Degradation of 2,4-dichlorophenol from aqueous using UV activated persulfate: Kinetic and toxicity investigation

Article abstract of DOI:10.1039/c6ra11166a

2,4-DCP is a high-toxicity phenol compound, which is difficult to remove, harmful to the health of people and seriously influences the aquatic ecosystems. In this study, the degradation of 2,4-DCP using UV/persulfate (UV/PS) process was investigated for the first time. The results showed pseudo-first-order rate constants of 2,4-DCP photo-degradation by UV/PS was 35.1 × 10^-3 min^-1. The reaction rate constants increased with pH increasing from 5 to 7 and then decreased at pH 8. Different anions (Cl^-, HCO₃^- and NO₃^-) in water presented different effects on the photo-degradation reaction. The photo-degradation rates of 2,4-DCP in three actual water conditions (Xidong water works, Xijiu reservoir, Henshan reservoir) were higher than in the ultrapure water. Two possible (hydroxylated and dechlorinated) pathways for the degradation of 2,4-DCP by UV/PS were proposed. The luminescent bacteria inhibition rate greatly decreased with the concentration of 2,4-DCP decreasing in the reaction process.

Full text of DOI:10.1039/c6ra11166a

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Degradation of 2,4-dichlorophenol from aqueous
using UV activated persulfate: kinetic and toxicity
investigation†
Cite this: RSC Adv., 2016, 6, 100056
ab
a
a
a
a
a
Juxiang Chen, Naiyun Gao,* Xian Lu, Meng Xia, Zhenchuan Gu, Chuang Jiang
a
and Qiongfang Wang
2,4-DCP is a high-toxicity phenol compound, which is difficult to remove, harmful to the health of people
and seriously influences the aquatic ecosystems. In this study, the degradation of 2,4-DCP using UV/
persulfate (UV/PS) process was investigated for the first time. The results showed pseudo-first-order rate
ꢁ3
ꢁ1
constants of 2,4-DCP photo-degradation by UV/PS was 35.1 ꢀ 10 min . The reaction rate constants
ꢁ
3ꢁ
increased with pH increasing from 5 to 7 and then decreased at pH 8. Different anions (Cl , HCO and
3ꢁ
NO ) in water presented different effects on the photo-degradation reaction. The photo-degradation
Received 29th April 2016
Accepted 29th September 2016
rates of 2,4-DCP in three actual water conditions (Xidong water works, Xijiu reservoir, Henshan reservoir)
were higher than in the ultrapure water. Two possible (hydroxylated and dechlorinated) pathways for the
degradation of 2,4-DCP by UV/PS were proposed. The luminescent bacteria inhibition rate greatly
decreased with the concentration of 2,4-DCP decreasing in the reaction process.
DOI: 10.1039/c6ra11166a
www.rsc.org/advances
based on activated carbon adsorption and membrane ltration,
1
Introduction
they all produced secondary pollution on the physical materials
10–12
Chlorophenols (CPs) constitute a particular group of priority and not really removed from the environment;
the chemical
toxic pollutants listed by the US EPA in the Clean Water Act and methods are mainly based on some oxidizing or reducing
1,2
by the European Decision 2455/2001/EC. They have acted as agents, such as potassium permanganate, ferric salt, chlorine
the raw materials of wood, paints, vegetable bers, paper, and so on, which may cause color, turbidity, and even more
13,14
leather and disinfectants for many years. Environmental harmful by-products in water;
the biological methods have
contamination with these chemicals occurs from industrial two drawbacks. On the one hand, it is difficult to cultivate the
effluents, decolouration of paper and paper mill effluents, microorganisms. On the other hand, the 2,4-DCP is toxic to the
15–17
agricultural runoff, breakdown of chlorophenoxyacetic acid microorganisms, so the biological methods are controlled.
herbicides and hexachlorobenzene and from spontaneous It is therefore necessary to nd the effective method for the
formation following chlorination of water for disinfections and degradation of 2,4-DCP.
3,4
deodorization. They have been found more in the wastewater
Advanced oxidation technologies (AOTs) represent high
than in the rivers and lakes. 2,4-Dichlorophenol (2,4-DCP) was efficiency and easy operational methods for degrading toxic and
one of the chlorophenols widely presented in aquatic environ- difficult degradation organic compounds. Those AOTs make
ment. It has been extensively used in pesticide, plasticizer, fuel full use of hydroxyl radicals (OHc) to form a high redox potential
5
–8
18–21
and other many productions,
a priority control pollutant in China due to its high toxicity and UV, Fenton-like (H
which has been listed as (E
O
¼ 2.7 V).
