Hybrid); and amorphous and nanocrystalline hybrids after the sorption of ..... Brunauer, S.; Emmett, P. H.; Teller, E., Adsorption of gases in multimolecular layers.
Supporting Information
Interface Induced Growth and Transformation of PolymerConjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum 23Na-23Na MAS NMR Correlation Spectroscopy Study Jiri Brusa*, Libor Koberaa+, Martina Urbanováa, Barbora Doušovác, Miloslav Lhotkac, David Koloušekc, Jiří Koteka, Pavel Čubac, Jiri Czerneka, Jiří Dědečekb
a)
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic b)
J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 2155/3, 182 23 Prague 8, Czech Republic c)
University of Chemistry and Technology Prague, Technicka 5, Prague, Czech Republic
+)
University of Ottawa, Department of Chemistry and CCRI, 10 Marie Curie Pvt. D’Iorio Hall, Ottawa, Ontario K1N6N5, Canada
S1. Synthesis of hybrid inorganic-organic geopolymers The hybrid inorganic-organic geopolymers were prepared according to the reaction scheme depicted in Figure S1. During the activation period ta the aqueous solution of sodium metasilicate (52 g, Zaklady Chemiczne Rudniki S.A., Poland) was activated by powdered sodium hydroxide (8.5 g, LachNer, Neratovice, Czech Republic). In this way the required amount of alkali ions allowing compensation of negative charge of AlO4- units was added, and depolymerization of siloxane oligomers was initiated. During the sol-gel period tb the solution of 3-amino propyl trimethoxy silane (3.7 g, APTMS, Sigma-Aldrich, Czech Republic) was admixed, and polycondensation reactions involving sodium metasilicate units and APTMS occurred. Duration of activation and sol-gel periods vas systematically varied in the range from 0 to 48 hours. The total reaction time ta+tb was, however, kept constant at 48 hours. Subsequently, finely powdered kaolin (70 g, Sedlec quarry, Czech Republic) calcinated at 750 °C for 6 hours was added into the activated solution and the whole mixture was homogenized for 45 minutes. At the end of this period the resulting product exhibited gel-like consistence. In the next step, the corresponding amount of solution of 4,4`isopropylidenediphenol diglycidyl ether (4.7 g, DGEBA, Sigma-Aldrich, Czech Republic) and water (19.4 g) were added to the mixture and mixed well for additional 45 minutes. At this moment polyaddition reactions leading to the formation of polymeric network started. The organic components (APTMS and DGEBA) were added in equimolar ratio and the final amount of the organic phase in the reaction mixture was ca. 8 wt. % (estimated for completely dry system). Finally, the resulting homogeneous pastes were placed into the Teflon mold to create testing specimens (cylinders with diameter = 1.5 cm and height = 3.0 cm). To remove air bubbles that can be entrapped it the prepared paste the Teflon mold was placed on a vibration table and vibrated 10 min. The total chemical composition of reaction mixtures was adjusted to be SiO2/Al2O3 = 3.6, Na2O/Al2O3 = 1, H2O/Na2O = 8. For reaching of high conversion of all polymerization reactions and to obtain wellcured inorganic-organic hybrids the testing specimens were allowed to stand for 7 days at ambient temperature and atmospheric pressure. Growing of crystalline zeolites was initiated by the hydrothermal synthesis (HT) in a Teflon-lined autoclave at 140 °C during a 14-days period (tht). SI1
Figure S1. Scheme of the synthesis of hybrid inorganic-organic geopolymers
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S2. Scanning Electron Microscopy
Scanning Electron Microscopy Am-Hybrid
Nano-Hybrid
10 μm
10 μm
2 μm
2 μm
Figure S2. SEM micrographs of the prepared geopolymer hybrids. The data presented in the left- and right-hand columns represent amorphous and nanocrystalline geopolymer hybrids, respectively.
