The Study of Photolysis of Single Nonylphenol Isomer

Min Liu

1,2

, Li Lin

1,2

, Haiyang Jin

1,2

Zhuo Huang

1,2

, Liangyuan Zhao

1,2

, Xiaohuan Cao

1,2

, Caixiang

Zhang

and Xiaoping Liao

asin Water Environmental Research Department, Yangtze River Scientific Research Institute, Wuhan430010, PR China;

Key Lab of Basin Water Resource and Eco-environmental Science in Hubei Province, Yangtze River Scientific Research

Institute, Wuhan 430010, PR China;

State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR

China.

Email: caixiangzhang@yahoo. com.

Keywords: Photolysis behaviour, photolysis rate, nonylphenol isomer, identified products, pathway

Abstract: To better understand the photolysis behavior of technical nonylphenol (tNP) under low-pressure mercury

lamp (20 W) with light source (λ=253.7 nm), the study of the photolysis of single nonylphenol isomer

(NP

) and tNP were carried out. The result showed that NP

and tNP were removed quickly, the photolysis

rate of tNP was higher than that of NP

. H

accelerated remarkably the degradation of NP

. Identified

products of photolysis of NP

were probably 4 (2,6-dimethyl-2-heptyl)-1,2-benzenediol or 2 (2,6-dimethyl-

2-heptyl)-1,5-benzenediol, The photolysis of NP

seemed to proceed through two pathway: 4 (2,6-

dimethyl-2-heptyl)-1,2-benzenediol was generated by the reaction of NP

and O

· radicals, the reaction of

and ·OH radicals that produced by the photolysis of H

O maybe the precursor of 2 (2,6-dimethyl-2-

heptyl) -1, 5-benzenediol, but the H

oxidised the intermediate products could not be detected by GC-MS.

1 INTRODUCTION

Nonylphenol (tNP) was one of endocrine disruptors

(EDCs) due to its estrogenic effect, which was

produced by the degradation of the nonionic

surfactant (NPEO). tNP was more stable, toxic and

accumulate than the NPEO, which was stable in

water (Kannan et al., 2003; Xia et a1., 2013) and had

a significant toxicity effect on zebrafish embryos at

2 µg·L-1 (Zhang et al., 2017). tNP was found in

sewage sludge during the 80s (Giger et al., 1984 ),

and a large amount of tNP were detected on surface

water, groundwater, soil, sediment, air and so on

(Guenther et al., 2002; Liu et al., 2013; Careghini et

al., 2015; Chen et al., 2013; Peng et al., 2016). tNP

was included in the European Union water

framework directive as a new hazardous substance.

The tNP levels was limited at 6.6 µg·L-1 in fresh

water and 1.7µg·L-1 in the seawater (Brooke and

Thursby, 2005).

The degradation rate of tNP under the UV was

about 1.3 times higher than that of natural light

source (Neamţu and Frimmel, 2006). The straight

chain of NP (4-n-NP) degradation rate reached 90%,

after 4 h under certain conditions (Martínez et al.,

2013; Li et al., 2012). The study of degradation of

tNP showed that hydroxyl free (·OH) could

promoted the degradation of tNP under the266 nm

laser flash photolysis and 254 nm photolysis (Zhang

et al., 2012). The above researchers mainly studied

the photolysis of nonylphenol with tNP or 4-n-NP as

the research object, but tNP was composed of a

variety of nonylphenol monomers, and the para

nonylphenol (4-NPs) was mainly composed of alkyl

side chains, which accounted for 86~94%

(Eganhouse et al., 2009). Some study showed that

the photolysis products of the tNP was 4-nonyl-

catechol (Li et al., 2012), but others showed that the

photolysis products of the tNP might be phenols,

aldehydes and carboxylic acids. Therefore, further

research was needed for the photolysis mechanism

of nonylphenol. NP38 monomer was one of 4-NPs,

which was common in the tNP (Eganhouse et al.,

2009; Shan et al., 2011). In this study, NP38 was

chosen as the research object, and its photolysis

Liu, M., Lin, L., Jin, H., Huang, Z., Zhao, L., Cao, X., Zhang, C. and Liao, X.

