Supplementary data for

Role of the Propagation Reactions on the

Hydroxyl Radical Formation in Ozonation and

Peroxone (Ozone/Hydrogen Peroxide)

Processes

Yongze Liu, Jin Jiang,* Jun Ma,* Yi Yang, Congwei Luo, Xiaoliu Huangfu, Zhongkai

Guo

State Key Laboratory of Urban Water Resource and Environment, School of

Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin

150090, China

Corresponding Authors: Dr. Jin Jiang and Prof. Jun Ma

Phone: 86-451-86283010; fax: 86-451-86283010; e-mail: jiangjinhit@126.com (J. J.);

majun@hit.edu.cn (J. M.)

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2 Tables (Table S1- S2)

3 Texts (Text S1- S3)

5 Figures (Figure S1- S5)

Table S1 - Complication of rate constants relevant to the present study

No. Reaction Rate constant

(M-1s-1)

pKa Reference

1 tBuOH + OH• → products 6×108 (Buxton et al., 1988)

2 MeOH + OH• → products 9.7×108 (Buxton et al., 1988)

3 H2O2 + OH• → H2O + HO2• 2.7×107 (von Gunten, 2003)

4 HO2- + OH• → H2O + O2

•- 5.6×109 (von Gunten, 2003)

5 O3 + HO2- → products 9.6×106 (Staehelin and Hoigné,

1982)

5 H2O2 ↔ HO2- + H+ 11.8 (Staehelin and Hoigné,

1982)

6 HCO3- + OH• = HCO3

• + OH- 8.5×106 (von Gunten, 2003)

7 CO32- + OH• = CO3

•- + OH- 3.9×108 (von Gunten, 2003)

8 HCO3- ↔ CO3

2- + H+ 10.3 (von Gunten, 2003)

9 pCBA + OH• → products 5×109 (Buxton et al., 1988)

Table S2 - The original data of OH• exposures and scavenging capacities at 1.5 g

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O3/gDOC reported by Lee, et al. (2013) and the Ф values calculated by the

competition method.

WastewatersDOC

(mg/L)Scavenging

capacities (s-1)

Ozone dose (M)a

OH• exposures (M×s)b

Calculated Ф values by the competition

method (i.e., Eq. (6))

KOWWTP 4.7 1.10E+05 1.47E-04 6.50E-10 0.49

RWWTP 4.7 1.20E+05 1.47E-04 4.46E-10 0.36

LaWWTP 6 1.30E+05 1.88E-04 4.30E-10 0.30

LoWWTP 26.4 3.00E+05 8.25E-04 7.34E-10 0.27

AWWTP 7 1.50E+05 2.19E-04 6.20E-10 0.43

CCWRD 7.1 1.20E+05 2.22E-04 6.00E-10 0.32

MWRDGC 5.7 1.40E+05 1.78E-04 7.00E-10 0.55

WBMWD 15 3.00E+05 4.69E-04 7.30E-10 0.47

PCU 7 1.80E+05 2.19E-04 4.11E-10 0.34

GCGA 6.3 2.00E+05 1.97E-04 5.40E-10 0.55

a. The O3 doses were obtained by [DOC] × 1.5 (gO3/gDOC).b. These data were estimated from the Figure 3 in Yunho Lee and coworker.

Text S1 - The apparatus of UV photolysis and the experimental procedures.

A collimated beam apparatus, consisting of four low-pressure mercury lamp (254

nm, GPH212T5L/4, 10 W, Heraeus) positioned 30 cm above a circular stirred reactor

chamber, was employed for photolysis experiments (Bolton and Linden, 2003). The

reactor chamber was 5.65 cm in diameter, and the water path length was 4.00 cm. The

incident light intensity at 254 nm was determined by the Iodide-Iodate chemical

actinometer, and the value was (8.69 ± 0.37) × 10-8 Einstein L-1 s-1 (Rahn et al., 2003).

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During the UV irradiation at wavelength of 254 nm, H2O2 splits apart into two

OH•, and the rate of OH• generation is depicted as Eq. (S1) (Crittenden et al., 1999).

