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 (R 2 = 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.

Four secondary amides have been prepared by the Schotten-Baumann reaction between model anilines (Pa1-4: p-XC6H4NH2: X1: H; X2:CH3; X3:COCH3; X4: CN) and methacryloyl chloride using aqueous THF/NaOH mixture at 0°C. MS1, MS2 and MS4 liquid monomers are obtained whereas MS3 is a solid monomer. Mass radical copolymerization of the different monomers (MS1-4) with N-vinyl-2-pyrrolidone yields to the corresponding four copolymers. All the monomers have been characterized by IR, 1H and 13C NMR. The (CP1-4) have been characterized by IR spectra, microanalysis, Tg ° and Mv. The kinetics of aniline delivery to give anilinium cations (PaH+)1-4 from solid MS3 and CP1-4 dispersed in water (pH= 1.2, 37°C) showed that aniline delivery from the different supports is controlled by a diffusion process and not the rate of amide hydrolysis. The amount (%) of free anilinium cations is inversely proportional to the molecular weight of polymeric supports. Accordingly, the monomer MS3 gave the largest amount of free anilinium cations (PaH+) 1-4

The present study aimed to investigate the adsorption capacity of two anionic dyes, namely, Congored (CR) and Coralene Dark Red2B (DR), onto prepared alginate (Alg) and chitosan(Cs) biopolymer films. The two biopolymers were combined at different mass ratios using a “solvent-cast” process to incorporate their unique properties and evaluate their effectiveness in removing the dyes. All samples were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and determination of point of zero charge (pHpzc). The swelling ratios were determined by gravimetric measurements. The effects of pH, adsorption time, thickness, temperature and initial concentration of CR and DR dyes on the adsorption results were studied systematically. The dye adsorption kinetics showed that the Alg/Cs films at % proportions of 75/25, 50/50, 25/75 and 0/100 reached equilibrium from 30 min to 180 min with high removal efficiencies that varied between 222.30 mg/g and 842.36 mg/g. The adsorption mechanism of CR and DR onto the synthesized biofilms was confirmed through Langmuir isotherm and the kinetics fitted well by the pseudo-second-order model, suggesting a monolayer and chemisorption process. The thermodynamic results demonstrated the spontaneity and the feasibility of the process as well as the exothermic nature. Hence, the findings revealed that the Alg/Cs biofilms could be employed as potential natural adsorbents for the removal of anionic dye pollutants from aqueous environments.

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