M. L. Botelho

Radiolytic degradation mechanism of gallic acid and its end-products

Gallic acid is one of the most representative biorecalcitrant phenolic compounds present in cork processing wastewater. In this communication, chemical oxidation of gallic acid was studied by gamma irradiation as an advanced oxidation process. This technology turns out to be an advantageous tool for the degradation of gallic acid. The results obtained by UV-Vis and electrospray ionization mass spectrometry (ESI-MS) techniques are in agreement concerning the suitability of this technique to degrade gallic acid. ESI-MS and ESI-MS(2) monitoring of the non-irradiated and irradiated gallic acid solutions leads to the identification of the main intermediate products. Based on the overall results obtained a consistent mechanism of radiolytic degradation of gallic acid is proposed. The application of radiation as a tool to increase the biodegradability of wastewaters is an important issue from the perspective of Green Chemistry.

Dose mapping of a 60Co irradiation facility using PENELOPE and MCNPX and its validation by chemical dosimetry

The Monte Carlo simulation programs PENELOPE and MCNPX have been used for simulating the dose rate distribution in a (60)Co gamma irradiator. The simulated isodose curves obtained for each simulation code were validated comparing them to the dose measurements performed with a Fricke solution, which is a standard dosemeter widely used in radiation processing for calibration purposes. The agreement between the simulated values and the measurements indicates the effectiveness of both codes in performing the dose-mapping simulation for gamma irradiators.

Local laser-decolorizing of gamma-ray irradiated silicate glass

Local decolorizing of gamma-ray irradiated silicate glasses has been studied under thermal annealing by a laser beam. The influence of the beams exposure time was studied, showing that an increase of the glass temperature on the irradiated areas can locally induce complete decolorizing (bleaching) of glass. In this work, the heat conduction differ- ential equation is solved by numerical approach using the finite element method and results are compared by experimental analysis. Although much work is being developed in the fields of color centers creation and its decay by heat, this work presents the first systematic study on near- infrared decolorizing of gamma-irradiated float silicate glasses. C 2011 So-