Fotoquímica de contaminantes atmosféricos

8/10/2019 Fotoqumica de contaminantes atmosfricos

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I s a t i s M . C i n t r n

L a b . R a f a e l A r c e P h . D


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RELEVANCENPAH

Ubiquitous pollutant.Emitted from the incomplete combustion ofcombustible fossil and biomass.

2-NF: secondary pollutant generated fromatmospheric reactions between hydroxylradicals (OH) and fluoranthene.


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FORMATION OF 2-NITROFLUORANTHENE IN THEATMOSPHERE

Add reference of this synthesis


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RELEVANCE

2-nitrofuorantheneMutagenic and carcinogen properties

One of the most prevalent Nitro-PAHin aerosol (Wilson et al., 1995)Occurrence in PM 10-2.5 y PM 2.5


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SIGNIFICANCEPollutant can react via hydrogen abstraction from phenolic compounds fromtriplet excited state.Co-solutes: Phenol and 4-hydroxy-3-methoxybenzoic acid (vanillic acid)

Similar oxidation potential specific effect of structure Objectives

Study the effect of phenolic co-solutes on the rate of photodegradation of 2-NF under anaerobic or aerobic conditions in methanol .Determine whether the presence of co-solutes results in the creation of newphotoproducts.

HypothesisThe photodegradation of 2-NF is accelerated by the presence of co-solutes.


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EXPERIMENTAL PROCEDURE

2-NF 3.0x10 -5 Mphenol co-solute

in methanolPurge Irradiate

UV-visFluorescenceHPLC UV-vis

300-400nm

N2


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Photochemistry of 2-Nitrofluoranthenewith co-solute phenol in methanol

NO 2

+

OH

CH 3 OH

N 2h

Photoproducts


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UV-vis spectra for 2NF solutions in methanol atdifferent irradiation times

Legend(irradiation time)t=0 min

t=30 min

Wavelength (nm)

A b s


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A b s

Wavelength (nm)

UV-vis spectra of 2NF with co-solute phenol solutions inmethanol a different irradiation times

A b s .


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Fluorescence spectra of 2NF with co-solute phenolsolutions in methanol a different irradiation times

Legendt=5min

t=10min

t=30mint=60mint=90min

t=120mint=240min


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Chromatogram of the irradiated solution (30 minutes) of 2-NFwith co-solute phenol in methanol.

2NF

F#1 F#2 F#3

La estructura que tienes dibujada del nitrofluoranteno es el de la posicion 3 y no la 2


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UV-Vis spectra for the photoproduct # 1 of 2NF and phenol co-solute in methanol at 30 minutes of irradiation.

m A u

Wavelength (nm)


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m A u

Wavelength (nm)


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m A u

Wavelength (nm)



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2-Nitrofluoranthene with co-solute 4-hydroxy-3-methoxybenzoic acid (vanillic acid)


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UV-vis spectra of 2NF with co-solute vanillic acid solutions inmethanol at different irradiation times


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Fluorescence spectrum of photodegradation 2-NF andvanillic acid co-dissolved in methanol at differentirradiation times.

Legendt=0min

t=10min

t=20mint=40mint=60min

El mximo en el eje de y debe ser 400


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Chromatogram the irradiated solution of 2-NF withvanillic acid in methanol after 30 minutes

2NF

F#4F#5

La estructura que tienes dibujada del nitrofluoranteno es el de la posicion 3 y no la 2


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Kinetics of photoproducts from 2nf and vanillic acid co-dissolved in methanol at different times of irradiation

0

5000

10000

15000

20000

25000

30000

35000

0 5 10 15 20 25 30

P e a

k A r e a

( A )

Irradiation time (t)

Photoproduct # 4

Photoproduct # 5


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UV-Vis spectra for the photoproduct # 1 of 2-NF and vanillicacid co-solute in methanol at 30 minutes of irradiation.

m A u

Wavelength (nm)


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m A u

Wavelength (nm)

UV-Vis spectra for the photoproduct # 2 of 2NF and vanillicacid co-solute in methanol at 30 minutes of irradiation.


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y = -0.0027x - 0.0142

y = -0.0595x - 0.0037

-2

-1.5

-1

-0.5

0

0.5

0 20 40 60 80 100 120 140 160

l n ( A / A 0 )

Irradiation time (t)

Photodegradation rate of 2-NF with phenols co-solutes inmethanol

Photodegradation in phenol

Photodegradation in vanillic acid


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CONCLUSIONS

The photoreactions of 2-nitrofluoranthene is accelerated with both

co-solutes.

Since 2-NF does not exhibit fluorescence, the increase in thefluorescence band near 500nm suggests a formation ofphotoproducts.

The photoproducts have a larger epsilon than the 2-NF in thevisible region.


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CONCLUSIONS

P h e n o l

The formation of 3 photoproducts was observed with co-solutephenol.

The band around 480nm increase for the first 30 minutes ofreaction demonstrating the formation of photoproducts #1 and

#2.

After 30 minutes of reaction with co-solute phenol, degradation ofthe photoproducts is also observed.


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CONCLUSIONSVani l l i c ac id

The formation of 2-photoproducts was observed with co-solute 4-hydroxy-3-methoxybenzoic acid.

The band around 500nm shows an increase as the photodegradationoccurs.

2-nitrofluoranthene degrades more rapidly with vanillic acid than withphenol.

* Photoproducts are different suggesting reactions from phenolsintermediaries.

* The results are opposed with what we expected steric hindrance does not

influence in the rate of photodegradation.

* 2 OH groups in vanillic acid increase in probability of reaction.


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ACKNOWLEDGEMENTS

Lab IntegrantsDr. Rafael Arce

Salvador Gavald

Luis Piero

Melanie Burgos

Zulma GarcaYisaira Daz

RISE Program NIH Grant: 2 R25 GM061151

Fotoquímica de contaminantes atmosféricos

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