[en] The γ-radiolysis of a cyclohexene-carbon dioxide mixture in the liquid phase at -18⁰C has been studied. When the mole fraction of carbon dioxide was low, carbon dioxide behaved as an electron scavenger and slightly suppressed the formation of the hydrogen and hydrocarbon products: 2,2'-bicyclohexenyl, cyclohexane, 3-cyclohexylcyclohexene, bicyclohexyl, 1-cyclohexylcyclohexene, and 1,3-cyclohexadiene. Along with this suppression, the formation of cyclohexanol was observed. At the high mole fraction of carbon dioxide, the main products were carbon monoxide and the oxygen atom-addition products: cyclohexene oxide, cyclohexanone, and cyclopentane-carbaldehyde. The material balance for oxygen atoms was good. The formation ratio of the addition products suggests that the precursors of the addition products are the ground-state oxygen atoms. These oxygen atoms are probably produced by the direct radiolysis of carbon dioxide. As the CO₂ mole fraction approached unity, the G-values of the addition products and other oxygenated compounds including 2-cyclohexenone and 2-cyclohexenol sharply increased. This suggests that there is another source of oxygen atoms which is suppressed by the presence of cyclohexene. The reactions may be CO₂⁺+CO₂^-→CO+O+CO₂ and CO₂⁺+cyclohexene→CO₂+cyclohexene⁺. The formation of 2-cyclohexenone and 2-cyclohexenol may be explained in terms of the reaction between the cyclohexenyl radicals and oxygen molecules eventually produced. To support the elucidation of the reaction mechanism, the radiolysis in the solid phase at 77K and the mercury-photosensitized reaction of a nitrous oxide-cyclohexene mixture in the gas phase have also been studied. (auth.)

[en] In water treatment by ionizing radiation ·OH is suggested to initiate the degradation of organics. In these reactions mostly carbon centred radicals form. Here we show that other inorganic radicals also highly contribute to the initiation of degradation. Cl"- and HCO_3"- in the treated water reacting with "·OH transform to Cl_2"·"- and CO_3"·"-. In their reactions C-centred radicals form, too. The reactions of e_a_q"- and H"· water radiolysis intermediates may also produce carbon centred radicals. The C-centred radicals react readily with dissolved O_2, this is the starting step of the gradual oxidation. (author)

[en] Mechanistic studies were made on hydroxyl radical and hydrated electron reaction with Sulfanilic Acid Azochromotrop (SPADNS) as model azo dye in dilute aqueous solution. SPADNS contains 4,5-dihydroxynaphthalene-2,7-disulfonic acid part and 4-sulfophenylazo group. To establish the details of the reaction mechanism the reactions of two simpler molecules without 4-sulfophenylazo part were also studied: one of them contained one (in position 4, II), the other two (in positions 4 and 5, III) -OH groups. Hydroxyl radicals react with these molecules with radical addition to the naphthalene-2,7-disulfonic acid part. The adduct hydroxycyclohexadienyl type radical decays in radical-radical reactions, or undergoes a (pH dependent) water elimination to yield naphthoxy radical. The radical decay takes place on the ms timescale. Degradation efficiencies are 0.6-0.8. Hydrated electron in the case of the two simpler molecules reacts with the rings, while in the case of dye with the azo bond. Electron scavenging is followed by protonation, this reaction in the case of II and III yields cyclohexadienyl, while with the dye hydrazo radical. The efficiency of degradation with II and III is 0.2-0.6, while for SPADNS it is close to 1.

[en] The radiation-induced decolouration and degradation of aqueous solutions of azo dyes and their model compounds (anilines, phenols, triazines) are reviewed together with practical applications and the experimental methods (pulse radiolysis, steady-state gamma radiolysis, as well as end-product analysis) used for studying the reactions. The proposed mechanisms and the rate coefficients for the reactions of ^·OH, e_aq^- and ^·H water radiolysis intermediates with the dye molecules and with model compounds are summarized

[en] The radiolytic degradation of Triton X-100 surfactant was investigated at concentrations below and above the critical micelle concentration (CMC, ∼ 0.23 mmol dm^-3) in air saturated aqueous solutions. At low concentrations the degradation took place both on the aromatic head and on the polyethoxylates chain, while above CMC it was shifted towards the chain. The CMC was higher in irradiated solutions at 10 Gy by a factor of 2, at 20 kGy by a factor of 3 than in the un-irradiated solution. The degradation of clofibric acid in the presence of TX-100 was more effective outside the micelles than inside them. (author)

[en] The reaction of 2-hydroxy-2-propyl (IP) radical with 12 acrylate type monomers in aqueous solutions was investigated by means of pulse radiolysis: the molecular structure effects and the mechanisms were evaluated. Radicals were generated either in the reaction of hydrated electron with acetone and subsequent protonation or in the H abstraction reaction by OH radicals from i-propanol. IP radical reacts with acrylamides and acrylic acid esters in radical addition reaction of the type: (CH₃)₂(OH)C ^· + CH₂ =CH-C(O)R ^→ (CH₃)₂(OH)C-CH₂-C ^·H-C(O)R with rate coefficients between 3.2 x 10⁷ and 1.9 x 10⁸ mol^-1 dm³ s^-1. Rate coefficients of the reaction with maleic acid (neutral), dimethyl- and diethyl maleate are between 1.3 x 10⁸ and 4.7 x 10⁸ mol^-1 dm³ s^-1. The values for dimethyl- and diethyl fumarate are ca. one order of magnitude higher. However with maleates and fumarates there is also a few percent contribution from the electron transfer reaction of the type (CH₃)₂(OH)C ^· + ROOC-CH=CH-COOR + H₂O ^→ ROOC-CH=CH-C ^·O^-OR + (CH₃)₂CO + H₃O⁺. In neutral solutions and at pH ∼3 and ∼9, the same rate coefficients were measured. However, in dialkyl maleate and -fumarate solutions between pH 9.5 and 10.5, a base catalyzed decomposition of the IP radical adduct was observed forming electron adduct: ROOC-C((CH₃)₂(OH)C)H-C ^·H-COOR + OH^-→ ROOC-CH=CH-C ^·O^-OR + (CH₃)₂CO + H₂O. Molecular structure effects were evaluated using log k-σ _p and log k-LUMO plots

[en] Cotton-cellulose was functionalized using gamma-irradiation-induced grafting of glycidyl methacrylate (GMA) to obtain a hydrophobic cellulose derivative with epoxy groups suitable for further chemical modification. Two grafting techniques were applied. In pre-irradiation grafting (PIG) cellulose was irradiated in air and then immersed in a GMA monomer solution, whereas in simultaneous grafting (SG) cellulose was irradiated in an inert atmosphere in the presence of the monomer. PIG led to a more homogeneous fiber surface, while SG resulted in higher grafting yield but showed clear indications of some GMA-homopolymerization. Effects of the reaction parameters (grafting method, absorbed dose, monomer concentration, solvent composition) were evaluated by SEM, gravimetry (grafting yield) and FTIR spectroscopy. Water uptake of the cellulose decreased while adsorption of a pesticide molecule increased upon grafting. The adsorption was further enhanced by β-cyclodextrin immobilization during SG. This method can be applied to produce adsorbents from cellulose based agricultural wastes. - Highlights: → Fundamentals of two grafting methods for biomass utilization as adsorbents. → Simultaneous grafting is more efficient and useful than the pre-irradiation one. → Methanol/water/surfactant combined solvent gives the best grafting yield. → Grafted cellulose increased hydrophobicity and adsorption of phenolic compounds. → Improved adsorption by bonding β-cyclodextrin during simultaneous grafting.