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Supplementary Material

The fate of dichloroacetonitrile in the UV/Cl2 and UV/H2O2 processes: Implications on

potable water reuse

Submitted to:

Environmental Science: Water Research & Technology

Ran Yina, *, Zhuozhi Zhonga, Li Linga, *, Chii Shanga, b

a. Department of Civil and Environmental Engineering, the Hong Kong University of Science

and Technology, Clear Water Bay, Kowloon, Hong Kong

b. Hong Kong Branch of Chinese National Engineering Research Center for Control &

Treatment of Heavy Metal Pollution, the Hong Kong University of Science and Technology,

Clear Water Bay, Kowloon, Hong Kong

* Corresponding authors: Address correspondence to Ran Yin: Tel: (852) 5489 3675; E-mail:

ryin@connect.ust.hk.

The Supplementary Material contains: 1 Text, 9 Figures and 1 Scheme.

Electronic Supplementary Material (ESI) for Environmental Science: Water Research & Technology.This journal is © The Royal Society of Chemistry 2018

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Table of Contents

Text S1: Detailed procedures for calculation of steady-state concentrations of ClO- and HO2-

and their second-order rate constants towards DCAN...............................................................3Fig. S1. The experimental setup in this study. ...........................................................................4Fig. S2. Absorbance changes under UV254 irradiation employing iodide/iodate as chemical actinometry.................................................................................................................................5Fig. S3 Photolysis of dilute H2O2 under UV irradiation at 254 nm. Conditions: [H2O2]0 = 100 μM, 22 °C...................................................................................................................................6Fig. S4. The absorption spectrum of DCAN (in black) and the emission spectrum of UV lamps (in red). ............................................................................................................................7Fig. S5. Time-dependent degradation of DCAN by water hydrolysis, UV photolysis, H2O2, Cl2, UV/H2O2 and UV/Cl2 processes. Conditions: [DCAN] = 1 μM, [Chlorine] = [H2O2] = 500 μM, pH = 5.0, UV intensity = 0.54 μW/cm2.......................................................................8Figure S6. The pseudo first-order rate constants of DCAN degradation by nucleophilic attack and radical oxidation as a function of (a) Cl2 dosage in UV/Cl2 process and (b) H2O2 dosage in UV/H2O2 process. Conditions: [DCAN] = 1 uM, UV intensity = 0.54 μW/cm2, pH = 6, [Cl2] = [H2O2] = 50, 100 and 500 μM........................................................................................9Fig. S7. The photo-decomposition of (a) Cl2 in the UV/Cl2 process and (b) H2O2 in the UV/H2O2 process. Conditions: [chlorine] = [H2O2] = 500 μM, pHs = 5 and 6, UV intensity = 0.54 μW/cm2. ...........................................................................................................................10Fig S8. Comparison of cost effectiveness for 1-order of DCAN degradation by using UV/Cl2 and UV/H2O2 processes in 1 m3 of water. Conditions: [DCAN] = 1 uM, UV intensity = 0.54 μW/cm2, pH = 6, [Chlorine] = [H2O2] = 500 μM. ...................................................................11Fig. S9. The degradation products of DCAN by chlorination (b) and in the UV/Cl2 process (c). Conditions: [chlorine] = 500 μM, pHs = 6, UV intensity = 0.54 μW/cm2. .......................12Scheme S1. Proposed pathways of DCAN degradation in the UV/Cl2 and UV/H2O2 processes...................................................................................................................................................13

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Text S1: Detailed procedures for calculation of steady-state concentrations of ClO- and HO2-

and their second-order rate constants towards DCAN.

The steady-state concentrations of ClO- and HO2- can be directly obtained from Eqs. S1 – S4.

The second order rate constant of ClO- and HO2- towards DCAN was calculated in Eq. S5,

where is the pseudo first order rate constant of DCAN degradation by ClO- (in the 𝑘'𝑂𝐶𝑙 ‒

absence of UV) and [ClO-] is the steady state concentration of ClO- that was obtained from

Eqs. S1 – S4.

