Electronic Supplementary Material (ESI) for Environmental Science: Nano. This journal is © The Royal Society of Chemistry 2015
Electronic Supplementary Information Extremely High Arsenic Removal Capacity for Mesoporous Aluminium Magnesium Oxide Composites Wei Li,‡a Dehong Chen,b Fang Xia,a,c Jeannie Z. Y. Tan,a,b Pei-Pei Huang,d Wei-Guo Song,d Natalita M. Nursama,b and Rachel A. Caruso*a,b a
b
CSIRO Manufacturing, Clayton South, Victoria, 3169, Australia. Particulate Fluids Processing Centre, School of Chemistry, The University of Melbourne,
Melbourne, Victoria, 3010, Australia. c
School of Engineering and Information Technology, Murdoch University, Murdoch, West
Australia, 6150, Australia. d
Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese
Academy of Sciences, Beijing, 100190, P. R. China. ‡ Present address: International Iberian Nanotechnology Laboratory (INL), Avenida Mestre José Veiga, Braga, 4715-330, Portugal.
Corresponding author email:
[email protected]
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Table S1 Physical properties of the mesoporous aluminium magnesium oxide composites calcined at 900 °C. Sample
SBET
PSD
Vsp
Phase
[m2 g-1]a [nm]b
[cm3 g-1]c
172.8
10.80
0.45
γ-Al2O3
meso-90Al10Mg-900 174.9
10.84
0.47
γ-Al2O3 & MgAl2O4 spinel
meso-80Al20Mg-900 144.1
12.08
0.41
γ-Al2O3 & MgAl2O4 spinel
meso-70Al30Mg-900 91.6
13.52
0.31
γ-Al2O3 & MgAl2O4 spinel
meso-50Al50Mg-900 121.9
13.41
0.36
MgAl2O4 MgO
spinel
&
cubic
meso-30Al70Mg-900 101.4
8.57
0.27
MgAl2O4 MgO
spinel
&
cubic
meso-Al-900
a
SBET = BET specific surface area obtained from nitrogen adsorption data in the P/P0 range from 0.05 to 0.20. b PSD = pore size distribution determined by using the BJH method from the adsorption branch. c Vsp = single point pore volume calculated from the adsorption isotherm at P/P0 = 0.98.
Table S2 As(V) adsorption kinetic parameters of the mesoporous aluminium magnesium oxide composites calcined at 400 °C. Samples
Pesudo-second-order kinetic parameters k [g mg-1 min-1]
qe [mg g-1]
R2
1.02×10-4
147.71
0.999
meso-90Al10Mg-400 9.25×10-5
125.63
0.996
meso-80Al20Mg-400 7.14×10-5
178.57
0.998
meso-70Al30Mg-400 5.20×10-5
181.82
0.996
meso-50Al50Mg-400 5.76×10-5
165.84
0.998
meso-30Al70Mg-400 2.67×10-4
74.52
0.998
meso-Al-400
meso-Mg-400
1.62×10-4
207.90
0.999
Al-400
1.35×10-4
17.30
0.897
2
Table S3 As(V) adsorption isotherm parameters of the mesoporous aluminium magnesium oxide composites calcined at 400 °C. Sample
meso-Al-400
Highest adsorptionLangmuir isotherm capacity [mg g-1]a qm [mg g-1] b R2
Freundlich isotherm KF
1/n
R2
299.03
271.83
0.4057 0.9716 94.55
0.1806 0.8621
meso-90Al10Mg-400 430.92
333.29
0.2536 0.8485 100.43 0.2100 0.9437
meso-80Al20Mg-400 502.97
422.09
0.0590 0.8902 95.85
0.2456 0.9795
meso-70Al30Mg-400 487.56
438.80
0.0321 0.8916 89.69
0.2531 0.9838
meso-50Al50Mg-400 466.02
416.25
0.0292 0.8778 86.18
0.2486 0.9730
meso-30Al70Mg-400 396.06
587.45
0.0022 0.8630 18.33
0.4482 0.9212
meso-Mg-400
912.32
928.95
0.1296 0.9692 242.32 0.2346 0.8059
Al-400
72.20
72.48
0.0259 0.9120 15.42
0.2362 0.9635
a
The highest adsorption capacity was achieved using an initial arsenic concentration of 1020 mg L-1.
