A new gel-like film was generated on the surface of silicate fiberglass (FG) under hydrothermal treatment with tetramethylammonium hydroxide (TMAH) water solution. By means of scanning electron microscopy (SEM)/high resolution transmission electron microscopy (HRTEM), H-1 NMR magic angle spinning (MAS), and diffuse reflectance infrared fourier transform spectroscopy (DRIFTS), we revealed this film is a phase with density less than pristine FG, where TMA species, as the H2S adsorption sites, are confined. Indeed, FGs modified in this way exhibited a rather high dynamic adsorption capacity which was proportional to concentration of TMA cations bonded with very basic oxygen of Broensted acid residue. The N-modified FG sorbents showed good regenerability when in the presence of water, and the adsorbed hydrogen sulfide on the TMA(+)-E-O--Si ion pair was easily desorbed at room temperature. This gives grounds to conclude that the process of hydrogen sulfide sorption on N-modified FGs is reversible and proceeds without a loss of adsorption capacity. Indeed, N-modified FGs remained stable during several adsorption-desorption cycles.