Investigation and modeling of physicochemical properties of bentonite-chitosan composites versus the concentration of chitosan added by intercalation

Abstract

This study attempts to understand the relationship between structural and physicochemical changes of clay modified by a chitosan intercalation, and to valorize the clay-chitosan composites for wastewater treatment purpose. More precisely, the main aim was a characterization and modeling of the physicochemical properties of clay-polymer composites (especially bentonite-chitosan composites) versus the concentration of chitosan added by intercalation. We first developed a method for intercalating chitosan into the clay matrix, with different polymer concentrations (6g/L, 12g/L, 18g/L, 24g/L, 27g/L and 30g/L). Second, we carried out a characterization of the structural and physicochemical properties of clay-polymer composites based on X-Rays Diffraction (XRD), Fourier Transform Infrared (FTIR) and Scanning Electric Microscopy (SEM). In particular, the results of these analyses show that the measured pores within the composites with chitosan concentrations 6g/L and 30g/L are of nanometric order, while the composite at 12g/L is rather of microscopic order. Third, XRD measurements allow the determination of the clay interlayer space (basal distance) and particles size versus the polymer concentration. For basal distance, we have demonstrated the existence of five regimes depending on the value of the polymer concentration, namely (i) dilute regime, (ii) first semi-dilute regime, (iii) well-regime, (iv) second semi-dilute regime and (v) saturation regime. Finally, these bentonite-chitosan composites may be used as kinds of filtration membranes for wastewater, retaining, for example, a dye whose adsorption quantity was found to be improved by an amount of 76.92 %.