Table S4 As(V) adsorption isotherm parameters of the mesoporous aluminium magnesium oxide composites calcined at 900 °C. Sample
meso-Al-900
Highest adsorptionLangmuir isotherm capacity [mg g-1]a qm [mg g-1] b R2
Freundlich isotherm KF
1/n
R2
79.21
76.36
0.5496 0.9748 38.29
0.1203 0.8421
meso-90Al10Mg-900 92.61
87.76
1.9477 0.9732 46.58
0.1134 0.8331
meso-80Al20Mg-900 70.94
58.45
1.4830 0.9254 32.65
0.1090 0.9206
meso-70Al30Mg-900 43.78
35.42
0.7144 0.8900 20.10
0.1036 0.8942
meso-50Al50Mg-900 97.56
91.32
0.5279 0.8189 46.71
0.1163 0.7739
meso-30Al70Mg-900 165.85
159.01
1.079
0.1397 0.7750
0.9087 71.23
a
The highest adsorption capacity was achieved using an initial arsenic concentration of 1020 mg L-1.
Table S5 As(III) adsorption isotherm parameters of the mesoporous aluminium magnesium oxide composites calcined at 400 °C.
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Highest adsorptionLangmuir isotherm capacity [mg g-1]a qm [mg g-1] b
R2
114.85
120.49
0.1091
0.9815 15.37 0.3171 0.9497
meso-90Al10Mg-400 143.12
157.58
0.0192
0.9901 18.10 0.3336 0.8784
meso-80Al20Mg-400 390.59
424.26
0.0011
0.9320 2.19
0.8137 0.9861
meso-70Al30Mg-400 330.58
416.24
0.0018
0.9452 3.21
0.7288 0.9720
meso-50Al50Mg-400 240.78
394.71
0.0022
0.9919 4.18
0.6243 0.9918
meso-30Al70Mg-400 120.39
196.06
0.0019
0.9731 1.91
0.6264 0.9694
meso-Mg-400
848.72
0.1007
0.9214 162.8 0.2945 0.7509
Sample
meso-Al-400
812.84
Freundlich isotherm KF
R2
1/n
a
The highest adsorption capacity was achieved using an initial arsenic concentration of 820 mg L-1. Table S6 Atomic ratios of the mesoporous aluminium magnesium oxide composites calcined at 400 °C before and after adsorption of 400 mg L-1 of As(V) at pH 3.0 or As(III) at pH 7.0 obtained from XPS analysis. Sample
Atomic ratio Al
Mg
Al/Mg
As
meso-Al-400
16.07
0
0
As(V)-meso-Al-400
25.85
0
4.61
As(III)-meso-Al-400
17.27
0
2.23
Meso-80Al20Mg-400
1.37
6.22
4.54
0
As(V)-meso-80Al20Mg-400
10.31
1.11
9.29
3.07
As(III)-meso-80Al20Mg-400
17.06
1.72
9.92
4.41
meso-Mg-400
0
10.39
0
As(V)-meso-Mg-400
0
20.6
5.9
As(III)-meso-Mg-400
0
13.86
3.38
4
Figure S1 A photoograph of thhe as-preparred mesoporrous aluminnium magneesium oxidees calcined C. at 400 °C
5
F Figure S2 T TEM imagees of (a) m meso-50Al500Mg-400, (bb) meso-30Al70Mg-4000 and (c) m meso-Mg-4400. P Particle sizee distributioon of (d) meso-50Al50 m 0Mg-400, (e) meso-300Al70Mg-4000 and (f) m meso-Mg-4400. T TEM imagees of (g) meso-Al-9000, (h) meeso-90Al100Mg-900, (i) meso-800Al20Mg-9000, (j) meeso770Al30Mg-9900 and parrticle size ddistribution of (k) mesoo-70Al30M Mg-900. Oveer 150 nanooparticles w were aanalyzed forr particle sizze distributioon statistics by using sooftware Nannomeasure 11.25 and Oriigin 9.0.
