Adsorption of 4,4’ ‐ iso propylidene diphenol and diphenylolpropane 4,4’ dioxyaceticacid from aqueous solution on kaolinite

Abstract

The adsorption of 4,4 ‐ iso propylidene diphenol (Bis‐phenol A) and diphenylolpropane 4,4 dioxyaceticacid (Bis acid A2 ) on kaolinite type clay have been studied as the function of their solution concentration and temperature. The adsorption rates at low concentrations of Bis ‐ phenol A was found to fit the first‐order equation with two kinetic steps. In all cases, the first step of adsorption was more rapid than the second one. The results indicated that the adsorption rate is controlled by either a film diffusion or a intra‐particle diffusion. It can be concluded that the adsorption reaction begins with the film diffusion. Since the film‐diffusion rate is much higher than the rate of intra‐particle diffusion, the reaction is governed by intra‐particle diffusion in the second step. In the case of Bis acid A2 only one kinetic step was observed corresponding to the film diffusion mechanism. Using the Arrhenius equation, the activation energies for both systems were evaluated. The corresponding values of thermodynamic parameters were calculated using Eyring's equation of absolute reaction rate. The adsorption data of Bis ‐ phenol A and Bis acid A2 were fitted to Freundlich and B.E.T isotherms, respectively. The results could be interpreted in terms of a parallel orientation of Bis acid A2 molecules on the adsorbent surface.

Key words:

• Adsorption rate
• film diffusion
• intra‐particle diffusion
• Freundlich type isotherm
• B.E.T type isotherm
• bisphenol A
• bis acidA2.