessory (Agilent)) system. Before the arsine gen­
eration, As(V) was reduced to As(III). For this purpose, 100 μL of the
solution containing 2.5% KI + 2% ascorbic acid was added to the
Eppendorf vessel containing 900 μL of the sample solution, the waiting
time for the reduction to As(III) was 1 h. The generation of arsine was
performed in the presence of 0.2% NaBH4 in 0.2% NaOH. 100 μL of the
sample solution (containing As(III)) was injected by using a micro sy­
ringe to 3 mol L− 1 HCl. Argon containing 3% addition of oxygen was

2.3. Characterization of materials
The adsorption/desorption isotherms were measured at − 196 ◦ C
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Microporous and Mesoporous Materials 328 (2021) 111484

used as a carrier gas, atomization was carried out at 710 ◦ C. The spec­
trometer settings during measurement were as follows: wavelength –
193.7 nm, lamp current – 10 mA, delay - 5 s, time of measurement - 25 s.
The peak area was used for integration.
The desorption studies were carried out in a batch system consisting
of about 0.0005 g of As-loaded sorbents and 2 mL of desorption media.
The suspensions were shaken for 24 h at 20 ◦ C. Centrifugation was

applied to separate the liquid and the solid. The concentration of As in
the liquid phase was measured with the FI HG AAS technique.
In the case of CRMs the recovery of As was calculated as the ratio of
concentration measured to certified value, whereas for As-spiked Lublin
tap water it was calculated according to the equation:
(
)
cmstw − cmptw
Recovery =
× 100%
(2)
cstw

adhere to the hydrophilic part of the P123 micelle or to the silanol group
to form cationic species participating in the self-assembly process [25].
The substitution of some protons by zirconyl cations probably leads to
the increase of the diameter of P123 micelles and, the same, to the
extension of SBA-15 pore diameters.

2.5. Analytical procedure

3.1.2. XRD
The application of the XRD technique allows assessing the influence
of ZrOCl2 addition during the synthesis on the order degree of the ob­
tained materials. In the case of pristine SBA-15, three intensive (100),
(110), and (200) reflections are observed at the small-angle XRD pat­
terns (Fig. 1), which indicate the ordered hexagonal structure of the
material. The addition of ZrOCl2 to the reaction mixture leads to a slight
decrease in the intensity of (100) reflex and a significant one in the in­
tensity of two other reflections, as evidenced by patterns of SBA/Zr-0.5

and SBA/Zr-1. Thus, the ordering of SBA-15 deteriorates in the presence
of zirconyl chloride. The deterioration of ordering is also observed when
SBA-15 is modified by TMPED. However, it is worth mentioning that the
ordering of TMPED-modified SBA-15 is slightly improved when 0.5
mmol of ZrOCl2 is added to the reaction mixture, which is reflected by
the increase of the (110) and (200) reflects on SBA/TMPED/Zr-0.5
compared to SBA/TMPED.

First, to oxidize As(III) to As(V), KMnO4 was added to the water
sample to obtain the concentration of 5∙10− 5 mol L− 1 [23]. After an
hour, the pH of 20 mL of the water sample was adjusted to 3.5 by the
addition of HNO3. Then 20 mg of sorbent SBA/TMPED/Zr-0.5 was
added to the sample and the mixture was shaken for 24 h at 25 ◦ C. After
that, the sorbent was separated from the solution through filtration and
dried at 100 ◦ C to constant weight. About 10–14 mg of dry sorbent as
weighted in the Eppendorf vessel, and 0.25 mL of 30% HCl was added. In
order to obtain the total desorption of As from sorbent, the Eppendorf
vessel was placed in an ultrasound bath for 20 min. The determination of
As in the solution obtained after desorption was performed by the FI HG
AAS technique. Before the arsine generation, As(V) was reduced to As
(III). For this purpose, 100 μL of the solution containing 2.5% KI + 2%
ascorbic acid was added to the Eppendorf vessel containing sorbent and
0.25 mL of 30% HCl. Then 650 μL of water was added to reach the
volume to 1 mL. The waiting time for the reduction of As(III) was 1 h.
Before the FI HG AAS determination, the solution was separated from
the sorbent by centrifugation. The measurement conditions were the
same as for the determination of As in the solutions used for adsorption
(See Paragraph 2.4.).

