The process of atrazine degradation, its mechanism, and the formation of metabolites using UV and UV/MW photolysis

Article abstract of DOI:10.1016/j.jphotochem.2017.07.022

The photolytic degradationmechanism of atrazine using a UV reactor andUV/MW (electrodeless discharge lamp (Hg-EDL)) was investigated. After 120?s of UV photolysis partial degradation of atrazine had been observed and a subsequent formation of degradation products of atrazine-2-hydroxy, therefore, defining the path of atrazine degradation through UV photolysis. This system after 1200?s of exposure to UV radiation had not reached full degradation of atrazine, and its metabolite (atrazine-2-hydroxy), was the main by-product obtained for the process. When performing photolysis through the UV/Microwave combined methodcomplete atrazine degradation was obtained within a 5?s interval, besides the formation of five (5) degradation products, which are HAT, DEAT, DIAT, DEHAT and DIHAT. Therefore, defining the path of the photolytic degradation process through the UV/Microwave combined method. The total degradation of its metabolite (HAT) was observed for the period of 120?s of exposure to UV/MW radiation, and after that time there had been no signcorresponding to the respective compounds. The tests with the isolated microwave radiation were not efficient in the degradation of the atrazine and, therefore, the respective isolated energy is not applicable.The control of atrazine degradation and consequent formation of metabolites were accompanied by a high-performance liquid chromatography with a UV/Vis detector.

Full text of DOI:10.1016/j.jphotochem.2017.07.022

Accepted Manuscript
Title: The process of atrazine degradation, its mechanism, and
the formation of metabolites using UV and UV/MW
photolysis
Authors: Ailton. J. Moreira, Aline C. Borges, Luis F.C.
Gouvea, Tatiana C.O. MacLeod, Gian P.G. Freschi
PII:
S1010-6030(17)30274-5
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jphotochem.2017.07.022
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Journal of Photochemistry and Photobiology A: Chemistry
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Revised date:
Accepted date:
2-3-2017
6-7-2017
20-7-2017
Please cite this article as: Ailton.J.Moreira, Aline C.Borges, Luis
F.C.Gouvea, Tatiana C.O.MacLeod, Gian P.G.Freschi, The process of atrazine
degradation, its mechanism, and the formation of metabolites using UV
and UV/MW photolysis, Journal of Photochemistry and Photobiology A:
Chemistryhttp://dx.doi.org/10.1016/j.jphotochem.2017.07.022
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1
The process of atrazine degradation, its mechanism, and the formation of
metabolites using UV and UV/MW photolysis.
Ailton. J. Moreira1, Aline C. Borges1, Luis F. C. Gouvea1, Tatiana C. O. MacLeod1, Gian P. G.
Freschi1*
LAFFEQ, Institute of Science and Technology, Federal University of Alfenas, UNIFAL-MG
37715-400, Poços de Caldas- MG, Brazil
*Corresponding author. Tel.: +55 35 3697-4710
E-mail address: gianpgfreschi@gmail.com (Gian Paulo G. Freschi)

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Graphical Abstract
HIGHLIGHTSDegradation mechanism process and metabolites/products using different energies.
- Photolytic oxidation of atrazine was studied using different energies.
- Degradation rates of atrazine were quantitatively better and more fast using UV/MW system
- Degradation products, were identified using liquid chromatography and standard solution of
the formed metobolites/products
Abstract
The photolytic degradationmechanism of atrazine using a UV reactor andUV/MW (electrodeless
discharge lamp (Hg-EDL)) was investigated. After 120 seconds of UV photolysis partial degradation of
atrazine had been observed and a subsequent formation of degradation products of atrazine-2-hydroxy,
therefore, defining the path of atrazine degradation through UV photolysis. This system after 1200 seconds
of exposure to UV radiation had not reached full degradation of atrazine, and its metabolite (atrazine-2-
hydroxy), was the main by-product obtained for the process. When performing photolysis through the
UV/Microwave combined methodcomplete atrazine degradation was obtained within a 5 second interval,
besides the formation of five (5) degradation products, which are HAT, DEAT, DIAT, DEHAT and DIHAT.
Therefore, defining the path of the photolytic degradation process through the UV/Microwave combined

