Radiolytic decolouration of aqueous solutions of food dyes

Abstract

The radiolysis of aqueous solutions of 20 mg/l food dyes E102, E104, E122, E124, E129, E132, E133, E142, E151 and E155, which are representatives of four common classes, was studied. At a dose of up to 1.5 kGy with access to air, radiolysis leads to almost complete decolouration of solutions with a yield of 0.03–0.11 μmol J−1. The lowest decolouration yield (≈0.03) is observed in the case of dyes E133 and E155 with several chromophore units, while the highest yields are characteristic of the simpler dyes E129, E132 and E142. Half decolouration doses range from 200 to 600 Gy. Up to 60% decolouration for all dyes, there is a single type of correlation between the absorbed dose and the degree of decolouration. Color degradation is accompanied by a decrease in chemical oxygen demand (up to 10%), the appearance of suspended solids and an increase in biodegradability. The fundamental and practical features of electron-beam treatment of aqueous solutions are considered.