3.1.3. SEM

SEM analysis were carried out to shed the light on the morphologies
of the hybrid Zr/silica and Zr/organosilica materials. The formation of
disc-like SBA/Zr and egg-like particles of SBA/TMPED/Zr materials is
presented in Fig. 2. Both discs of SBA/Zr and eggs of SBA/TMPED/Zr are
arranged in chains, reaching about 20 μm for SBA/Zr and about 10 μm
for SBA/TMPED/Zr. The formation of SBA/Zr and SBA/TMPED/Zr hy­
brids was proved by SEM-EDX (See ESM - Table S1). In the case of SBA/
Zr-0.5 except of disk-like, also spherical particles which were not found
for the other studied materials are observed.. Increasing the amount of
ZrOCl2 from 0.5 to 1 mmol added during synthesis of SBA-15 favors the
formation of narrow discs, which are especially clearly visible for SBA/
Zr-1. Increasing the amount of ZrOCl2 from 0.5 mmol to 1 mmol during
the synthesis of TMPED-modified SBA-15 does not significantly affect
the morphology of the obtained particles.
Despite the morphological differences between SBA/Zr and SBA/
TMPED/Zr samples, it has to be emphasized that the synthesis of both
pristine and TMPED-modified SBA-15 in the presence of ZrOCl2 leads to
the complete change of the morphology of the obtained particles. As can
be seen in our previous work [26] for pristine and amine-modified

where:cmstw – As concentration measured for As-spiked tap water,cmptw As concentration measured for pristine tap water (without any addition
of As) containing only naturally occurring As,cstw – theoretical As con­
centration being a result of tap water spiking.

3. Results
3.1. Characterization of materials
3.1.1. Nitrogen adsorption/desorption isotherms
In order to access the impact of ZrOCl2 on the porosity of SBA-15 type
materials, nitrogen adsorption/desorption isotherms were determined
(see Supplementary Fig. S1). All of the relations were classified as type

IV isotherms with H1 hysteresis loops according to the International
Union of Pure and Applied Chemistry (IUPAC) classification, which are
typical for mesoporous materials [24]. The structural parameters
calculated based on experimental data are presented in Table 1. The
modification of SBA-15 by TMPED does not change the surface area and
pore volume of the material. Whereas the introduction of ZrOCl2 into the
reaction mixture results in the decrease of the mentioned parameters.
Wherein the decrease is proportional to the amount of added zirconyl
chloride. Both the lowest surface area of 550 m2 g− 1 and pore volume of
0.88 cm3 g− 1 are observed for SBA/TMPED/Zr-1. The increase of the
pore diameter of the materials synthesized in the presence of ZrOCl2
suggests that zirconyl ions influence on self-assembly of the polymer
micelle and the silica precursor for both unmodified and amine-modified
SBA-15. It seems that zirconyl cation may replace hydrogen ions and

Fig. 1. Small angle XRD patterns of synthesized materials.
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Microporous and Mesoporous Materials 328 (2021) 111484

Fig. 2. SEM images of synthesized materials.

SBA-15 synthesized without the addition of ZrOCl2 worm-like particles
are obtained, while the addition of ZrOCl2 leads to the creation of discs
or eggs.

probably originates from H2AsO4− ions. Thus As(V) is boned as oxoan­
ions both by Zr and N atoms. The positively charged Zr(IV) ions present
in the Zr–O groups and the positively charged amine groups cause the
attraction of As(V) anions, which facilitates the formation of bonds be­
tween As and N or O atoms.