3
method. The total degradation of its metabolite (HAT) was observed for the period of 120 seconds of
exposure to UV/MW radiation, and after that time there had been no signcorresponding to the respective
compounds. The tests with the isolated microwave radiation were not efficient in the degradation of the
atrazine and, therefore, the respective isolated energy is not applicable.The control of atrazine degradation
and consequent formation of metabolites were accompanied by a high-performance liquid chromatography
with a UV/Vis detector.
Keywords: Atrazine; degradation products; photolysis; mechanism.
1.
Introduction
Many studies have tried to address the contamination of the environment through a new perspective
that goes beyond the exclusive concern to the original contaminant released directly into the most diverse
ecosystems[ 1 ] . This new approach seeks among its main objectives the understanding of the many changes
these various compounds pass through the environment, which allows us to act more effectively in
promoting environmental preservation[ 1, 2 ].
Organic compounds have drawn attention to this new perspective, since new substances are
synthesized each year, standing out among these agrochemicals[ 3, 4 ]. Studies have shown that attention
on the behavior of compounds (mainly synthetic) to the environment must be doubled since it causes serious
problems of environmental degradation, because they interact in various ways in the environment, resulting
in more toxic compounds than originally[ 5, 6 ].
Exposure to chemicals (pesticides) can result in clinical changes throughout the life of people
exposed. However, even though some pesticides havebeen used for many years, it is difficult to make a
conclusionabout their actionsin living organisms, since many are applied simultaneously[ 7-9 ].
Environmental conditions may directly or indirectly influence the production of toxins. The data presented
by (Maazouzi, 2016), demonstrates that atrazine-desethyl (DEAT) exerted toxicity in 4 different aquatic
species evaluated, and this toxicity was verified in concentrations ranging from 0.1 to 100 mg L-1. For
example, in G. Pulex species, the mortality was greater than 50% for the exposure to DEAT of 5 mgL-1 after
96 h[ 10 ].

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In a recent study, it has been shown pesticide combinations can influence the development of
plants.The fact of relevance was the first evidence that atrazine-2-hydroxy, the metabolite resulting in
atrazine degradation, acts to induce metabolic disorders of living organisms[ 11 ]. It should be noted that
the concern about monitoring degradation products hasalready been discussed, but with greater emphasis
on the class of well-known compounds[ 9, 12 ].
Currently, the Advanced Oxidation Processes (AOP's) have shown the greatest potential in the
removal of persistent organic compounds, whereas the most varied combinations of physical and chemical
processes have enabled a significant removal of the polluting agent in an extremely short time (hours,
minutes, seconds )[ 13, 14 ], as opposed to biological processes, which for the majority to present potential,
still need further studies[ 15 - 17].
It stands as a common characteristic of the most recent work, the search for understanding the
formation mechanisms of products of degradation of pollutants, which can be influenced directly or
indirectly in function of the treatment process used[1, 14, 18 ].
In the most widely use AOP’s of the degradation of persistent compounds, photocatalytic processes
using various types of radiation, have been greatly addressed[ 14, 19 ], therefore, the vast majority of UV
photolytic processes alone havea low potential for degradation. In general, UV radiation is used with
oxidizing chemical agents and/or photocatalysts[ 20 ].
Recently, microwave radiation has been investigated for the organic synthesis process, which has
allowed better yields in obtaining products. Furthermore, highlighting that the reaction mechanisms can be
changed and accelerated, therefore, allowing less formation of unwanted intermediates in the
synthesis.Consequently, this demonstrates the significant influence of the use of microwave radiation in
chemical processes[ 21 ].
The operation of different energy in the effluent treatment process is of great importance, since
photocatalytic studies using a micro porous mineral assisted by the conducted microwave[ 22 ]allowed not
only a good degradation rate, but also obtained new intermediates resulting from photolytic degradation,
which may be of interest depending on the toxicity of these species.

