Preparation and characterization of chitosan extracted from shrimp shells waste and chitosan film: application for Eriochrome black T removal from aqueous solutions

In this paper, chitosan (CS) was successfully extracted from shrimp shells waste at two deacetylation temperatures (90 °C and 40 °C). The obtained chitosan at 90 °C showed better physicochemical properties compared to the one prepared at 40 °C with a degree of deacetylation DA = 88%, molecular weight M = 353 KDa, viscosity η = 0.469 dL/g and pKa = 6.49, and its structure was confirmed by Fourier transform infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. The extracted CS was utilized as a film for the adsorption of Eriochrome black T (EBT) dye from aqueous solutions under various experimental conditions. Experimental results showed that the synthesized film exhibited excellent adsorption ability for EBT with an adsorption capacity of 413 mg/g at pH 4.66 for an initial dye concentration of 200 mg/L at 20 °C. The kinetics of adsorption were found to be of pseudo-second order with a high coefficient of determination (R² = 0.9999). Furthermore, the thermodynamic analysis revealed that the adsorption of EBT dye was an endothermic and spontaneous process. Freundlich model fitted well to the experimental data, the numerical value of n = 1.064 indicates that adsorption of EBT onto CS film is favorable. All these results confirm that chitosan-based films prepared from shrimp shells waste could be considered as promising materials for dye removal and as alternatives to expensive adsorbents.