There are many examples of AOTs including
2
+
2
O
2
/Fe ), UV/TiO
O /Fe /UV), all of which have been shown to degrade 2,4-
2 2
2 2 2
/H O , photo-Fenton
2
+
9
resistant to degradation. So the removal of 2,4-DCP in water (H
has attracted considerable attention. Many researchers have DCP effectively.
2
2–25
Recently, an innovative oxidation tech-
ꢁ
focused on the development of all kinds of methods to reduce nology based on the generation of sulfate radical anions (SO
c )
4
the 2,4-DCP pollution. For example: physical, chemical and has aroused great attention and was found as an alternative
biological strategies. However, the physical methods are mainly technology for water decontamination application. And the
reason is that persulfate (PS, E
other oxidants such as ozone and has a higher oxidation ability
O
ꢂ 3.2 V) is more stable than
a
2ꢁ
State Key Laboratory of Pollution Control and Resource Reuse, Tongji University,
aer being activated. Generally, peroxydisulfate (S
2
O
8
) or
Shanghai 200092, China
ꢁ
ꢁ
peroxymonosulfate (HS O ) can be activated forming SO c or
2
5
4
b
College of Architecture and Civil Engineering, Xinjiang University, Urumqi 830047,
26,27
OHc by heat, UV and transition metals.
Some literature has
China
ꢁ
proved that both SO c and OHc are existing in the experimental
4
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c6ra11166a
condition and played important role in the degradation of 2,-
1
100056 | RSC Adv., 2016, 6, 100056–100062
This journal is © The Royal Society of Chemistry 2016

View Article Online
Paper
RSC Advances
28
MIB and geosmin when the persulfate was activated by UV. It HPLC apparatus equipped with a C18 column (150 mm ꢀ 4.6
ꢁ
has been reported that SO4c could efficiently degrade many mm ꢀ 5 mm) was calibrated and tested prior to injection of the
organic pollutants and exhibit a stronger oxidative ability than samples. Mixtures of acetonitrile (HPLC grade, $99.9%) ultra-
2
9–31
ꢁ
OHc.
However, SO4c is more selective than OHc reacting pure water (70/30, the ultrapure water contained 0.1% of formic
ꢁ
with many organic substrates. Previous work related to SO
4
c
acid before mixing) were used as the mobile phase, and the ow
ꢁ
1
based on AOPs mostly aimed at the removal efficiency and rate was 1.0 mL min . Solution pH was measured using an
kinetics studies of other organic compounds. However, there Acumen AB15 pH meter from Fisher Scientic. The actual water
are few literatures about the degradation of 2,4-DCP by UV- including of Henshan reservoir, Xijiu reservoir, Xidong water
activated persulfate.
works were all sampled from the actual source of water. pH,
2
ꢁ
ꢁ
ꢁ
ꢁ
In this study, the main objectives of this study were (1) to CO3 /HCO3 , NO3 /NO2 , TOC and other water quality
evaluate the feasibility of UV/PS to degradate the 2,4-DCP; (2) to indexes were detected every time. A certain concentration
investigate the kinetics of the removal of 2,4-DCP by UV/PS solution of 2,4-DCP was diluted with the actual water at each
under different initial PS dosages; (3) to determine the inu- time.
ence of the pH and environment factors on the photo-
The intermediate products were measured by GC-MS-MS
degradation of 2,4-DCP; (4) to compare the degradation (Thermo TSQ Quantum Access MAX, USA) with a chromato-
efficiencies of two reservoirs, a water plant raw water and ultra graphic column (30 m ꢀ 0.25 mm ꢀ 0.25 m, Thermo, USA). The
pure water background conditions; (5) to investigate the inter- temperature process was programmed as: initial temperature
ꢃ
ꢃ
mediate products and propose the possible degradation 80 C, residence time: 10 min and then improved to 100 C at
ꢃ
ꢁ1
pathway of photo oxide of 2,4-DCP with UV/PS; (6) to evaluate a rate of 10 C min residence 2 min. The temperature was
ꢃ
ꢃ
ꢁ1
the acute toxicity during photo-oxidation process.
raised to 250 C at an increasing temperature rate of 5 C min
.
