2:1 dioctahedral smectites as a selective sorbent for dioxins and furans:: Reactivity index study

A suitable sorbent from the dioctahedral smectite family for the sorption of 2,3,7,8-terachlorinated/brominated dibenzo-p-dioxins (TCDD,TBDD), tetrachlorinated/brominated dibenzo furans (TCDF, TBDF) is investigated by means of a range of reactivity index using density functional theory (DFT). From the values of the local softness and the charge on the hydrogen atom of the bridging/structural (occurring on the surface) hydroxyl attached to the octahedral/tetrahedral metal site present in smectite, used as first approximation to the local hardness, it is concluded that the local acidities of the inorganic material systems are dependent on several characteristics that are of importance within the framework of the hard and soft acids and bases (HSAB) principle. We first aimed to rationalize an understanding to locate the active site of dioxins and furans by the local softness calculation. We compared its activity with that of the OH group of both octahedrally and terahedrally substituted members of the dioctahedral smectite family. We compared the probability of surface hydrogen bonding with that which resulted from the interaction of bridging hydroxyl present at the octahedral site in clays. By the interaction between systems, we validate the proposition for designing a novel qualitative way to choose the best sorption material both in terms of isomorphous substitution of clays and the nature of the interacting molecule.