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Intrinsic activity of SBA-like silica in the catalytic ozonation of organic pollutants
R.Ouargli, S.Larouk, I. Terrab, R.Hamacha, N.Benharrats, A.Bengheddach , A.Azzouz *
SUPPORTING INFORMATION
1. SBA synthesis procedures
Triblock copolymer Pluronic P123, (EO20PO70EO20, MW = 5800, Sigma–Aldrich), Pluronic F127 block-copolymer (EO106PO70EO106;
MW=12600, Aldrich), Tetraethyl orthosilicate (TEOS, Si(OC2H5)4, MW =208.33), Hydrochloric acid (HCl, 37%, Fluka), phenol (ACCUGEN), oxalic
acid (99.5% purity, supplied by Anachemia Canada Inc.), orange G (Biochem.Chemopharma), High-purity water (Milli-Q) were used for the the
synthesis of mesoporous SBA-15 and SBA-15 silica's. The other reagents used were of analytical.
SBA-15-like silica was prepared as fully described elsewhere [10]. In a typical synthesis, 6 g of Pluronic P123 was dissolved in 45 g of water and
180 g of 2 M HCl solution and stirred at 308 K until total dissolution. TEOS (12.5 g) was added to that solution and stirred at 308 K for 20 h. The mixture
was then aged at 373 K for 24 h. The white powder was recovered by filtration, washed with water and dried at 323 K overnight. The product was
calcined at 773 K for 6 h at a 1 K/min heating rate. Synthesis of SBA-16-like silica was carried out according to another procedure reported by literature
[26]. Thus, a 0.47 g amount of P123 and 2.33 g quantity of F127 were dissolved in a mixture of 24 g of water, and 113 g of HCl (2M) were added under
stirring at 300 K for 1 hour. After complete dissolution, 10.4 g of TEOS were added and the water-copolymer mixture was stirred 20 h at 310 K. The
resulting suspension was transferred into tightly closed vessel heated at 383 K without stirring for 48 h. The white solid powder obtained was
successively filtered, washed repeatedly with deionized water, air dried and calcined at 773 K for 6 h at a 1 K.min-1 heating rate.
2. Thermal programmed desorption measurements
Thermal programmed desorption of carbon dioxide (CO2-TPD) were used to assess the basicity and the hydrophilic character of the catalyst
surface, expressed in terms of the CO2 and water retention capacities values (CRC and WRC, respectively) (Table S1).
Table S1. CRC of SBA samples assessed by TPD measurements between 20 and 80oC
mL dry CO2 injected
per 40 mg SBA sample*
1.5
50
100
200
300
500
26
27
28
CRC (micromol.g-1)
SBA-15
SBA-16
14.5
9.3
32.5
12.4
37.8
14.5
38.4
19.5
75.0
13.4
52.3
16.5
WRC (picomol.g-1)
SBA-15
SBA-16
1.02
0.61
0.95
0.85
1.04
0.51
0.94
0.67
1.15
0.60
1.09
0.36
* Prior to TPD measurements, dry CO2 was contacted with fresh SBA samples for 12h, without any previous
dehydration. The CO2 and water retention capacities values (CRC and WRC, respectively) were used
to express the surface basicity of the SBA catalysts and their hydrophilic character, respectively.
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3. UV-Vis spectra and calibration curve in water (Fig. S1)
I is worth mentioning that the max value shifted from 190 nm to 195 nm as OA concentration increased from 10-4 to 10-3 M, most likely due
change in the proportion of the protonated form. For the sake of accuracy, a calibration curve was plotted on the basis of average max values assessed
between 192 and 193 nm. Under these conditions, the molar extinction coefficient of OA was found to be 2.79 L.mmol-1.cm-1 with a high correlation factor
(R2) of 0.9969.
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Fig. S1.UV-Vis spectra and calibration curves of oxalic acid (a), phenol (b) and orange G (c)
in water at intrinsic pH at room temperature.