Eq. S1𝐻𝑂𝐶𝑙↔𝐶𝑙𝑂 ‒ + 𝐻 + 𝑝𝐾𝑎 = 7.5

Eq. S2[𝐶𝑙𝑂 ‒ ] =

[𝑓𝑟𝑒𝑒 𝑐ℎ𝑙𝑜𝑟𝑖𝑛𝑒]

1 + 10𝑝𝐾𝑎 ‒ 𝑝𝐻

Eq. S3𝑂𝐻 ‒ + 𝐻2𝑂2↔𝐻2𝑂 + 𝐻𝑂2‒ 𝑝𝐾𝑎 = 11.8

Eq. S4[𝐻𝑂2

‒ ] =[𝐻2𝑂2]

10𝑝𝐾𝑎 ‒ 𝑝𝐻

Eq. S5𝑘'𝐶𝑙𝑂 ‒ = 𝑘𝐶𝑙𝑂 ‒ 𝐷𝐶𝐴𝑁[𝐶𝑙𝑂 ‒ ]

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Fig. S1. The experimental setup in this study.

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0 60 120 180 240 3000.0

0.2

0.4

0.6

0.8

1.0

1.2

Ab

sorb

ance

Time (s)

y = 0.0037x+0.1142R2 = 0.9936

Fig. S2. Absorbance changes under UV254 irradiation employing iodide/iodate as chemical

actinometry.

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0 10 20 30 40 50 60-0.16

-0.14

-0.12

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

ln(C

/C0)

Time (min)

y = -0.00238xR2= 0.9974

Fig. S3 Photolysis of dilute H2O2 under UV irradiation at 254 nm. Conditions: [H2O2]0 = 100

μM, 22 °C.

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200 250 300 350 400

5

10

15

20

Wavelength (nm)

Mol

ar ab

sorp

tion

coef

ficien

t (M

-1cm

-1)

0

20

40

60

80

100

UV la

mp

irrad

iance

(W

/cm2 /n

m)

0

Fig. S4. The absorption spectrum of DCAN (in black) and the emission spectrum of UV

lamps (in red).

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0 10 20 30 40 50 60-0.5

-0.4

-0.3

-0.2

-0.1

0.0

Hydrolysis UV photolysis H2O2

Chlorine UV/H2O2

UV/Cl2

Ln(C

/C0)

Time (min)

Fig. S5. Time-dependent degradation of DCAN by water hydrolysis, UV photolysis, H2O2, Cl2,

UV/H2O2 and UV/Cl2 processes. Conditions: [DCAN] = 1 μM, [Chlorine] = [H2O2] = 500 μM,

pH = 5.0, UV intensity = 0.54 μW/cm2.

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0 400 800 12000

1

2

3

4

5

6

k (

10-3 m

in-1)

Nucleophilic attack Radical oxidation

Chlorine concentration (M)

(a)

Equation y = a + b*xAdj. R-Squar 0.99885 0.8951

Value Standard Errok Intercept -0.0464 0.04096k Slope 0.00458 1.09833E-4k Intercept 2.01207 0.08787k Slope 0.00192 4.52263E-4

0 400 800 12000

1

2

3

4

5

k (

10-3 m

in-1)

Nucleophilic attack Radical oxidation

H2O2 concentration (M)

(b)

Equation y = a + b*xAdj. R-Squar 0.98935 0.81256

Value Standard Errok Intercept -0.0320 0.08033k Slope 0.00384 2.81273E-4k Intercept 1.77527 0.18211k Slope 0.0011 3.53475E-4

Figure S6. The pseudo first-order rate constants of DCAN degradation by nucleophilic attack

and radical oxidation as a function of (a) Cl2 dosage in UV/Cl2 process and (b) H2O2 dosage in

UV/H2O2 process. Conditions: [DCAN] = 1 uM, UV intensity = 0.54 μW/cm2, pH = 6, [Cl2] =

[H2O2] = 50, 100 and 500 μM.

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Fig. S7. The photo-decomposition of (a) Cl2 in the UV/Cl2 process and (b) H2O2 in the

UV/H2O2 process. Conditions: [chlorine] = [H2O2] = 500 μM, pHs = 5 and 6, UV intensity =

0.54 μW/cm2.

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Fig S8. Comparison of cost effectiveness for 1-order of DCAN degradation by using UV/Cl2 and UV/H2O2 processes in 1 m3 of water. Conditions: [DCAN] = 1 μM, UV intensity = 0.54 μW/cm2, pH = 6, [Chlorine] = [H2O2] = 500 μM.

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(d) HAA standard

Fig. S9. The degradation products of DCAN by chlorination (b) and in the UV/Cl2 process (c).

Conditions: [chlorine] = 500 μM, pHs = 6, UV intensity = 0.54 μW/cm2.

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Scheme S1. Proposed pathways of DCAN degradation in the UV/Cl2 and UV/H2O2 processes.