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The combination of different types of energy and photocatalytic materials allowed 98.5% of atrazine
mineralization and by-products in a period of 20 minutes[ 14 ].Reports that the microwaves allowedthe
semiconductor activation of materials (graphene/TiO2 for example)creating, in some cases, micropores
which can absorb the radicals, pollutants or precursors[ 23 ]. Furthermore, it accelerates the oxidative
processes due to the fact that the initial processing occurs on the surface even when taken in conjunction
with UV radiation.
For the photolytic and photocatalytic processes, Hg-EDL lamps were applied using the combined
MW-UV energy. Therefore, allowing a better distribution of radiation alongside the system emitting 3 times
more UV than conventional lamps. Thus, this eliminated the need to use equipment or materials that absorb
undesirable fractions of UV / VIS radiation[ 21 ].
Found that the products formed duringatrazine degradation are directly related to the process used,
the studied hydrolysis process (producing 11 degradation products)[ 24 ]. Another study evaluated the
photocatalysis-assisted process associated with microwave energy [ 22 ] andtwo degradation mechanisms
have been proposed forming 10 degradation products.
Effluent treatment processes that allow degradation of the pollutant in a short time are of great
importance in the industry, which, when generating large volumes of effluents, must treat them quickly so
as not to cause impacts on the environment. It is also important to highlight that the search for total
mineralization is important, and treatment processes that achieve this goal are of great industrial application.
In addition, the work demonstrates what type of treatment processes of persistent organic compounds
have influence over the metabolic pathways of degraded compounds. This work aims to understand the
influence of different photolytic processes (UV and UV/MW) in the formation of atrazine metabolites,
seeking to contribute to the understanding of the compound degradation processes and its possible behavior
toward the environment.
2.
Experimental
2.1 Materials and equipment
A UV-Vis HACH DR 5000 spectrophotometer combined with a 1 cm optical path quartz cell was
used for preliminary determination through molecular absorption measurements. The equipment having a

6
wavelength range of 190 to 1100nm with manual and automatic selection was employed with a scanning
speed of 900 nmmin-1, 1 nm steps and a spectrum band width of 2 nm.
Photolytic Experiments in the UV region were performed in a 50 mL glass beaker, placed in a
wooden reactor, internally lined with aluminum foil. Its internal dimensions were 46cm (length) x 30cm
(width) x 31cm (height). In addition, it also consisted of 6 low-pressure mercury Philips lamps TUV 15W
/ G15T8 - Long Life - UV - C (λmax = 254 nm) and 2 Cooler Axial AC FAN Models FZY12038 HBL.
Photolytic studies using microwave (MW) and ultraviolet (UV) energies were performed on
commercial equipment such as: a Panasonic NN7856BK, 220V, 60Hz, having a microwave frequency of
2450 MHz and a potency of 1500W as well as a mercury discharge lamp electrode, and an Hg- EDL (UMEX
GmbH Dresden, Hg:254 nm, Germany) with a sample compartment of quartz of 10mL. Photolytic studies
using microwave energy were run on the same equipment in the absence of the Hg-EDL lamp.
The Chromatographic analyses were performed on a High Performance Liquid Chromatograph
(HPLC) Agilent 1220 Infinity LC, equipped with an automatic sample, an oven temperature control column,
a UV/Vis detector system and a chromatographic column Zorbax Eclipse Plus C18, 4.6 x 250mm, 5μm. The
processing of chromatographic data was administered by the Agilent OpenLAB Chromatography Data
System Software (CDS) EZChrom.
2.2 Reagents and analytical solution
Standard solution (stock) of Atrazine (ATZ), Atrazine-desethyl (DEAT), Atrazine-2-hydroxy (HAT)
Atrazine-desisopropyl (DIAT) 1000 mg L-1, Atrazine-desethyl-desisopropyl (DEDIAT) 1071 mg L-1,
Atrazine-desethyl-2-hydroxy (DEHAT) 1006 mg L-1 and Atrazine-desethyldesisopropyl-2-hydroxy
(DEDIHAT) 200 mg L-1 were prepared by dissolving the respective reagents (Riedel-de-Häen, Sigma
Aldrich, Germany) in methanol HPLC grade (JT Backer). The patterns of Atrazine-desethyldesisopropyl-
2- hydroxy 200 mg L-1 and Atrazine-desisopropyl-2 hydroxy (DIHAT) of 990.5 mg L-1 were prepared in
HPLC grade methanol (JT Backer) and 1 mL of hydrochloric acid of 1 mol L-1 for better solubilization of
the respective reagents, which were then used for preparation of interim standards.A phosphate buffer

