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 (pH_pzc). 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.

In this study, we characterised the pectin extracted from peels of Algerian Citrus sinensis and evaluated its antibacterial action, antioxidant activity and anticoagulant effect. Pectin was extracted under acidic conditions using hydrochloric acid for PCT-1 and citric acid for PCT-2 and determining their physicochemical properties using Fourier-Transform Infrared spectroscopy (FTIR), X-ray powder diffraction (PXRD), differential scanning calorimetry (DSC), yield, the degree of methylation, water content and ash content. In addition, the FTIR results showed desired banding characteristics, and their thermal properties evaluated using DSC showed that the thermal degradation was around 240 °C. XRD results show that PCT-1 and PCT-2 are amorphous and have similar characteristics to commercial pectin. On the other hand, the antibacterial action showed that PCT-1 and PCT-2 have no effect on Pseudomonas aeruginosa and E. coli bacteria, unlike Staphylococcus epidermidis, where it showed considerable antibacterial action. The antioxidant activity of PCT-1 and PCT-2 was observed using the 2,2 diphenyl-1-picrylhydrazyl (DPPH) method; the absorbance values recorded for PCT-1 and PCT-2 confirmed their antioxidant potential explained by the presence of several free hydroxyl groups in the PCT-1 and PCT-2 structure. On the other hand, our findings indicate that PCT-1 and PCT-2 do not have a marked anticoagulant effect but have acceptable potential and can be used as anticoagulants for the treatment of thrombotic diseases with fewer side effects compared to the widely used heparin. These results suggest that pectin from the peels of Algerian Citrus sinensis has potential properties as a biomaterial for several biomedical applications.

This work investigates the conversion of orange peel waste into effective biomaterials. Two pectins were first extracted from these peels under acidic conditions using citric acid (PCT-1) or hydrochloric acid (PCT-2), then thoroughly characterized and finally tested for biomedical applications. The characterization of pectin was carried out using various analytical techniques including Fourier-transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry. The biomedical application of the extracted pectins demonstrates that neither PCT-1 nor PCT-2 have an antibacterial effect on Pseudomonas aeruginosa or E. coli . Nevertheless, a significant antibacterial effect was observed on the Staphylococcus epidermidis strain. This highlights their potential use for the treatment of some infectious diseases and particularly against Gram-positive strains. Besides, the extracted pectins exhibit a high potential use as antioxidants. Although PCT-2 does not display marked anticoagulant activities, PCT-1 shows an interesting potential to be valorized as an anticoagulant. All these results show that pectins extracted from orange peel waste can be valorized as effective biomaterials with numerous biomedical applications.

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.