Electronic Supplementary Material
Selenium Catalyzed Fe(III)-EDTA Reduction by Na2SO3: A Reaction-Controlled Phase Transfer
Catalysis
Kaisong Xiang a, Hui Liua,b,*, Bentao Yang a, Cong Zhang a, Shu Yang a, Zhilou Liu a, Cao Liu a,
Xiaofeng Xie a, Liyuan Chai a,b, Xiaobo Mina,b,*
(a School of Metallurgy and Environment, Central South University, Changsha, 410083, China
b
Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution,
Changsha, 410083, China)
Corresponding authors:
Hui Liu*1: Tel.: +86 0731 88830875; Fax: +86 0731 88710171; Email address: huiliucsu@163.com;
Xiaobo Min*2: Tel.: +86 0731 88830577; Fax: +86 0731 88710171; Email address: mxbcsu@163.com;
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Fig. S1 Fe(III)-EDTA conversion after adding Na2SO3 solution then Na2SeSO3 solution. Fe(III)EDTA solution (50ml, 10mmol/L) was added with 50ml 1 mol/L Na2SO3 solution and then 10ml
0.2 mol/L Na2SeSO3 solution after 30min at 25 oC. The addition of Na2SeSO3 at the reaction time
at 30 min greatly enhances the Fe(III)-EDTA conversion.
Fe(III) conversion/%
80
a
b
c
fitting curve for a
fitting curve for b
fitting curve for c
60
40
20
0
0
5
10
15
20
25
30
Time/min
Fig. S2 Fe(III)-EDTA conversion after adding Na2SO3 solution (a), Na2SeSO3 solution (b) and Na2SO3
/ Na2SeSO3 mixture (c). Fe(III)-EDTA solution (50 ml, 10 mmol/L) was added with 50 ml 1 mol/L
Na2SO3 solution (a), 10 ml 0.2 mol/L Na 2SeSO3 solution diluted with 40 ml H2O (b), and 10 ml 0.2
mol/L Na2SeSO3 solution mixed with 40 ml 1 mol/L Na2SO3 solution separately. All the reduction
experiments were performed at 25 oC.
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Fig. S3 The ion chromatography of reference solution (a, 100 mg/L Na2SeO3, mixed with 80 mg/L
SO42-) and diluted solution (100) from Na2SO3-Na2SeSO3-Fe(III)-EDTA reduction system
(b) .The ion chromatography shows that peak I mismatches with the peak of SeO32- which means
there is no SeO32- formed in the Na2SO3-Na2SeSO3-Fe(III)-EDTA reduction system. Peak II
matches well with peak of SO42- which should be ascribed to the oxidation of SO32- or SeSO32- in
the reduction system.
Fig. S4 FT-IR spectra of Na2SeSO3 solution with varied concentration. (a) 0.04 mol/L, (b) 0.1
mol/L and (c) 0.2 mol/L. The above mentioned Na2SeSO3 solution was diluted by 1 mol/L Na2SO3
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solution. The peaks at 930 cm-1 corresponding to the S-O bond from SO32- are little changed
because the SO32- concentration of tested samples are the same. The peaks at 993cm-1 and 1117
cm-1 grow with the concentration of Na2SeSO3, which can be deduced that the characteristic peaks
ascribed to Se-S bond and S-O bond from SeSO32- are located at 993cm-1 and 1117 cm-1.
Fig. S5 EDS result of the red precipitate.
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Table S1. The Fe(III)EDTA conversion rates at different temperature.
Conversion rates
Temperature
Without catalyst
With catalyst
25 oC
9.3%
47.6%
45 oC
15.6%
54.6%
60 oC
19.4%
69.4%
Note: Fe(III)-EDTA solution (50 ml, 10 mmol/L) was added with 50 ml 1 mol/L Na2SO3 solution, and 10 ml 0.2 mol/L Na2SeSO3
solution mixed with 40 ml 1 mol/L Na2SO3 solution separately.
Table S2. The calculation of peak area of S-O bonds from SO32- and S-O, Se-O bonds from SeSO32in HATR-FTIR spectra of Figure 3.
Spectrum b
Spectrum c
(cm-1a.u.)
(cm-1a.u.)
1117 cm-1
7.6876
13.8057
≈1/2*
993 cm-1
3.0476
5.9807
≈1/2
930 cm-1
25.9931
64.2088
<1/2
Locations
*The
Ratio of b/c
ratio is actually 11% higher than 1/2. It should be ascribed to the over-lap of S-O bond from
SO42- oxidized from SO32- by Fe(III)-EDTA.
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Characterizations

Ion Chromatograph (IC)
The selenium speciation analysis is measured using a Metrohm 861 ion chromatograph (IC)
with a conductivity detector. The eluent was 3.2 mmol/L Na2CO3 and 1.0 mmol/L NaHCO3 at a
flow rate of 0.7 mL/min. Na2SeO3 (100 mg/L) mixed with SO42- was employed as reference
solution for the determination of SeO32- and SO42-.

Energy Dispersive Spectroscopy (EDS)
Elemental analysis for the recovered catalyst was identified by EDS using an EDX-GENESIS
spectrometer (EDAX, Ltd., USA). No treatment was done for the tested sample after vacuum
drying at 40 oC.
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