[en] A study on the decomposition of a surfactant (SDBS) and of four emerging pollutants (ofloxacin, carbamazepine, benzophenone-3, benzophenenone-4) in a multicomponent system is presented. These pollutants are decomposed in water by a few types of Advanced Oxidation Processes. The remediation methods included UV and γ-rays, all running in atmospheric conditions. It is shown that UV degradation methods can be improved by adding a photocatalyst (TiO₂), or a radical mediator (H₂O₂). The processes were monitored step by step, by determining the concentration of pollutants by UV, HPLC and a specific surfactant selective kit, and measuring the total organic carbon content. (author)

[en] Unless the radiolytic reducing species are neutralised or converted into oxidising species, an EB remediation system cannot be considered a true Advanced Oxidation Processes (AOP). A water/H₂O₂ system irradiated by UVC mercury lamps constitutes a widely used OH production method. Employing H₂O₂ in radiolysis as well, an enhancement of the oxidative efficiency of an EB treatment can be obtained. Pulse radiolysis measurements of an aerated aqueous/H₂O₂/KSCN system have been systematically undertaken to assess the optimal H₂O₂ concentration. By linearly fitting a competition kinetics relationship, it is found that the scavengeable extra-yield of OH is ΔG(OH)=0.24 μmol J⁻¹ (R=0,9958), while the maximum experimental yield is measured G(OH)_max=(0.52±0.02) μmol J⁻¹ when [H₂O₂]=5–10 mM. Exceeding these concentrations the OH yield drops off. - Highlights: ► The OH yield in the presence of H₂O₂ is assessed by pulse radiolysis with the objective of enhancing the EB treatment of polluted water. ► A ΔG(OH)=0.24 μmol J⁻¹ is obtained at 5–10 mM H₂O₂ in H₂O/air. ► The EB method is a neat Advanced Oxidation Process in the presence of H₂O₂.

[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] The radical cation of (phenoxymethyl)oxirane (PGE^radical+) is generated by pulse radiolysis in dichloromethane solution and by direct action of radiation on the title compound. In the pure system its UV-vis spectrum is characterized by two bands at 340 and 430nm, such that the electronic structure corresponds to a dipole bearing the positive charge on the phenoxy side. At the same time, the phenoxy-oxirane bridge is weakened. Then, the radical cation fragments into a phenoxonium ion and an oxyranylmethyl radical (k_PGE-fragm=1.16x10⁷s^-1). The latter immediately rearranges to an allyloxyl radical by ring opening. It is then conceived that the action of onium salts, as radiation curing initiators of phenoxy-oxirane derivatives, occurs after epoxy ring opening

[en] The performances of remediation processes initiated by ionizing radiation on ofloxacin are investigated in ambient conditions. The effectiveness of the decomposition of ofloxacin has been assessed both by γ-rays and electron beam in various aqueous solutions differentiated by the dissolved gases (Air or oxygen saturated) and H₂O₂. By HPLC it is shown that ofloxacin is removed according to a first order process vs. dose in any system. O₂ accelerates the decomposition rate, while H₂O₂ does not seem to enhance any oxidation effect. The simultaneous oxidative-reductive treatment (no additive) demonstrated to have better mineralizing performances than the fully oxidative one (H₂O₂ present). Mineralization by γ results to be more efficient than by EB. The Total Organic Carbon decrease was investigated in dependence of dose and of the ^• OH production rate. The latter parameter was changed over 7 orders of magnitude by controlling dose rate and/or by adding H₂O₂. A steep increase of acidity remarks the phases of fluorine-carbon bond break. - Highlights: • The oxidative-reductive and solely-oxidative decompositions show similar efficiencies. • The mid range intermediates of a typical AOP are refractory to mineralization. • Both decomposition and mineralization processes fit a first order dependence on dose. • Fluorine-carbon bond is retained in earlier ofloxacin fragments. • EB mineralization is sluggish due to anoxic conditions.