Degradation of compounds present in cork boiling water by gamma radiation
Artigo de Conferência
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resumo
Cork boiling water is an aqueous and complex dark liquor with high
concentration of phenolic compounds such as phenolic acids and tannins [1, 2], which
are considered biorecalcitrants [2]. Ionizing radiation has been widely studied as an
alternative technology for the degradation of organic contaminants without the addition
of any other (e.g.: Fenton technologies).
The aim of this work was to identify the compounds present in cork boiling water
and further evaluate the resulting stable degradation products after gamma irradiation.
The irradiation experiments of standard solutions were carried out at room
temperature using a Co-60 experimental equipment. The applied absorbed doses
were 20 and 50 kGy at a dose rate of 1.5 kGy/h, determined by routine dosimeters [3].
The identification of radiolytic products was carried out by HPLC-DAD-ESI/MS. The
phenolic compounds were identified by comparing their retention times and UV–vis
and mass spectra with those obtained from standard compounds, when available, as
well as by comparing the obtained information with available data reported in the
literature.
Concerning the obtained results and the literature review, the main cork
wastewater components are: quinic, gallic, protocatechuic, vanillic, syringic and ellagic
acids. Based on this, we used protocatechuic, vanillic and syringic acids as model
compounds to study their degradation by gamma radiation in order to identify the
corresponding radiolytic products. Standard aqueous solutions were irradiated and the
derivatives of each model compound are represented in figure 1. The obtained results seem to demonstrate that the derivatives of the parent
compounds could also be phenolic acids, since it was observed the loss of 44 u (CO2)
from the [M-H]- ions. Gallic and protocatechuic acids are identified as derivatives of
vanillic and syringic acids, and gallic acid as a protocatechuic acid derivative.
Compound 5 ([M-H]- at m/z 169) was tentatively identified as 2,4,6-trihydroxybenzoic
acid, since its fragmentation pattern (m/z 151, 125 and 107) is similar to that previously
reported in literature [4]. The structure of compound 7 was proposed based on the
molecular ion and its fragmentation and compound 6 remains unknown.
