Impregnation of metals on supports

The impregnation occurs by diffusion or wetting. For diffusion, the time estimated is  

In the impregnation with interaction with the solid, there are covalent and ionic bindings. The pH is the most important parameter and indicates superficial electric charges. If the resultant electric charge is zero, it is known as zero electric charge and identified as isoelectric point (IP), where the electric charges are compensated. In this state, neither the solution nor the colloidal system does transport electric charges. 

If acid surface (+) exchange anions If surface (—) basics exchange cations 

proton H+ can exchange cations of type Ni +, Pd +, Pt +, and Au. Hydroxyls OH can exchange complex anions. 

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