Performance Enhancement of Kaolin/Chitosan Composite-Based Membranes by Cross-Linking with Sodium Tripolyphosphate: Preparation and Characterization

Ultrafiltration membrane based on chitosan/adipic acid: Synthesis, characterization and performance on separation of methylene blue and reactive yellow-145 from aqueous phase

Here, we report for the first time using of the nontoxic chitosan/adipic acid cross-linked membrane CS/AA in the separation of methylene blue and reactive yellow-145 from aqueous phase. The reason we chose adipic acid as a cross-linking agent is because it gives the cross-linked membrane moderate flexibility due to the presence of four methylene groups in its structure. The structure of the cross-linked membrane CS/AA and their properties were confirmed through, FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and BET analysis. The thermal properties of membrane indicated an improvement in its flexibility and hydrophobicity, but this improvement was accompanied by a decrease in its thermal stability. pHpzc value and porosity of the CS/AA were 7.88, and 73.95 % respectively. The average pore radius distribution ranged from 2 to 27 nm. The prepared cross-linked membrane provides spontaneous and continuous purification of water with a high efficiency. This is due to the membrane CS/AA ability to separate methylene blue and reactive yellow-145 from the aqueous phase almost completely. The results revealed that the removal efficiency and permeation flux for MB were 100 % and 1 L/m2.h respectively at initial dye concentration of (4,8) mg/L, at 1 bar, and the removal efficiency and permeation flux for RY-145 were (94,96) % and (1.06, 2.09) L/m2.h respectively at 100 mg/L and at (1,1.5) bar. Such cross-linked nanopore polymer membranes provide a new approach for emerging novel purification systems, principally in the field of environmental field.

Development of a chitosan and whey protein-based, biodegradable, colorimetric/fluorescent dual-channel monitoring label for real-time sensing of shrimp freshness

To address the growing and urgent need for quick and accurate food spoilage detection systems as well as to reduce food resource wastage, recent research has focused on intelligent bio-labels using pH indicators. Accordingly, we developed a dual-channel intelligent label with colorimetric and fluorescent capabilities using black lycium anthocyanin (BLA) and 9,10-bis(2,2-dipyridylvinyl) anthracene (DSA4P) as colorimetric and fluorescent indicators within a composite film consisting of chitosan (Cs), whey protein (Wp), and sodium tripolyphosphate (STPP). The addition of STPP as a cross-linking agent significantly improved the hydrophobicity, mechanical properties, and thermal stability of the Cs/Wp composite films under low pH conditions. After the incorporation of BLA and DSA4P, the resulting dual-channel intelligent label (Cs/Wp/STPP/BLA/DSA4P) exhibited superior hydrophobicity, as indicated by a water contact angle of 78.03°. Additionally, it displayed enhanced mechanical properties, with a tensile strength (TS) of 3.04 MPa and an elongation at break (EAB) of 81.07 %, while maintaining a low transmittance of 28.48 % at 600 nm. After 25 days of burial in soil, the label was significantly degraded, which showcases its eco-friendly nature. Moreover, the label could visually detect color changes indicating volatile ammonia concentrations (25-25,000 ppm). The color of the label in daylight gradually shifted from brick-red to light-red, brownish-yellow, and finally light-green as the ammonia concentration increased. Correspondingly, its fluorescence transitioned from no fluorescence to green fluorescence with increasing ammonia concentration, gradually intensifying under 365-nm UV light. Furthermore, the label effectively monitored the freshness of shrimp stored at temperatures of 4 °C, 25 °C, and - 18 °C. Thus, the label developed in this study exhibits significant potential for enhancing food safety monitoring.

Green Fabrication of Sustainable Porous Chitosan/Kaolin Composite Membranes Using Polyethylene Glycol as a Porogen: Membrane Morphology and Properties

One of the major challenges in membrane manufacturing today is to reduce the environmental footprint by promoting biobased raw materials and limiting the use of toxic solvents. In this context, environmentally friendly chitosan/kaolin composite membranes, prepared using phase separation in water induced by a pH gradient, have been developed. Polyethylene glycol (PEG) with a molar mass ranging from 400 to 10,000 g·mol^-1 was used as a pore forming agent. The addition of PEG to the dope solution strongly modified the morphology and properties of the formed membranes. These results indicated that PEG migration induced the formation of a network of channels promoting the penetration of the non-solvent during the phase separation process, resulting in an increase in porosity and the formation of a finger-like structure surmounted by a denser structure of interconnected pores of 50-70 nm in diameter. The hydrophilicity of the membrane surface increased likely related to PEG trapping in the composite matrix. Both phenomena were more marked as the PEG polymer chain was longer, resulting in a threefold improvement in filtration properties.