Atrazine adsorption by acid-activated zeolite-rich tuffs

Two different acid-activated zeolite-rich tuffs were evaluated as potential adsorbents for atrazine removal from water. The materials investigated were: Neapolitan yellow tuff (NYT, containing 37% phillipsite and 17% chabazite) and a clinoptilolitic tuff from Eskisehir (Turkey) (T-CPL, 79% clinoptilolite). The T-CPL tuff exhibited the highest adsorption capacity. Atrazine adsorption, estimated by batch method, was likely to involve electrostatic interactions obeying a pseudo-second-order kinetic model, whereas hydrogen bonds did not appear to playa significant role. Pre-treatment of tuffs with increasing concentrations of HCl resulted in a sharp increase of atrazine adsorption capacity, followed by a progressive reduction for both types of tuff. The effects of acidification on zeolites were investigated by spectrophotometric measurement of dealumination and by FT-IR and XRD analysis. The results suggested that acid activation of zeolites enhanced their ability to bind atrazine, which accounts for the initial increase of the adsorption. Acid activation, however, attacked the zeolite structure, particularly of zeolites rich in aluminium or poor in silicon, e.g., phillipsite and chabazite. The alteration of the zeolite structure by acid could account for the decrease of atrazine adsorption observed with both tuff types and for the absolute low adsorption of NYT relative to T-CPL. The results of this exploratory investigation thus, indicate that acid-activated clinoptilolitic tuff could be considered a suitable material for removing atrazine and similar chemical compounds from water. (C) 2010 Elsevier B.V. All rights reserved.