The toxicity evaluation experiment was executed with long-
32
term micro toxicity analysis method (LTM). The data was
measured with the Power Wave micro plate spectrophotometer
2
Materials and methods
2.1 Chemical
(Biotech Instruments Inc.) and was analyzed with Aptos so-
All the chemicals were at least of analytical grade and used as ware. For the test chemicals, 12 diluted concentration series in
received. The chemical compounds 2,4-DCP, potassium perox- three parallels and 24 controls were arranged in the white 96-
ydisulfate (PDS), benzoic acid (BA), sodium carbonate, sodium well standard opaque plates with 12 rows and 8 columns
bicarbonate, sodium chloride, sodium nitrate, nitrous acid were (Corning Corp.). The volume of the 2,4-DCP was 100 mL, the
purchased from Sinopharm Chemical Reagent CO., Ltd. Meth- total volume was 200 mL. The toxicity or effect of 2,4-DCP to Q67
33
anol (MeOH) and acetaminophen (HPLC grade) was supplied by was expressed as the inhibition ratio (IBR) according to the
Sigma-Aldrich Co. The demanded solutions were prepared aer following formula:
necessary dilutions with ultra-pure water (18.2 MU cm, Milli-Q)
I
0
ꢁ I
t
IBR ¼
ꢀ 100%
(1)
for batch studies. The bacteria of toxicity evaluation experiment
were Qinghai Vibrio (Vibrio qinghaiensis sp.-Q67, or Q67), which
was purchased Beijing Hamamatsu Hikaruko technology
Limited by Share Ltd.
I
0
where I
t
is the average RLU of Q67 exposed to the test toxicant (3
parallels) and I refers to the average RLU of Q67 exposed to the
0
controls (12 parallels). Three duplicates were at least done at the
same time. The experimental data were analyzed using APTox
soware.
2.2 Experimental procedure
All the experiments were conducted with quasi parallel beam
instrument, which is designed according to the International
Association of ultraviolet light standard. A low pressure Hg
lamp (75 W, emmition at 253.7 nm, Tianjin Xinjing Co., China)
was installed in a sealed cylindrical tube. Lamp above
quiescently-stirred Petri dishes was employed for the batch UV/
PS studies. At predetermined time intervals, samples were taken
and mixed with excess methanol (v/v ¼ 4 : 1) to quench the
reaction before analysis. The pH of the reaction solution was
adjusted by phosphate buffer (2 mM) solutions to desired value;
all the experiments were replicated at least two times inde-
pendently. The error bars in ngers represent the standard
deviation among replicates.
3
Results and discussion
3.1 Effect of PS on the removal efficiency of 2,4-DCP with
and without UV
The degradation efficiency of 2,4-DCP in the PS, UV, and UV/PS
processes at pH 6.6 are compared and shown in Fig. 1. Negli-
gible degradation of 2,4-DCP was observed using PS alone at
a concentration of 900 mM, because of less than 4% of degra-
dation percentage. With the presence of UV, the degradation of
2,4-DCP was progressively increased. Thereaer, the degrada-
tion increased gradually. However, 46% of 2,4-DCP was
degraded in 45 min by UV alone, which was in accordance with
other reports and consistent with their strong UV absorption at
2.3 Analytical methods
34,35
254 nm.
In contrast, the degradation yield reached to about
The 2,4-DCP concentration was measured by high performance 96.4% at the same reaction time for UV/PS process. The results
liquid chromatography (HPLC Shimadzu-2010, Japan) with indicated the presence of PS accelerated the photo-oxide effi-
a UV detector, and its detection wave length was 230 nm. The ciency, and the degradation efficiency of 2,4-DCP was nearly two
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 100056–100062 | 100057

View Article Online
RSC Advances
Paper
Fig. 1 Degradation of 2,4-DCP in PS, UV, UV/PS processes; processes condition: [2,4-DCP]
0
¼ 6 mM, 2 mM phosphate buffer, pH ¼ 7.0, [PS] ¼
0
ꢃ
9
00 mM, 25 ꢅ 1 C.
ꢁ
times than UV without PS, it could attribute to SO4c and OHc
36
were formed when the PS was activated by UV in this process.
Moreover, from the inserting gures in Fig. 1, the pseudo-rst
rate constants for 2,4-DCP using PS, UV and UV/PS process
ꢁ
3
ꢁ3
ꢁ3
ꢁ1
were 0.4 ꢀ 10 , 6.2 ꢀ 10 and 35.1 ꢀ 10 min , respec-
tively. These results also demonstrate the UV/PS is feasible for
the 2,4-DCP degradation.