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29
S3. Si and 13C CP/MAS NMR Spectroscopy
29
29
Si CP/MAS and Si MAS NMR
a) Am-Hybrid
Nano-Hybrid Q4(4-0Al)
4
Q (4-0Al) Q3 T3 3
2
T2
T
T
-50
-100
-50
ppm
ppm
13
b)
C CP/MAS NMR Nano-Hybrid 5
150
O
1
9
3
3,19, 20
8
100
50
24
ppm
O
23
7, 13
4, 16
6,8,14, 18
12
2
2,21, 22
14
4
7
CH3
24
50
23
2,21, 22
10
3,19, 20
6,8,14, 18 5,9,15, 17
4, 16 7, 13
15
HO
Si
100
10 13
NH
O
6
CH3
5,9,15, 17
23
18
16
O
20
Si
150
19
11, 12
O
21
22
10
17
OH 24
11
11, 12
Am-Hybrid
Si
-100
ppm
Figure S3. 29Si CP/MAS (black), 29Si MAS (red) and 13C CP/MAS NMR spectra of the prepared nanocrystalline and amorphous geopolymer hybrids. The chemical structure of the secondary epoxide network with numbered of carbon atoms is presented above the 13C CP/MAS NMR spectra. The number of scans accumulated for the recording of the presented 29Si CP/MAS, 29Si MAS and 13C CP/MAS NMR spectra was following: NS = 36000; 4000 and 6000, respectively.
SI4
S4. Deconvolution of 29Si MAS NMR spectra
Nano-Hybrid
Am-Hybrid
Amorphous 4 Q (nAl); 87%
4
Q (2Al); 26%
4
Q (1Al); 15% 4
Q (3Al); 13%
Amorphous 4 Q (0Al); 13%
Amorphous 4 Q (nAl); 37% 4
Q (4Al); 6% 4
Q (0Al); 4%
Figure S4a. Deconvolution of 29Si MAS NMR spectra of the amorphous geopolymer hybrid (AmHybrid) and nanocrystalline geopolymer hybrid (Nano-Hybrid). The number of scans accumulated for the presented 29Si MAS NMR spectra was 4096, and the recycle delay was set to 10 s.
When deconvoluting the 29Si MAS NMR spectra we used several combinations of initial models. We always kept constant 29Si NMR chemical shifts of the signals and let variable the intensities and linewidths of the signals. However, the models with the linewidths of the signals larger than 4 ppm and 15 ppm predicted for the crystalline and amorphous fractions, respectively, were excluded from subsequent considerations. The presented results shown in Figure S4a represent the best fit with the best overlap between the experimental spectrum and the model (e.g. 98.52% for Nano-Hybrid system). We repeated deconvolution several times. Using the selected models with reasonable linewidths we calculated average intensities of individual components. These values were subsequently used for calculating Si/AlFR ratio. This way we estimate uncertainty of Si/AlFR ratio to be ca. ± 0.1.
SI5
To obtain quantitative 29Si MAS NMR spectra we optimized the recycle delay by using a simplified T1(29Si) saturation-recovery experiment with variable recycle delay ranging from 0.5 to 64 s (see scheme below). RD
π/ 2
π/ 2
RD heteronuclear decoupling
heteronuclear decoupling
1H
RD heteronuclear decoupling
π/ 2
heteronuclear decoupling π/ 2
29Si
As demonstrated on Figure S4b due to the presence of paramagnetic Fe2+/Fe3+ impurities originating from kaolin the recycle delay allowing complete 29Si magnetization recovery is ca. 4-8 s for Am-Hybrid and Nano-Hybrid systems. This finding indicates that the recycle delay D1 = 10 s is sufficiently long to obtain 29Si MAS NMR data suitable for quantitative analysis.
2.0 s 1.0 s
0.5 s
Figure S4b. The T1(29Si) saturation recovery-filtered 29Si MAS NMR spectra of the nanocrystalline hybrid (Nano-Hybrid) measured at different recycle delays (0.5; 1.0; 2.0; 4.0; 8.0 and 16.0 s).
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S5. Processing of 2D 27Al and 23Na TQ/MAS NMR spectra For readers who are not familiar with this type of spectral processing, we present the following brief description. In general, by executing the standard three-pulse 2D 3Q/MAS NMR experiment, the anisotropic contribution resulting from the 2nd order quadrupolar interaction is separated from the isotropic chemical shift and quadrupole-induced isotropic shift. These individual spectral contributions are then aligned along different directions of the resulting 2D spectrum (Figure S5a).
