Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g⁻¹ for MB and copper ions removal, respectively.

Fungal infections have been considered a primary cause of the postharvest losses of citrus fruits. Therefore, it is necessary to find low-cost and high antifungal activity materials for preventing the decay of citrus fruits after harvest. In this study, squid chitosan nanoparticles (SCNs) were prepared from squid pen chitosan and used as a biofungicide against three citrus fungal pathogens in both in vitro and in vivo evaluations. The prepared SCNs had a mean size of ca. 56 nm and a high zeta potential of +98.7 eV with a narrow size distribution. At a range of 50–250 ppm, the SCN concentration of 200 ppm exhibited the highest activity in totally inhibiting the growth of Lasiodiplodia pseudotheobromae, Alternaria alternate, and Penicillium digitatum in in vitro tests where these fungi were isolated from symptomatic fruits and identified. Furthermore, after 12 days of incubation at 30 ± 0.2 °C and high relative humidity in in vivo studies, the infection area of the sample treated at 250 ppm completely suppressed fruit disease symptoms. The results demonstrate that prepared SCNs efficiently control postharvest citrus fruit diseases. These findings recommend applying SCNs as a potential candidate for citrus fruit storage.

Increasing dairy waste presents significant challenges for sustainable disposal. In this study, expired milk was utilized as a casein source to produce biodegradable films, thereby valorizing dairy by-products. Recovered casein, chitosan as a bio-reinforcer, and glutaraldehyde (GA) were combined via solution casting to fabricate the films. Casein blended with chitosan to form continuous, self-supporting films with uniform thickness and stable morphology. The film properties depended on the mixing ratio. Films with a 3:5:2 weight ratio (casein/chitosan/GA) exhibited a smoother surface, higher tensile strength (10.18 ± 0.04 MPa), and lower swelling compared to those with the 4:5:1 formulation. These results indicate that chitosan reinforces the composite matrix structure. The films demonstrated significant degradation under high humidity, indicating good biodegradability. However, none of the films exhibited antimicrobial activity against Escherichia coli. These films may serve as potential eco-friendly packaging materials for low-moisture foods, thereby supporting sustainable food processing and packaging.