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.
The present paper exposes the lead adsorption from synthetic effluents using natural and available materials. Pine, beech and fir sawdust's were used and compared for their lead adsorption ability. To optimize the sorption phenomenon, some process parameters were studied namely temperature, pH, contact time, initial Pb(II) concentration, sawdust's dosage and granulometry, stirring speed and medium salinity. The materials were characterized by FTIR spectroscopy, X-ray diffraction and fluorescence. The results demonstrated that the pine sawdust gave the best level for lead adsorption (15.5 mg/g) in the following conditions and at 23 ± 2°C of temperature : pH 5.45 ± 0.05, 100 mg/L of initial Pb(II) concentration and 10 g (per liter of solution) of pine sawdust composed from granules with mean diameter lower than 500 lm. As well, the adsorption kinetics seem to satisfy to Langmuir isotherm model.
The paper discusses the enzymatic behaviour of a series of copolymers composed of alginate grafted with poly(ε-caprolactone) (PCL) of various lengths and degrees of substitution. The study is focused on viscosity measurements and pyrene probe fluorescence with or without two enzymes: alginate lyase, which breaks the alginate backbone; and esterase, which breaks PCL pendent groups. Alginate lyase is inactive at pH = 3.8 and degrades quickly all copolymers at pH = 6.3. The degradation is not complete and is slowed down by the presence of PCL. Esterase degrades only copolymers with long pendent PCL groups. It has no effect on copolymers when PCL has a length of 530 g mol −1 . These systems are good candidates for controlled release of drugs using an enzymatic method.
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