Phenol UV-Vis spectrophotometry in water showed two major adsorption bands that dramatically decrease with decreasing concentrations. The
first band observed at 207-215 nm was ascribed ton-* electron transition between the oxygen electron pair and the phenyl group. Phenol calibration
curve for this band gave a slope which accounts for an absorption coefficient of 4.89 L.mmol-1.cm-1 (with a correlation factor R2 of 0.9873). The second
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band recorded at approximately 270 nm showed an absorption coefficient of 1.39 L.mmol-1.cm-1 (with a correlation factor R2 of 0.9900), and corresponds
to -* electron transition occurring in the phenyl ring ().The third adsorption band at 192 nm must be due to σ-σ* electron transition in the O-H bond
of water molecule. In pure water this band should lie at lower wavelength, but phenol protonation in water is expected to produce a bathochromic effect.
Phenol has two pKa values of 6.4 (PhOH2+/PhOH) and 9.95 (PhOH/PhO-), and is assumed to undergo two protonation processes in water according to
the pH level. In water, a 10-2 M phenol concentration accounts for a pH around 2.0, and phenol is supposed to be totally protonated within the
concentration range 0-10-2 M. Beer-Lambert’s law can be applied within the whole phenol concentration investigated (0-1 mmol.L-1) for the 270 nm
band, but only at phenol concentration not exceeding 0.4 mmol.L-1 for the 207-215 nm band.
Accurate assessment of the molar extinction coefficients of each organic substrate was achieved using the slopes of the calibration curve for each
characteristic UV-Vis band (Table S2).
Table S2. Molar extinction coefficients of the probe molecules studied in water
Molar extinction coefficients (L.mmol-1.cm-1) a
192-193
207-215
259
270
328
421
478
max (nm)
2.79
Oxalic

acid
R2
0.9969
4.89
1.39

Phenol
R2
0.9873
-0.9900
15.75
10.78
6.14
20.88

Orange G
R2
0.914
0.9839 0.9672 0.9985
a
The molar extinction coefficient was assessed in the concentration range [0, 0.5.10-3M]
for oxalic acid, [0, 0.4.10-3M] for phenol and [0, 0.07.10-3M] for orange G.
Compound
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4.
Additional details for HPLC-TOF-MS analysis and product identification
The organic substrates and other ozonation intermediates were identified and quantified using tandem mass technique (MS–MS) in multiple reaction
monitoring (MRM) mode and exact mass measurements via (ESI–TOF). Multiple reactions monitoring (MRM) is a selective and sensitive LC–MS/MS
technique in which each ionized compound gives a distinct precursor-to-product ion transition. Peaks containing co-eluting compounds were resolved by
monitoring for specific precursor-to-product ion transitions. Confirm of the exact masses and empirical formulae of each of the identified structures were
achieved using another instrument (ESI–TOF) under the same conditions. MRM acquisition was carried out for each intermediate by monitoring
transitions of the combination of the parent ion mass and the fragment ions.
The measurements were performed under the following operating conditions:
Table S3. Operating conditions for HPLC-TOF-MS analysis
Agilent 1200 Series HPLC
Column : Agilent Eclipse Plus C18 (3 x 50 mm, 1.8
μm), at room temperature
Mobile phase A: H2O + 0.1% formic acid
Mobile phase B: ACN + 0.1% formic acid
Injection volume: 20 μl
Solution gradient slope in time:
Temps (min)
0.0
1.0
3.0
10.0
10.5
12.0
12.1
16.0
%B
5.0
5.0
30.0
60.0
95.0
95.0
5.0
5.0
Agilent TOF-MS 6210
Ionization source:
through electronébulization (electrospray ionization, ESI)
Mode: négative
Mass range : m/z 50-1000
Source temperature: 350 °C
Source voltage : 4000 V
The data were processed by the Mass Hunter software; ii. In system 2, the same aforementioned column was used. A similar HPLC equipment under
similar conditions was connected to an Agilent 6210 electrospray ionization-time-of flight MS-analyzer (ESI–TOF) in positive ESI mode, at a capillary
voltage of 4000 V, nebulizer pressure of 35 Psi, a gas temperature of 350⁰C, drying gas flow: 11.5 L.min-1 and voltages of 125 V and 60 V for the
fragmentor and skimmer, respectively. The analysis error and mass resolving power of the time-of-flight mass spectrometer in terms of mass accuracy
was 5 ppm. A reserpine solution with m/z 609.2807 for [M+H]+ ion was used as an internal standard for mass reference
The mass axis was calibrated over the m/z range of 50-1000. MS spectra were recorded over the m/z 50-500 range at a scan rate of 0.5 seconds per
spectrum. The data recorded were processed with Agilent Mass Hunter Workstation software. The LC–TOF system was equipped with Agilent software
that allowed calculating and generating the molecular formula of each compound according to its mass spectrum obtained during analysis, whereas the
triple quadrupole MS/MS system was used to confirm the product ions.