7
solution pH = 7.0 (19.5 mmol L-1 KH2PO4 / 30.5 mmol L-1 K2HPO4) was prepared by dissolving the
respective salts (Sigma Aldrich, USA).
Acetonitrile and methanol, HPLC grade (JT Backer) were used in the preparation of solutions and
processes linked to chromatographic analysis. It is important to point out, since the objective of this study
was to evaluate the influence of isolated ultraviolet (UV) and microwave (MW) energies and associated
energies (UV/MW) in the atrazine degradation processes. The respective herbicide solutions were prepared
in ultrapure water and not in environmental matrices. We attempted to eliminate any matrix interferences
in the tests and so the application process of real samples can be administered in future work.
An atrazine solution was prepared from a stock solution (stock) with a concentration of 3 mg L-1 to
implement the photolytic trials. All solutions were prepared from analytical grade chemicals and ultra-pure
water with a minimum of 18.0 M-1 Ω.cm resistivity obtained in a Milli-Q Plus system (Millipore, Bedford,
MA, USA). The samples/standards were stored in high density polypropylene bottles (Nalgene ®) and were
kept refrigerated.
2.3 Photolytic degradation of atrazine
Aliquot 10 mL of atrazine solution of 3 mg L-1 were transferred to 50 mL glass beaker and inserted
into the UV chamber and remain exposed to radiation (constant stirring). For assays using photolysis
UV/MW 10mL aliquot sample were transferred to the sample chamber presents the mercury discharge lamp
Hg EDL electrode (UMEX GmbH, 254nm, Dresden, Germany) supported in 250 mL glass beaker in a
microwave equipment Panasonic NN7856BK operating at full power. After exposure to electromagnetic
radiation in intervals of time from 0 to 20 min (UV) and 0 to 4 min (UV / MW), the samples were analyzed
by spectrophotometry (preliminary studs) and high-performance liquid chromatography with UV / Vis
detection, following the procedure described Fig. 1.
2.4 Identification of atrazine and degradation products.
Aqueous absorbance of atrazine and degradation products in a concentration of 1mg L-1 was
determined by molecular spectrometry and the experimental spectral wavelengths of the herbicide Atrazine
and 7 (seven) of its degradation products were selected by analytical wavelengths. This procedure was