Figure S5a. 2D 27Al 3Q/MAS NMR spectrum of kyanite measured by the three-pulse sequence with zfilter. No shearing transformation was applied. Labels ‘A’, ‘CS’ and ‘QIS’ describe anisotropic axis, isotropic chemical shift axis and axis of quadrupole-induced isotropic shift, respectively. Three different AlO6 structural units are clearly identified. The anisotropic contribution of the quadrupolar interaction representing the dependence of NMR frequency on the orientation of the crystal in the magnetic field, and causing broadening of the resulting NMR signal, is aligned along the axis A given by the ratio R (I; p), while the centre of gravity of the NMR signal is given by the sum of the isotropic chemical shift, aligned along the chemical shift axis CS defined by the parameters (-p; 1), and the quadrupole-induced isotropic shift that runs along the QIS axis with its slope is determined by the ratio ξ [1, 2]:
ξ = −p
4I ( I + 1) − 3 p 2 4I ( I + 1) − 3
The quadrupole-induced isotropic shift (δQIS) is a parameter that is unique for each pair (I; p) and that therefore specifically influences the position of each 2D NMR signal in the 2D spectrum. This influence results in a slight shift of the resulting NMR signal in the 3Q dimension (F1) from the real values of the isotropic chemical shift (δCS). 2D MQ/MAS NMR correlation spectroscopy has become popular because it provides high-resolution NMR spectra of half-integer nuclei. The benefit of this approach comes from its ability to separate the second-order quadrupolar coupling for every chemically distinct site according to the corresponding isotropic chemical shift. However, applying the original three-pulse sequence, the anisotropic second-order quadrupolar signal is aligned along an anisotropy axis (A) that is tilted relative to the direction of the single-quantum F2 axis with a slope of k (Figure S5a). For the triplequantum coherence of a spin with I = 5/2, the parameter k reaches the value k = 19/12. Consequently, the sky-line projection into F1 axis reflects not only isotropic values but also residual quadrupolar SI7
broadening. To remove this tilt, various spectral processing procedures (shearing transformations) have been proposed. Among them, the most useful is the single-axial isotropic shearing transformation operating in the indirect dimension ν1 according to the following equation [3]:
ν 1' 1 a ν 1 = ν 2 0 1 ν 2 where the factor a plays a crucial role. If a = -k = -19/12, the indirect evolution dimension ν1 loses the anisotropic term and the projections onto the ν1’ axis are dominated by the isotropic chemical shift and isotropic quadrupole-induced shift (δCS and δQIS, respectively). Consequently, the isotropic shearing separates the anisotropic term along ν1 axis and the projections onto the ν1’ axis are dominated by narrow isotropic contributions. This process generally transfers the anisotropy axis (A), which becomes parallel to ν2 axis, thus the projection on the newly defined triple-quantum δ3Q axis (F1) of the sheared spectrum becomes isotropic and highly resolved, while the F2 axis gives pQfiltered spectra basically corresponding to single quantum MAS NMR spectrum (Figure S5b). This spectral processing is an ideal choice for the analysis of well-ordered systems because the ISOsheared spectra of crystalline systems are characterized by narrow projections in the F1 dimension. A complete theoretical description and further details concerning all of the shearing procedures can be found in recently published comprehensive papers [3, 4].
Figure S5b. 27Al 3QMAS NMR spectrum of kyanite obtained with isotropic shearing transformations. The axes of NMR parameters that represent the isotropic chemical shift (δCS), the isotropic quadrupolar shift (δQIS), and the second-order quadrupolar splitting (Qcc) are shown as dashed lines marked as CS, QIS, and A, respectively.