3.1.4. X-ray photoelectron spectroscopy
In order to determine the mechanism of As(V) adsorption onto SBA/
TMPED/Zr type materials, XPS spectra of SBA/TMPED/Zr-0.5 and Asloaded SBA/TMPED/Zr-0.5 were recorded and compared. In SBA/
TMPED/Zr-0.5 and As-loaded SBA/TMPED/Zr-0.5 zirconium is pre­
sent in the fourth oxidation state, as evidenced by the doublet of 3d 5/2
and 3/2 peaks at 183.2 and 185.6 eV, respectively (See ESM Fig. S4 a
and S4 b.) [27]. The doublet of Cl 2p 3/2 and ½ at 198.3 and 199.9 eV
observed for the pristine SBA/TMPED/Zr-0.5 indicates the presence of
chlorine which is probably bonded with Zr atoms. The peak of chlorine
disappears when As(V) is adsorbed, thus it can be concluded that Cl−
ions are released to the solution due to the adsorption of arsenic. The
comparison of the XPS signals of oxygen obtained for pristine and
As-loaded sorbent (Fig. S4 c and d, respectively) leads to the conclusion
that arsenic is adsorbed as oxo-anion. For both materials two forms of
oxygen are distinguished. O 1s peak at 532.9 eV reflects the presence of
Si–O bonds [28], while the one at 530.9 eV [27] is the evidence of
oxygen-metal bonds. The participation of the second form of oxygen
increases almost twice (from 3.4 to 7.8 atomic %), as the result of arsenic
adsorption. The energies of As 3d 5/2 and 3d 3/2 peaks equal to 45.5
and 46.2 eV (Fig. S4 e), respectively indicate the presence of As(V) on
the surface [29]. However, As(V) oxo-anions are bonded not only with
Zr but also with amine groups. For the spectrum of N 1s region of
pristine SBA/TMPED/Zr-0.5 three peaks at 400.0, 401.5, and 402.4 eV
(Fig. S4 f) corresponding to primary, secondary, and protonated amine

groups can be distinguished after deconvolution [30]. After adsorption
the fourth peak appeared at the N1s region, the binding energy of 407.3
eV (Fig. S4 g) proves that N atoms are bonded with oxygen [31], which

3.2. Adsorption studies
3.2.1. pH influence
As(V) species dissociate according to the reactions [32]:
H3 AsO4 ​ (aq) ​ ⇌ ​ H+ ​ (aq) ​ + ​ H2 AsO4− ​ (aq)K1 ​ = ​ 10−

2,5

(3)

H2 AsO4 − ​ (aq) ​ ⇌ ​ H+ ​ (aq) ​ + ​ HAsO4 2− ​ (aq)K2 ​ = ​ 10−

6,96

(4)

HAsO4 2− ​ (aq) ​ ⇌ ​ H+ ​ (aq) ​ + ​ AsO4 3− ​ (aq) ​ K3 ​ = ​ 10−

11,24

(5)

Due to the fact that the speciation of As(V) and the sorbent surface
protonation are pH-dependent, the relation of adsorption vs. initial pH
value was determined and presented in Fig. 3. In the case of pristine
SBA-15, As(V) uptake is negligible in the studied pH range. For SBA/Zr0.5 and SBA/Zr-1 materials, adsorption significantly increases compared
to pristine SBA-15. The highest values are reached for initial pH between

1.6 and 2.9. Higher pH is favorable for the deprotonation of the sorbent
surface, which results in the repulsion of As(V) anions and a significant
decrease of adsorption. It was concluded that the adsorption of As(V)
onto SBA/Zr-0.5 and SBA/Zr-1 is associated with the presence of pro­
tonated zirconium species Zr − OH+
2 , which electrostatically attract
H2AsO4− ions. In the studied pH range, solvated H2AsO4− ions form the
stable inner-sphere complexes with the Zr modified silica surface [33].
The maximum adsorption efficiency onto SBA/Zr-0.5 and SBA/Zr-1 was
attained at pH 2.9. Consequently, all the subsequent adsorption exper­
iments with the application of SBA/Zr-0.5 and SBA/Zr-1 were carried
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Microporous and Mesoporous Materials 328 (2021) 111484

Fig. 3. The effect of initial pH on the adsorption of As(V), t = 24 h, T = 25 ◦ C,
cAs(V)=10 mg L− 1, m = 0.005 g, V = 5 mL.

Fig. 4. Adsorption isotherms of As(V) onto studied materials, t = 24 h, T =
25 ◦ C, pHSBA, SBA/Zr-0.5, SBA/Zr-1 = 2.9, pHSBA/TMPED, SBA/TMPED/Zr-0.5, SBA/TMPED/
Zr-1 = 3.5, m = 0.005 g, V = 5 mL.