8
important for the identification of atrazine and the preliminary evaluation of possible products formed during
the photolytic process. The results obtained contained in Fig. 2- A.
2.5 Monitoring of the degradation products of atrazine.
After photolytic assays, 30 uL of the solution were injected into the liquid chromatograph Agilent
1220 LC Infinity by means of autosampler, being used for the chromatographic separation Eclipse Zorbax
C18, 4.6 x 250 mm, 5 um.The chromatographic conditions were using an elution gradient (v/v): 0 to 3
minutes, 0% (ACN) / 100% PO43- buffer (pH = 7), 3 to 10 minutes. 20% (ACN) / 80% PO43- buffer (pH =
7), 10 to 20 min, 70% (ACN) / 30% PO43- buffer (pH = 7) 20 to 25min 90% (ACN) / 10% PO43- buffer (pH
= 7) detecting 221nm, a mobile phase flow rate of 1 mL min-1 and a controlled temperature of 25 ° C.
3.
Results and Discussion
The results show molecular absorption at intervals of very close wavelengths of different atrazine and
its metabolites, making inconclusive qualitative and quantitative analysis of species using only molecular
absorption by spectrophotometry of UV/Vis, whereas, significant absorption values were observed for
metabolites of atrazine at 221nm, as can be seen onTable 1.It is noteworthy that this technique can provide
interesting information for preliminary studies of atrazine once the signs are monitored specificallyfor
individual compounds or group compounds.
Fig. 2 shows molecular absorption results for the photolytic processes UV (B), MW (C) and UV/MW
(D), and it can be observed that the MW process was the only one to show no degradation of Atrazine with
consequent formation of degradation products, which can be accompanied by the appearance of new
absorption bands. Since the new bands were not observed in the microwave process, the samples were not
monitored by HPLC-UV.
As shown in Fig. 2A and 2D, the molecular absorption drop at 221 nm (ATZ) (points 1 and 3,
respectively) is accompanied by increased molecular absorption near 240 nm (points 2 and 5, respectively),
showing preliminarily, that the origin of degradation of atrazine has compounds with higher molar
absorptivity in the region of 240 nm, in this case HAT (240 nm), DEHAT and DIHAT (both at 234 nm).
Fig. 2C shows that even though there is a decrease in molecular absorption in the region of 221 nm
(ATZ), (point 3) there is no increase in molecular absorption in any monitored spectral region, showing that

9
none of the metabolites evaluated in this work are formed, and therefore it was not necessary to perform
sample monitoringthrough HPLC – UV. Only the products preliminarily observed by UV / Vis
spectrophotometry were monitored through chromatographic analysis.
3.1 Monitoring atrazine anddegradation products after UV photolysis.
The evolution of analytical dataobtained after UV irradiation of the atrazine sample of3mg L-1 (Fig.
3 - A) showed that photolysis is effective after 120 seconds of irradiation. This is where we can observe
18% of decrease in the sign of atrazine. It is also observed that the most significant decrease in the sign of
atrazine (34%) occurs at the time of 300 seconds of photolysis. At the same time there is an increase of the
signcorresponding to HAT, which is due to hydroxylation of halogenated carbon.
Most importantly, the C-Cl bond was not affected by the resonance of pi electron, unlike the C-N
bonds present in the triazinic oring, where nitrogen has an unpaired electron. Therefore, the insertion of a
hydroxyl radical in the system by means of water photolysis allows greater stability to the chemical structure
(Fig.4-A), as described in the literature[ 25 ]. This promotes the replacement of chlorine present in the
triazinic oring via the hydroxylation mechanism since this position possesses a larger energy imbalance. In
addition, it is also worth mentioning that the stability of the ring for the hydroxyl form is higher than the
stability for the chlorinated one, since the hydroxyl radical enables electronic resonance of a C-OH bond.
Consequently, giving greater stability to the molecular structure[ 26 ].
During UV photolysis of atrazine the minority formation of DEAT was verified (0.16 mg L-1 in 20
minutes). The result of the dealkylation mechanism promoted by direct photolysis was reported as a possible
mechanism of degradation of atrazine by (C. Chen et al. 2009) [ 29 ]. However, his studies have emphasized
that the preferential route of atrazine degradation is hydroxylation-dehalogenation and, therefore, the results
obtained in this work are reported in the literature.
Before photolysis, the chromatogram shows a sign corresponding to the DEDIHAT in the non-
irradiated sample. It is possible that this signal corresponds to a contamination, and not a degradation
product, since in all chromatograms were observed at the same level of the signal even after a significant
increase in irradiation time. The results herein are according to some published data showing that atrazine-
2-hydroxyis always observed as one of the initial products of the atrazine degradation step[ 1, 27 ].

