The radiolytic bleaching of neat aerated methylene blue solutions is relatively stable, when irradiated to doses in the range of 50 to 500 Gy and measured at the main peak of absorption band of the dye (664 nm). The useful range can be extended up to about 5 kGy if the aqueous dye solution contains about 0.1% ethanol by volume and to 10 kGy with 5% ethanol. By increasing the concentration of the dye in the presence of 5% ethanol doses up to about 30 kGy can be measured. The spectrophotometric readings have to be made during a period of post irradiation stability of 24 hours, after which there is about a 10% increase in absorbance over the next three days due to regeneration of the dye by spontaneous oxidation. Since the industrial grade monovalent dye salt is very inexpensive and is relatively non-toxic, it may be used for dosimetry studies in quality control tests of electron beam processing of large volumes of waste water, when typical doses in the range of 5-30 kGy are required. The influences of dose, dose rate and solute concentration on the bleaching process have been investigated in terms of the decrease of the absorbance of the dye.
- Gamma and electron irradiation
- Ionizing radiation
- Methylene blue dye
- Radiation dosimetry
ASJC Scopus subject areas