out at pH 2.9.
SBA/TMPED/Zr materials also adsorb H2AsO4− ions; however, the
maximum uptake is reached at initial pH of 3.5. Contrary to SBA/Zr
materials, in the case of SBA/TMPED/Zr, the rapid decrease of adsorp­

tion associated with the increasing of initial pH is not observed. It was
stated that the modification of SBA/Zr materials with TMPED leads to
the creation of the material, which efficiently sorb As(V) anions in a
wide pH range. The presence of amine groups probably facilitates the
adsorption of As(V) caused by electrostatic interactions between pro­
tonated amine groups and H2AsO4− anions. Thus, to obtain sorbent
quantitatively removing As(V) from the solutions of various pH, the
introduction of Zr and amine groups to organosilica structure is neces­
sary. Further studies using SBA/TMPED/Zr and SBA/TMPED sorbents
were carried out at a pH of 3.5.

adsorption, when even small changes of the size of the mesopores and
micropores significantly change the adsorption properties [34,35].
The initial run of isotherms obtained for all four ZrOCl2 modified
materials proves the possibility of quantitative removal of As(V) from
the solutions of initial As(V) concentration not exceeding 2 mg L− 1 and
hereby ensures the usefulness of sorbents for analytical purposes. The
ideal sorbent used for analyte preconcentration is expected to ensure
quantitative adsorption over the widest possible pH range because the
possibility of preconcentration in a wide range of pH considerably
simplifies the sample preparation procedure. Among the synthesized
sorbents, this requirement is met by materials SBA/TMPED/Zr-0.5 and
SBA/TMPED/Zr-1. In Table 2 the comparison of chosen sorbents used
for As species preconcentration is presented.
3.2.3. Interferents
The effects of coexisting anions found in natural waters (such as
chlorides, nitrates, and phosphates) on As(V) adsorption onto SBA/
TMPED/Zr-0.5 and SBA/TMPED/Zr-1 were investigated (Fig. 5). Chlo­
rides and nitrates in the range of concentration between 0.0001 and
0.01 mol L− 1 have no significant effect on the adsorption of arsenate on

SBA/TMPED/Zr-0.5 and SBA/TMPED/Zr-1. For higher concentrations
of both anions, the adsorption of arsenate slightly decreases; however,
for 1 mol L− 1 coexisting anions solution, the adsorption value is not
lower than 60% of the value obtained in the solution containing no
chlorides or nitrates. Thus, both sorbents can be useful for preconcen­
tration of As(V) from the waters containing low concentrations of
chlorides and nitrates. The adsorption of arsenates is significantly
impaired when only 0.001 mol L− 1 of phosphates are present in the
solution. When As(V) is adsorbed from 0.1 mol L− 1 phosphate solution
the adsorption is only 3% of the value obtained in a phosphate-free
solution. Thus SBA/TMPED/Zr-0.5 and SBA/TMPED/Zr-1 materials
are not suitable for the preconcentration of As(V) from the solutions
containing more than 0.0001 mol L− 1 of phosphates; however, both
materials can be successfully applied for the preconcentration of As(V)
from drinking water. Phosphates decrease the As(V) adsorption because
of the similar coordination chemistry and affinity for zirconium (hydr)
oxides as arsenate. Phosphates form the same inner-sphere complexes
and hereby effectively reduce sorbent’s capacity for adsorption of ar­
senates [33].

3.2.2. Adsorption capacity
In Fig. 4, As(V) adsorption isotherms are presented. The maximum
static adsorption capacities are strictly dependent on the TMPED
modification and the amount of Zr used for the synthesis of sorbents. The
maximum adsorption capacity of As(V) obtained onto pristine SBA-15 is
only 1 mg g− 1, whereas, for SBA/Zr-0.5 and SBA/Zr-1, 8 and 14 mg g− 1
are reached, respectively. A further increase of adsorption capacities is
observed for sorbents modified by both ZrOCl2 and TMPED. Maximum
static adsorption capacity of SBA/TMPED, SBA/TMPED/Zr-0.5 and
SBA/TMPED/Zr-1 are 5, 24 and 32 mg g− 1, respectively.

