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Titolo:
Flocculation kinetics of an ochre suspension in salt(NaCl)-containing aqueous media in the presence of anionic and cationic acrylamide copolymers
Autore:
Mjagchenkov, VA; Proskurina, VY; Gromova, YY; Bulidorova, GV;
Indirizzi:
Kazan State Technol Univ, Fac Phys & Colloid Sci, Kazan, Russia Kazan State Technol Univ Kazan Russia Phys & Colloid Sci, Kazan, Russia
Titolo Testata:
COLLOID AND POLYMER SCIENCE
fascicolo: 5, volume: 279, anno: 2001,
pagine: 468 - 478
SICI:
0303-402X(200105)279:5<468:FKOAOS>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
GRAFTING POLYELECTROLYTES; POLYMER ADSORPTION; FINE PARTICLES; POLYACRYLAMIDE; MODEL;
Keywords:
flocculation; ionic strength; ionogenic copolymers; sedimentation kinetics; viscosimetry;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Mjagchenkov, VA Kazan State Technol Univ, Fac Phys & Colloid Sci, Kazan, Russia Kazan State Technol Univ Kazan Russia ci, Kazan, Russia
Citazione:
V.A. Mjagchenkov et al., "Flocculation kinetics of an ochre suspension in salt(NaCl)-containing aqueous media in the presence of anionic and cationic acrylamide copolymers", COLLOID P S, 279(5), 2001, pp. 468-478

Abstract

The sedimentation kinetics of an ochre suspension in salt (NaCl)-containing aqueous media was studied in the presence of ionogenic (anionic, A, and cationic, C) acrylamide copolymers with high molecular weight (M > 2 x 10(6)) using a VT-0.5 torsion balance. The ionic strength of the dispersion medium varied in the wide range from 0.001 N to 0.4 N. The flocculation proceeded predominantly by a 'bridge' mechanism, and the fraction of macromolecules inactive in the acts of floccule formation was significantly higher for Ccopolymer as compared with A copolymer. A drastic fall in the flocculatingactivities of A and C copolymers when passing from salt-free to salt-containing media is caused mainly by two following events:1. The change in the conformational state of macromolecules, primarily, intheir effective dimensions2. The participation of a certain part of electrolyte in the formation andmodification of an electrical double layer around disperse phase particlesAfter introducing binary compositions of A and C flocculants into salt-containing media their resultant flocculating effect depends on the introduction mode of polymeric components. A strong difference in the magnitudes of the flocculating effect for A and C copolymers is observed in water. In the region of high ionic strengths (0.1-0.4 N) this difference becomes far lessdistinct. The flocculating activities of A and C copolymers were compared when introduced as the first (lambda (A) and lambda (C)) and the second (lambda (A)' and lambda (C)') additives. It was shown that lambda (A)/lambda (A)' > 1 and lambda (C)/lambda (C)' > 1. Such relationship between lambda (A) and lambda (A)', lambda (C) and lambda (C)' indicates that selective interactions between A and C copolymers play an essential role in the flocculation processes. The last statement was indirectly confirmed in the present work by the data of electrochemical and viscosimetric studies. When using C copolymer as the second additive in the region of low ionic strengths its main function undergoes reversal, and the copolymer begins to operate not asa flocculant, but as a stabilizer of disperse phase particles (lambda (C) < 0).

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Documento generato il 20/09/20 alle ore 07:48:28