(S1)

where ФOH• is the quantum yield of OH• radical at wavelength of 254 nm, and due to

recombining effects, ФOH• is 1.00 in the bulk solution (Baxendale and Wilson, 1957);

I0 is the incident light intensity at 254 nm as shown above; A is the fraction of light

absorbed by the bulk solutions, A= 2.303b(εH2O2CH2O2+εHO2-CHO2-+εSCS), εH2O2 =

17.9~19.6 M-1 cm-1, εHO2- = 220 M-1 cm-1, εSCS is the absorbance of other compounds in

water matrix at 254 nm, b is the water path length; fH2O2 is the fraction of absorbed

light that is absorbed by H2O2 and HO2-, fH2O2 = 2.303b(εH2O2CH2O2+εHO2-CHO2-)/A.

Based on Eq. (S1), samples were irradiated at calculated duration time to achieve

several various doses of OH• (date was shown in Figure (S3)). Herein, the initial

concentration of H2O2 was applied at 4.0 mM, and the decrease of [H2O2] could be

ignored at the photolysis time in the present study, thus the rate of OH• generation

was constant.

Text S2 - The methanol assay for OH• yield determination.

The reactions involved in the formation of formaldehyde when OH• attacks

methanol is given by reactions (S2-S7) (Goldstein et al., 2007). OH• abstracts an H-

atom, producing major •CH2OH (reaction (S2)) and minor CH3O• and CH3O• can be

quickly converted into •CH2OH through a 1,2-H shift (reaction (S3)). The formed

•CH2OH reacts with O2 to produce the corresponding peroxyl radicals (•OOCH2OH)

(reaction (S4)). The peroxyl radicals undergo unimolecular decay into HCHO and

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superoxide (O2•-/HO2

•) (reaction (S5)). The peroxyl radicals react with superoxide to

produce HOOCH2OH (reaction (S6)), which consequently decay into HCHO

(formaldehyde) and H2O2 (reaction (S7)). Thus, the reaction (S6) does not affect the

yield of HCHO per unit of OH•. In addition, the bimolecular decay of peroxyl radicals

into HCOOH (reaction (S8)) competes with their unimolecular decay (reactions (S5)

and (S6)). Under the conditions where reaction (S8) can be ignored, the yield of

HCHO is equal to that of OH•.

OH• + CH3OH → •CH2OH + H2O k3 = 9.7×108 M-1s-1 (S2)

OH• + CH3OH → CH3O• + H2O → •CH2OH + H2O (S3)

•CH2OH + O2 → •OOCH2OH k4 = 4.5×109 M-1s-1 (S4)

•OOCH2OH + OH- → HCHO + O2•- + H2O k5 = 1.8×1010 M-1s-1 (S5)

•OOCH2OH + O2•- → HOOCH2OH + O2 (S6)

HOOCH2OH→ HCHO + H2O2 (S7)

2•OOCH2OH → products (HCOOH) 2k8 = (0.4-2.2)×109 M-1s-1 (S8)

Formaldehyde was determined by the Hantzsch method (Nash, 1953). Briefly, 5

mL of water sample was mixed with 2 mL of reagent (2 M ammonium acetate, 0.05

M acetic acid, 0.02 M acetylacetone), heated for 30 min at 50°C in the dark. It was

found that, H2O2 at high concentration would bleach the color in Hantzsch method.

Catalase (from bovin liver aqueous suspension, 40000~60000 units/ mg protein,

Sigma-Aldrich) was attempted to catalyze the decomposition of H2O2 before the

reagent addition. However, the H2O2 was at too high concentration (e.g., [H2O2]0 = 4

mM) and failed to be effectively decomposed under the present experiment

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conditions. Therefore, in the presence of H2O2, some corrections for the Hantzsch

method were conducted. As shown in Figure (S5), the molar absorption coefficients

(ε) at 412 nm were corrected to be 7549, 6892, and 6206 M-1 cm-1 in the presence of 0,

1 and 4 mM H2O2, respectively.

