Multiscale investigation of a bioresidue as a novel intercalant for sodium montmorillonite

This paper investigates the efficacy of a novel bioresidue (made from biomass) for organic modification of sodium montmorillonite clay. To this end, montmorillonite was biomodified using a solution-intercalation processing technique. The results of experiments, carried out using techniques of XRD, FTIR, TGA, and oscillatory rheometry, showed that strong interactions exist between certain molecular species of bioresidue (e.g., amide and carboxyl groups) and silicate platelets of montmorillonite clay, leading to a highly intercalated clay structure. An atomic-level analysis using density functional theory (DFT) was also employed to study the effect of the bioresidue's polar functional groups on the basal d-spacing of montmorillonite. On the basis of DFT results, the overall increase in the gallery spacing observed for amide and carboxyl intercalants could be attributed to the ion- dipole and dipole-dipole interactions and, most importantly, reduction in positive charge of the gallery space. This reduction of positive charge promotes the steric repulsive interactions between the montmorillonite layers that is manifested in an increase of the basal d-spacing.