Supporting Information

Excellent performance of cobalt impregnated activated carbon in peroxymonosulfate

activation for acid orange 7 oxidation

Tianyin Huang a,b, Jiabin Chen a*, Zhongming Wang a, Xin Guo b, John C. Crittenden b*

a School of Environmental Science and Engineering, Suzhou University of Science and

Technology, Suzhou, 215001, P. R. Chinab School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta,

Georgia 30332, United States

* Corresponding Authors. Phone: +86 0512 68096895; Fax: +86 0512 68096895.

Email: chenjiabincn@163.com (Jiabin Chen).

Phone: 404-894-5676; Fax: 404-894-7896.

john.crittenden@ce.gatech.edu (John C. Crittenden).

Journal: Environmental Science and Pollution Research

Date Prepared: January 21, 2017

Texts: S1-S6

Tables: S1-S2

Figures: S1-S12

Pages: 12

Texts

Text S1

PMS (2KHSO4.K2SO4.KHSO5, Oxone), methanol (MeOH), tert-butyl alcohol (TBA),

phenol were obtained from Sigma-Aldrich and used without purification. Analytical grade

Cobalt nitrate (Co(NO3)2∙6H2O), hydrochloric acid (HCl), sodium hydroxide (NaOH), sulfuric

acid (H2SO4), anhydrous sodium sulfate (Na2SO4), sodium nitrite (NaNO2), sodium thiosulfate

(Na2S2O3) were obtained from Shanghai Chemical Reagent Company. Deionized (DI) water

was produced using a Millipore Milli-Q Ultrapure Gradient A10 purification system.

Text S2

The GAC was purchased from Tianjin Damao Chemical Reagent Company, and was

ground and sieved to obtain small GAC particles with 60-80 mesh (0.18-0.25 mm). Then it

was soaked in 5% HCl for 30 min, and then washed in the ultrasonic bath (KQ-200KDE,

China) for 15 min to remove the impurities and ash. Afterwards, it was washed with the DI

water for several times until neutral pH was achieved, and then dried in the oven at 110 C for

12 h. For synthesis of GAC/Co, a fixed amount of GAC was impregnated in a Co(NO3)2

solution using stirring for 24 h. Then it was evaporated in a rotary evaporator (RE-52CS-1,

China) at 60 C under vacuum. Afterwards, the solid was calcined at 600 C in nitrogen gas

for 3 h, and was further calcined at 300 C in air. The calcined sample was washed with DI

water for several times, dried in an oven at 105 C, and stored in a desiccator before use.

Text S3

The degradation products of AO7 were determined by gas chromatography-mass

spectrometry (GC-MS, Agilent 7890A/5975C). NaCl (1 g) was added to 5 ml aliquots of

filtered sample and the pH was adjusted to 2 using H2SO4. Then the solution was extracted

with 30 ml of CH2Cl2 for 3 times (10 ml × 3). The extract was dehydrated with Na 2SO4, and

then evaporated in a rotary evaporator at 40 C to final volume of 1 ml. The concentrated

products were determined on GC-MS equipped with HP-5MS (30 m × 0.25 mm × 0.25 μm).

Injection was performed in the splitless mode at an injection temperature of 250 C, and with

an injection volume of 1 μL. The carrier gas was helium at a constant velocity of 1 ml/min.

The initial oven temperature was set at 40 C for 2 min, and then increased to 100 C at the

rate of 12 C/min. After this it was subsequently increased to 200 C at 5 C/min, and then

temperature was raised at 20 C/min and for 10 min and kept at 270 C. Mass spectra were

obtained in EI mode with electron energy 70 eV.

Text S4

Degradation of AO7 increased with increasing dosage of PMS (Fig. S3A). To be specific,

when equivalent molar ratio of PMS and AO7 (0.057 mM) were present, only 67%

degradation of AO7 was observed at 60 min. However, when the molar ratio of PMS/AO7

was increased to 3:1, almost complete degradation of AO7 was achieved at 60 min.

Furthermore, when the ratio further raised to 5:1, 10:1, and 20:1, complete degradation was

obtained over 30, 20, and 15 min, respectively. Effect of GAC/Co loading on removal of AO7

is shown in Fig. S3B. In the absence of PMS, the removal of AO7 increased with increasing

loading of AC/Co, which could be attributed to the higher adsorption sites for AO7. In the

presence of PMS, significant degradation of AO7 was observed at 60 min with 0.1 g/L

GAC/Co. When the loading of GAC/Co raised from 0.1 to 0.8 g/L, the degradation of AO7

also gradually increased, with less time required for the complete removal of AO7.

