Masamitsu Washino

The radiation-induced degradation of azo dyes in aqueous solutions

Abstract The aqueous solutions of Acid Red 265, Acid Red 37, Reactive Red 8, Reactive Red 3, Direct Red 79 and Direct Blue 78 were easily decolored by gamma radiation. For the oxygen- and nitrogen-saturated solutions, the degree of decoloration, the change of pH, the TOC reduction, the COD reduction and the amount of carbon dioxide formed were measured as functions of dose. After decoloration, the dye molecules are degraded to the lower molecular weight compounds, mainly, such as organic acids, and finally to carbon dioxide. The degradation reaction is promoted markedly by oxygen.

Radiation treatment of exhaust gases—I. Oxidation of NO and reduction of NO2

Abstract Nitrogen oxides were irradiated by electron beams at low concentrations ranging from 50–1000 ppm in nitrogen and the mixture of nitrogen and oxygen at 100°C. In nitrogen, the NO was decomposed to mainly nitrogen and oxygen with the G-value of 1.7. In the presence of oxygen, effects of initial concentrations of NO, NO2 and oxygen on the changes of NO and NO2 concentration were studied. Oxidation of NO and reduction of NO2 take place simultaneously and an empirical equation, (NO)/(NO)2)2 = 0.027 ppm-1, was found at 3% oxygen under irradiation above 4 Mrad when the NO2 concentration is higher than 60 ppm. These reactions are considered to proceed by oxygen atom produced by the irradiation of the mixture of nitrogen and oxygen.

Radiation treatment of exhaust gases. IV. Oxidation of NO in the moist mixture of O2 and N2

Abstract A NO-H2O-O2-N2 gaseous mixture was irradiated by electron beams of 1.5 MeV at various reaction conditions. The decrease in [NO] was much larger for the moist mixture than for the dry mixture. The NO was easily oxidized to NO2 and finally to HNO3 in the moist mixture. The rate of NO consumption in the mixture increased with increasing H2O- and O2-concentrations and with lowering irradiation temperature from 150 to 100°C. The G(-NO) obtained in lower dose was 7.5 in the moist mixture of NO(100–500 ppm), H2O(8.4%), O2(11.4%) and N2(80.2%) at 120°C. The formed HNO3 reacted with NO to form NO2.

Radiation treatment of exhaust gases—II. Oxidation of sulfur dioxide in the moist mixture of oxygen and nitrogen

Abstract Moist and dry mixtures (1400 ppm SO 2 , 20% O 2 , ca . 80% N 2 ) were irradiated by electron beams at 100°C. In the dry mixture, SO 2 was not consumed by irradiation. On the other hand, SO 2 was oxidized to H 2 SO 4 with G (-SO 2 ) of 5.3 in the presence of moisture. The G (-SO 2 ) was reduced to a limiting value of 0.9 in the presence of a radical scavenger such as NO 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 , or 1,3-C 4 H 6 . The G (-SO 2 ) was not affected by the addition of SF 6 . The radiolytic oxidation of SO 2 is induced mainly by the OH radical and the O atom.

Radiation treatment of exhaust gases. V. Effect of NH3 on the removal of NO in the moist mixture of O2 and N2

Abstract NO was irradiated by electron beams of 1.5 MeV in the NH3-containing mixture of H2O, O2 and N2. The NO removal was larger in the mixture with NH3 than without NH3. The rate of NO removal in the mixture with NH3 increased with the concentrations of NH3 to 600 ppm, H2O to 4.4%, and O2 to 3.0%, leveling off above those concentrations. The rate decreased with increasing irradiation temperature. NO2, HNO3, N2O and small amounts of NH4NO3 were found as products in irradiation of the mixture with NH3. Formation of NO2 and HNO3 was markedly supressed, and N2O formation was enhanced by the addition of NH3. The solid NH4NO3 was found below about 70°C. NO removal is considered to be brought about not only by the oxidation of NO with O atom, OH and HO2 radicals, but also by reduction with NH2 radical.

