Photocatalytic transformation of postharvest fungicides for citrus in aqueous solution
using nanostructured photocatalysts
1,2
Zenydia R. Marín , Rita R.N. Marques1, Claudia G. Silva1, Joaquim L. Faria1, Marcos
Fernández3, M.I. Fernández,2 J.A. Santaballa,2 Moisés Canle L2.
[email protected]
1LCM
– – Laboratory of Catalysis and Materials – Associate Laboratory LSRE-LCM,
Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua
Dr. Roberto Frias s/n, 4200-465 Porto, Portugal.
2
Chemical Reactivity & Photoreactivity Group, Dept. of Physical Chemistry & Chemical
Engineering, Faculty of Sciences & CICA, University of A Coruña, E-15071 A Coruña, Spain.
3
Institute of Catalysis and Petrochemistry. CSIC. c/ Marie-Curie, 2. E-29049 Madrid, Spain.
Imazalil (IMZ), Thiabendazole (TBZ) and ortho-Phenyl phenol (OPP) are postharvest fungicides,
commonly applied to citrus as a cocktail. The extensive use of these and other fungicides has
helped improve the amount and quality of citrus available for their increasing global demand.
However, only a small amount of these compounds fulfil their objective, the rest being
incorporated into environment, mainly through soil and water, where they become a risk for living
organisms [1]. Moreover, postharvest fungicides are normally eliminated by washing, the
generated residues going directly to sewage. It has been proved that these fungicides resist
conventional water treatments [2-4], thus entering the category of persistent organic pollutants
(POPs). Therefore, it has become urgent to design alternative treatment methods to eliminate
and / or reduce POPs such as IMZ, TBZ, OPP and their degradation products. Heterogeneous
photocatalysis has shown to be very efficient for the elimination / abatement of fungicides [5],[6].
In this work we have studied the direct phototransformation of IMZ, TBZ and OPP and also the
photocatalytic transformation of IMZ and OPP with different nanostructured photocatalysts, both
in suspension and as films. TBZ did not show adsorption onto the photocatalysts surface, and
therefore it was not possible to study its photocatalysis.
Intermediate and final photoproducts were identified and appropriate phototransformation
mechanisms were proposed in each case.
Cl
Cl
hν
N
N
CH2
CH
OCH2CH
N
CH2
Cl
H
NH2
Cl
O
H
N
TBZ
Cl
+
photocatalyst
IMZ
N
N
OH
Cl
S
N
OH
hν
H
N
S
N
+
254 nm
N
N
+ ...
N
+
...
O
OH
OH
hν
+
+ ...
photocatalyst
OPP
OH
O
Acknowledgements.
This work was supported at UDC through project ACI2010-1093 (Ministerio de Ciencia e
Innovación) and by UDC’s own research funding. At UPorto it was supported by project PEstC/EQB/LA0020/2013, financed by FEDER through COMPETE – Programa Operacional Factores
de Competitividade, and FCT – Fundação para a Ciência e a Tecnologia, and co-financed by
QREN, ON2 and FEDER (Project NORTE-07-0124-FEDER-0000015).
ZRM acknowledges financial support for her predoctoral stay at UPorto through the INDITEXUDC 2014 pre-doctoral stays call.
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