Samir Benykhlef’s research while affiliated with Djillali Liabes University Sidi Bel Abbès and other places

Biopolymers have become more and more attractive nowadays for both experimental and theoretical studies because of their importance in our daily life. In this contribution, the electronic properties and reactivity behavior of some biomonomers; chitin and chitosan have been thoroughly investigated theoretically using density functional theory (DFT) B3LYP/6-31G(d) level of theory. The regioselectivity of these molecules has been rationalized by using both Fukui and Parr indices in order to explain and show the most probable sites to be attacked towards nucleophiles and electrophiles. For the three studied monomers, the oxygen and nitrogen atoms were found to be the most reactive sites. Parr functions and Fukui functions found to be complementary while explaining the possible regioselectivity.

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.

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. Copyright © 2012 Society of Chemical Industry