Adsorption of aqueous nitrophenols on clinoptilolite

The adsorption of o-, m- and p-nitrophenols on clinoptilolite type natural zeolite has been studied as a function of the solution concentration and temperature. The adsorption rates were observed to be equal to the first-order kinetics. The rate constants were calculated for 25.0-40.0-50.0 degreesC at constant concentration. The activation energies, (E-a) for nitrophenoles adsorption on zeolite, were estimated using the Arrhenius equation. Thermodynamic parameters were calculated for all nitrophenols. Adsorption isotherms of o-, m- and p-nitrophenols on natural zeolite were determined. These isotherms were modeled according to the Freundlich and Langmuir adsorption isotherms. The isotherms for nitrophenols on clinoptilolite were assigned as L curves. The L curve of p-nitrophenol is two step while the L curves of o- and m-nitrophenols are one-step. (C) 2001 Elsevier Science B.V. All rights reserved.