Adsorption and partial catalytic oxidation of hydrogen sulfide to elemental sulfur using facilely prepared materials derived from sludge of groundwater treatment

Abstract

Realizing the use of biogas as fuel or a gas engine, it is needed to upgrade to natural gas standards when it comes to pure biomethane, meaning impurities must be removed to a certain low concentration. Among these tasks, hydrogen sulfide (H2S) removal steadfastly gets the most attention. In the present work, partial catalytic oxidation was used to convert H2S to less harmful forms. Adsorbents/catalysts applied to this process were prepared from the sludge of a groundwater treatment plant using a simple combination of drying and calcination methods. As a relevant result, the as‐prepared sample (dried at 105°C for 24 h) exhibited high activity, with 90 ± 2% H2S conversion after 120 min of reaction time, while the sample calcined at about 500°C for 5 h (TP‐500) showed the highest H2S conversion (96 ± 2%); the lowest 28 ± 1% belonged to the case of TP‐700. The main compositions of the TP‐500 sample were crystalline calcite and amorphous iron oxides. The average size of calcite crystallites was ~45 nm, with a specific surface area of ~76 m2/g. Moreover, the presence of oxygen in the catalytic process and the “self‐outflow process” of sulfur desorption were the vital keys that allowed the partial H2S oxidation to take place continuously. After a reaction time of 2 h, the adsorption capacity of the best sample was 460.8 mg/g. Thus, it is obvious that inexpensive catalysts derived from sludge precursors can be effectively used for H2S removal from mixtures with air, supporting the treatment of raw biogas in the coming time.