Charge in the Presence of Specific Adsorption

FIGURE 5.25 Zeta potential as a function of pH for goethite particles in absence and presence of phosphate ions, in 0.01 M KNO3. (, thick solid line) absence of phosphate ( , thin solid line) 10 M PO (A, dotted line) 10 M PO (0, dashed line) 10 M PO . (Reprinted from J. Colloid Interface Sci., 285, Antelo, J. et al.. Effects of pH and ionic strength on the adsorption of phosphate and arsenate at the goethite-water interface, 476-486. Copyright 2005, with permission from Elsevier.) 

FIGURE 5.26 Potentiometric titration curves of Mn02 (3.33 g L 214 g i) in the presence of different concentrations of phosphate. The pH was initially adjusted to 3.0 with HNO3. (Reprinted from J. Colloid Interface Sci., 301, Mustafa, S. et al., pH effect on phosphate sorption by crystalline Mn02, 370-375. Copyright 2006, with permission from Elsevier.) 

Generally speaking, to obtain the surface charge composition in the presence of specific adsorption, the preceding methods alone usually do not suffice. Modeling of the interface with the adsorption reactions is required, and independent measurements, for example, of adsorption isotherms, are very useful if not unavoidable. These topics will be considered in Part III. 

This chapter is built on the foundations laid by its predecessors, especially Chapters 3 and 4, and all together serve as basis for the next chapter, where we leave the interaction between a particle and the solution to enter the study of the interaction between particles thanselves. Besides, the concepts developed here and in Chapter 3 are necessary to understand further topics related to ion binding in Part III. 

Abendroth, R. P. 1970. Behavior of a pyrogenic silica in simple electrolytes. Journal of Colloid and Interface Science 34, no. 4 (December) 591-596. doi 10.1016/0021-9797 (70)90223-7. 

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Lyklema, J., Points of zero charge in the presence of specific adsorption, J. Colloid Inter/. Sci., 99, 109, 1984. 

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