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5. Ozonation of oxalic acid
Fig. S2. UV-Vis spectra of oxalic acid at different ozonation times without catalyst (a) and evolution in time of the 195 nm band (b).Initial OA
concentration: 10-3M at intrinsic pH.
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113
HPLC-ToF-MS analysis of oxalic acid
114
115
116
117
118
119
120
Fig. S3. MS spectrum and LC retention time for oxalic acid after 5 min ozonation without catalyst. No apparent oxalic acid degradation was registered
when no catalyst was used, and only weak decomposition yields not exceeding 3-5 % were noticed within this reaction time in the presence of SBA
catalysts, regardless to the catalyst amount employed.
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6.
HPLC-ToF-MS analysis of phenol and derivatives after ozonation without catalyst
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127
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Fig. S4. MS spectrum and LC retention time for phenol after 1 min ozonation without catalyst.
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135
In negative analysismode of LC-ToF-MS, the closest molecular ion ([M−H]− ion) has an m/z factor equal to the molecular weight of the corresponding
neutral molecule minus 1 (z=1; m/z=M-1). On the basis of this hypothesis, a wide variety of OG derivatives were detected, the most predominant
identified being summarized in Table S4.
Table S4. Identification of the main intermediates by LC-ESI (+) TOF for phenol ozonation (with and without catalyst).
Intermediate
Retention
time (min)
Formula
Measured
mass
Discrepancy from
theoretical mass (ppm)
Phenol
5.553
C6H6O
94.0418
-1.1
Benzoquinone
3.83
C6H4O2
108.0210
-0.22
Structure
O
Muconic acid
4.40
C6H6O4
3.79
HO
OH
O
Maleic acid
Glyoxal
1.058
1.01
C4H4O4
C2H2O2
116.0121
58.0055
2.58
H
O
O
H
2.12
HO
Oxalic acid
0.603
C2H2O4
89.9954
O
136
137
138
139
140
141
142
143
144
145
146
8
O
0.47
OH
147
148
149
150
151
152
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157
158
159
7. UV-Vis analysis in SBA-catalyzed phenol ozonation
The various catalyst amounts used in these experiments correspond to 1, 2, 3, 4 and 5 mg of SBA-like silica’s dispersed in 20 mL samples of
phenol solution. Both catalysts were used as solid powders in their original particle sizes.
Fig. S5. UV-Vis spectra of phenol after 5 min ozonation with different amounts of as-synthesis (a) and calcined (b) SBA-15 and SBA-16 (c and d,
respectively) as compared with phenol UV-Vis spectrum in water. Phenol concentration: 10-3M.
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8.
Ozonation of orange-G
Fig. S6. UV-Vis spectra of orange G after 5 min ozonation with different amounts of as-synthesis (a)
and calcined (b) SBA-15 and SBA-16 (c and d, respectively). OG concentration: 10-4M.
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167
a
168
169
170
171
172
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180
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185
186
b
Fig. S7. Relative absorbance versus amount of as-synthesized SBA15 (a) and SBA-16 (b).
Ozonation time: 5 min; OG initial concentration: 10-4M.
The relative absorbance (A/Ao) was calculated for each UV-Vis band as the absorbance registered for a given ozonation mixture divided by the
absorbance of the 10-4M OG concentration after ozonation during 5 min. The values of (A/Ao) for a given adsorption band should be respectively
proportional to the amounts of unconverted groups belonging to the OG molecule after ozonation. The starting point of each curve corresponds to
the relative absorbance of an OG solution after ozonation during 5 min. The various catalyst amounts used in these experiments correspond to 1,
2, 3, 4 and 5 mg of SBA-like silica’s dispersed in 20 mL OG solution samples. Both catalysts were used as solid powders in their original particle
sizes, as already reported in section 3.2.
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Fig. S8. Total ion current chromatogram after orange-G ozonation without catalyst
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Fig. 9. Total ion current chromatogram after orange-G ozonation in the presence of SBA-16.