SI8
S6. 27Al 3Q/MAS NMR spectra - Biaxial Q-shearing
27
Al 3Q/MAS NMR spectra Biaxial Q-shearing
a)
Am-Geo
Nano-Geo
F2
ppm
ppm CS
20
F2 CS
20
A
A
AlIV3
40
40
F1
IV
Al
60 80
70
1
60
IV
Al
QIS
60
2
50
QIS
80
ppm
70
ppm
50
ppm
Nano-Hybrid
Am-Hybrid
b)
60
ppm
F2 CS
20
F1
F2 CS
20
40
F1
A
A
40
60
60
QIS
80
70
60
50
ppm
QIS
80
ppm
F2
ppm
CS
20
60
50
ppm
Pb Nano-Hybrid
Pb Am-Hybrid
c)
70 2+
2+
F1
F2 CS
20
F1
A
A
40
40 60
60
QIS
80
70
60
50
ppm
QIS
80
70
60
50
ppm
Figure S6. 27Al 3Q/MAS NMR spectra of the reference polymer-free amorphous and nanocrystalline geopolymers (a, Am-Geo, Nano-Geo); amorphous and nanocrystalline hybrids (b, Am-Hybrid, NanoHybrid); and amorphous and nanocrystalline hybrids after the sorption of Pb2+ (c, Pb2+ Am-Hybrid, Pb2+ Nano-Hybrid). The spectra were processed by the biaxial Q-shearing transformation.
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S7. Schematic and idealized graphical representation of various Al and Na sites
AlIV2
AlIV1 O
+
Na
O
IV
Al
O
O
1
O
Al
O
H
IV
Si
2
O
O
AlIV3
+
H
mobile rotating
IV
Al
3 IV
Al
3
Figure S7a. Simplified graphical representation of the aluminum sites AlIV1, AlIV2 and AlIV3.
+
Na +
Na
+
+
Na
Na
+
Na
+
Na
+
Na
+
Na
+
Na +
Na +
Na
+
Na
+
Na
+
Na +
Na
Figure S7b. Graphical representation of the sodium sites in the crystalline of Na2CO3.
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S8. Mechanical testing The compressive strength σe of the prepared test specimens (cylinders with diameter = 1.5 cm and height = 3.0 cm prepared from modified and unmodified geopolymer systems before and after the final hydrothermal step) was measured using an INSTRON 5800R-series universal testing machine, model 6025. The compression speed was 5 mm/min. Each result is the mean of 5 experiments. As determined for the testing specimens (Table S1) the presence of secondary organic network significantly improves durability and mechanical integrity of the geopolymeric hybrids. The increase in mechanical strength reaches 20 % for the hybrid organic/inorganic systems opposite to unmodified reference geopolymers. Considerable reinforcement of the aluminosilicate matrix provided by the epoxy network was observed even in the systems tested before the hydrothermal (HT) synthesis.
Table S1. The comparison of compression strength of the prepared nanocrystalline and amorphous geopolymer hybrids and analogous unmodified reference geopolymers (Nano-Hybrid, Am-Hybrid, Nano-Geo and Am-Geo, respectively). Compression strength σ (Mpa) Sample Final products Before HT synthesis
Am-Hybrid 82 ± 4 80 ± 5
Nano-Hybrid 45 ± 4 78 ± 6
Am-Geo 69 ± 4 65 ± 7
Nano-Geo 34 ± 4 60 ± 5
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S9. Surface characterization Equilibrium adsorption isotherms of nitrogen were measured at 77 K using a static volumetric adsorption system (ASAP 2020 and 2050 analyzers, Micromeritics, Norcross, USA). The adsorption isotherms were fitted using the Brunauer-Emmett-Teller (BET) method for specific surface area [5], the micropore volume by the t-plot method [6], and the pore-size distribution by the Barrett-JoynerHalenda (BJH) method [7]. The distribution of unmodified and hybrids geopolymer systems pore diameters relating to the pore area are given in Figure S8 and summarized results are listed in Table S2. The derivative curves showed sharp peaks about 4 nm for both crystalline systems and dominant peak about 9 nm for amorphous geopolymers. From the SBET (Table S2) and pore volume (Figure S8) is clear that modification of geopolymer structure enhanced the specific surface. The comparison of SBET and “tPlot External Surface Area” provides information about porosity of prepared hybrid geopolymers. The amorphous hybrid geopolymer can be defined as mesoporous material and the nanocrystalline hybrid geopolymer as microporous material. It can be supposed that nanocrystalline materials contains dominant fraction < 4 nm pore diameter. This is confirmed by “t-Plot Micropore volume” parameter, where modified nanocrystalline systems exhibit highest value.
