Abstract
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.
Highlights
Dyes are considered as ones of the most worldwide employed chemicals
This paper aims to (1) extract chitin from local source: shrimp shell, and to produce CS by two deacetylation methods depending on the used temperature, (2) to assess the composition and physicochemical properties of the produced CS through adapted measures such as conductometry and pH metric titration, viscosimetry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (DRX) and differential scanning calorimetry (DSC), (3) to design CS film and assess its potential in removing Eriochrome black T (EBT) dye from aqueous solutions under various experimental conditions in batch mode and (4) to explore the main involved mechanisms in this adsorption process
Extracted chitosan was characterized through the assessment of its degree of deacetylation, its molecular weight, its pKa and solubility (Table 2 and Fig. 3) as well as specific analyses such as FTIR, DSC and X‐ray diffraction (XRD) analysis (Fig. 4)
Summary
Dyes are considered as ones of the most worldwide employed chemicals. Under certain conditions, they could present a real menace to the environment in general and to water resources in particular through the establishment of the eutrophication process. Adsorption onto low-cost materials has pointed out as one Shellfish shells are biowastes that could be responsible for pollution in coastal areas These biowastes could be valorized and used as resources for the production of chitin and chitosan, through three-stage extraction, namely demineralization, deproteinization and deacetylation (Mohammed et al 2013). As a crystalline polysaccharide with high molecular weight, is the second most abundant organic compound, after cellulose on earth It is considered as a natural fiber that is found in shells of marine animals, such as shrimps and lobsters, insect shells and in the wall of several fungi and yeasts (Rinaudo 2006; Kumari and Rath 2014). Chitin is often linked to the other major constituents of the carapace, forming covalent bonds with 30–40% proteins and
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