Supplemental Material
Roles of oxysulfur radicals in the oxidation of acid orange 7 in the
Fe(III)–sulfite system
Danna Zhou1*, Yanan Yuan2, Shaojie Yang2, Hong Gao1, Long Chen3
1 Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan,
430074, P. R. China
2 Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry
and Environmental Biotechnology, School of Resources and Environmental Science,
Wuhan University, 430079, P. R. China
3 Department of Chemical and Environmental Engineering, University of California,
Riverside, Riverside, California, 92521, US.
1. Major reactions in Fe(III)-sulfite system
Table S1. Summaries of Reactions in the Fe(II/III)-Sulfite Complex System in Aqueous
Solution Containing AO7.
Reactions
Rate/equilibrium
No.
constants (k / M−1 s−1)
a
FeSO3+ → Fe2+ + SO3−
k3 = 0.19 s−1 1
(1)
Fe2+ + HSO3− → FeHSO3+
log K1 = 4 2
(2)
FeHSO3+ + 1/4O2 → FeSO3+ + 1/2H2O
k2 = 1.69 × 103 3
(3)
1
SO3− + O2 → SO5−
1–2.3 × 109 4-7
(4)
SO5− + HSO3− → SO3− + HSO5−
≤ 3 × 105 8
(5)
SO5− + HSO3− → SO42− + SO4− + H+
~1.2 × 104 9
(6)
HSO3− + SO4− → SO42− + H+ + SO3−
7.5 × 108 10
(7)
SO4− + H2O → SO42− + HO + H+
6.6 × 102 s-1 11
(8)
SO4− + OH- → SO42− + HO
1.4 × 107 11
(8)
HO + AO7 → Product w
1.2 × 1010 12
(9)
SO4− + AO7 → Product x
8.07 × 109 13
(10)
SO5− + AO7 → Product y
1.2 × 107 b
(11)
SO3− + AO7 → Product z
2.1 × 106 b
(12)
a
Second order rate constants are given unless otherwise indicated.
b
This work.
2. Experimental set-up
Mixture of the dye,
sulfite, and other
probes
Pipettor
Fe(III) solution
Deuterium Tungsten
lamp Halogen lamp
CCD detector
Quartz cuvette
Light source
Optical fiber
Magnetic stirr
Optical fiber spectrometer system
Working station
Scheme S1. Diagram of reaction set-up with optical fiber spectrometer system as on-line
analysis equipment.
2
3. Variations of dissolved oxygen
DO detection was made with a DO meter (Hach, USA) in a 200-ml beaker
containing all the reactants at the same concentrations as that in micro reaction system.
-1
DO (mg L )
Variation of DO changes during reactions are shown in Fig. S1.
7
6
5
4
3
2
1
0
-1
Fe(II)
Fe(III)
0
5
10
15
20
time (min)
Figure S1. Variations of dissolved oxygen in the Fe(III)/Fe(II)-sulfite systems during
oxidation of AO7 at pH 3. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Fe(II)]0 = 0.1 mM,
[Na2SO3]0 = 1.0 mM. [AO7]0 = 0.029 mM.
4. Reactions of AO7 at different initial concentrations
3
[AO7]0 mM
0.0058
0.015
0.029
0.044
0.058
0.06
0.05
C (mM)
0.04
0.03
0.02
0.01
0.00
0
5
10
15
20
time (min)
Figure S2. Oxidation of AO7 at different initial concentration of AO7 ([AO7]0) in the
Fe(III)-sulfite system at pH 3. The initial concentrations of AO7 were 0, 0.0058, 0.014,
0.029, 0.044 and 0.058 mM respectively. Initial Conditions: [Fe(III)]0 = 0.1 mM,
[Na2SO3]0 = 1.0 mM. k = 0.09941 min-1 = 1.66 × 10-3 s-1. k = 0.07574 min-1 = 1.26 ×
10-3 s-1.
5. Inhibition of oxidation by EtOH
4
1.0
0.8
C/C0
0.6
0.4
[EtOH]0 / [AO7]0
0.2
0.0
2
0;
4
10 ;
0
5
3
10 ;
5
10 ;
10 ;
5
4.5x10
10
15
20
time (min)
Figure S3. Effect of EtOH on the oxidation of AO7 in the Fe(III)-sulfite system at pH 3.
The initial concentrations of EtOH were 0, 2.9, 29, 290, 2900 and 13100 mM
respectively. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM, [AO7]0 =
0.029 mM.
6. Inhibition of oxidation by TBA
5
1.0
0.8
C/C0
0.6
0.4
[TBA]0/ [AO7]0
0.2
0.0
0;
4
2x10 ;
0
3
4
2x10 ;
10 ;
4
5
5x10 ;
10
5
10
15
20
time (min)
Figure S4. Effect of TBA on the oxidation of AO7 in the Fe(III)-sulfite system at pH 3.