3.2 Effect of dosages of PS
ꢁ
Since OHc or SO
4
c
were generated by UV activated sodium
persulfate have been conrmed by Section 3.1 part, the amount
ꢁ
of OHc or SO
4
c
were decided by the dosage of sodium persul-
fate. The concentrations of 100, 300, 500, 700 and 900 mM PS
were chosen to study the change rate constants with the
increasing of initial concentration of PS. The reaction can be
expressed as the following eqns:
Fig. 2 Effect of initial PS concentration on the degradation of 2,4-
DCP; process condition: [2,4-DCP]
0
¼ 6 mM, 2 mM phosphate buffer,
pH ¼ 7.0.
d½2; 4-DCPꢄ
a
ꢁ
¼ kobs½2; 4-DCPꢄ
(2)
dt
ꢁ
1
degradation rate constant kobs and the oxidant dosage
[oxidant] ), they were found to have a linear relationship and
accord with the formula (3):
The kobs (min ) is the pseudo-rst-order kinetic constant, as
the Fig. 2 indicated the disposed rate of 2,4-DCP during UV/PS
process within 45 min increased with the dosage of PS
increasing.
(
0
2
k
obs ¼ 0.039[PS]
0
+ 0.1863, R ¼ 0.999
(3)
In whole, the trend showed that the greater the amount of
oxidant dosages was, the higher removal rate of 2,4-DCP was
achieved. The degradation rate constants of 2,4-DCP were tted
by pseudo-rst-order kinetics under the conditions of adding
In the study of UV/H
2
O
2
degradation of phenol in water of
37
Olmez-Hanci T. when the oxidant dosage is less than 30 mM, it
was found the degradation rate constant increased with the
increasing of oxidant dosage. However, when the oxidant
dosage is too high (>30 mM), the quenching reaction of free
radicals with oxidants will happen, which lead to decrease the
ꢁ
ꢁ1
3
amounts of oxidant. The reaction rate constants are 4.7 ꢀ 10
,
,
ꢁ
3
ꢁ3
ꢁ3
ꢁ3
1
0.6 ꢀ 10 , 15.3 ꢀ 10 , 28.7 ꢀ 10 and 35.1 ꢀ 10 min
when the oxidant dosage are 100, 300, 500, 700 and 900 mM,
respectively. Through the tting of the pseudo-rst-order
100058 | RSC Adv., 2016, 6, 100056–100062
This journal is © The Royal Society of Chemistry 2016

View Article Online
Paper
RSC Advances
degradation rate of pollutants. While in this experiment, the highest among in the pH 5, 6, 7, then the degradation rate and
maximum amount of oxidant dosage was far more than 30 mM the kobs is the highest in pH 7. In an alkaline solution, one
and it was not observed that the reaction rate of high oxidant aspect: with a higher redox potential of sulfate radical and
dosage decreased.
hydroxyl ions combined to generate a large number of lower
ꢁ
redox potential hydroxyl radicals. Another aspect: SO
4
c
may
play a role in scavenging OHc and slowing down the 2,4-DCP
degradation rate. Relatively more hydroxyl radicals are formed
at pH 8 compared to pH 7 in accordance with eqn (6) and (7).
Therefore, it is likely that more hydroxyl radicals would be
scavenged at pH 8 by sulfate ions than at pH 7; thereby the
above two reasons resulted in decreases in 2,4-DCP degradation
rates at pH 8 and a relatively improved performance at pH 7.
3
.3 Effect of pH
2
ꢁ
ꢁ
4
+ UV / 2SO c
S
2
O
8
(4)
(5)
(6)
2
ꢁ
+
8ꢁ
O
S
2
O
8
+ H / HS
2
8ꢁ
ꢁ
42ꢁ
+
HS
2
O
/ SO
4
c
+ SO
+ H
ꢁ
42ꢁ
+
4
SO c
+ H
2
O / SO
+ OHc + H
(7) 3.4 Effect of anions
In actual water body, it contains a large number of anions, for
SO4cꢁ
ꢁ / SO42ꢁ
+ OHc
+ OH
(8)
(9)
2ꢁ
ꢁ
2ꢁ
ꢁ
ꢁ
example: SO
4
, Cl , CO
3
, HCO
3
and NO , and so on. To
3
ꢁ
ꢁ
82ꢁ
2
O
some extent, the anions of the water body will affect the
SO
4
c
+ SO
4
c
/ S
degradation rate of the target pollutants. So, three kinds of
ꢁ
2ꢁ
anions, Cl , CO
3
ꢁ
ꢁ
5ꢁ
and NO3 , with high concentrations and
SO
4
c
+ OHc / HSO
(10)
great inuence in the water were investigated. Once these
anions were added to the system, it will produce many reac-
Fig. 3(a) describes the photolysis of 2,4-DCP in different pH tions, as shown in eqn (11)–(24):
condition; it demonstrated this reaction process can be well
ꢁ
ꢁ
Cl + OHc / ClOHc
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
described by the pseudo-rst-order kinetics. As the Fig. 3(b)
shows, the maximum degradation rate constant of 2,4-DCP
occurred at near neutral pH (i.e., pH 7) over the range of pH
used in this study. The kobs increased with the pH improved
from 5 to 7, and then decreased in pH 8, which is in accordance
ꢁ
+
ClOH c + H / HClOHc
HClOHc 5 Clc + H
2
O
3
8,39
with the results of Chenju Liang and Goulden, P.D.
