Photochemical degradation study of aqueous solutions of polyrthyleneglicol, polyacrylamide and polyvinylpyrrolidone. / Estudo da degradação fotoquímica de soluções aquosas de polietilenoglicol, poliacrilamida e polivinilpirrolidona.

AUTOR(ES)

Jeanne Aparecida Giroto

DATA DE PUBLICAÇÃO

2007

RESUMO

The aim of this work is to apply advanced oxidative processes to study the degradation of industrial wastewater containing water-soluble polymers. Kinetic constants of reactions involved in the oxidation processes were calculated by molecular modeling. In the experimental part the degradation of polyvinylpirrolidone (PVP), polyacrylamide (PAM) and polyethyleneglycol (PEG) was studied by photo-Fenton and UV/H2O2 processes. Intermediates of the degradation processes were identified by HPLC and the molecular weight distribution was monitored by GPC. In the experiments with PAM and PVP phase separation was observed, and more than 85% of the DOC was removed. The following intermediate acids were identified: acetic, malonic, formic and oxalic. The molecular weight distribution curves measured by GPC indicate that distinct reaction paths exist for each process studied, although the analysis of intermediates formed during the degradation of PAM was not conclusive with respect to acrylamide formation. The kinetic constants for the reactions involving hydrogen abstraction from PEG chain by hydroxyl and alkylperoxy radicals were calculated. The molecular modeling results confirm that hydrogen abstraction from polymeric chain by alkylperoxy radicals is the determinant step in the oxidation process for PEG and PAM. Polyacrylamide possesses three sites for attack by hydroxyl radicals and the favored path is the abstraction of tertiary hydrogen atom, followed by secondary hydrogen. The abstraction of the amide hydrogen was more difficult. The mechanism proposed for acrylamide formation was not the preferential reaction path. This was expected since acrylamide was not detected in the experiments with a limit detection of 50 ppb.

ASSUNTO(S)

polyacrylamide soluções aquosas photochemical degradation polyvinylpyrrolidone efluentes (tratamento químico) molecular modeling polyethylenoglicol modelagem molecular fotoquímica polímeros sintéticos

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