Formation and structure of polystyrene latex aggregates obtained by flocculation with cationic polyelectrolytes: 1. Adsorption and optimum flocculation concentrations
✍ Scribed by Leif Eriksson; Barbro Alm; Per Stenius
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 1008 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0927-7757
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✦ Synopsis
The adsorption of modified polyacrylamide polye!ectrolytes and their efiect on the flocculation of negatnrly charged polystyr:ne latex were investigated. Conditions were chosen so mat the adsorbed poly;ncrs approached cquilibrlum configuration before the occurrence of appv-iable flocculation. Polymers with ver> Io'r\ charge densit? (a fur pcrwx chargsd monomers) lorm loops and tads at .IC latex surface and flocculate the latex by hrldging. Pol~mcr~ i\ith higher charge adsorb in a flat configuration and fioccuiate the latex by net charge neutralization. possibly leading to long-range attraction between positively and negatively charged domains on different particles. Minima in the ratio cf :he :otaf polymer charge adsorbed at the plateau level to the total charge on the latex occur 'it intermediate pol~mci-charge densities. At these densities :he mean distance between charged groups on the polymers matches the mean distance between charged groups on the latex. izt maximum adsorption of highly charged polymers. the latex psrticles acquire a high posi!ive charge. The reasw for this :: that thz mean distance between positive charges on the polymer is smaller than the distance betwecr, charpes on the '!a. so that ion binding of the polymer to the ionized LJ aurfacc group\ cannot take place withou: simultaneous attachment of&n excess of positiw charge to the la:ex surface. Kqr'words: Cationic polyelectrc:ytes: Bocculaiion; polystyrene latex aggregates introduction
Mauy important technological processes involve the separation and de.w&r'ng of disperse systems with particle sizis ranging from several micrometers down to fractions of a micrometer. Separation % usuaity strongly enhanceb if the particles can be aggregated mto structures that promote rapid release and drainage of the soivent. In many appiicaticns ubutrai polymers or poiyelectroiytes are used as efficient floccuiants with regard to dosage/ response ratio as well as to pot properties. Thus.