Under
ꢁ
ꢁ
Clc + Cl 5 Cl2c
ꢁ
acidic conditions, additional SO
4
c
could be formed due to
acid-canalization as show in eqn (5) and (6). However, as
40
2
3
ꢁ
3ꢁ
ꢁ
¼ 4.3 ꢀ 10ꢁ7
CO
+ H
2
O / HCO + OH (k
1
)
8
ꢁ1 ꢁ1
shows in eqn (8) (ref. 41) (k
9
¼ 8.1 ꢀ 10 M
s
, pH ¼ 5.8) and
42
ꢁ
ꢁ
ꢁ
ꢁ
eqn (9), the higher SO
4
c generation rate causes higher radical
HCO3 + OHc / OH + CO c ,
3
concentrations, which could favor radical with radical reactions
2ꢁ
ꢁ
ꢁ
CO
3
+ OHc / OH + CO
3
c ,
or radical with radical scavenger reactions, over radical with
ꢁ
organic reactions, so the concentration of SO c in pH 7 was the
4
3ꢁ
4
ꢁ
42ꢁ
ꢁ
+ HCO
3
HCO + SO
c
/ SO
c ,
2
ꢁ
ꢁ
2ꢁ
ꢁ
CO3 + SO4c / SO4 + CO3c
3ꢁ
2ꢁ
2
NO / NO + 1/2O
ꢁ
ꢁ
NO3 / NO c + Oc
2
ꢁ
ꢁ
Oc + H
2
O / OHc + OH
2ꢁ
2
ꢁ
OHc + NO / NO
c + OH
ꢁ
ꢁ
2ꢁ
SO4c + NO3 / NO c + SO
4
3
As the Table S1† shows, the photo-oxidation rate of different
ꢁ
2ꢁ
ꢁ
concentrations of Cl , CO
3
and NO
3
were tted by the
2
pseudo-rst-order model. The R values were all above 0.95. As
shows in the Fig. 4(a). The reaction rate of 5 mM chlorine ion
was lower than that of without chlorine ions and then signi-
cantly increased with the increasing of chlorine ion concen-
tration between 10 mM and 200 mM. It can attribute to the
small concentration of chlorine ion consumed some OHc. While
Fig. 3 Degradation of 2,4-DCP under different pH by UV/PS; process
condition: [2,4-DCP]
0
¼ 6 mM; [PS] ¼ 900 mM.
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 100056–100062 | 100059

View Article Online
RSC Advances
Paper
3ꢁ
ꢁ
anions of solution were HCO and OH (the alkalinity value was
ꢁ
mainly determined by the value of HCO3 ). The pH value of 2,4-
DCP solution is improved from acidic, neutral to alkaline value
with the increasing of initial concentration of carbonate. As the
conclusions of the parts 3.3 with the pH value became from acidic,
neutral to alkaline value, the reaction rate constant is increased

rstly and then decreased. However, when the concentration of
ꢁ
4
carbonate ion is too high, it will react with the OHc and SO c
according with the eqn (16)–(19). So low concentration of
carbonate ion obviously promoted the reaction process and higher
initial carbonate concentration has begun to inhibit the reaction.
ꢁ
As the Fig. 4(c) described, with the increasing of NO3
concentration, the removal rate of 2,4-DCP increased signi-
ꢁ
cantly. Owing to NO
NO
NO
3
can generate the oxidation active factor
(
3
c) under UV light irradiation eqn (20)–(24) condition. The
c is also a high redox potential (2.5 V) radical, though the
redox potential is lower than SO
3
ꢁ
4
c , while the formation
amounts of NO c are enough to oxide the 2,4-DCP completely.
