Zeta potential manipulation

Understanding of the structure of the adsorbed surfactant and polymer layers at a molecular level is helpful for improving various interfacial processes by manipulating the adsorbed layers for optimum configurational characteristics. Until recently, methods of surface characterization were limited to the measurement of macroscopic properties like adsorption density, zeta-potential and wettability. Such studies, while being helpful to provide an insight into the mechanisms, could not yield any direct information on the nanoscopic characteristics of the adsorbed species. Recently, a number of spectroscopic techniques such as fluorescence, electron spin resonance, infrared and Raman have been successfully applied to probe the microstructure of the adsorbed layers of surfactants and polymers at mineral-solution interfaces. 

Adsorption of the collectors such as dodecylamlne and fatty acids is reported to be strongly influenced by electrical double layer forces. In this study, manipulation of the electrostatic forces by adding sodium chloride was attempted to achieve the desired separation. Suitable separation of apatite from dolomite was achieved with dodecylamine hydrochloride in the presence of sodium chloride. Zeta potential measurements revealed that sodium chloride acts as an indifferent electrolyte for dolomite, but causes a shift In the Iso-electric point of apatite. 

Examples of properties tuned significantly via primarily surface chemistry manipulation include physiochemical ones like zeta potential and isoelectric point. Surface wettability is a good example where both structural and surface chemical parameters have been optimized in order to achieve superhydrophobicity with mesoporous and macroporous silicon (Cao et al. 2006 Ressine et al. 2008). 

Knowledge of the zeta potential of a clay slurry, and the abiUty to manipulate this by adding particular monovalent or polyvalent ions, by modifying the pH, and/or by altering the viscosity by altering the proportions of solids, are at the... 

Chapters 10 and 11 are devoted entirely to aspects of colloid stabihty. First, the essential concepts of the electrical and van der Waals forces between colloid particles are presented with special emphasis on the concepts of the zeta potential, double-layer thickness and Hamaker constants. Then, the DLVO theory for colloidal stability is presented. This is a major tool in colloid chemistry and we discuss how stability is affected by manipulating the parameters of by the classical DLVO theory. Chapter 11 closes with a presentation of kinetics of colloid aggregation and structure of aggregates. Chapters 12 and 13 are about emulsions and foams, respectively - two important categories of colloid systems where DLVO and other principles of colloid and surface science are apphed. In this case, DLVO is often not sufficient. Steric forces and solvation effects are not covered by the classical DLVO and their role in colloid stabihty is also discussed in Chapter 12. 

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