Clinoptilolite from Gordes (Turkey) was treated with HCl, HNO3 and H2SO4 solutions of varying concentrations (from 2.0 M to 6.0 M) at 90 degrees C for 4 h to evaluate its potential for possible applications in hydrogen storage. X-ray diffraction, X-ray fluorescence and nitrogen adsorption techniques were applied for characterization of the zeolites. Hydrogen adsorption capacities of clinoptilolite samples were found in the range between 1.609 and 2.391 mmol/g. The effects of the acid modification process on the structure and hence hydrogen adsorption was evaluated according to the obtained results. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.