Experimental and theoretical study of dyes adsorption process on chitosan-based cryogel

In this research, the adsorption of three synthetic dyes dissolved in an aqueous solution on chitosan cryogel beads (Q-C-EGDE) was compared. The effect of the pH of the solution on the adsorption capacity of each dyes was analyzed. Furthermore, the kinetics and adsorption isotherms were compared, at temperatures of 283.15 K, 303.15 K and 323.15 K, and the kinetic and adsorption equilibrium data were fitted to three mathematical models, respectively. The biosorbent was characterized by scanning electron microscopy (SEM), the nitrogen physisorption BET method and Fourier transform infrared spectroscopy (FTIR). The characterization results show that the cryogel is composed of low-surface, macroporous, porous grooved walls. The functional groups that took part in the adsorption were mainly amino groups (NH₃⁺). When comparing the adsorption capacities, it was found that the dyes adsorb in the following order Blue 1 > Red 2 > Yellow 5 reaching capacities from 1600 mg/L to 850 mg/L. The results of the adsorption and mathematical modelling suggest that the process is regulated mainly by physisorption and is largely limited by mass transfer mechanisms within the cryogel, where the electrostatic charges present affect adsorption. The latter was corroborated by the Monte Carlo simulation.

Development of standardized method for the quantification of azo dyes by UV-Vis in binary mixtures

The azo dyes, Yellow 5 (Y5), Red 2 (R2) and Blue 1 (B1), quantified in solutions and in mixtures of binary dyes, were studied by means of UV-Vis spectroscopy. In this work was used a CIE algorithm developed in Visual Basic for Applications (VBA). The CIE algorithm is based on the tristimulus chromaticity diagram, as an alternative to the shielding effect that arises in dye mixtures, and it can also be applied to complex quantification methods such as HPLC (High Performance Liquid Chromatography). The results obtained through of the algorithm, showed a higher accuracy from 97 to 99% in relation with similar UV-Vis quantification methods. In contrast, linear methods only managed to reach an accuracy from 78 to 98%. Additionally, the algorithm yielded significant similar values to the UHPLC reference method. The results showed that the method CIE algorithm was accessible and reliable to quantify binary mixtures of the dyes used which suggests the possibility to apply this method on other dyes, within the limits of quantification obtained in this study (0.076-24.56 mg/L) and the pH values from 2 to 10.

Combined antibacterial/tissue regeneration response in thermal burns promoted by functional chitosan/silver nanocomposites

We report the combined antibacterial/tissue regeneration responses to thermal burns promoted by functional chitosan/silver nanocomposites (CS/nAg) with ultralow silver content (0.018wt.%, 7-30nm). Our approach allows one to produce CS/nAg nanocomposites without silver nanoparticles (nAg) agglomeration, with bactericide potency higher than 1wt.% of nAg (ca. 10nm) content and, promoting the healing process in controlled thermal burns. CS/nAg films exhibit high antibacterial activity against S. aureus and P. aeruginosa after 1.5h of incubation, demonstrating the bacterial penetration into hydrated films and their interaction with nAg. Additionally, exceptional healing of induced thermal burns was obtained by increasing myofibroblasts, collagen remodeling, and blood vessel neoformation. These factors are associated with epiderma regeneration after 7days of treatment with no nAg release. Our results corroborate the controlled synthesis of nAg embedded in CS matrix with combined antibacterial/biocompatibility properties aiming to produce functional nanocomposites with potential use in wound dressing and health care applications.