Kinetics of free radicals decay reactions in cellulosic-based heritage materials disinfected by gamma-radiation
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2017
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INTERNATIONAL CONFERENCE ON APPLICATIONS OF RADIATION SCIENCE AND TECHNOLOGY
Resumo
Disinfection by
-radiation of cultural heritage artefacts and archived materials has been
successfully applied in recent years. Radiation processing used for cultural heritage disinfection
has several advantages when compared to conventional methods (e.g., chemical
gases) mainly related to the safety, efficiency, reliability, capacity, process time and safety for
users and the environment. However, more research is still required to study undesirable
effects (side-effects) which may appear in sensitive materials as a function of the absorbed
radiation dose. Some conservators and restorers are frequently worried about possible
long-term effects in irradiated materials (post-effects). During the irradiation process, some
energetic and unstable chemical species called free radicals appear in the treated matter.
They disappear in different ways, interacting either with each other or with the artefact
compounds thus becoming responsible for disinfestation and irradiation side-effects.
The kinetics of free radical decay reactions depend on the absorbed dose, the properties
of irradiated material among others. In this study, contemporary paper samples were
irradiated using
-radiation from 60Co with different absorbed doses. The absorbed dose
range was chosen taking into account the effective values to promote insect eradication,
fungal disinfection and sterilization. The decay kinetics of the cellulose free radicals induced
by irradiation was analyzed using electron paramagnetic resonance. Several spectra were
obtained at room temperature for each applied absorbed dose immediately after irradiation
as reference measurements. To understand the free radical decay process, additional spectra
were obtained for different decay times up to almost 50 days after irradiation. De-noising
treatment of the original obtained spectra signals were performed using wavelets. Free
radical populations, proportional to the spin concentrations, were found by integrating
the electron paramagnetic resonance signal curves. Comparison of spectra was done by
normalizing the calculated area corresponding to cellulose spin concentration, taking first
measurement after irradiation as 100%. Further analyses and calculations were made to
study the half-life and the kinetics models of the free radicals created. X-ray diffraction
was carried out to identify crystalline phases and the effect of ionizing radiation on the
crystalline structure of cellulose in paper. Scanning electron microscopy and scanning
electron microscopy energy dispersive spectrometry were performed to analyze structure
modifications induced by ionizing radiation, identifying cellulose fibre agglomeration zones
and to quantify chemical elements.
Results show that for the sterilization dose, 80% of the cellulose free radicals induced by
ionizing radiation disappear in almost 40 days and for disinfection dose in 8 days. It can be
concluded that if no modifications (side-effects) appear in the irradiated material after the
radical decay time, the material will stay stable for the remaining lifetime. Results showed
that the proposed method using electron paramagnetic resonance is suitably to study the
behaviour of radicals on cellulosic-based cultural heritage materials.
Como referenciar
VASQUEZ, P.; KODAMA, Y.; RODRIGUES JUNIOR, O.; GARCIA, R.H.L.; OTUBO, L.; SANTOS, P.S. Kinetics of free radicals decay reactions in cellulosic-based heritage materials disinfected by gamma-radiation. In: INTERNATIONAL CONFERENCE ON APPLICATIONS OF RADIATION SCIENCE AND TECHNOLOGY, April 24-28, 2017, Vienna, Austria. Abstract... Vienna: IAEA, 2017. p. 355-355. Disponível em: http://repositorio.ipen.br/handle/123456789/27775. Acesso em: 29 Mar 2024.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.