Supporting Information for
Study on the mechanism of cerium oxide catalytic ozonation for
controlling the formation of bromate in drinking water
Qun Wanga,*, Zhichao Yanga, Jun Mab, Jiangchuan Wanga,
Lin Wanga, Mingkun Guoa
a. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong
University, Chengdu 610031, China.
b. School of Municipal and Environmental Engineering, Harbin Institute of
Technology, Harbin 150090, China.
This PDF file includes:
2 Texts, and 3 figures are available for further information addressing
experimental procedures, and additional data.
* To whom correspondence should be addressed.
E-mail Address: zcyang_swjtu@126.com
Phone: +8618215559048.
Fax: +86-28-66367584.
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List of supporting materials
Text S1. The detailed information for experimental procedures
Text S2. Calculation of HSO4- concentration in the bulk solution
Figure S1. Concentration profiles of Br- and HOBr/OBr- and the corresponding total
bromine mass balance during ozonation and MgO catalytic ozonation
Figure S2. Concentration profiles of Br- and HOBr/OBr- and the corresponding total
bromine mass balance during ozonation and FeOOH catalytic ozonation
Figure S3. Evolution of dimensionless pCNB concentration with reaction time in
ozonation and CeO2 catalytic ozonation at different temperature
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Text S1. The detailed information for experimental procedures
1. Ozonation and catalytic ozonation
(i) The experiments to investigate bromate formation during ozonation with
different catalysts.
After the steady ozone concentration (5.21 mg/L, 108.54 μM) reached, the ozone
gas was shut off. 22.5 μM KBr solution was then instantly introduced into the reactor.
In the catalytic ozonation, after addition of KBr solution, MgO, FeOOH or CeO2
(0.1g) was immediately added into the reactor. The reactor was then sealed and
magnetically stirred. The samples (9.5 mL) withdrawn at predetermined intervals
from sampling port were added into colorimetric tubes with the addition of 0.5 mL
sodium sulfate (Na2SO3) solution (0.025 mol/L) in advance. Then, the samples were
filtered through 0.45-μm glass fiber filters (Whatman) to remove the catalyst particles
and divided into three parts for Br-, BrO3- and HOBr/OBr- measurements. The filters
were pretreated with a small amount of samples to remove the impact of the filters on
the target compounds.
(ii) The experiments to investigate the oxidation of pCNB by ozonation and
catalytic ozonation.
After the steady ozone concentration (0.40 mg/L, 8.33 μM) reached, the ozone
gas was shut off. pCNB solution (80 μg/L, 0.507 μM) was then instantly introduced
into the reactor. In the catalytic ozonation, after addition of pCNB solution, FeOOH or
CeO2 (0.1g) was immediately added into the reactor. The reactor was then sealed and
magnetically stirred. The samples withdrawn at predetermined intervals were filtered
through 0.45-μm glass fiber filters (Whatman) to remove the catalyst particles after
the residual ozone has been quenched by 0.025 mol/L sodium sulfate (Na2SO3)
solution. The filters were pretreated with a small amount of samples to remove the
impact of the filters on the target compounds.
(iii) The experiments to investigate the effect of inorganic ions on bromate
formation catalytic ozonation.
After the steady ozone concentration (5.21 mg/L, 108.54 μM) reached, the ozone
gas was shut off. 13.75 μM KBr solution and Na2SO4 or NaNO3 solution (1mM, 2mM,
5mM and 10mM in the four experiments respectively) were then successively
introduced into the reactor immediately. In the catalytic ozonation, 0.1g FeOOH or
CeO2 was also instantly added into the reactor following the above operation. The
reactor was then sealed and magnetically stirred. The samples (9.5 mL) withdrawn at
predetermined intervals from sampling port were added into colorimetric tubes with
the addition of 0.5 mL sodium sulfate (Na2SO3) solution (0.025 mol/L) in advance.
Then, the samples were filtered through 0.45-μm glass fiber filters (Whatman) to
remove the catalyst particles and divided into three parts for Br-, BrO3- and
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HOBr/OBr- measurements. The filters were pretreated with a small amount of
samples to remove the impact of the filters on the target compounds.
(iv) The experiments to investigate the calcination temperature of CeO2 on the
bromate formation during catalytic ozonation.
After the steady ozone concentration (5.21 mg/L, 108.54 μM) reached, the ozone
gas was shut off. 13.75 μM KBr solution was then instantly introduced into the
reactor followed by the CeO2 samples calcined at different temperature (at a dose of
0.1 g). The reactor was then sealed and magnetically stirred. The samples (9.5 mL)
withdrawn at predetermined intervals from sampling port were added into
colorimetric tubes with the addition of 0.5 mL sodium sulfate (Na2SO3) solution
(0.025 mol/L) in advance. Then, the samples were filtered through 0.45-μm glass
fiber filters (Whatman) to remove the catalyst particles and divided into three parts for
Br-, BrO3- and HOBr/OBr- measurements. The filters were pretreated with a small
amount of samples to remove the impact of the filters on the target compounds.
2. Adsorption
(i) The adsorption of pCNB on the catalyst.
The catalyst was added into the 1L reactor followed by addition of pCNB
solution (80 μg/L, 0.507 μM) and at the same time, timing was started. The reactor
was then sealed and magnetically stirred. The samples withdrawn at predetermined
intervals were filtered through 0.45-μm glass fiber filters (Whatman) to remove the
catalyst particles. The filters were pretreated with a small amount of samples to
remove the impact of the filters on the target compounds.
(ii) The adsorption of SO42- ions on the catalyst.
The catalyst was added into the 1L reactor followed by addition of Na2SO4
solution (1.42 mg/L, 10 μM) and at the same time, timing was started. The reactor
was then sealed and magnetically stirred. The samples withdrawn at predetermined
intervals were filtered through 0.45-μm glass fiber filters (Whatman) to remove the
catalyst particles. The filters were pretreated with a small amount of samples to
remove the impact of the filters on the target compounds.
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Text S2. Calculation of HSO4- concentration in the bulk solution
The dissociation equilibrium exists between SO42- and HSO4-:
SO42- + H+
HSO4Distribution fraction (δ) was employed to calculate the HSO4- concentration.
Distribution fraction (δi) refers to the percentage of target ion (i) concentration
account for the total concentration after reaching the acid-base balance according to
the following equation S1 (for an example of HSO4-):
 HSO 

