Reactivities of Polystyrenic Polymers with Supercritical Water under Nitrogen or Air. Identification and Formation of Degradation Compounds

Abstract

Supercritical water oxidation (SCWO) could offer a viable treatment alternative to destroy the organic structure of ion-exchange resins (IER) that are radioactive process wastes and which contain radioactivity. The GC/MS technique was used successfully to identify the low-concentration degradation compounds that are present in the cold liquid effluent after SCWO of polystyrenic IER at 380 °C (25.5 MPa). The study of the behavior of these IER in supercritical water enhances the role of temperature and the role of supercritical water in the degradation process. With the exception of acetic acid, the identified compounds are aromatic. The functional groups are released during the heating time, and they do not interfere in the degradation process. The oxidation involves a complex set of reaction pathways. A mechanism including parallel and competitive reactions is proposed.

Dissolution and mineralization of ion exchange resins: differentiation between heterogeneous and homogeneous (photo-)Fenton processes

“…These radicals are reacting along three reaction channels: 21 hydrogen abstraction, electrophilic addition to p-systems and electron transfer. In the case of the IER used in this work (sulfonated and 1,4-divinyl-benzene cross-linked polystyrene), hydrogen abstraction would mainly concern the tertiary C-centers of the polystyrene backbone (reaction (11)), (11) whereas electrophilic addition to p-systems would occur on the aromatic moieties of the polymer substrate (reaction (12)). (12) In the present work, oxidative degradation of IER suspended in aqueous solutions and mineralization of the dissolved fragments by the Fenton and photo-Fenton processes were investigated in detail.…”

“…incineration, 7 thermal decomposition, 8-10 acid "digestion" 11 as well as wet oxidation. 12 Only few results are known concerning a controlled (partial) oxidation of polystyrene-based IER by hydrogen peroxide (H 2 O 2 ) and catalyzed by transition metal ions (Fenton or Fenton-type processes 13 ). In most cases, authors analyzed the progressively reduced capacities of the oxidized IER, 14, 15 but some publications report rates of carbon dioxide (CO 2 ) 16, 17 and sulfate (SO 4 2-) evolution.…”

p53 codon 72 polymorphism (C/G) and the risk of human papillomavirus‐associated carcinomas in China

“…It is a refractory compound in the SCWO. This is the reason why a number of articles about the SCWO of acetic acid can be found in literature 26–31. Li et al15 kinetic model considers acetic acid as an intermediate oxidation product.…”

Réalisation d’une référence nationale pour les microsphères de 90Y utilisées en radiothérapie interne sélective

“…Cette méthode permet en outre de diminuer de façon draconienne le volume des déchets radioactifs. C'est pour cela que dès les années 1950, des procédés de mise en solution, totale ou partielle, des résines échangeuses d'ions ont été étudiés tels que l'incinération [10], la décompo-sition thermique [11], l'oxydation en milieu humide [12] ou la dissolution en milieu acide. Parmi ces possibilités, les trois premières méthodes nécessitent le recours à des températures élevées, avec le risque de perdre la radioactivité en phase gazeuse.…”