6
mage (a), X XRD patternn (b) and thhe nitrogen gas sorption isotherm (c) of the Figure S3 TEM im s Al-4400 synthesiized in the aabsence of tthe P123 sofft template. control sample
a
0.1
q (Å-1 )
0 0.2
Intensity (a.u.)
Intensity (a.u.) 0.0
meso-Al-900 0 meso-90Al10 0Mg-900 meso-80Al20 0Mg-900 meso-70Al30 0Mg-900 meso-50Al50 0Mg-900 meso-30Al70 0Mg-900 meso-Mg-90 00
b
meso-A Al-900 meso-9 90Al10Mg-900 0 meso-8 80Al20Mg-900 0 meso-7 70Al30Mg-900 0 meso-5 50Al50Mg-900 0 meso-3 30Al70Mg-900 0 meso-M Mg-900
0.3
10
20
30 0
40
50 0
60
70 0
80
2 2-Theta (deg gree)
Figure S4 (a) Syncchrotron SA AXS and (bb) wide angle XRD pattterns of meesoporous aaluminium magnesiium oxide samples withh varying M Mg/Al molarr ratios calciined at 900 °°C.
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Intensity (a.u.)
Mg
C 1s
Au ge r
O 1s
Mg 1s meso-Mg-400
Mg 2p Mg 2s
Mg 1s meso-80Al20Mg-400
Al 2s O2
s
meso-Al-400
Al 2p
0
200
400
600
800
1000
1200
1400
Binding Energy (eV) Figure S5 The full XPS survey of meso-Al-400, meso-80Al20Mg-400 and meso-Mg-400.
8
Volume Adsorbed (cm 3 g -1 )
a
500 400 300
meso-Mg-900 meso-30Al70Mg-900 meso-50Al50Mg-400 meso-70Al30Mg-900 meso-80Al20Mg-900 meso-90Al10Mg-900 meso-Al-900
200 100 0 0.0
0.2
0.4
0.6
0.8
1.0
Relative Pressure (P/P0 ) 0.14
b
dV/dD (cm3g-1 nm-1 )
0.12 0.10 0.08 meso-Al-900 meso-90Al10Mg-900 meso-80Al20Mg-900 meso-70Al30Mg-900 meso-50Al50Mg-900 meso-30Al70Mg-900 meso-Mg-900
0.06 0.04 0.02 0.00 0
20
40
60
Pore Diameter (nm)
80
100
Figure S6 Nitrogen gas sorption isotherms of the mesoporous aluminium magnesium oxides with varying Mg/Al molar ratios calcined at 900 °C and (b) the corresponding pore size distribution derived from the adsorption branches based on the BJH model. Each subsequent curve is shifted up the y axis by 30 cm3 g-1 in (a) and 0.01 cm3 g-1 nm-1 in (b), for clarity.
9
2 200
meso-Al-900 meso-90Al10Mg-900 meso-80Al20Mg-900 meso-70Al30Mg-900 meso-50Al50Mg-900 meso-30Al70Mg-900
As(V) uptake (mg g-1)
150
100
50
0 0
200
400
600
80 00
1000 0
1200 -1
Equilibrium concentrration of As(V) A (mg L ) V) on mesooporous alum minium maagnesium oxxides with Figure S7 Adsorpttion isotherrms of As(V varying Mg/Al mollar ratios caalcined at 9000 °C. Expeerimental coonditions: doose = 0.5 g L-1, initial m 10 to 1000 mg L-1. pH = 3.00, the initiall As(V) concentration rranged from
Figure S8 S Distributtion of As(V V) and As(IIII) species under differrent pH valuues. Reprodduced with permissiion [P. Ravvenscroft, H H. Brammerr, K. Richarrds, Arsenicc Pollution:: A Global Synthesis, Wiley-B Blackwell, U USA 2009, ppp. 25]. Coppyright 20009, John Willey & Sons.