The Study of Photolysis of Single Nonylphenol Isomer.

In Proceedings of the International Workshop on Environment and Geoscience (IWEG 2018), pages 82-86

ISBN: 978-989-758-342-1

pathway was discussed, which provided a theoretical

basis for the final fate of tNP in water environment.

2 MATERIALS AND METHODS

2.1 Materials

tNP was bought from Fluka with 99.9% (Germany),

(purity, >99%) was synthesized by friedel-

crafts alkylation with 2, 6-dimethyl-2-hepty and

phenol in laboratory (Vinken et al., 2002),

Methanol, n-hexane and Dichloromethane were

chromatographic grade (CNW, Germany). Ultrapure

water (18.2 MΩ·cm) produced by a Mili-Q system,

200 mg·L

-1

stock solutions of NP

was prepared

with methanol, the solutions were prepare by adding

an appropriate of stock solution in methanol with

ultrapure water to obtain final concentration 5 mg·L

of NP

2.2 Experiment Design

Photolysis batch experiments in water: each

photolysis experiment had two replicates. The

irradiation device with quartz test tubes (volume: 35

, average optical path length: 6 cm) in this study

referred to our previous work (Jia et al., 2009). In

brief, the experiment was carried out by using low-

pressure mercury lamp (20 W) as light source

(λ=253.7 nm).Those samples that were wrapped by

the aluminum toil and kept in the dark set as control

group. All Samples were taken at certain time

intervals during the irradiation.

2.3 Extraction and Analysis

tNP and NP

determination in water: the water

samples were extracted by liquid-liquid extraction

method. 10 ml of sample was transferred to

separating funnel and extracted three times with 10

ml of DCM, the collected samples were enriched to

about 0.5 ml by a rotary evaporator (Buchi,

Switzerland) and transferred into 2 ml of blown

bottle. They were dried under a gentle nitrogen

stream and redissolved in 0.4 ml of methanol to

being detected by High Performance Liquid

Chromatography (HPLC, 1100-UVD, Agilent

Technologies, USA) (Jia et al., 2009), the crude

products of NP38 were identified by Gas

Chromatograph-Mass Spectrometer (GC-MS, 6890-

5975N, Agilent Technologies, USA) (Shan et al.,

2011).

3 THE RESULTS AND

DISCUSSION

3.1 The Photolysis tNP and NP

In the text, Figure.1 shows that tNP and NP

can be

efficiently degradated by 78.36% and 69.61%

respectively in an hour through UV photolysis, it

was similar to the degradation of octylphenol (4-OP)

under low pressure mercury lamp (Liao et al., 2009).

The photolysis rate of tNP was fast than NP

, due to

the presence of more isomers in tNP that was easy to

degradation than NP

. The decay of the tNP in our

study was prominently faster than reported under the

simulate sunlight (Li et al., 2012), which proved UV

light could efficiently decompose tNP.

3.2 The Effect of H

to the

Photolysis of NP

Figure.2 shows that only 6.4% and 4.3% of NP

existed in the experimental group containing

20mmol·L

-1

and 50mmol·L

-1

solution, but the

monomer still had 58.2%, after 60 min, in the

solution without H

. This indicates that H

greatly promoted the photolysis process of NP

, and

the higher concentration of H

was more

beneficial to the photolysis of NP

monomers.

Figure 1: Photolysis of NP

and tNP in ultrapure water,

Control group (tNP, 5 mg·L

-1

). Initial condition: pH=6.59,

T=25 ℃, t=8 hours.

The Study of Photolysis of Single Nonylphenol Isomer

Figure 3 shows that the degradation products of

in H

solution were different from those of

in ultrapure water system, the total ion

chromatogram (TIC) was shown. A was NP

(the

peak time is 12.26 min). B was intermediate

photolysis product (the peak time is 19.72 min), but

it wasn’t detected in the TIC diagram of H

solution, because its intermediate product was

further oxidized to be other substances had different

photolysis pathways.

