The ongoing development of nanotechnology has raised concerns regarding the potential risk of nanoparticles (NPs) to the environment, particularly aquatic ecosystems. A relevant aspect that drives NP toxicity is represented by the abiotic and biotic processes occurring in natural matrices that modify NP properties, ultimately affecting their interactions with biological targets. Therefore, the objective of this study was to perform an ecotoxicological evaluation of CeO₂NPs with different surface modifications representative of NP bio-interactions with molecules naturally occurring in the water environment, to identify the role of biomolecule coatings on nanoceria toxicity to aquatic organisms. Ad hoc synthesis of CeO₂NPs with different coating agents, such as Alginate and Chitosan, was performed. The ecotoxicity of the coated CeO₂NPs was assessed on the marine bacteria Aliivibrio fischeri, through the Microtox® assay, and with the freshwater crustacean Daphnia magna. Daphnids at the age of 8 days were exposed for 48 h, and several toxicity endpoints were evaluated, from the molecular level to the entire organism. Specifically, we applied a suite of biomarkers of oxidative stress and neurotoxicity and assessed the effects on behaviour through the evaluation of swimming performance. The different coatings affected the hydrodynamic behaviour and colloidal stability of the CeO₂NPs in exposure media. In tap water, NPs coated with Chitosan derivative were more stable, while the coating with Alginate enhanced the aggregation and sedimentation rate. The coatings also significantly influenced the toxic effects of CeO₂NPs. Specifically, in D. magna the CeO₂NPs coated with Alginate triggered oxidative stress, while behavioural assays showed that CeO₂NPs coated with Chitosan induced hyperactivity. Our findings emphasize the role of environmental modification in determining the NP effects on aquatic organisms.

Among the seafood used globally, shellfish consumption is in great demand. The utilization of these shellfish such as prawn/shrimp has opened a new market for the utilization of the shellfish wastes. Considering the trends on the production of wealth from wastes, shrimp shell wastes seem an important resource for the generation of high value products when processed on the principles of a biorefinery. In recent years, various chemical strategies have been tried to valorize the shrimp shell wastes, which required harsh chemicals such as HCl and NaOH for demineralization (DM) and deproteination (DP) of the shrimp wastes. Disposal of chemicals by the chitin and chitosan industries into the aquatic bodies pose harm to the aquatic flora and fauna. Thus, there has been intensive efforts to develop safe and sustainable technologies for the management of shrimp shell wastes. This review provides an insight about environmentally-friendly methods along with biological methods to valorize the shrimp waste compared to the strategies employing concentrated chemicals. The main objective of this review article is to explain the utilization shrimp shell wastes in a productive manner such that it would be offer environment and economic sustainability. The application of valorized by-products developed from the shrimp shell wastes and physical methods to improve the pretreatment process of shellfish wastes for valorization are also highlighted in this paper.

Macroscopic utilization of nanomaterial provides a new idea for the research and development of novel adsorbent, which can enhance efficiency in the adsorption and elution process. In this paper, nano-polypyrrole (PPy) was dispersed into two inexpensive and renewable biomass materials, gelatin (Gel) and chitosan (CS), to fabricate a novel photo/electric-sensitive hydrogel, Gel/CS/PPy. The micro-network of Gel/CS/PPy shows a high adsorption rate of 94.2% for acid fuchsine (AF). Furthermore, with the addition of polypyrrole, Gel/CS/PPy has the characteristic of photo/electric response, which can improve the elution efficiency of AF from the adsorbent. The results showed that the elution efficiency could be increased by 4 times with photo-assistance, and about 2 times with electro-assistance. Predictably, using the methods described in this article, high-quality adsorbents can be designed for more organic pollutants. Graphical abstract

