ADSORPTION OF 4,4'-ISO-PROPYLIDENE-DIPHENOL AND DIPHENYLOLPROPANE-4,4'-DIOXYACETICACID FROM AQUEOUS-SOLUTION ON KAOLINITE

The adsorption of 4,4' - iso propylidene diphenol (Bis-phenol A) and d iphenylolpropane 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 st eps. In all cases, the first step of adsorption was more rapid than th e second one. The results indicated that the adsorption rate is contro lled by either a film diffusion or a intra-particle diffusion. It can be concluded that the adsorption reaction begins with the film diffusi on. Since the film-diffusion rate is much higher than the rate of intr a-particle diffusion, the reaction is governed by intra-particle diffu sion in the second step. In the case of Bis acid A2 only one kinetic s tep 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 c alculated using Eyring's equation of absolute reaction rate. The adsor ption data of Bis - phenol A and Bis acid A2 were fitted to Freundlich and B.E.T isotherms, respectively. The results could be interpreted i n terms of a parallel orientation of Bis acid A2 molecules on the adso rbent surface.