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195
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207
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HPLC-TOF-MS analysis of the main intermediates after OG ozonation
No catalyst EIC m/z 422.9962 – Orange G + O (C16 H12 N2 O8 S2)
Fig. S10. Evolution in time of the amount of the OG+O intermediate after ozonation without catalyst
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Series 2 SBA16 EIC m/z 422.9962 – Orange G + O (C16 H12 N2 O8 S2)
Fig. S11. Evolution in time of the amount of the OG+O intermediate after ozonation in the presence of SBA-16.
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No Catalyst EIC m/z 109.0295 – Catechol or Hydroquinone C6H6O2
Fig. S12. Evolution in time of the amount of Catechol or Hydroquinone after ozonation without catalyst
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230
Series 2 EIC m/z 109.0295 – Catechol or Hydroquinone C6H6O2
Fig. S13. Evolution in time of the amount of catechol or hydroquinone after ozonation in the presence of SBA-16.
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232
No Catalyst Mass spectra 5.1 min – Catechol or Hydroquinone C6H6O2 exact mass [M-H]- 109.0295
m/z 100-250
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234
235
Fig. S14. Mass spectra of catechol or hydroquinone after ozonation without catalyst.
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240
241
242
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244
Series 2 Mass spectra 4.9 min– Catechol or Hydroquinone C6H6O2 exact mass [M-H]- 109.0295
m/z 100-250
Fig. S15. Mass spectra of catechol or hydroquinone after ozonation in the presence of SBA-16.
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246
247
248
249
250
Series 2 EIC m/z 115.0037 – Maleic acid C4H4O4
Fig. S16. Evolution in time of the amount of maleic acid after ozonation in the presence of SBA-16.
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254
255
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257
Series 2 Mass spectra – Maleic acid C4H4O4 exact mass [M-H]- 115.0037
m/z 100-185
Fig. S17. Mass spectra of maleic acid after ozonation ozonation in the presence of SBA-16.
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260
261
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263
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No Catalyst EIC m/z 147.0088 – Phthalic anhydride C8H4O
Phthalic anhydride not detected in the no-catalyst series
-peak at 0.8 min is not close enough to exact mass
Series 2 EIC m/z 147.0088– Phthalic anhydride C8H4O3
Fig. S18. Evolution in time of the amount of phthalic anhydride (C8H4O3) after ozonation in the presence of SBA-16.
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270
271
No catalyst EIC m/z 165.0193 – C8H6O4 Phthalic acid
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275
Fig. S19. Evolution in time of the amount of phthalic acid (C8H4O3) after ozonation without catalyst.
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280
281
Series 2 EIC m/z 165.0193 – C8H6O4 Phthalic acid
Fig. S20. Evolution in time of the amount of phthalic acid (C8H4O3) after ozonation in the presence of SBA-16..
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Fig. S21. Evolution of the mass spectra of the reaction mixture from SBA-16-catalyzed OG ozonation during the first 5 min of ozonation.
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292
In negative mode, the closest molecular ion ([M−H]− ion) has an m/z factor equal to the molecular weight of the corresponding neutral molecule minus
1 (z=1; m/z=M-1). Using this hypothesis, a wide variety of OG derivatives were detected, but only the most predominant are summarized in Table S5.
Table S5. Some of the main derivatives identified after Orange-G ozonation for 5 minutes with and without catalyst
Probable molecule
Mass of the molecular ion detected
m/z
Observed Discrepancy (ppm)
[M-H]-
Compound
identified
HPLC retention
time (min)
Molecular formula
M (g.mol.-1)
Orange-G (M)
C16H12N2O7S2
408
407.0013
407.0008
5
5.9
M+O
C16H12N2O8S2
424
422.9962
422.9973
2.5
5.7
Comment
Highest without SBA
M + 2O
C16H12N2O9S2
440
438.9911
438.9918
1.5
5.7
Highest without SBA
M + 3O
C16H12N2O10S2
456
454.9861
454.985
2.3
5.4
M - SO3
C16H12N2O4S
328
327.0445
327.045
1
8.6
Barely observed
Phthalic acid
C8H6O4
166
165.0193
165.0197
2.2
3.8; 5.7
Catechol
Hidroquinone
C6H6O2
110
110
109.0295
109.0295
109.0297
109.0297
2
2
4.9
4.9
Maleic acid
C4H4O4
116
115.0037
115.0029
7
1.1
293
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