Text S5

Degradation of AO7 was pH dependent (Fig. 3A). AO7 degradation significantly

increased with pH increasing from 2 to 6. 50% of initial AO7 still remained after 60 min for a

pH 2. Complete removal was observed 30 and 20 min for an initial pH of 4 and 6,

respectively. When pH further increased to pH 8, only a slight increase of AO7 degradation

was observed. However, the degradation of AO7 significantly decreased when the initial pH

was 10. Accordingly, a slightly alkaline initial pH was the most favorable initial pH for AO7

degradation.

We also monitored the variation of pH during the degradation of AO7, and the results are

included in Fig. 3A. When the initial pH was 10, the pH gradually decreased from pH 10 to 8

during the reaction. The pH was slightly decreased when the initial pH was 2 and 4. However,

the pH dropped significantly to pH 4 when the initial pH was 6 and 8. The pH drop could be

attributed to the generation of protons during the activation of PMS (equation 1) [1].

SO4·- + H2O →SO4

2- + HO· + H+ (1)

Text S6

To further clarify whether AO7 was mineralized or not, the TOC of the reaction solution

were determined during the reaction, and the results were shown in Fig. S13. The results

showed that removal efficiency of TOC was 40% and 50% at 15 and 30 min, respectively, i.e.,

the decrease of TOC mainly observed at the initial 15 min. The rapid mineralization of AO7

took place rapidly in the initial 15 min, and subsequently slowed down, which was possibly

attributed to the difficult mineralization of intermediate, and difficult decomposition of PMS

at lower concentration of PMS in the later reaction time [2]. It was noted that the peaks of 484

and 310 nm characteristics of azo bond and the naphthalene structure disappeared at 30 min.

The destruction of azo bond and naphthalene ring could not guarantee the complete

mineralization of AO7. A great deal of intermediates likely existed in the reaction systems.

Thus the degradation products were also identified.

Tables

Table S1. Rate constants of AO7 under different conditions

Test no. Rate constant(min-1) R2

PMS 0.00008 0.98

AC + PMS 0.0050 0.99

Co/AC + PMS 0.1683 0.98

Table S2. Proposed structures of the main products

CompoundRetention time

(min)Chemical name Chemical structure

A 15.292 phthalic acid

B 17.509 coumarin

C 18.401phthalic

anhydride

D 18.825 phthalimide

E 22.791

1,2-

naphthoquinon

e

Figures

Fig. S1. XRD spectra of AC/Co and AC.

Fig. S2. SEM images of AC/Co (a) and AC (b).

(a) (b)

Fig. S3. Impact of PMS concentration (A) and AC/Co loading (B) on the degradation of AO7

in the AC/Co activated PMS system. (A) [AO7]0 = 0.057 mM, [AC/Co] = 0.3 g/L, T = 25 C;

(B) [AO7]0 = 0.057 mM, [PMS]0/[AO7]0 = 5 : 1, T = 25 C.

Fig. S4. Degradation of AO7 in the presence of PMS at different pHs. [AO7] 0 = 0.057 mM,

[PMS]0/[AO7]0 = 5 : 1, T = 25 C.

Fig. S5. Decolorization of AO7 with HOCl alone.

Fig. S6. Effect of NaCl on AO7 degradation with the addition of radical quencher (phenol).

[AO7]0 = 0.057 mM, [AC/Co] = 0.3 g/L, [PMS]0/[AO7]0 = 5 : 1, [phenol]0/[AO7]0 = 2000 : 1,

T = 25 C.

Fig. S7. Effect of NH4+ on the degradation of AO7 in the AC/Co activated PMS system.

[AO7]0 = 0.057 mM, [AC/Co] = 0.3 g/L, [PMS]0/[AO7]0 = 5 : 1, T = 25 C.

Fig. S8. Effect of MeOH on the degradation of AO7 in the AC/Co activated PMS system.

Fig. S9. Effect of TBA on the degradation of AO7 in the AC/Co activated PMS system.

Fig. S10. Effect of phenol on the degradation of AO7 in the AC/Co activated PMS system.

Fig. S11. Comparison of the color in the continuous-flow effluents from SPE tubes packed

with AC (A) and AC/Co (B).

40.32 L (336 h)

28.8 L (240 h)

25.92L (216 h)

23.04L (192 h)

20.16 L (168 h)

0 h

20.16 L (168 h)

17.28L (144 h)

14.4 L (120 h)

11.52 L (96 h)

8.64 L (72 h)0 h

（B）

（A）

Fig. S12. TOC variation during AO7 degradation in the AC/Co activated PMS system.

References

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microwaveactivated persulfate: effects of temperature, pH, and chloride ions, Front. Env.

Sci. Eng. 6 (2012) 17-25.

[2] S. Yang, X. Yang, X. Shao, R. Niu, L. Wang, Activated carbon catalyzed persulfate

oxidation of Azo dye acid orange 7 at ambient temperature, J. Hazard. Mater. 186 (2011)

659-666.