10
& & & &
100
100
80
80 60 60 40 40 20
20 0
-
As(V) only NO3
Cl
-
SO42-
CO 32-
SiO32-
3-
As(V) removal percentage (%)
As(V) uptake (mg g -1)
120
meso-Al-400 meso-80Al20Mg-400 meso-70Al30Mg-400 meso-Mg-400
0
PO4
Co-existing anions
Figure S9 Effect of co-existing anions on the adsorption capacities of meso-Al-400, meso80Al20Mg-400, meso-70Al30Mg-400 and meso-Mg-400 for As(V). Experimental conditions: dose = 0.5 g L-1, initial pH = 6.0, initial As(V) concentration = 50 mg L-1; initial concentration of co-existing anions: 10 mg L-1 of NO3-, 200 mg L-1 of Cl-, 200 mg L-1 of SO42-, 50 mg L-1 of CO32-, 50 mg L-1 of SiO32- or 50 mg L-1 of PO43-.
11
meso-80Al200Mg-400, ((c) and (d) m meso-MgFigure S10 TEM iimages of ((a) meso-All-400, (b) m -1 V) solution at an initial pH of 3.0. 400 afteer adsorptionn of 400 mgg L of As(V
c
After ads sorption of As(III)
After ads sorption of As(V)
After adsorp ption of As(III)
After adsorp ption of As(V)
MgO Mg(OH)2 Unindexed phase p
Intensity (a.u.)
Intensity (a.u.)
b
Intensity (a.u.)
a
After adsorption of As(III)
After adsorption n of As(V)
mes so-Mg-400 meso-80Al20Mg-400
meso-Al-400 20 0
40
60
2-Theta (degree)
8 80
20
40
60
2-Theta (degre ee)
80
20
40
60
80
2-T Theta (degree)
Figure S11 XRD ppatterns of tthe adsorbennts before aand after adsorption of 400 mg L-11 of As(V) and As(III) at the innitial pH off 3.0 and 7.00, respectivvely: (a) meso-Al-400, (b) meso-800Al20MgMg-400. 400 andd (c) meso-M
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a
O 1s
C 1s
b
O 1s
C 1s
Au ge r
As 2p
Mg 2p
As 2p
As Auger
meso-80Al20Mg-400
As 3d Al 2p meso-Al-400
Mg 1s
Mg
meso-Mg-400
N 1s
Intensity (a.u.)
Intensity (a.u.)
Mg 1s
meso-Mg-400
As Auger
As 3d
meso-80Al20Mg-400
Mg 2p Mg 2s
meso-Al-400
Al 2s Al 2p
0
200
400
600
800
1000
Binding Energy (eV)
1200
1400 0
200
400
600
800
1000
1200
1400
Binding Energy (eV)
Figure S12 The full XPS survey of meso-Al-400, meso-80Al20Mg-400 and meso-Mg-400 after adsorption of 400 mg L-1 of (a) As(V) and (b) As(III). Experimental conditions: dose = 0.5 g L-1, initial pH for As(V) and As(III) adsorption is 3.0 and 7.0, respectively.
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meso-Al-400 after adsorption of As(V) after adsorption of As(III)
74.81 eV 74.75 eV
65
70
75
80
40
85
42
Al 2p
meso-80Al20Mg0-400 after adsorption of As(V) after adsorption of AS(III)
74.83 eV 74.65 eV
65
80
85
45.89 eV As(V)-O
45.8 eV As(V)-O
e
42
44
48
50
40
42
45.9 eV As(V)-O
40
As 3d-Mg 2p
42
f
44
46
48
50
52
54
Binding Energy (eV) 50.6 eV Mg-O
h 44.5 eV
As 3d
44.8 eV As(III)-O
52
50.4 eV Mg-O
40
44
46
48
Binding Energy (eV)
44.96 eV
50
52
As 3d-Mg 2p
44.7 eV As(III)-O 45.6 eV As(V)-O 50.8 eV Mg-O
42
44
46
48
50
52
54
Binding Energy (eV) 49.64 eV
As 3d-Mg 2p 49.4 eV
As(III)-O Intensity (a.u.)
Intensity (a.u.)
75
Binding Energy (eV) As 3d-Mg 2p
g
40
70
46
Intensity (a.u.)
Intensity (a.u.)