The rapid growth of human population and global industrialization has resulted in the generation of larger amounts of wastewater containing various pollutants, among which toxic heavy metals. Adsorption is efficient for this purpose, but its application is limited by the high cost of adsorbent materials. Chitosan (CS) and phosphorylated microcellulose (PMC) have a high potential as low-cost and effective adsorbents for water remediation. Nonwoven CS/PMC nanocomposite fiber mats were produced by electrospinning with up to 50% by weight of PMC. The thermal, chemical, and morphological properties of the mats were studied. Batch adsorption trials were carried out using Cd²⁺ ions. Kinetics and isotherm models were tested against experimental results and the thermodynamic properties were calculated. Results showed that the pseudo-second order model best fitted experimental data and suggested chemisorption as the mechanism for Cd²⁺ removal. Langmuir isotherm best described equilibrium data reaching the maximum adsorption capacity of 283 mg/g at 60 °C. This high value was attributed mainly to the large amount of phosphate groups, which require less energy to capture the metal cations. Thermodynamic evaluation suggested that the adsorption is a spontaneous endothermic reaction. These results confirm that CS/PMC mats are easy to produce, and provide high adsorption capacity in simulated wastewater containing Cd²⁺. These laboratory-based adsorption experiments will assist in selecting/ranking of potential candidate matrices, and scale-up development of technologies for complex wastewater applications.

In this work was studied the single-component and multi-component abatement of metals in water using a hydrogel based on chitosan. The maximum single-component abatement capacities of cadmium (Cd) and lead (Pb) were 234.84 and 482.83 mg of metal per g of dried hydrogel at pH 6 and 40 °C, according to the Sips isotherm. The value for iron (Fe) was 386.59 mg g⁻¹ at pH 4 and 40 °C, according to the Langmuir isotherm. The best kinetic fits were determined using the pseudo-second-order model, whereas the thermodynamic parameters inferred spontaneous, favorable abatement phenomena. Lower abatement capacities were determined for multi-component studies due to the hydrated ionic radius and electronegativity of the metals. The abatement processes were confirmed by scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectra, indicating reversible chemical interactions between the hydrogel binding groups and Cd, Pb, and Fe. Such hydrogel proved to be a potential functional biopolymer for the treatment of water and wastewater contaminated by heavy metals. Graphical abstract

In the present study, millimeter CS-TPP@MnFe₂O₄ gel beads (particle size 3–4 mm) were prepared by the sol-gel process using the embedding method, and its performance of Cu(II) and influence factors were studied. The effect of various parameters such as the gel bead addition amount, adsorption time, temperature, pH, and competitive substances (anion and cationic) was studied. The surface and properties of gel beads were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The experimental results showed that the optimal pH for adsorption of Cu(II) by CS-TPP@MnFe₂O₄ was 5–7, the adsorption of Cu(II) reached equilibrium at 24 h, and the maximum adsorption capacity could reach 125.70 mg g⁻¹ at 298.15 K by Langmuir isotherm model. K⁺, Na⁺, Cl⁻, NO₃⁻, and SO₄²⁻ had little effect on the adsorption, and Ca²⁺, Mg²⁺, and H₂PO₄⁻ inhibited the adsorption, and SiO₃²⁻ and humic acid (HA) promoted the adsorption of Cu(II) by the adsorbent. After five adsorption-desorption experiments, the desorption rate of gel beads reached 89.3%, and the adsorption capacity of Cu(II) was still high. In conclusion, the CS-TPP@MnFe₂O₄ gel beads are a type of stable and effective materials to remove Cu(II) from water.

A novel polymer/activated carbon composite was prepared in this study by one-step chemical activation of Sargassum horneri, followed by surface modification with chitosan, a widely abundant biopolymer. The prepared composite was used as adsorbent to remove one of the most toxic metal ions, Cr(VI), from aqueous solution. Surface characterization tests revealed the material to be predominantly mesoporous with the specific surface area of 293.4 m²·g⁻¹ and the average pore diameter of 6.27 nm. Enhanced uptake capacity of Cr(VI) by the prepared composite was obtained due to the presence of more metal-binding functional (amino and hydroxyl) groups on its surface. Extremely fast adsorption rate of Cr(VI) was also achieved due to the porous structure of the prepared composite. This study has clearly shown that Sargassum horneri can be a potential alternative precursor for carbon-based adsorbents and the proper designed polymer/AC composites can be tailor-made adsorbents for heavy metal removal.