Figure 2: The effect of H

upon the photolysis of NP

Initial conditions: C

= 0.5 mg·L

-1

, pH= 6.59, T = 25 ℃,

t=120 min.

Figure 3: TIC analysis of NP

in ultrapure water after UV

illumination for 60 min.

3.3 The Photolysis Pathways of NP

Figure 4 and Figure 5 shows that the MS spectrum

of the NP

was mainly included 135 (100), 136

(10), 121 (5), 119 (2), 107 (15) and the MS spectrum

of the B was mainly included 151 (100), 152 (10),

137 (5), 123 (11), 135 (2), because Hydrogen atom

on the benzene ring of the NP

was substituted by

hydroxyl group produced B, 135→151, 107→123,

136→152, 121→137, 119→135. 4 (2, 6-dimethyl-2-

heptyl)-1, 2-benzenedio and 2 (2, 6-dimethyl-2-

heptyl)-1, 5-benzenediol was produced by

photolysis of NP

( Corvini et al., 2005).

Figure 4: A bar graph of NP

38.

Figure 5: A bar graph of B.

Figure 6 showed two photolysis pathways of

. On the one hand, NP

was in the excited state

and transferred into the 4-nonyl benzoxy radical

with active ortho hydroxyl group at low-pressure

mercury lamp (20 W) , O

was formed after the O

IWEG 2018 - International Workshop on Environment and Geoscience

captured electron. The 4 (2, 6-dimethyl-2-heptyl)-1,

2-benzenedio (Figure 6-A) was produced when the

4- nonyl benzoxy radical was attacked by the O

On the other hand, hydrogen atoms on adjacent

carbon atoms of NP

were more susceptible to be

replaced by the hydroxyl and was converted to 2 (2,

6-dimethyl-2-heptyl)-1, 5-benzenediol (Figure 6-B),

due to the alkyl side chain of NP

had the electron

cloud density on the opposite substituent of the

benzene ring (Vinken et al., 2002). There were

different products from 4-n-NP after photolysis (Li

et al., 2012), because of more complex structure of

the alkyl side chain on NP

than that of 4-n-NP.

This study indicated that the structure of tNP had a

certain effect on its photolysis behavior.

Figure 6: The possible photolysis pathways of NP

38.

4 CONCLUSIONS

The photolysis behavior of NP

was studied under

the conditions of different initial concentration and

different concentration of H

with low pressure

mercury lamp as the light source. the degradation

products of NP

were identified by GC-MS, and the

possible degradation pathways of NP

were

analyzed. NP

and tNP were removed quickly under

the UV radiation. The photolysis rate of tNP was

higher than that of NP

. Photolysis would not stop

until all of them disappeared from solution. H

accelerated remarkably the degradation of NP

was degraded about 93.6% and 95.4% in H

20 mmol·L

-1

and 50 mmol·L

-1

. Identified resulting

products were probably 4 (2, 6-dimethyl-2-heptyl) -

1, 2-benzenediol or 2 (2, 6-dimethyl-2-heptyl)-1, 5-

benzenediol. The photolysis of NP

seemed to

proceed through two pathway mechanisms: 4 (2, 6-

dimethyl-2-heptyl)-1, 2-benzenediol was generated

by the reaction of NP

and O

radicals; The

reaction of NP

and ·OH that produced by the

photolysis of H

O maybe the precursor of 2 (2, 6-

dimethyl-2-heptyl) -1, 5-benzenediol, but the H

oxidized the intermediate products so that it could

not be detected by GC-MS.

ACKNOWLEDGEMENT

This work was supported by Young Elite

Sponsorship Program by CAST (Grant

2015QNRC001), the National Natural Science

Foundation of China(Grants 51309019), State-level

Public Welfare Scientific Research Institutes Basic

Scientific Research Business Project of China

(CKSF2017062/SH).

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