The slight decrease of the specific surface area and the simultaneous
widening of the mesopores being the result of SBA-15 modification with
increasing amounts of ZrOCl2 does not cause the decrease of As(V)
adsorption. Increasing the amount of ZrOCl2 used for the synthesis
resulted in an improvement of the adsorption capacity of the materials
towards As(V) ions. Similar relationship was obtained for the series of
SBA/TMPED materials modified with increasing amounts of ZrOCl2. In
this case, despite the decrease of the specific surface area from 738 m2
g− 1 for SBA/TMPED to 550 m2 g− 1 for SBA/TMPED/Zr-1 and the
decrease of the pore volume, the adsorption of As(V) increased over 6
times. Thus, the surface chemistry is of key importance for the adsorp­
tion of As(V) ions on the studied materials. Minor changes in the porous
structure of modified SBA-15, including changes of micropores, do not
have such a significant effect on the adsorption properties shown in
relation to As(V) present in aqueous solutions as it is in the case of gas
5


J. Dobrzy´
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Microporous and Mesoporous Materials 328 (2021) 111484

Table 2
Comparison of the condition of As species preconcentration by solid phase extraction method.
Analyte

Adsorbent

Matrix

Detection technique

Eluent

LOD [ng L− 1]

Adsorption capacity
[mg g− 1]

EF

Ref.

As(III), As(V),
AsBet,
cacodylate
As(III), As(V)

PSTH-functionalized
magnetic NP/GO

Water,
biological
samples
Water

HPLC-ICP-MS

1.1 - As(III), 0.2 - As

(V), 3.8 - AsBet, 0.5
- cacodylate
–

1.6 - As(III), 5.0 - As
(V), 3.2 – cacodylate,
1.1 - AsBet
2.68

–

[36]

ICP-OES

0.1% m/v TU +
0.1% m/v CS in
NaOH pH 12.0
2 mol L− 1 HNO3

[37]

As(III), As(V)

CdS nanoflowers

food

ICP-OES

1 mol L−

0.5 – As(III), 0.8 - As
(V)
0.23–1.85

137 As(III)
145 As(V)
–

As(III) –
400, As(V)
− 300
100

[39]

Inorganic and
organic As
species
As(V)
As(III), As(V)
As(III)
As(III), As(V)
As(III), As
inorganic
As inorganic
As(V)
As(V)

Polyaminesfunctionalized silica

Ti (IV)-modified vinyl
phosphate magnetic
nanoparticles
Amine/ALIQUAT 336/
CNTs composite
Nickel–zinc ferrite NP

1

HNO3
− 1

[38]

Fish, meat

HPLC-ICP-MS

0.1 mol L
NaOH

Cannabis oil

XRF

–

100

10

10,000

[40]

Water

spectrophotometry
HG AAS
ICP-OES
HG AAS

2 mol L−

Fe3O4/MnO2 composite

Water

0.5 mol L−

1

HCl

–

–

[45]

Al2O3/GO
Zr/amine-modified
silica

Water
Water

Slurry sampling HG
AAS
XRF
HG AAS

20 - As(III), 30 - As
inorganic
2.9

966
900 As(III)
833 As(V)
20.4

[42]
[43]

Seawater

35.8 As(III)
62.5 As(V)

140
45 - As(III),
50 As(V)
–

[41]

Water, food
Water

150 - As(III), 100 As(V)
1.3
30

100

Protein laminated GO
2D carbon sheets/
MnFe2O4 composite
PTFE

2 mol L− 1
NaOH
1 mol L− 1 HCl
0.5 mol L− 1 HCl

–
10 mol L−

1

HCl

20
25

43.9
32

294
12.5

[46]
This
work

1

HCl

[44]

AsBet – arsenobetaine, CNTs - carbon nanotubes, CS – 1-cysteine, EF – enrichment factor, GO - graphene oxide, HPLC-ICP-MS - high-performance liquid chroma­
tography in combination with inductively coupled plasma mass spectrometry, XRF - X-ray Fluorescence Spectroscopy, ICP OES - Inductively Coupled Plasma Optical
Emission Spectrometry, NP – nanoparticles, PSTH - [1,5-bis(2-pyridyl)3-sulfophenylmethylene] thiocarbonohydrazide, PTFE – polytetrafluoroethylene, TU – thiourea.

3.2.4. Desorption
The possibility of quantitative As species desorption from SBA/
TMPED/Zr sorbents was studied using hydrochloric and nitric acids. As
can be seen in Fig. 6 As species are totally removed from SBA/TMPED/

Zr-0.5 and SBA/TMPED/Zr-1 when at least 6 mol L− 1 HNO3 is applied.
When 10 mol L− 1 hydrochloric acid is used desorption reaches 75 and
93% for SBA/TMPED/Zr-1 and SBA/TMPED/Zr-0.5, respectively.
However, after 20-min, sonication of SBA/TMPED/Zr-0.5/HCl suspen­
sion quantitative desorption of As is observed. Hence, to ensure the

Fig. 5. The effect of chlorides, nitrates and phosphates on the adsorption of As
(V) onto SBA/TMPED/Zr-0.5 and SBA/TMPED/Zr-1, t = 24 h, T = 25 ◦ C, pH =
3.5, m = 0.005 g, V = 5 mL, c = 8.8 mg L− 1.

