Green biosorbents based on chitosan-montmorillonite beads for anionic dye removal

Chitosan/KSF-montmorillonite beads were prepared at 1-25% w/w ratios by reaction of the biopolymer and the clay mineral with sodium tripolyphosphate as crosslinking agent. The synthesized biocomposites were characterized by CHN elemental analysis, XRD (X-Ray diffraction), FTIR (Fourier transform infrared), C-13 NMR (Nuclear magnetic resonance), thermogravimetry, SEM (Scanning electron microscopy), TEM (Transmission electron microscopy) and measurements of point of zero charge (pHpzc). The results suggested that hybrid materials were properly obtained and also their properties were improved compared to the pristine chitosan and montmorillonite. Further, the beads were evaluated in the adsorption of Remazol Blue under batch operations obtained for different conditions at pH (2-8), contact time (0-660 min) and dye concentration (100-1600 mg L-1). Kinetic and equilibrium sorption parameters were evaluated using pseudo-first and pseudo-second rate models and Langmuir and Freundlich equations. The results were promising and suggested that the sorbents can be applied for removing anionic dyes from wastewater even in acidic medium.