The study reports the preservative efficacy of Bunium persicum (Boiss) essential oil (BPEO) against fungal and aflatoxin B₁ (AFB₁) contamination of stored masticatories and boosting of its efficacy through encapsulation into chitosan. BPEO was chemically characterized through GC-MS analysis, which revealed γ-terpinene as the major compound. The BPEO at 1.2 μL/mL concentration completely inhibited the growth of toxigenic strain of Aspergillus flavus (AF-LHP-PE-4) along with 15 common food borne moulds and AFB₁ secretion. The BPEO exerts its antifungal action on plasma membrane, as confirmed through ergosterol inhibition, alteration of membrane fluidity and enhancement of cellular ions and 260 and 280 nm absorbing material leakage. The antiaflatoxigenic mechanism of action of BPEO was confirmed through methylglyoxal reduction. Further, BPEO showed strong antioxidant activity (IC₅₀ = 7.36 μL/mL) as measured by DPPH· assay. During in situ investigation, BPEO completely inhibited AFB₁ production in model food (Phyllanthus emblica) system without altering the sensory properties and also exhibited high LD₅₀ value (14,584.54 μL/kg) on mice. In addition, BPEO was encapsulated into chitosan, characterized and tested for their potential to inhibit growth and AFB₁ production. The mean particle size, PDI and zeta potential of formed BPEO-loaded chitosan nanoparticle (CS-Np-BPEO) were performed to confirm successful encapsulation. The result revealed nanoencapsulated BPEO showed enhanced activity and completely inhibited the growth and AFB₁ production by AF-LHP-PE-4 at 0.8 μL/mL. Based on findings, it could be concluded that the BPEO and its encapsulated formulation can be recommended as a potential plant-based preservative against fungal and aflatoxin contamination of stored masticatories.

The objectives of this research were to evaluate the maintenance of water quality when using chitosan foam filters in water recirculation systems during the cultivation of Nile tilapia and to verify the zootechnical performance and the hepatic and branchial histopathological changes, in comparison with the use of biological filter with bioballs. Two Nile tilapia cultivation trials were carried out (trial 1: 35-L tanks; trial 2: 130-L tanks), using six individual water recirculation systems, consisting of a culture tank, decantation tank, submerged pump for recirculation, aeration and external filter. The physical and chemical parameters related to water quality were evaluated every 48 h. At the end of each trial, the fish biometrics was performed to obtain final weight, feed conversion, and survival. In trial 2, the histopathological analysis of the hepatopancreas and gills was performed and the organ index was calculated. The daily averages of the physical and chemical parameters of the water quality, the zootechnical performance of the fish, and the organ indexes of the treatments of trials 1 and 2 were compared by the t test (p ≤ 5%). There were no significant differences in final weight, feed conversion, survival, or organ indexes between treatments (p > 0.05) in relation to the two trials. It was observed that the use of the filter with chitosan foam in the water recirculation systems resulted in lower or equal concentrations of total ammonia, nitrate, and dissolved orthophosphate, and maintained the same or higher alkalinity than in tanks with bioball biological filter. It is recommended to change the chitosan foam every 30 days of cultivation. The use of water recirculation systems with treatment using filters filled with chitosan foam during the cultivation of Nile tilapia is equally effective or better than the use of a biological filter with bioballs.

Bentonite/chitosan composite was synthesized and characterized by different techniques including XRD, FT-IR, SEM and TEM to detect its physicochemical properties. The composite was introduced in realistic purification application to reduce the dissolved iron content in raw groundwater sample by fixed-bed column system. The plotted breakthrough curves and the related mathematical parameters revealed that the column achieves iron removal percentage of about 69% from 6.6 L of water after adjusting the factors affecting the system at 3 cm bed thickness, 5 mL/min flow rate, 5 mg/L concentration and pH 6. Applying the column system to remove iron from groundwater under the same conditions can achieve iron removal percentage of about 69% from a total volume of 8.2 L of water. The interaction of the metal on the column was attained after 18 hours and the saturation time was attained after 27.5 hours which revealed the high performance of the composite in the designed column system for the purification of groundwater.