Electrokinetic Potentials of Clay Surfaces Modified by Polymers

✍ Scribed by Ivan Sondi; Ognjen Milat; Velimir Pravdić

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 998 KB
• Volume: 189
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.4753

✦ Synopsis

The model is This paper describes the influence of two polymers, fulvic acid known as constant basal surface charge (CBSC) (16). The (FA) and polyacrylic acids (PAAs) of comparable molecular mass, charge at edge surfaces is due to oxy-hydroxy groups, deon the electrokinetic potential of model surfaces encountered in pends on pH, and shows an amphoteric character. It arises clay minerals: silica (SiO 2 ), aluminum oxide (g-Al 2 O 3 ), and gibbfrom protolytic equilibria, adsorption, and desorption. site [g-Al(OH) 3 ]. Measurements at pH 6.5 { 0.2 show that FA Hahn and Stumm (1), Tipping and Heaton (19), Tipping and PAAs modifiy the potentials of aluminum oxide and gibbsite, and Higgins (20) point out that adsorbed organic substances, but leave the silica surface unchanged. A chlorite clay mineral

especially polymers, mask to some extent the physicochemi-(ripidolite), milled to increase the numbers of oxy-hydroxy groups cal properties of underlying surfaces and dominate surface at newly created surfaces, was exposed to FA and PAAs, carriers of carboxylic groups, to study their influence on electrokinetic interactions of particles with the aquatic medium. Humic subpotential. The key to the interaction is that polymers hold metal stances are important contributors to organic films covering ions (Al, Mg, Fe) in the edge surfaces, while siloxane groups show marine particles (6, 7, 21). The adsorption-desorption belimited interaction or none at all. The results offer an explanation havior of humic substances on mineral surfaces in solid/liquid of why clay mineral particles are always negatively charged in systems has gained increasing interest in recent investigations natural waters.