74.51 eV
44
45.0 ev
c
Binding Energy (eV)
Binding Energy (eV)
d
As 3d
45.88 eV As(V)-O
Intensity (a.u.)
b Intensity (a.u.)
Intensity (a.u.)
74.44 eV
Intensity (a.u.)
Al 2p
a
46
48
50
52
Binding Energy (eV)
54
56
40
Mg-O-H 50.3 eV Mg-O
42
44
46
48
50
52
54
Binding Energy (eV)
Figure S13 (a) Al 2p XPS peak of meso-Al-400 before and adsorption of As(V) and As(III), (b) As 3d peak of meso-Al-400 after adsorption of As(V), (c) As 3d peak of meso-Al-400 after adsorption of As(III), (d) Al 2p XPS peak of meso-80Al20Mg-400 before and after adsorption of As(V) and As(III), (e) As 3d and Mg 2p peak of meso-80Al20Mg-400 after adsorption of As(V), (f) As 3d and Mg 2p peak of meso-80Al20Mg-400 after adsorption of As(III), (g) and (h) As 3d and Mg 2p peak of meso-Mg-400 after adsorption of As(V) and As(III), respectively. Experimental conditions: dose = 0.5 g L-1, initial concentration of As(V) or As(III) = 400 mg L-1; initial pH for As(V) and As(III) adsorption is 3.0 and 7.0, respectively.
As shown in Figure S13a and d, for both meso-Al-400 and meso-80Al20Mg-400, the Al 2p peak shifts towards lower binding energy after adsorption of As(V), while the Al 2p peak moves slightly towards higher binding energy after As(III) adsorption. This difference in the Al 2p peak shift after adsorption of As(V) or As(III) over meso-Al-400 and meso-80Al20Mg-400 is likely to be due to the following reasons: 1. The initial pH is different for adsorption of As(V) or As(III) over the samples for the XPS measurement. In this work, the initial pH for As(V) and As(III) adsorption on both meso-Al-400
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and meso-80Al20Mg-400 is 3.0 and 7.0, respectively. The initial pH affects the different dominant arsenic speciation, As(V) (H2AsO4-) and As(III) (H3AsO30), which in turn caused the different shift of the Al 2p peak when forming Al-O-As bonds during the XPS measurement. 2. There are various models of surface complexes for the arsenic (including As(V) and As(III)) immobilization on aluminium oxy-hydroxides and other metal hydroxides/oxides. Most publications proved that arsenic can be adsorbed onto variable-charge adsorbent surfaces by inner-sphere complexation (ligand exchange to form chemical bonding) and/or outer-sphere complexation (electrostatic interaction or hydrogen bonding)(Geoderma 2001, 100, 303–319). The type of sorption mechanism for a particular ion is greatly affected by environmental factors such as pH and ionic strength. For the inner-sphere surface complex, there are four molecular configurations including bidentate binuclear, bidentate mononuclear, monodentate binuclear and monodentate mononuclear (Geochimica et Cosmochimica Acta 2012, 83, 205–216; Geochimica et Cosmochimica Acta 2001, 65, 1211-1217). For each configuration, acid-base or non-dissociative sorption could be included (Journal of Molecular Structure: THEOCHEM 2006, 762, 17–23; Geochimica et Cosmochimica Acta 2012, 83, 205–216). The specific mechanism would be elucidated by X-ray absorption spectroscopy (XAS) including EXAFS and XANES. Generally, the adsorption mechanism is considered to be different for As(V) or As(III) immobilized on the aluminium oxides, although there is no consensus on the exact mechanism applied for either As(V) or As(III). Most publications reported that As(V) predominantly forms inner-sphere bidentate binuclear complexes with the surface of aluminium oxide (Chemosphere 2004, 55, 1259-1270; Journal of Colloid and Interface Science 2001, 234, 204–216; Environmental Science & Technology 2005, 39, 5481-5487; Environmental Toxicology and Chemistry 2006, 25, 3118-3124; Journal of Colloid and Interface Science 2001, 235, 80–88; Applied Geochemistry 2013, 31, 79–83; Environmental Science & Technology 2011, 45, 9687–9692), while some papers claimed the inner-sphere