Development of Mn or Fe sulfides in the interlayer space of raw and Al-pillared bentonite

Abstract

Preparation of metal sulfide nanoclusters (Mn or Fe) confined in the interlayer space of a bentonite either with or without previous Al2O3-pillaring was investigated by H2S-sulfidization of Mn²⁺- or Fe²⁺-exchanged Al2O3-pillared bentonite as potential strategy to control growth and mean final size of interlayered, MnS or FeS-like polynuclear nanoclusters. The materials were characterized by elemental analysis, cation exchange capacity, low-angle powder X-ray Diffraction, N2 adsorption isotherms, simultaneous thermal analysis (DTA/TGA), diffuse reflectance UV-vis spectroscopy and high-resolution X-ray photoelectron spectroscopy. Interlayered metal sulfides were successfully obtained in pretty short time of reaction (only ~12 h). Optimal set of preparation conditions was established promoting stabilization of the interlayered metal sulfides, whereas preserving typical layered stacking of the starting clay: (i) ratio H2S/M²⁺(incorporated) = 50 mol/mol (M = Mn²⁺ or Fe²⁺); (ii) temperature of sulfidization = 100 °C; (iii) 200 °C for final thermal treatment, irrespective the type of atmosphere used (inert-N2 or oxidizing-air) and (iv) acid-base neutralization prior to thermal treatment did not enhance thermal stability. The most efficient Al-pillaring was achieved with 20 meq Al³⁺/g clay in terms of both higher XRD 001 basal reflection and narrower distribution of alumina-pillars. HR-XPS and DR-UV-vis analyses of the best materials with every transition metal evidenced formation of polysulfide groups and blue-shift of the absorption signal as a consequence of the modification performed on the layered aluminosilicate. Development of Mn or Fe sulfides in the interlayer space of.... Available from: https://www.researchgate.net/publication/323399710_Development_of_Mn_or_Fe_sulfides_in_the_interlayer_space_of_raw_and_Al-pillared_bentonite [accessed Apr 18 2018].