Chemical trapping of gaseous H⁠2S at high and low partial pressures by an iron complex immobilized inside the montmorillonite interlayer

A stable hybrid material (Mt-Fe(III)Phen) formed by intercalation of the μ-oxo Fe(III)-phenanthroline complex [(OH⁠2)⁠3(Phen)FeOFe(Phen)(OH⁠2)⁠3]⁠4+ (Fe(III)Phen) in montmorillonite (Mt) is able to immobilize H⁠2S in gaseous phase with high efficiency even at extremely low pressures. DR UV–vis and I.R. spectroscopies, elemental analysis, X-ray powder diffraction, thermal analysis coupled with evolved gas mass spectrometry, and X-ray absorption spectroscopy show that the material has high adsorption capacity, performs fast H⁠2S trapping and is long-lasting. Moreover, even extremely low levels of H⁠2S can be removed easily and quickly from gaseous phase using a suitable amount of the trapping material. The immobilization mechanism likely involves a redox reaction between iron (III) and one S⁠2− ion, followed by the binding of a second S⁠2− ion to the metal centre. The process takes place at room temperature, is reversible for several cycles, and does not require pre-treatment of neither gaseous H⁠2S nor the adsorbent material. Therefore, this modified montmorillonite is a promising material to get rid of H⁠2S in processes of environmental interest and to obtain gaseous (and gasifiable) high quality hydrocarbons in fuels refineries.