3
ꢁ
Therefore, the existence of NO3 can promote the degradation
of 2,4-DCP to a certain extent. The result is in good accordance
43
with that of Ghauch in the literature of ibuprofen removal by
heated persulfate.
3.5 Photolysis effect under the condition of actual water
samples
The photo-degradation of 2,4-DCP in raw water of water works
and reservoir water were conducted to assess the performance
of UV/PS in dealing with real waters polluted with trace 2,4-DCP.
As shown in Fig. 5, the degradation efficiency of 2,4-DCP in raw
water was much higher than that in the deionized water. The
degradation rates in ultrapure water, Henshan reservoir, Xijiu
reservoir, and Xidong waterworks are about 86.3, 89.6, 94.5, and
9
6.7%, respectively. As the Table S2† shows there are low
ꢁ
ꢁ
ꢁ
concentration (<5 mM) of NO
3
, Cl , HCO
3
in three kinds
actual water sources. The sections of 3.4 parts demonstrate the
ꢁ
ꢁ
low concentration of NO
3
, HCO
3
can promote the photo-
ꢁ
degradation obviously while the low concentration of Cl can
Fig. 4 Degradation of 2,4-DCP by UV/PS under different initial
ꢁ
2ꢁ
ꢁ
concentrations of anion. (a) Cl , (b) CO
3
, (c) NO ; the initiation
3
ꢁ
1
concentration of 2,4-DCP is 1 mg L ¼ 6 mM; [PS] ¼ 900 mM; the
concentration of anions are 0, 5, 10, 100, 200 mM, respectively.
the high concentration of chlorine ion can accelerate the
formation of Clc which according with the eqn (11)–(14). Many
Clc are generated and the oxidation reduction potential of Clc is
higher than that of OHc, which improved the reaction rate
obviously.
As the Fig. 4(b) shown, the degradation rates increased with
increasing carbonate ion concentration from 0 to 100 mM and
then began to decrease when the carbonate concentration was 200
Fig. 5 Effects of actual water samples on the degradation of 2,4-DCP,
1
mM. As the reaction (15) and the k constant indicated the main
process condition: [2,4-DCP]
0
¼ 6 mM, [PS] ¼ 900 mM.
0
100060 | RSC Adv., 2016, 6, 100056–100062
This journal is © The Royal Society of Chemistry 2016

View Article Online
Paper
RSC Advances
Fig. 6 Proposed reaction pathway of the photodegradation of 2,4-DCP in UV/PS oxidation process. Process condition: [2,4-DCP]
900 mM.
0
¼ 6 mM, [PS]
0
¼
3ꢁ
inhibit the reaction slightly. The NO concentrations are so detected aer the samples were exposed to the luminescent
little in three actual water bodies that the difference of effect bacteria for 0.25, 0.5, 1, 2, and 3 h, respectively. As shown in the
ꢁ
ꢁ
can be neglected. The HCO3 concentrations are larger than Cl
Fig. 7. The inhibition rate degradate from 98% to 10% in 45 min
in three actual water bodies. Overall, the promotion effect of when the solution was contacted to the photo bacteria for 3 h,
anion on photolysis is larger than that of inhibition. So the the inhibition rate degradate from 97% to 8% in 45 min when
degradation rates of actual water bodies are higher than the the solution was contacted to the photo bacteria for 2 h, the
free-anion ultra pure water. Owing to the concentration of inhibition rate degradate from 96.3% to 7.8% in 45 min when
ꢁ
ꢁ
HCO
3
of Xidong waterworks is the largest and the Cl
the solution was contacted to the photo bacteria for 1 h, the
concentration is the least among three actual water bodies. inhibition rate degradate from 95% to 6% in 45 min when the
While the anion condition of Henshan reservoir water is the solution was contacted to the photo bacteria for 0.5 h, the
opposite. So the degradation rate of Xidong waterworks is the inhibition rate degradate from 94% to 9% in 45 min when the
highest and Henshan is the least.
solution was contacted to the photo bacteria for 0.25 h. From
the value we can see the inhibition rate signicantly decrease
with the degradation of 2,4-DCP by UV/PS and the relative
inhibition rate were almost the same 89% within 3 h.
