New N-guanidinium chitosan/silica ionic microhybrids as efficient adsorbent for dye removal from waste water.

N-guanidinium chitosan acetate, a new chitosan derivative, was prepared via direct guanylation reaction between chitosan and cyanamide in the presence of scandium (III) triflate. Treatment of N-guanidinium chitosan acetate with 3-(trihydroxysilyl)-1-propanesulphonic acid followed by sol-gel reaction allowed accessing N-guanidinium chitosan silica hybrid material. The new ionic microhybrid was characterized using 13C and 29Si solid state NMR, IR spectroscopy, scanning electron microscopy and thermogravimetry. Further studies in the area of separation indicated very high adsorption capacity for cationic dyes such as methylene blue (MB), with capacities up to 935 mg/g. The adsorption kinetics can accurately be described by pseudo second-order model. Equilibrium adsorption data showed a better fit with Langmuir adsorption isotherm model. Recycling test showed that the ionic microhybrid can be reused in at least five adsorption-desorption cycles. These results open new perspectives and possibilities for the design of novel hybrid adsorbents for industrial and environmental applications.