10
Thus, based on the above explanation, after the UVphotolysis time, it is defined thatHAT (3.35 mg
L-1 in 20 minutes of UV photolysis) was the only product found for the degradation of ATZ, and thereby
the degradation pathway can be represented in Fig.4-A. The unique formation of HAT evidences the
selectivity of the degradation process, which may be useful for other technological applications.
3.2 Monitoring of atrazine metabolites after UV/MW photolysis.
The evolution of analytical dataobtained after UV/MW photolysis of an atrazine solution of3mg L-1
(Fig.3-B) showed elevated efficiency of photolysis had already been obtainedin 5 seconds of exposure, as
can be seen in the total disappearance of the signcorresponding to atrazine and the appearance of
signcorresponding to HAT, DIAT, DEAT, DEHAT and DIHAT. The mechanism of hydroxylation of
halogenated carbon (Fig.4-A) is similar to degradation by UV photolysis and verifies preferential formation
of HAT (2.31 mg L-1 in 0.5 minutes) in the respective time. However, in just 5 seconds HAT, DIAT, DEAT,
DEHAT and DIHAT could be observed in concentrations of 1.96 mg L-1, 0.03 mg L-1, 0.09 mg L-1, 0.12 mg
L-1 and 0.41 mg L-1, respectively which was unlike the process using UV radiation alone.
The DIHAT can be formed by the degradation of ATZ and / or HAT, although the second possibility
is more acceptable since, after 30 seconds of photolysis, it is the rapidly decreasing HAT degradation signal.
In addition, at the same time that the DIHAT signal increased in the absence of ATZ (which had been
completely degraded in less than 5 seconds of irradiation), DEHAT formation is observed, confirming that
the hydroxylation process is the principal pathway in the degradation mechanism of atrazine.
It is also noted that the DIAT and DEAT products are formed through the UV/Microwave combined
method, but in very low quantities, demonstrating that hydroxylation is still the preferential route when
compared to direct photolysis. Thus, atrazine dealkylation products (DIAT and DEAT) may be proposed as
the precursors of the DIHAT and DEHAT products after the hydroxylation process, but this pathway is not
the most acceptable, since no significant amounts of halogenated products (DIAT and DEAT) were
composed.
In the sign corresponding to 5, 60, 90 and 120 seconds (Fig.3-B), there is formation (0.083 to 0.5
min), reduction (0.5 to 1.5 min) and complete disappearance of HAT (from 2.0 min). Fig.4-B describes the
proposed mechanism for photolytic degradation of atrazine by UV / MW process.

11
The UV/Microwave combined methoddemonstrates a high system capacity to form hydroxyl radicals,
since all of the atrazine undergoes degradation by hydroxylation of halogenated carbon in only 5 seconds of
exposure, and then dealkylation occurs forming the DIHAT and DEHAT. The DEAT and DIAT products
demonstrate possible direct photolysis, but on a very small scale.
The kinetic study of the different processes revealed that the degradation of atrazine by UV photolysis
follows a pseudo kinetic order first. The degradation constant of 0.0597 min -1 and R2 = 0.991 (Figure 3 –
C) was verified, accordingly, in agreement with the results found in literature, where values of k = 0.0617
min-1 were observed [ 30 ].
The results obtained in this study are in agreement with the data observed by N. Ta et al. [ 31 ]which,
when studying Atrazine degradation in an aqueous solution using a mercury lamp there was no electrode
discharge. It obtained a degradation total of Atrazine 10 mg L-1 in 8 minutes In addition, the verification
of the products reported in this work enabled to define the same mechanism of degradation that is proposed
in this study for the compounds detected through high performance liquid chromatography with UV
detection.
It is important to note that in the study carried out by N. Ta et al. [ 31 ], the reactor was composed of
an electrodeless mercury lamp discharge containing different characteristics from the ones used in this study.
The finding of the total degradation of Atrazine 3 mg L-1 obtained in 5 seconds is related to the fact that the
reactor used in this work has a sample compartment (a 10 mL high permeability synthetic quartztube) in the
center of the lamp. Moreover, the low external permeability of the synthetic quartz walls allow UV radiation
from the electronic excitation of the Hg vapor be reflected to the center of the lamp, concentrating the largest
amount of the UV radiation at this position, and consequently significantly increasing the degradation of the
respective herbicide and degradation products
The data presented in Table 2 show that, for different processes, different degradation by-products
can be monitored, indicating that parameters such as energy type, reactor configuration, catalyst addition
(among other parameters) influence the degradation of atrazine. In this way, the information contributes to
the selection of atrazine degradation processes, which allow the generation of by-products in less quantity,
or less toxicity to the ecosystem. The respective work shows that through the combined UV / Microwave