Fig. 6. Desorption of As in the presence of HCl and HNO3, m = 0.0005 g, Vr =
2 mL, ASBA/TMPED/Zr-0.5 = 20.2 mg g− 1, ASBA/TMPED/Zr-1 = 28.9 mg g− 1, t = 24 h,
T = 25 ± 0.5 ◦ C.
6


J. Dobrzy´
nska et al.

Microporous and Mesoporous Materials 328 (2021) 111484

quantitative desorption of As from SBA/TMPED/Zr-0.5 to 10 mol L− 1
HCl, a 20-min sonication step was introduced to the analytical proced­
ure. The As desorption by HNO3 before HG AAS determination was not
recommended due to oxidative properties of the acid, which potentially
could hinder the reduction of As(V) to As(III) before arsine generation.
Despite the necessity to use small volumes of concentrated hydro­
chloric acid for As species desorption, the proposed materials allow
quantitative preconcentration of As(V) even from solutions of a con­
centration exceeding 2 mg L− 1, therefore their recommendation is

justified. Ideally, As species could be desorbed using milder reagents,
but be aware that much larger amount of hydrochloric acid is used in the
hydrogen generation step from NaBH4 than in the arsenic desorption
step.

Table 3
Results of As(V) determination in tap water and certified reference materials by
FI HG AAS.
CRM

Determined
concentration [μg L− 1]

Certified concentration
[μg L− 1]

Recovery
[%]

NRCAQUA-1
SRM 1640a

0.212 ± 0.045

0.222 ± 0.014

95

7.92 ± 0.088

8.01 ± 0.067

99

Sample

Spiked concentration
[μg L¡1]
0
0.2
0.5
1.0
2.0

Determined
concentration [μg L¡1]
0.201 ± 0.014
0.407 ± 0.013
0.708 ± 0.032
1.18 ± 0.028
2.31 ± 0.037

Recovery
[%]
–
102
101
98
105

Lublin tap
water

3.2.5. Analytical figures of merit and validation
Analytical figures of merit of the method were studied using SBA/
TMPED/Zr-0.5 as solid sorbent and the analytical procedure described
in section 2.5. The good linearity of the calibration curve was observed
in the range of 2–40 μg L− 1 with an the acceptable correlation coefficient
of 0.9989. The limits of detection (LOD) and quantification (LOQ) were
calculated as LOD = 3SD/a and LOQ = 3SD/a, where SD is the standard
deviation of 10 replicate blank signals and a is the slope of the cali­
bration curve after the extraction process, assuming that the enrichment
factor was 12.5. LOD ad LOQ were 0.025 μg L− 1 and 0.086 μg L− 1,
respectively. The relative standard deviation (RSD%) of the method (0.5
μg L− 1 of As(V) ions, n = 5) was 4.5%.
The accuracy of the method was verified by determining the ele­
ments in the standard reference materials NRC-AQUA-1 (drinking
water) and SRM 1640a (freshwater) as well as by analyzing the spiked
amount of arsenic to real samples. The experimental results presented in
Table 3 are in good agreement with certified and spiked values. The
recoveries are justifiable for trace analysis, in the range of 95–105%.

– review & editing, Supervision.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.micromeso.2021.111484.

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4. Conclusion
In this work, a Zr/amine-modified SBA-15 was synthesized, charac­
terized, and applied for simple As(V) preconcentration before its further
FI HG AAS determination. Zr/amine-modified SBA-15 was found to be
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CRediT authorship contribution statement
´ ska: Conceptualization, Methodology, Validation,

Joanna Dobrzyn
Formal analysis, Investigation, Writing – original draft, Writing – review
& editing, Visualization, Project administration. Rafał Olchowski: Re­
sources, Writing – review & editing. Emil Zięba: Investigation, Re­
sources. Ryszard Dobrowolski: Conceptualization, Resources, Writing
7


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