3.6 Intermediate products and possible degradation
pathways
To investigate the intermediates of the 2,4-DCP transformation
by UV/PS process, a reaction mechanism based on the GC/MS/
MS was proposed in Fig. 6. Two possible pathways for the
degradation of 2,4-DCP by UV/PS were proposed: (a) 2,4-DCP is
hydroxylated and formatted the isomers 3,5-dichlorocatechol,
4
,6-dichlororesorcin, 2,4-dichlororesorcinol. These intermedi-
ꢁ
ates may be further oxidized by OHc and SO4c to form the
products such as maleic acids or fumaric acids. (b) 2,4-DCP is
dechlorinated: the process is initiated by the breaking of the C–
Cl-bond at para position on the benzene ring of 2,4-DCP by OHc
ꢁ
and SO
4
c , simultaneously generate the intermediate products
of chlorohydroquinone and 4-chlorocatechol and further
ꢁ
oxidized by OHc and SO
4
c
to maleic acids or fumaric acids.
Parts of these organic acids were mineralized to CO and H O
2
2

nally. This was in good agreement with the research results of
44,45
degradation pathway of W. Z. Tang and W. Chu.
3
.7 Toxicity assessment
Fig. 7 The concentration–response curves of 2,4-DCP to Q67 at five
different exposure times. The data in the figures were represented as
In this study we used the Vibrio qinghaiensis sp.-Q67 to measure
the transformation products toxicity. The bioluminescence was mean and standard deviation calculated from the three replicates.
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 100056–100062 | 100061

View Article Online
RSC Advances
Paper
1
6 D. T. Sponza and A. Uluk ¨o y, J. Environ. Manage., 2008, 86,
4
Conclusions
121–131.
This study has demonstrated the process of UV/PS was a high 17 D. T. Sponza and C. Cıgal, Desalination, 2009, 245, 1–18.
effectively process to remove 2,4-DCP in actual water body. The 18 C.-W. Wang and C. Liang, Chem. Eng. J., 2014, 254, 472–478.
reaction followed the rst-order kinetics. The value of kobs 19 Y. Lee, D. Gerrity, M. Lee, S. Gamage, A. Pisarenko,
ꢁ
3
ꢁ3
ꢁ1
increased signicantly from 4.7 ꢀ 10 to 35.1 ꢀ 10 min , as
R. A. Trenholm, S. Canonica, S. A. Snyder and U. von
Gunten, Environ. Sci. Technol., 2016, 50, 3809–3819.
the dosage of PS increased from 100 mM to 900 mM. The optimal
reaction pH value was 7. In general, low concentration of anions 20 R. Norman, P. Storey and P. West, J. Chem. Soc. B, 1970, 1087–
in water presented promoting effect on the reaction. The
1095.
degressive bioluminescence inhibition rate value indicated that 21 D. E. Pennington and A. Haim, J. Am. Chem. Soc., 1968, 90,
the toxicity signicantly decreased with the degradation of 2,4-
3700–3704.
DCP. While the high content PS were very toxic on the biolu- 22 E. Laurenti, E. Ghibaudi, S. Ardissone and R. P. Ferrari, J.
minescence, so low concentration PS in UV/PS process is
Inorg. Biochem., 2003, 95, 171–176.
feasible to degradate the organic matter. All of this provides 23 R. Li, Y. Gao, X. Jin, Z. Chen, M. Megharaj and R. Naidu, J.
a theoretical and practical signicance for degradation of other
chlorophenols and persistent refractory organic compounds.
Colloid Interface Sci., 2015, 438, 87–93.
24 A. Dixit, A. J. Tirpude, A. Mungray and M. Chakraborty,
Desalination, 2011, 272, 265–269.
2
5 A. J. Luna, O. Chiavone-Filho, A. Machulek, J. E. F. de Moraes
and C. A. Nascimento, J. Environ. Manage., 2012, 111, 10–17.
Acknowledgements
This research group acknowledges the nancial support 26 Q. Zhang, J. Chen, C. Dai, Y. Zhang and X. Zhou, J. Chem.
provided by the National Natural Science Foundation of China
Technol. Biotechnol., 2015, 90, 701–708.
No. 51178321; No. 51208364), the National Major Project of 27 C. Liang, Y.-Y. Guo and Y.-R. Pan, Int. J. Environ. Sci. Technol.,
(
Science & Technology Ministry of China (No. 2012ZX07403-001;
2014, 11, 483–492.
No. 2008ZX07421-002). The authors greatly thank Shushen Liu 28 P. Xie, J. Ma, W. Liu, J. Zou, S. Yue, X. Li, M. R. Wiesner and
Professor group of Tongji University for supplying the toxicity
evaluation experiment.
J. Fang, Water Res., 2015, 69, 223–233.
29 Y.-J. Shih, Y.-C. Li and Y.-H. Huang, J. Taiwan Inst. Chem.
Eng., 2013, 44, 287–290.