Radiation treatment of exhaust gases. VII. NO decomposition in NO-N2 and NO-rare gas mixtures.:NO Decomposition in NO-N 2 and NO-Rare Gas Mixtures

The NO decomposition by electron beam irradiation was studied in the NO-N2 and NO-rare gas mixtures. The NO decomposition yields, G (−NO) at low doses in the case of the 500 ppm NO initial concentration were 4.04.4 and 1.2 for the NO-N2, NO-He and NO-Ar mixtures respectively. A small amount of NO2 was formed by irradiation of these mixtures. The NO decomposition is mainly attributable to the attacks of N and N4 + (or N2 +), formed by the radiolysis of N2on NO in the NO-N2 mixtureand to the attacks of R+ and R*, formed by the radiolysis of a rare gas (R)on NO in the NO-rare gas mixture. The NO decomposition in the NO-N2 mixture was depressed markedly by the addition of a small amount of O2. This may be mainly attributable to scavenging of N and N4 + (or N2 +) by O2.

Radiation treatment of exhaust gases. IX. Analysis of NO and NO2 decomposition in NO-N2 and NO2-N2 mixtures by computer simulation.:Analysis of NO and NO 2 Decomposition in NO-N 2 and NO 2 -N 2 Mixtures by Computer Simulation

The computer simulation method has been applied to the analysis of the NO and NO2 decomposition in the NO-N2 and NO2-N2 mixtures by electron beam irradiation. The calculated results regarding the NO and NO2 decomposition were in good agreement with the experimental results in both mixtures. The NO and NO2 decomposition is mainly induced by the radical reactions and is hardly induced by the ion reactions. That is, the NO decomposition in the NO-N2 mixture is mainly induced by the attack of N formed by the radiolysis of N2. The NO2 decomposition in the NO-N2 mixture is induced not only by the attack of N, but also by the attack of O formed through the reaction of NO2 with N at low doses. At high doses, the decomposition of NO formed through the reactions of NO2 with N and with O is mainly induced by the attack of N, in contrast to the NO2 decomposition by the attacks of N and O at low doses. The G value of the formation of N(G(N)) by the computer simulation was 2.0.

Radiation treatment of exhaust gases—VI. Effects of CO and H2 on the removal of NO and NO2 in the moist mixture of O2 and N2

Abstract The effects of CO and H 2 on the removal of NO and NO 2 were studied in the mixture of H 2 O, O 2 and N 2 irradiated by electron beams of 1.5 MeV energy at 120°C. In the NOH 2 OO 2 N 2 mixture, the NO removal and the corresponding NO 2 formation were enhanced markedly by the addition of CO or H 2 , but not by CO 2 . In the NO 2 H 2 OO 2 N 2 mixture, the NO 2 removal was markedly suppressed by the addition of CO up to 0.88% and was not observed in the presence of CO above 1.5%. These effects of CO on the removal of NO and NO 2 may be brought about by the scavenging of OH radical by CO to produce H atom, leading to the formation of HO 2 radical which oxidizes NO to NO 2 .

Radiation treatment of exhaust gases. VIII. NO2 decomposition in NO2-N2 and NO2-rare gas mixtures.:NO 2 Decomposition in NO 2 -N 2 and NO 2 -Rare Gas Mixtures

The NO2 decomposition by electron beam irradiation was studied in the NO2-N2 and NO2-rare gas mixtures. The NO2 decomposition yields, G (-NO2), at low doses in the case of the 500 ppm NO2 initial concentration were 2.9, 10.4 and 5.9 for the NO2-N2, NO2-He and NO2-Ar mixtures respectively. A large amount of NO was formed by irradiation of these mixtures. The G (NO) was almost equal to the G (-NO2). The N2O was also formed in the NO2-N2 mixture. The NO2 decomposition is mainly attributable to the attack of N, formed by the radiolysis of N2, on NO2 in the NO2-N2 mixture, and to the attacks of R+ and R*, formed by the radiolysis of a rare gas (R), on NO2 in the NO2-rare gas mixture. The NO2 decomposition in the NO2-N2 mixture was depressed markedly by the addition of a small amount of O2. This may be mainly attributable to the regeneration of NO2 by the reaction of NO with O.

Radiation Treatment of Exhaust Gases, (X): Formation of N2O in Irradiation of NH3-Containing Mixture of H2O, O2 and N2

Effects of NH3, NO, NO2 and SO2 on the N2O formation were studied in the mixtures of H2O, O2 and N2 irradiated with electron beams of 1.5 MeV energy. In the H2O-O2-N2 mixture, the N2O formation was enhanced markedly by addition of a small amount of NH3. This enhancement may be brought about by the reaction of NH3 with OH radical to form NH2 radical leading to the formation of N2O. In the NH3-H2O-O2-N2 mixture, the formation of N2O was suppressed effectively by addition of NO, NO2 and SO2. The N2O formation was not affected by the irradiation temperature range of 80–200°C.