This work demonstrates that iron-enriched natural zeolitic volcanic tuff (Paglisa deposit, Cluj county, Transilvania, Romania) resulting from a previous use as adsorbent in wastewater treatment can be recycled into effective electrode modifier applied to the electrocatalytic detection of hydrogen peroxide. After physico-chemical characterization of tuff samples using various techniques such as chemical analysis. X-ray diffraction, scanning electron microscopy, infrared spectroscopy. BET analysis and X-ray photoelectron spectroscopy, the electrochemical response of the iron-enriched zeolites was studied on the basis of solid carbon paste electrodes modified with these samples. The results indicate that iron centers in the zeolite are electroactive and that they act as electrocatalysts in the voltammetric and amperometric detection of H2O2. Best performance was achieved in phosphate buffer at pH 7, showing a sensitivity of 0.57 mA M-1 cm(-2), a detection limit down to 60 mu M, and a linear domain up to 100 mM H2O2. (C) 2010 Elsevier Ltd. All rights reserved.