Modification of natural clinoptilolite zeolite to enhance its hydrogen adsorption capacity

Abstract

In this study, natural clinoptilolite was treated with HCl, HNO3, and C2H2O4 at various concentrations (0.1, 0.5, and 1.0 M) at different temperatures (60, 70, and 80 °C) and treatment times (2, 3, and 4 h). The hydrogen adsorption capacity of natural clinoptilolite increased from 0.446 to 3.255 mmol/g after treating with 0.5 M HNO3 at 80 °C for 2 h. The correlation of the newly produced textural and structural properties with hydrogen adsorption ability is explained by characterizing the modified clinoptilolites using X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, and temperature programmed desorption of ammonia (NH3-TPD) measurements. The results show that the hydrogen adsorption capacity of modified clinoptilolites is associated with both the quantity and strength of the strong acid sites, in addition to the enhanced surface area and micropore volume. The hydrogen adsorption data for natural and acid-treated clinoptilolite samples at 77 K obeyed the Freundlich isotherm model.

Zeolite Properties, Methods of Synthesis, and Selected Applications

“…In addition, physicochemical modification of zeolites makes it possible to obtain materials with desired properties. Akyalcin et al [ 140 ] conducted an experiment to develop a method for obtaining hydrogen (H 2 ) storage materials. The authors used clinoptilolite, which they treated with various chemical compounds (HCl, C 2 H 2 O 4 , and HNO 3 ).…”

“…Clinoptilolite is the most abundant natural zeolite, forming extensive and abundant deposits throughout the world. It has a two-dimensional structure of 8-ring and 10-ring channels [ 116 ], and the Si/Al ratio is greater than 4, which makes it characterized by the high thermal stability of the structure [ 140 ]. It is also characterized by a high ion exchange capacity and a particular affinity for heavy metal cations.…”

“…Clinoptilolite contains the exchangeable cations Na + , K + , Ca 2+, and Mg 2+ [ 140 ], which allow ion exchange and are the basis of many processes, including drinking water treatment. These properties of zeolite, as well as economic considerations, determined the use of this natural zeolite in a study by Erdem et al [ 188 ] to remove Co 2+ , Cu 2+ , Zn 2+ , and Mn 2+ ions from industrial wastewater.…”