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Titolo:
Photocatalyzed degradation of polymers in aqueous semiconductor suspensions V. Photomineralization of lactam ring-pendant polyvinylpyrrolidone at titania/water interfaces
Autore:
Horikoshi, S; Hidaka, H; Serpone, N;
Indirizzi:
Meisei Univ, Frontier Res Ctr Global Environm Protect, Hino, Tokyo 1918506, Japan Meisei Univ Hino Tokyo Japan 1918506 Protect, Hino, Tokyo 1918506, Japan Concordia Univ, Dept Chem & Biochem, Montreal, PQ H3G 1M8, Canada Concordia Univ Montreal PQ Canada H3G 1M8 m, Montreal, PQ H3G 1M8, Canada
Titolo Testata:
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
fascicolo: 1, volume: 138, anno: 2001,
pagine: 69 - 77
SICI:
1010-6030(20010101)138:1<69:PDOPIA>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
AMINO-ACIDS; PHOTOOXIDATION; PHOTODEGRADATION; EXPOSURE; OXIDATION; RADIATION; DAMAGE; FILMS; DNA;
Keywords:
photo-oxidation; photodegradation; polyvinylpyrrolidone; 2-pyrrolidone; photocatalysis; titanium dioxide;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Hidaka, H Meisei Univ, Frontier Res Ctr Global Environm Protect, 2-1-1 Hodokubo, Hino, Tokyo 1918506, Japan Meisei Univ 2-1-1 Hodokubo Hino Tokyo Japan 1918506 18506, Japan
Citazione:
S. Horikoshi et al., "Photocatalyzed degradation of polymers in aqueous semiconductor suspensions V. Photomineralization of lactam ring-pendant polyvinylpyrrolidone at titania/water interfaces", J PHOTOCH A, 138(1), 2001, pp. 69-77

Abstract

The mechanism of photo-oxidation of the water-soluble polyvinylpyrrolidone(PVP) having a pendant five-membered lactam ring is complicated by the manner by which the macromolecule adsorbs on the TiO2 particle surface in a heterogeneous dispersion. Experimental results and computer simulation of theinitial process(es) infer three major steps for the photodegradation of the PVP structure. The first step is adsorption (or coagulation) of PVP on TiO2 particles as evidenced by the size distribution of TiO2 particles by dynamic light-scattering and by the electric charge on the TiO2 particle surface assayed by zeta -potential measurements. Molecular orbital simulations of initial processes were calculated at the AMI level using the MOPAC systemavailable in the CAChe package. The second step, namely attack of PVP by (OH)-O-. and/or (OOH)-O-. radicals, involves cleavage of the PVP main chain and opening of the lactam ring in the PVP structure probed by temporal UV spectral changes and by a decrease of the molecular weight using gel permeation chromatographic methods. Additional details of the photo-oxidation modeof the lactam ring was examined by a detailed examination of the photo-oxidation of the model compound 2-pyrrolidone to ascertain formation of (OH)-O-. radical adducts, opening of the lactam ring, and identification of intermediates by HPLC, and C-13- and H-1-NMR methods. The fnal major step in themechanism involves generation and subsequent conversion of the primary amine (methylamine from opening of the lactam ring) to yield ultimately NH4+ and NO3- ions, and conversion of the propanoic acid to acetic and formic acids and then to CO2. The effects of the extent of polymerization and variation in light intensity were examined using PVP samples having different hardness factors (hf) of 15 and 30, and different light intensities (namely, 1,2, 3 and 4 mW cm(-2)), respectively. (C) 2001 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 09/07/20 alle ore 17:51:25