monodentate mononuclear complexes (Environmental Science & Technology 2009, 43, 2537–2543) and co-existing inner-sphere, hydrogen bond and electrostatic interactions would dominate depending on the pH (Journal of Hazardous Materials 254– 255 (2013) 301– 309; Environmental Science & Technology 2006, 40, 7784-7789; Environmental Science & Technology 2005, 39, 3571-3579; Microporous and Mesoporous Materials 2014, 198, 101–114; Geochimica et Cosmochimica Acta 2008, 72, 1986–2004). The dominant complexes debated for As(III)-aluminium oxide surface complexation including outer-sphere (Chemosphere 2003, 51, 1001-1013; Journal of Colloid and Interface Science 2001, 234, 204–216; Soil Science Society of America Journal 70:2017–2027; Environmental Chemistry Letters 2013, 11, 289–294), non-dissociative inner-sphere complexes (Journal of Molecular
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Structure: THEOCHEM 2006, 762, 17–23), inner-sphere bidentate binuclear (Geochimica et Cosmochimica Acta 2012, 83, 205–216; Microporous and Mesoporous Materials 2014, 198, 101–114), a combination of inner-sphere bidentate binuclear and bidentate mononuclear (Chemosphere 2014, 113, 151–157), as well as co-existing mixtures of several surface innersphere complexes and outer-sphere complexes (Journal of Colloid and Interface Science 2001, 235, 80–88). Because of the different kinds of surface complexes obtained through chemical bonding (innersphere configurations) and possible discernable intervention from electrostatic outer-sphere complexes, the XPS peak shift is likely different between As(V) at pH 3.0 and As(III) at pH 7.0, even if the As(V) and As(III) species are chemisorbed onto the surface of meso-Al-400 and meso-80Al20Mg-400 forming As-O-M bonds. The different kinds of surface complexes have been reported to cause either a positive or negative Al 2p peak shift in the Fe/Al hydroxide when adsorbing different speciations of As(V), indicating that the Al 2p peak shift is not necessarily consistent even though an As-O-Al bond is formed. (Journal of Hazardous Materials 2015, 293, 97–104)
b
After adsorption of 400 ppm of As(V)
After adsorption of 400 ppm of As(III)
meso-Mg-400
c
meso-80Al20Mg-400
After adsorption of 400 ppm of As(V)
Transmittance
meso-Al-400
Transmittance
Transmittance
a
After adsorption of 400 ppm of As(V)
After adsorption of 400 ppm of As(III)
After adsorption of 400 ppm of As(III)
819 cm-1
3700 cm -1
4000
3500
3000
2500
2000
1500
1000
Wavelength Number (cm-1 )
500
4000
3500
3000
2500
2000
1500
1000
Wavelength Number (cm-1 )
500
4000
3500
841 cm -1
3000
2500
2000
1500
1000
500
Wavelength Number (cm -1 )
Figure S14 FTIR spectra of the vacuum-dried samples before and after adsorption of arsenic: (a) meso-Al-400, (b) meso-80Al20Mg-400 and (c) meso-Mg-400. Experimental conditions: dose = 0.5 g L-1, initial concentration of As(V) or As(III) = 400 mg L-1; initial pH for As(V) and As(III) adsorption is 3.0 and 7.0, respectively.
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300
As(V) uptake (mg g-1)
250 200 150 100 50 0 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Dose (g L-1) Figure S15 Effect of the adsorbent dose on the As(V) adsorption capacity of meso-Al-400. The mass of meso-Al-400 was 0.02 g, the initial pH was 3.0 ± 0.1 and the initial As(V) concentration is 420 mg L-1. The volume of As(V) solution was varied from 10 to 100 mL, resulting in the dose ranging from 0.2 g L-1 to 2.0 g L-1. Please note that the adsorbent dose was 0.5 g L-1 throughout the work. Figure S15 demonstrates that 0.5 g L-1 is the optimal adsorbent dose with the highest adsorption capacity (260 mg g-1) for As(V). When the dose was increased to 1.0 and 2.0 g L-1, the adsorption capacity was decreased by 25.4% and 42.3%, respectively.
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