12
method, hydroxylated by-products are preferred, these being less toxic than the chlorinated by-products,
which can be verified in larger amounts by the application of other processes.These findings support the
conclusion that UV/Microwave combined method are real alternatives for application in water treatment
processes and wastewater.It is also important to note that, according to the data of the World Health
Organization[ 28 ], halogenated degradation products, such as atrazine, exhibit higher toxicity as compared
to the hydroxylated product. Whereas the photolytic assisted process using amicrowave showed that the
degradation of atrazine is preferably made by ring hydroxylation. Moreover,this information contributes to
the studies of herbicide degradation and assists in obtaining degradation products that exhibit less toxicity
to the ecosystem.
4.
Conclusion
Degradation of atrazine was observed in both photolytic systems (UV and UV/MW) that were
studied.The photolytic system evaluated allowed the formation of anatrazine degradation route and the
identification of degradation products. In the both cases, initiallyatrazine-2-hydroxy (HAT) was formed due
to the production of hydroxyl radicals during the photolytic process. In the first process, (UV alone) HAT
was the single product. However, the second process (UV/MW) DIHAT and DEHAT was formed, due to
dealkylation of HAT, are also formed from DEAT and DIAT due to direct photolysis of ATZ. The UV/MW
process defines the formation of HAT produced by ATZ degradation and as a result DIHAT and DEHAT
was formed by dealkylation of HAT. The application of microwave assisted photolytic processes showed
high efficiency of atrazine degradation, proving to be a promising alternative for the treatment of effluents
containing the respective herbicide.
Acknowledgements
The authors would like to thank the Fundação de Amparo a Pesquisa do Estado de Minas Gerais
(FAPEMIG) for financial support (Processnumber: APQ-02823-14), Coordenação de Aperfeiçoamento de
Pessoal de Nível Superior (CAPES) and the Serviço Nacional de Aprendizagem Industrial de Minas Gerais
(FIEMG/SENAI-MG) for their fellowship.
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FIGURES CAPTIONS:
Figure 1:Experimental procedure for the study of atrazine degradation 3 mg L-1 solution through different
energies (source: author)
Figure 2: Identification of solution absorption spectra 1 mg L-1 of atrazine and metabolites (A) and
photolysis results of atrazine solution 3 mg L-1 using UV radiation (B), MW radiation (C), MW/UV
radiation (D).(source: the author).
Figure 3:Resultsobtained after photolyticassay varying the exposure time to UV radiation, 0 - 20 min (A),
UV / MW radiation, 0 – 4 min (B)and pseudo first order kinetic constant for UV photolysis(C).
(source: the author).
Figure 4: Mechanism of Atrazine degradation after UV irradiation (A) and atrazine degradation mechanism
after MW / UV radiation (B).(Source: the author)