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[ HSO4  ]
[ SO4 2 ]  [ HSO4  ]
(S1)
where [SO42-] represents the concentration of the deprotonated form of HSO4-.
Considering the pKa of HSO4- (1.99), which can be decribed as:
pK a   lg Ka
Ka 
(S2)
[ SO4 2 ][ H  ]
 10 pKa
[ HSO4  ]
(S3)
where Ka and [H+] represent the equilibrium constant and the concentration of H+,
respectively. [H+] can be calculated via pH value of the bulk solution:
pH   lg[ H

]
(S4)
Equation (S4) can be transformed to Equation (S5), as follows:
[ H  ]  10 pH
(S5)
Eqs. (S1), (S3) and (S5) can be used to calculate δHSO4-:
 HSO 

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[ HSO4  ]
10 pH

[ SO4 2 ]  [ HSO4  ] 10 pH  10 pKa
(S6)
where pH = 6.3. δHSO4- is calculated to be 4.89755×10-5.
Finally, the concentration of HSO4- can be calculated as follows (the maximum dosing
of [SO42-] = 10 mM):
[ HSO4  ]   HSO   ([ HSO4  ]  [ SO4 2 ])  4.89755 105 10  4.89755 104 mM
4
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Figure S1. Concentration profiles of Br- and HOBr/OBr- and the corresponding total
bromine mass balance during ozonation and MgO catalytic ozonation
Fig. S1 Concentration profiles of Br- and HOBr/OBr- and the corresponding total bromine
mass balance during ozonation and MgO catalytic ozonation. Brtot: sum of all bromine species (i.e.
Br-, HOBr, OBr- and BrO3-).
[Br–]0=1.8 mg/L, [O3]0=5.21 mg/L, catalyst dose=100 mg/L, T=18 °C, pH=6.30
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Figure S2. Concentration profiles of Br- and HOBr/OBr- and the corresponding total
bromine mass balance during ozonation and FeOOH catalytic ozonation
Fig. S2 Concentration profiles of Br- and HOBr/OBr- and the corresponding total bromine
mass balance during ozonation and FeOOH catalytic ozonation. Brtot: sum of all bromine species
(i.e. Br-, HOBr, OBr- and BrO3-).
[Br–]0=1.8 mg/L, [O3]0=5.21 mg/L, catalyst dose=100 mg/L, T=18 °C, pH=6.30
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Figure S3. Evolution of dimensionless pCNB concentration with reaction time in
ozonation and CeO2 catalytic ozonation at different temperature
Fig. S3 Evolution of dimensionless pCNB concentration with reaction time in ozonation and CeO2
catalytic ozonation at different temperature.
The colored lines: single ozonation; the dashed lines: O3/ CeO2
[O3]0=0.75±0.02 mg/L, [pCNB]0 = 80μg/L, catalyst dose= 100 mg/L, pH = 6.3, T = 17.4 °C
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