Text S3 - The description of the Rct concept.

The complex reactions in ozonation are summarized as follows:

(i) O3 + DOMI → OH•, kI, with the OH• yield of ФI (S9)

(ii) OH• + DOMp → ••• → O2•-, kp (S10)

(iii) O2•- + O3 → O3

•- → OH•, k, with the OH• yield of Ф (S11)

(iv) OH• + DOMs→ products, ks (S12)

where DOMI, DOMp, and DOMs represent the initiator, promoter and inhititor,

respectively; kI is the second-order rate constant of initiator with O3; kp and ks

represent the second-order rate constants of promoter and inhibitor with OH•,

respectively; k is the second-order rate constant of O3 with O2•-.

The rate of OH• formation can be described as Eq. (S13),

(S13)

The rate of OH• consumption can be described as Eq. (S14),

(S14)

The rate of O2•- formation is given as Eq. (S15),

(S15)

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The rate of O2•- consumption is given as Eq. (S16),

(S16)

Under the transient steady state (i.e., Eq. (S13) = Eq. (S14) and Eq. (S15) = Eq.

(S16)), it is obtained,

(S17)

(S18)

The combination of Eq. (S17) and (S18) gives,

(S19)

Thus, the Rct can be obtained,

(S20)

This new Rct description (S20) was similar with that obtained by Ee Ling Yong

and Yi-Pin Lin (Yong and Lin, 2012), except for the (1-Ф)kp[DOMp] in the

denominator which was not considered by the authors. The fact that the Ф value in the

reaction of O2•- + O3 → O3

•- → OH• was 100% (i.e., (1-Ф)kp[NOMp] = 0) could easily

explain that the presence of promoter did not affect the Rct values as they observed.

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0 20 40 60 80 100

-2.0

-1.5

-1.0

-0.5

0.0

slope = 0.0121s-1

slope = 0.0273s-1

Without 50 mM tBuOH With 50 mM tBuOH

ln([

O3]

/[O3]

0)

Time (s)

Figure S1 - O3 decay in the WcWWTP effluent in the presence and absence of 50

mM tBuOH. [O3]0 = 4.4 mg/L (92μM).

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.5

1.0

1.5

2.0

Ozo

ne In

stan

tane

ous

Dem

and

(mg/

L)

Ozone dose (mg/L)

Without 50mM tBuOH With 50mM tBuOH

Figure S2 - O3 consumption in the first rapid phase in the presence and absence of 50

mM tBuOH.

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0 5 10 15 20 25 30

0

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40

60

80

100

120

y = 3.3956x

Cal

cula

ted

OH

• rad

ical

s fo

rmat

ion

(M

)

Time (min)

Figure S3 - Calculated OH• radical formation by UV photolysis of H2O2.

Experimental conditions: [H2O2]0=4 mM, pH =8.0 (5 mM phosphate buffer).

0.0 5.0x10-11 1.0x10-10 1.5x10-10 2.0x10-10

0.0

1.0x10-5

2.0x10-5

3.0x10-5

4.0x10-5

5.0x10-5

R2 = 0.99y = 216920x

OH r

adic

als d

ose

(M)

OH radicals exposures (s)

Figure S4 - The OH• exposures in Suwannee River Fulvic Acid (IHSS) solution as a

function of given OH• doses. Experimental conditions: [H2O2]0 = 4 mM, pH = 8.0 (5

mM phosphate buffer), and TOC=8.60±0.05 mg/L.

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0.00 2.50x10-5 5.00x10-5 7.50x10-5 1.00x10-4

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0mM H2O2; y= 7549x, R2>0.99

1mM H2O2; y= 6892x, R2>0.99

4mM H2O2; y= 6206x, R2>0.99

Abs

orba

nce

at 4

12 n

m

HCHO (M)

Figure S5 - Corrections for the formaldehyde determination by the Hantzsch method

in the presence of 0, 1 and 4 mM H2O2.

References

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