Optimization of the spontaneous adsorption of food colors from aqueous medium using functionalized Chitosan/Cinnamaldehyde hydrogel.

Hydrogels are considered as practical and proficient materials in adsorption and removal of soluble lethal molecules from aqueous system. They are also rapid-decomposable and economical materials besides their diverse preventive claims. In current study, Cinnamaldehyde (C), a natural defensive compound and Chitosan (Ch), natural occurring bio-macromolecule are considered to develop bio-inspired hydrogel (ChC). The structural and surface characteristics of ChC (13C solid state NMR, FT-IR, UV-Vis and SEM) are investigated to confirm the successful grafting. The origami of gelation in ChC performs an excellent adsorption activity towards food dyes, Carmoisine (CA) and Tartrazine (TA), which are contaminated by the accumulation during excess release from catering and chemical industries in aqueous system. The adsorption performance is thoroughly screened by varying the pH, ChC dosage, dye concentration, contact time and temperature in aqueous system. Thermodynamic and Kinetics study suggest the natural tendency of adsorption with a good reusability up to 3 cycles. The main mechanism for spontaneous adsorption is initiated by capturing of TA/CA in porous surface followed by the ionic interactions and formation of H-bondings. ChC based adsorption is an excellent and potential approach to control the toxicants for the water-pollution and water-preservation.

Fabrication of lightweight and reusable salicylaldehyde functionalized chitosan as adsorbent for dye removal and its mechanism.

Bio-resources have a very significant role in current research approach for the synthesis of benign functionalized biological macromolecules for their stable structural integrity and inherent nature-inspired potentialities. Here, chitosan is used as a core moiety for designing of a porous adsorbent after the attachment of salicylaldehyde to remove the toxic dyes. Salicylaldehyde linked chitosan, with excellent surface porosity, lightweight, non-glucose and low-cost feature, makes it as an efficient adsorbent. The dye loaded material is very easy to remove from the top of the water as it is suspended on water. The physico-chemical characterizations are done by FTIR, rheology, SEM and swelling study. The removal efficiency is 98% and 99% for Crystal Violet and Rose Bengal from water respectively. The thorough adsorption with mechanistic approach shows the Freundlich model as an appropriate one and follows closely pseudo-second-order kinetics model. Thermodynamic study reveals the endothermic nature of the process. Moreover, the reusability of Salicylaldehyde linked Chitosan shows its persistence with the same amount and concentration of dyes in water up to three consecutive cycles. So, the chitosan based macromolecules can be a sustainable candidate in the current scenario for the removal of dyes without the dislocation of the water container.

Characterization of a fluorescent hydrogel synthesized using chitosan, polyvinyl alcohol and 9-anthraldehyde for the selective detection and discrimination of trace Fe3+ and Fe2+ in water for live-cell imaging.

A three-dimensional fluorescent hydrogel based on chitosan, polyvinyl alcohol and 9-anthraldehyde (ChPA) has been successfully designed and synthesized for the selective detection and discrimination of Fe3+ and Fe2+ in aqueous environment. The unique characteristics of ChPA has been confirmed by the Fourier-transform infrared spectroscopy (FTIR), rheological measurement, scanning electron microscopy (SEM), thermogravimetry and differential thermogravimetry (TG-DTG), ultraviolet-visible spectroscopy (UV-vis), fluorescence studies, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD) and dynamic light scattering (DLS). The emission intensity at 516 nm of the hydrogel has been enhanced remarkably with the addition of Fe3+ due to the inhibition of the photoinduced electron transfer (PET) process. However, it gets strongly quenched in the case of Fe2+ owing to chelation enhanced quenching (CHEQ). The probe (ChPA) causes no significant change in the fluorescence and becomes highly specific and sensitive towards Fe3+ and Fe2+ compared to other interfering heavy and transition metal ions (HTM). The detection limits of the sensor for the Fe3+ and Fe2+ are 0.124 nM and 0.138 nM, respectively. The probe is also promising as a selective sensor for the Fe3+ and Fe2+ in the fluorescence imaging of living cells. Thus, such a probe opens up new opportunities to improve the chitosan based fluorescent chemosensor having biocompatibility, biodegradability, sufficient thermal stability and stability in a wide pH range.