The initial concentrations of TBA were 0, 2.9, 29, 58, 290, 580, 1450 and 2900 mM
respectively. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM, [AO7]0 =
0.029 mM.
7. Inhibition of oxidation by aniline
6
1.0
0.8
C/C0
0.6
0.4
[Aniline]0/ [AO7]0
0;
10;
0.2
0.0
0
5
10
100
15
20
time (min)
Figure S5. Effect of aniline on the oxidation of AO7 in the Fe(III)-sulfite system at pH 3.
The initial concentrations of aniline were 0, 0.29, and 2.9 mM respectively. Initial
Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM, [AO7]0 = 0.029 mM.
8. Inhibition of oxidation by diphenylamine
1.0
0.8
C/C0
0.6
0.4
[Diphenylamine]0/ [AO7]0
0;
1;
10
0.2
0.0
0
5
10
15
20
time (min)
Figure S6. Effect of diphenylamine on the oxidation of AO7 in the Fe(III)-sulfite system
7
at pH 3. The initial concentrations of diphenylamine were 0, 0.029, and 0.29 mM
respectively. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM, [AO7]0 =
0.029 mM.
9. Inhibition of oxidation by PA in the absence of 1-hextanol
1.0
C/C0
0.8
0.6
0.4
[PA]0/ [AO7]0
0;
20;
0.2
0.0
0
5
1;
40
10
10
15
20
time (min)
Figure S7. Effect of PA ((1,2,3-C6H3(OH)3)) on the oxidation of AO7 in the
Fe(III)-sulfite system at pH 3. The initial concentrations of PA were over the range of 1
~ 40 × [AO7]0. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM, [AO7]0 =
0.029 mM.
10. Inhibition of oxidation by PA in the presence of 1-hextanol
8
1.0
0.8
C/C0
0.6
0.4
[PA]0/ [AO7]0
without 1-hexanol;
1;
5;
10
0.2
0.0
0
5
10
15
0;
20
time (min)
Figure S8. Effect of PA ((1,2,3-C6H3(OH)3)) on the oxidation of AO7 in the
Fe(III)-sulfite system in the presence of 1-hexanol at pH 3. The initial concentrations of
PA were over the range of 1 ~ 10 × [AO7]0. Initial Conditions: [Fe(III)]0 = 0.1 mM,
[Na2SO3]0 = 1.0 mM, [AO7]0 = 0.029 mM, [1-hexanol]0 = 29 mM.
11. Oxidation of AO7 in the absence of DO
9
1.0
0.8
C/C0
0.6
0.4
N2
Air
0.2
0.0
0
5
10
15
20
time (min)
Figure S9. Comparison of the oxidation of AO7 in the Fe(III)-sulfite system at pH 3 in
the presence of and absence of oxygen (N2 bubble). Initial Conditions: [Fe(III)]0 = 0.1
mM, [Na2SO3]0 = 1.0 mM, [AO7]0 = 0.029 mM. kobs, N2 = 0.0812 min-1 (0-2 min).
12. Inhibition of oxidation by PA in the absence of DO
10
[PA]0/[AO7]0
0.1
0.5
2
4
1.00
C/C0
0.98
0.96
0.94
0.92
0.90
0
5
10
15
20
time (min)
Figure S10. Effect of PA ((1,2,3-C6H3(OH)3)) on the oxidation of AO7 in the
Fe(III)-sulfite system in the absence of DO at pH 3. The initial [PA]0/[AO7]0 were 0.1,
0.5, 2 and 4 respectively. Initial Conditions: [Fe(III)]0 = 0.1 mM, [Na2SO3]0 = 1.0 mM,
[AO7]0 = 0.029 mM, N2 bubbling for 20 min.
13. Estimation of the quasi steady-state concentrations of oxysulfur radicals
In the Fe(III)-sulfite system, [SO4-]ss and [SO5-]ss in the presence of DO and
[SO3-]ss in the absence of DO are calculated as follows:
[𝑆𝑂4− ]𝑠𝑠 =
𝑘𝑜𝑏𝑠,𝑆𝑂4− (0.1506 − 0.0646)/60
=
= 1.78 × 10−13 𝑀
9
−
𝑘𝑆𝑂4 ,𝑆
8.07 × 10
[𝑆𝑂5− ]𝑠𝑠 =
[𝑆𝑂3− ]𝑠𝑠 =
𝑘𝑜𝑏𝑠,𝑆𝑂5−
𝑘𝑆𝑂5−,𝑆
=
0.0646/60
= 5.13 × 10−10 𝑀
2.1 × 106
𝑘𝑜𝑏𝑠,𝑆𝑂3− 0.0812/60
=
= 1.13 × 10−10 𝑀
𝑘𝑆𝑂3−,𝑆
1.2 × 107
11
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