16
Fig. 1.

17
Fig. 2.
0,5
ATZ
ATZ (221nm)
HAT (240nm)
B
A
1,0
0,8
0,6
0,4
0,2
0,0
0,083 min (white)
20,0 min (white)
0,083 min
0,5 min
1,0 min
1,5 min
2,0 min
5,0 min
15,0 min
20,0 min
DEAT (212nm)
DIAT (213nm)
DEDIAT (228nm)
DEDIHAT (229nm)
DEHAT (234nm)
DIHAT (234nm)
0,4
0,3
0,2
0,1
0,0
2
1
180
200
220
240
260
280
300
180
200
220
240
260
280
300
Wave-length (nm)
Wave-length (nm)
ATZ
ATZ
1,0
C
1,0
D
0,083 min (white)
2,0 min (white)
0,083 min
0,5 min
1,0 min
1,5 min
0,083 min (white)
5,0 min (white)
0,083 min
0,5 min
1,0 min
1,5 min
0,8
0,6
0,4
0,2
0,0
0,8
0,6
0,4
0,2
0,0
5
3
2,0 min
2,0 min
4,0 min
4
180
200
220
240
260
280
300
180
200
220
240
260
280
300
Wave-length (nm)
Wave-length (nm)

18
Fig. 3:
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
ATZ
HAT
DEAT
DIHAT
DEHAT
DIAT
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
A
B
ATZ
HAT
DEAT
0
5
10
15
20
0,0
0,5
1,0
1,5
2,0
Time (min)
Time (min)

19
Fig. 4:
Table 1: Molar absorptivity(ε) values for solution 1 mgL-1 of atrazine and metabolites at a wavelength of
221nm after reading spectrophotometer UV-Vis and quartz cuvette with optical path 1cm.
Molarity (mol L-1)
Compound
ATZ
Absorbance
0.094
ε / (L mol-1cm-1)
20274
4.64 x 10-06
5.07 x 10-06
HAT
0.098
19330

20
DIAT
DEAT
0.149
0.212
0.036
0.099
0.066
0.068
5.76 x 10-06
5.33 x 10-06
6.87 x 10-06
6.44 x 10-06
5.91 x 10-06
7.87 x 10-06
25866
39778
5240
DEDIAT
DIHAT
15361
11166
8643
DEHAT
DEDIHAT

21
Table 2:Comparative assessment of different Atrazine degradation processes listed in the literature and in the present work.
Degradation
Rate (%)
Degradation Processes
Radiation
Degradation Products
Autor
Photocatalysis using
composite graphene-
TiO2/SiO2
Ultraviolet
(UV)/Visible
(VIS)
Not identified
> 93
K. LI et al.
Photocatalysis using
TiO2 nanotube
suspensions
EIST, OIET, HAET
ADE, ODET
Microwave (MW)
G. ZHANQI
et al
100
Photocatalysis using
ZnO as catalyst under
natural sunlight
UV-A, UV-B e
UV-C
J. FENOLL
et al.
Not identified
70
Microwave catalysis in
mineral micropores
Degradation of atrazine
in micropores of zeolites
CBV-720
MW
MW
HAT and DIAT
100
100
HU, E. et al.
HU, E. et al.
HAT, DEAT, DIAT,
DEHAT, DIAHT,
DEDIHAT
HIET, CVVT,
OVAT, OIET, CDIT,
CDET, COEIT,
OOEIT, ODIT,
ODET, CIAT, CEAT,
COIOET, OIMT,
ODDT, OIAT,
Photolytic, Sonolytic e
Sonophotolytic
degradation of ATZ
UV and
Ultrasound (US)
XU, L.J. et
al.
100
OEAT, CDAT,
ODOIT, ODAT,
CAAT and
AMMELINE

22
AT, CEAT, HIET,
CAIT, HAITM,
CAAT, HVET,
HVAT, CDT, HDAT,
DVT, HAET,
Photolytic by
Electrodeless Discharge
Mercury Lamp
UV/MW
100
Ta, N. et al.
cyanuric acid
HAT, DIHAT,
DEAT, DIAT and
DEHAT.
UV/Microwave
combined method
THE
AUTOR
UV/MW
100