**Author details**

4 Ion Exchange Technologies

Anderko, 2001].

**Figure 1.**

**1.2. Ion exchange isotherm** 

[Zagorodni A. A., 2007]

than their concentrations [Bergaya et al., 2006];

*s*

(1)

(2)

Aa and <sup>s</sup>

<sup>B</sup> <sup>a</sup> the activities of

*m*

*m m*

Where m denotes the concentration of the specified ions at the surface. Ion exchange reactions may be described by the law of mass action using the activities of the ions, rather

> s B A s A B

a a <sup>K</sup> a a

these ions at the surface of the exchanger. K represents the thermodynamic equilibrium constant. To explain ion exchange equilibria some common models are used. First type of this model is based on the mass action law [Gorka et al., 2008; de Lucas et al., 1992; Melis et al., 1995; Valverde et al., 1999]. In the second group ion exchange is treated as an adsorption process [Gorka et al., 2008] and in the third, the solid phase is considered to provide sites with fixed charges for ion exchange, as well as sites on which molecular adsorption takes place[Gorka et al., 2008; Novosad & Myers,1982; Myers & Byington, 1986; Ioannidis &

B AS BS A

The ion exchange equilibrium can be qualified by suitable equilibrium isotherms. These isotherms are a graphical representation of the correlation between the equilibrium and experimental terms at constant temperature. The concentration of an ion in the solid expressed as a function of its concentration in the solution under specified conditions and at constant temperature. The most common ion exchange isotherm represents solidarity between ionic compositions of two phases: the ion exchange material and solution

*s B B s s A B*

*x*

where Aa and B <sup>a</sup> are the activities of ions A+ or B+ in solution <sup>s</sup>

Ayben Kilislioğlu *Department of Chemistry, Istanbul University, Turkey* 
