Hydrogen Sulfide Adsorption Mechanism and Breakthrough Curves of Highly Stable Na-, Na-H-, Ca- and K-Mordenites

Hydrogen sulfide (H₂S) is a hazardous gas found in natural gas and biogas, lethal over 100 ppm. When released into the atmosphere, it can turn into sulfur dioxide. One option to remove H₂S is using porous materials such as zeolites. Among them, mordenite stands out due to its channel structure, wide availability, and low cost. In this work, we evaluated the H₂S adsorption capacity of mordenite using a volumetric static method. The results show the adsorption capacity of H₂S in mordenite varies with the exchanged cation. The highest was measured in Na-mordenite (~4.08 mmol H₂S/g mordenite). The experimental breakthrough curves for this zeolite confirmed Langmuir-type adsorption and strong affinity between Na⁺ cations and H₂S. Despite this interaction, the XRD diffractograms of Na-mordenite show that the material retained its crystalline structure. More information about the differences in the amount of H₂S adsorbed in the zeolites caused by the change in exchanged cation was obtained by H₂S adsorption followed by FTIR spectroscopy. The spectra show differences in the position of the peaks related to the different adsorption modes of H₂S caused by a change in the polarizing power of the cations due to their charge and position inside the zeolite pores.