Abstracts Book - IMRC 2018

• SF5-O013 Invited Talk
KINETIC STUDIES OF THE PHOTOCATALYTIC DEGRADATION OF
DICLOFENAC
Edgar Moctezuma 1 , Elisa Leyva 1 , Carmen Lara Pérez 1 , Saúl Noriega 1
1 Universidad Autónoma de San Luis Potosí, Facultad de Ciencias Químicas, Mexico.
The photocatalytic oxidation of Diclofenac, which is a non-steroidal antiinflammatory
medication (NSAIDs) 1 , with TiO 2 illuminated with UV light have
been investigated in our laboratories in order to evaluate the effect of initial
reactant concentration on the reaction rate, to identify the most stable
intermediate organic reaction products and to elucidate the mineralization
reaction pathway. The experiments were carried out in a homemade reactor
system which has a Pyrex tube reactor (400 mL) illuminated with four UV-A light
lamps 2 . For each experiment, 250 mL of a Diclofenac water solution were
placed inside the glass reactor and mixed with 0.5 g of TiO 2 . Reaction samples
were analyzed by UV-vis spectroscopy, HPLC, TOC, FTIR, GC-MS and NMR. The
results of the analysis of samples by UV-vis spectroscopy indicate that
Diclofenac degrades slowly and undergoes gradual changes in its structure. The
first noticeable effect at short reaction times corresponds to the insertion of HO•
radicals in the aromatic rings. UV vis spectra also indicated that aromatic
compounds are mineralized via formation of unsaturated carboxylic acids of low
molecular weight. The fraction of reactant transformed into intermediate
organic products was evaluated by a material balance using the results of
analysis of the reaction samples by HPLC and TOC. The organic products and
the remaining reactant were extracted the reaction samples by liquid–liquid
extraction using with ethyl acetate 3 . The chemical structure of those
intermediate organic reaction products was determined by GC-MS, FT-IR and
NMR. Experimental results confirmed that the Diclofenac is efficiently degraded
by photocatalysis via hydroxylation of the aromatic rings to form 2- (2-
hydroxyphenyl) -ethanoic acid and 2,5-dichloroaniline. These organic products
are slowly oxidized to low molecular weight organic acids before being
completely mineralized to CO 2 and water. The kinetic parameters of the LH-HW
reaction rate equation for the photocatalytic degradation of Diclofenac were
calculated by non-linear regression using the experimental results of
concentration as a function of time.
References:
Kanakaraju, B. D. Glass, M. Oelgem, Green Materials for Energy, Products and