Experiments with Acid Blue 62 as a model compound for dyes were performed under steady-state conditions, using deoxygenated solutions as well as those saturated with N2O, oxygen or oxygen mixed with N2O. The yield of decoloration served as an indicator for the degradation process. Oxygen seems to inhibit radiation-induced decomposition of the dye in aqueous solution.
The decomposition of the non-ionic surfactant Triton X-100 in gamma-irradiated deaerated aqueous solution is mainly attributed to the attack of OH radicals and H atoms. The mechanisms of these reactions were investigated in detail, including the influence of pH and dose rate. The RCHOH radicals formed by OH attack on alcohol molecules can decompose the surfactant in aqueous solution.
Experiments with Triton X-100 as a model surfactant were performed under steadystate conditions, using deoxygenated solutions as well as those saturated with N2O, O2 or N2O/O2 mixtures. The Triton X-100 decomposition yield was dependent on the O2 content of the irradiated system. Oxygen promoted surfactant decomposition in aqueous solution containing only Triton X-100.
Pulse radiolysis of deaerated aqueous solutions of 4·10–5–2.4·10–3 mol dm–3 Triton X-100 gives rise to a transient species originating from the reactions of OH radicals and H atoms. The rate constants of these reactions were found to be 8.8·109 mol–1·dm3·s–1 and 1.25·109 mol–1·dm3·s–1, respectively, for Triton X-100 concentrations below CMC. The corresponding transient species were found to decay according to second order kinetics. The mechanism of the reactions involved including concentration effects is discussed.
The decoloration of Acid Blue 62 in aqueous solution was mainly attributed to the attack of the e
and OH radicals on the dye molecule. The mechanisms of these reactions were investigated in detail including the influence of pH, dose rate and oxygen.
The disproportionation of quinizarin semiquinones in methanol solutions of different pH has been investigated using the -radiolysis method. After60Co-irradiation of deaerated solutions the corresponding changes in the optical absorption spectra were recorded. In solutions of different pH the semiquinones disproportionate to give appropriate forms of quinizarin hydroquione which can react with oxygen to regenerate the parent compound. In neutral and acidic methanol the corresponding form of hydroquinone (1,4,9,10-tetrahydroxyanthracene) undergoes a transformation leading to formation of 9,10-dihydroxy-2,3-dihydro-1,4-anthraquinone which is unreactive towards oxygen.
Radiolytic reduction of merocyanine 540 (MC) in acidic (0.02 mol · dm–3 in H2SO4) and neutral methanol solution was studied by pulse radiolysis. The spectra centered around 400 and 700 nm of the MC reduced transients recorded in acidic methanol and in neutral solution were found to be quite similar but they disappeared with different rates suggesting that different radicals (MCH· and MC·–) were responsible for these spectra. The rate constant of ·CH2OH reaction with MC was found to be 7·108 mol–1·dm3·s–1.
Decomposition temperatures were correlated with frequencies of valence and deformation bond vibrations in a series of N-substituted derivatives of 2,4- and 2,6-dinitroanilines (DNA). These vibrations are directly influenced by the nitro group structure and by its resonance and inductive interaction with the benzene ring. Analysis of the infrared spectra reveals a great sensitivity of the frequency and hence the CAr- NO2 bond order on the substitution character of the amino group, whereas the frequencies of the valence vibrations of theo-nitro group are influenced to a small extent only. However, at the same time the valence vibration of CAr-NO2 is a sensitive indicator of the thermal stabilities of 2,4-DNA and 2,6-DNA.
The isothermal luminescence at 77 K of gamma-irradiated high density polyethylene, both with and without introduced admixtures (n-hexane, naphthalene) has been measured. The spectrum of emitted light was recorded and found to be identical with that of added compound. A reaction mechanism responsible for the isothermal luminescence consistent with the experimental results is proposed.