Uptake of arsenite and arsenate by clinoptilolite-rich tuffs

Clinoptilolite-containing rocks were used to study the possible uptake of a rsenite (H(3)ASO(3)) and arsenate (H2AsO4) species from aqueous solution. T wo samples also exhibited mordenite and erionite zeolitic phases. Batch and isotherm studies at pH 4 in the concentration range 0.1 < C < 4 mg l(-1) w ere performed. The experimental data were used to model Freundlich, Langmui r and Langmuir-Freundlich adsorption isotherms. Solutions were analyzed by means of ion chromatography coupled with inductively coupled plasma mass sp ectrometric detection (IC-ICP-MS). All zeolitic samples investigated remove d more H2AsO4- than H3AsO3 at equivalent arsenic concentrations. Although t he saturation capacity of the tuffs studied was inversely related to the si licium dioxide content and directly to the iron content in the acid-washed zeolite, the addition of iron did not significantly improve the removal eff iciency. Up to 98% of H3AsO3 were removed from a 500 mug As l(-1) solution by three of the samples studied after a contact time of 70 days. (C) 2001 E lsevier Science B.V. All rights reserved.