Abstract:
The adsorption of hydrogen sulfide (H2S) was studied using the adsorption calorimetric
method at a constant temperature of 303 K. The objects of study were CaA-type zeolites with different
cationic compositions and a carbon adsorbent obtained by microwave activation of Paulownia tomentosa
bark. The obtained adsorption isotherms were processed using the Dubinin–Radushkevich equation,
which made it possible to determine the adsorption capacity, characteristic energy, and the nature of the
interaction between H2S molecules and the active surface sites. The isotherm expressed in the three-
term form of the Volume Micropore Occupation Theory (VMOT) equation showed complete agreement
with the experimental data. Based on these equations, the adsorption isotherm was calculated up to the
saturation vapor pressure of H2S. Calorimetric results indicated a moderate exothermic effect typical of
predominantly physical adsorption accompanied by weak chemisorption on certain active centers.
Differences in the sorption behavior of zeolites and the carbon adsorbent were attributed to variations in
pore structure, surface polarity, and the concentration of active sites. The obtained results refine the
thermodynamic characteristics of the H2S-solid adsorbent system and can be applied to the development
of efficient technologies for the purification of natural and industrial gases from hydrogen sulfide.