Am-Hybrid
Am-Geo
Nano-Hybrid
Nano-Geo
Figure S8. Distribution of pore diameters determined for the prepared nanocrystalline and amorphous geopolymer hybrids and analogous unmodified reference geopolymers (Nano-Hybrid, Am-Hybrid, Nano-Geo and Am-Geo, respectively). Table S2. Specific surface SBET (m²/g), t-plot external surface area (m²/g), total pore volume (cm3/g) and t-plot micropore volume (cm3/g) determined for the nanocrystalline and amorphous geopolymer hybrids and unmodified geopolymers (Nano-Hybrid, Am-Hybrid, Nano-Geo and Am-Geo).
Am-Hybrid
SBET (m²/g) 57.8
t-plot external surface area (m²/g) 53.3
total pore volume 3 (cm /g) 0.17
t-plot micropore 3 volume (cm /g) 0.0021
Nano-Hybrid
124.4
20.8
0.13
0.0545
Am-Geo
28.6
25.9
0.15
0.0013
Nano-Geo
17.5
3.8
0.043
0.0072
Sample
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S10. Sorption of ionic particles Model solutions of Pb2+ ions were prepared by dissolving stoichiometric amounts of PbCl2 in distilled water in a range of concentrations from 1 x 10-4 to 8 x 10-4 mol.l-1. The pH of the PbCl2 solutions was 3.8. The powdered samples were washed with distilled water, dried at 60°C and finally sieved to 0.355 mm. A suspension of a model solution and solid sample (1-3 g.l-1) was shaken in a batch procedure at laboratory temperature (20°C) for 24 and 72 hours [8]. The residual Pb2+ in the supernatant was analyzed by atomic absorption spectrometry (AAS). The concentration of Pb2+ in aqueous solution was determined by a SpectrAA-880 VGA 77 unit (flame mode) and SpectrAA-300 apparatus (hydride process). The samples were pre-treated with a solution of HCl (36% v/w) and KI (50%) with ascorbic acid (10%). The detection limit was 0.05 ppm, and the standard deviation was experimentally determined to be 2.5% [9].
Pbsorption Pb2+ 0,4
A Am-Hybrid m C Nano-Geo
0,3
A Am-Geo
-1
qeq (mmol.g )
Cm Nano-Hybrid
0,2
0,1
0,00
0,02
0,04
0,06
0,08
0,10
-1
ceq (mmol.L )
Figure S9. Langmuir isotherms characterizing Pb2+ adsorption of the prepared nanocrystalline and amorphous geopolymer hybrids and analogous unmodified reference geopolymers (Nano-Hybrid, Am-Hybrid, Nano-Geo and Am-Geo, respectively).
The trends of metal ion adsorption by modified and unmodified geopolymer systems in aqueous solution were investigated as a function of the initial metal ion concentration. The adsorption of Pb2+ was almost quantitative on all of the tested samples (90 – 97%). Adsorption isotherms presented in Figure S9 illustrate effective adsorption running according to the Langmuir model with comparable theoretical adsorption capacity (0.20 – 0.26 mmol g-1) for all systems. The determined coefficient of adsorption isotherm as well as the Langmuir constant KL (Table S3), which characterize the binding energy of the adsorption-desorption process, attributed the strongest adsorption affinity for Pb2+ to the amorphous hybrid system (Am-Hybrid). In this system, the optimum pore size combined with large external surface was likely reached. A slightly reduced adsorption capacity was observed for the nanocrystalline systems, whereas the lowest adsorption affinity was exhibited by unmodified amorphous geopolymers. These findings indicate that the presence of an epoxy network combined SI13
with optimized nanocrystallization can effectively control the sorption capacity and affinity of geopolymeric hybrids toward metal cations.
