Experimental and DFT Study of Reaction Mechanisms in Removal of H2S in Ferrites

Abstract

The objectives of this work were to synthesize and characterize manganese ferrites via hydrochemistry under optimized conditions to evaluate the adsorption capacity and removal of H2S; calculation of the structural and electronic parameters involved in the process of adsorption between H2S and Fe3O4 surfaces as majority phase ferrites in manganese and discern the process of physisorption or chemisorption. Relating experimental and theoretical on the mechanism of adsorption data allow us to conclude the interaction of H2S with Fe3O4 and ferrites of manganese. The XRD patterns showed the majority of ferrites obtained magnetite phase. The adsorption capacity of H2S on Mn ferrites indicate that the adsorption depends on the amount of iron and temperature. The XRD patterns after adsorption of H2S show two corresponding to crystalline phases Fe3O4 and FeS2 orthorhombic. Estimates of the volume of magnetite surfaces and adsorption of H2S with Fe3O4 (111) with CRYSTAL09 code using the PBE0 functional and the data bases were performed using a modification of an iron base that improves the results of volume and surface adsorption H2S on Fe3O4 (111) in FeO-Fet termination. BSSE results in the calculation of the energy of adsorption of H2S were bridged site -17.50 kcal/mol base using Fe(III), -12.51 kcal/mol using the Fe(III) and Fe(II) bases simultaneously and -4.99 kcal/mol with the modified base. The energy of chemisorption process on octahedral iron was -48.42 kcal/mol, where the rupture of the -SH bond in the molecule and the formation of H2S and O-H bond occurs at the surface. The experimental and theoretical evidence suggests that the adsorption capacity of the ferrites is limited to 50 %, as is the majority magnetite phase and it has two ends Feo-Fet and Fet-O energetically favoured. However, the former is reacted with hydrogen sulfide.