3
0 Y.-J. Shih, W. N. Putra, Y.-H. Huang and J.-C. Tsai,
Chemosphere, 2012, 89, 1262–1266.
References
1
2
3
K. Hayward, Water, 1998, 21, 10–15.
31 H. Kola, T. Kuokkanen, I. V ¨a lim ¨a ki, P. Per ¨a m ¨a ki and
R. Lauhanen, Int. J. Environ. Anal. Chem. Technol., 2003, 83,
157–165.
32 J. Zhang, S.-S. Liu, Z.-Y. Yu, H.-L. Liu and J. Zhang, J. Hazard.
Mater., 2013, 258, 70–76.
T. H. H.-J. Stad, Anal. Chim. Acta, 1997, 341, 21–34.
M. Pera-Titus, V. Garcıa-Molina, M. A. Ba n˜ os, J. Gim ´e nez and
S. Esplugas, Appl. Catal., B, 2004, 47, 219–256.
S. Chaliha and K. G. Bhattacharyya, Catal. Today, 2009, 141,
4
5
6
7
8
225–233.
33 H.-L. Ge, S.-S. Liu, X.-W. Zhu, H.-L. Liu and L.-J. Wang,
Environ. Sci. Technol., 2010, 45, 1623–1629.
A. M. Abeish, H. M. Ang and H. Znad, J. Environ. Sci. Health,
Part A: Toxic/Hazard. Subst. Environ. Eng., 2015, 50, 125–134. 34 A. M. Al-Hamdi, M. Sillanp ¨a ¨a and J. Dutta, J. Alloys Compd.,
D.-Y. Ma, H.-F. Guo, K. Lu, Y. Pan and L. Qin, J. Coord. Chem.,
012, 65, 1610–1620.
2015, 618, 366–371.
35 N. Corin, P. Backlund and M. Kulovaara, Chemosphere, 1996,
33, 245–255.
36 R. Zhang, P. Sun, T. H. Boyer, L. Zhao and C.-H. Huang,
Environ. Sci. Technol., 2015, 49, 3056–3066.
2
W. Huan, Y. Yang, B. Wu, H. Yuan, Y. Zhang and X. Liu, Chin.
J. Chem., 2012, 30, 2849–2860.
M. H. Muhamad, S. R. S. Abdullah, A. B. Mohamad,
R. A. Rahman and A. A. H. Kadhum, J. Environ. Manage., 37 T. Olmez-Hanci and I. Arslan-Alaton, Chem. Eng. J., 2013,
013, 121, 179–190.
224, 10–16.
L. Dodgen, J. Li, D. Parker and J. Gan, Environ. Pollut., 2013, 38 C. Liang, Z.-S. Wang and C. J. Bruell, Chemosphere, 2007, 66,
2
9
182, 150–156.
106–113.
1
1
0 H. Jia and C. Wang, Chem. Eng. J., 2012, 191, 202–209.
1 L. F. Liu, P. H. Zhang and F. L. Yang, Sep. Purif. Technol., 40 D. A. House, Chem. Rev., 1962, 62, 185–203.
39 P. Goulden and D. Anthony, Anal. Chem., 1978, 50, 953–958.
2
010, 70, 354–361.
2 J. Wei, X. Xu, Y. Liu and D. Wang, Water. Res., 2006, 40, 348–
54.
3 D. He, X. Guan, J. Ma, X. Yang and C. Cui, J. Hazard. Mater.,
010, 182, 681–688.
41 P. Neta, R. E. Huie and A. B. Ross, J. Phys. Chem. Ref. Data,
1988, 17, 1027–1284.
42 U. K. Klaning, K. Sehested and E. H. Appelman, Inorg. Chem.,
1991, 30, 3582–3584.
43 A. Ghauch, A. M. Tuqan and N. Kibbi, Chem. Eng. J., 2012,
197, 483–492.
1
1
1
1
3
2
4 J. Su, S. Lin, Z. Chen, M. Megharaj and R. Naidu,
Desalination, 2011, 280, 167–173.
44 W. Tang and C. Huang, Environ. Technol., 1996, 17, 1371–1378.
5 E. Sahinkaya and F. B. Dilek, Biochem. Eng. J., 2006, 31, 141– 45 W. Chu, C. Kwan, K. Chan and S. Kam, J. Hazard. Mater.,
47. 2005, 121, 119–126.
1
100062 | RSC Adv., 2016, 6, 100056–100062
This journal is © The Royal Society of Chemistry 2016