Table S3. Parameters of Pb2+ adsorption onto modified and unmodified geopolymers: Langmuir constant KL (L.mmol-1), theoretical adsorption capacity Qtheor (mmol.g-1), maximum adsorption capacity qmax (mmol.g-1) and adsorption rate ε (%). sample Am-Hybrid Nano-Hybrid Am-Geo Nano-Geo
dosage (g l-1) 2 2 2 2
time (h) 24 24 24 24
qmax (mmol.g-1) 0.36 0.28 0.33 0.33
Qtheor (mmol.g-1) 0.26 0.25 0.21 0.23
KL (L.mmol-1) 3.18 0.87 0.27 1.04
ε (%) 97 95 90 93
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S11. 1H-23Na variable-contact-time (VCT) experiments
0.8 I
Na+5 Na+4
0.6 Na+1
0.4
Na+5
Na+4
Na+1
0.2 10
0
-10
-20
ppm
0 0
1000
2000
3000
4000τ, µs
5000
Figure S10. 1H-23Na variable-contact-time (VCT) build-up dependences determined for Na+1, Na+4, and Na+5 resonances detected in 23Na{1H} CP/MAS NMR spectra of the epoxy-modified nanocrystalline hybrid (Nano-Hybrid). The spectra displayed in the inset were measured with a contact time of 0.2, 2.0 and 4.5 ms, recycle delay of 2 s, and number of scans of 4096 (black, red and blue lines, respectively).
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S12. 23Na MAS NMR of Na2CO3
δiso = 6.4 ppm CQ = 1.1 MHz η = 0.2
δiso = -4.5 ppm CQ = 2.3 MHz η = 0.8
20
0
-20
ppm
Figure S11. 23Na MAS NMR spectrum and a line-shape simulation for Na2CO3. The spectrum was recorded with the number of scans of 16 and the recycle delay of 10 s.
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S13. 23Na MAS NMR of geopolymer hybrids before and after Pb2+ sorption
29
Si MAS NMR spectra
a)
b) Am-Hybrid 2+ Before Pb sorption
Am-Hybrid 2+ After Pb sorption
Nano-Hybrid 2+ Before Pb sorption
Nano-Hybrid 2+ After Pb sorption
Figure S12. 29Si MAS NMR spectra of the amorphous geopolymer hybrid (Am-Hybrid; a); and nanocrystalline geopolymer hybrid (Nano-Hybrid; b), recorded before and after Pb2+ sorption. The number of scans accumulated for the presented 29Si MAS NMR spectra was 4096, and the recycle delay was set to 10 s.
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References 1. J. P. Amoureux, C. Fernandez, Triple, Quintuple and Higher Order Multiple Quantum MAS NMR of Quadrupolar Nuclei, Solid State Nucl. Magn. Reson. 10 (1998) 211-223. 2. Y. Millot, P. P. Man, Procedures for Labeling the High-Resolution Axis of Two-Dimensional MQMAS NMR Spectra of Half-Integer Quadrupole Spins, Solid State Nucl. Magn. Reson. 21 (2002) 21-43. 3. John D. Gehman, John L. Provis, Generalized Biaxial Shearing of MQMAS NMR Spectra, J. Magn. Reson. 200 (2009) 167-172. 4. I. Hung, J. Trebosc, G.L. Hoatson, R.L. Vold, J.P. Amoureux, Z.H. Gan, J. Magn. Reson. 201 (2009) 8186. 5. Brunauer, S.; Emmett, P. H.; Teller, E., Adsorption of gases in multimolecular layers. Journal of the American Chemical Society 1938, 60, 309-319. 6. Webb, P. A. & Orr, C., Analytical methods in fine particle technology. Micromeritics Instrument Corp. 1997 7. Barrett, E. P.; Joyner, L. G.; Halenda, P. P., The determination of pore volume and area distributions in porous substances. I. Computations from nitrogen isotherms. Journal of the American Chemical Society 1951, 73, (1), 373-380. 8. Jiang, M.-q.; Wang, Q.-p.; Jin, X.-y.; Chen, Z.-l., Removal of Pb(II) from aqueous solution using modified and unmodified kaolinite clay. Journal of Hazardous Materials 2009, 170, (1), 332-339. 9. Dousova, B.; Grygar, T.; Martaus, A.; Fuitova, L.; Kolousek, D.; Machovic, V., Sorption of As-V on alumino silicates treated with Fe-II nanoparticles. Journal of Colloid and Interface Science 2006, 302, (2), 424-431.
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