Marine polysaccharide-based hydrogels for critical materials selective removal and recovery: A review

Injectable and self-healable supramolecular hydrogels assembled by quaternised chitosan/alginate polyelectrolyte complexation for sustained drug delivery and cell encapsulation

Hydrogels formed through phase separation during the complexation of oppositely charged polymers have unique properties, including fast self-assembly, hierarchical microstructures, and tunable properties. These features make them highly attractive materials for various biomedical applications, such as drug delivery, protective coatings, and surface adhesives. Notably, injectable polyelectrolyte complex (PEC) supramolecular hydrogels stand out for their minimally invasive administration and reduced trauma and side effects, providing attractive alternatives to covalent hydrogels, which are constrained by the irreversibility of their crosslinks, limiting their versatility and broader applicability. Sustainable marine-origin polysaccharides have been used for developing hydrogels due to their proven biocompatibility, non-cytotoxicity and wide bioavailability from renewable resources. In particular, chitosan (CHT) and alginate (ALG) have been widely employed to develop hydrogels, taking advantage of their opposite charge nature. However, the limited solubility of CHT under physiological conditions limits the range of bioapplications. Herein, we report the development of size- and shape-tunable PEC supramolecular hydrogels encompassing water-soluble quaternised CHT and ALG biopolymers, under physiological conditions, by polyelectrolyte complexation. The rheological and mechanical properties of the PECs are studied, demonstrating their injectability, self-healing behaviour, and cytocompatibility towards human adipose-derived stem cells. A sustained and controlled release of encapsulated fluorescein isothiocyanate-labelled bovine serum albumin is observed over fourteen days. This work paves the way for the design and development of advanced CHT-based injectable biomaterial platforms for a wide array of biomedical and biotechnological applications.

Advancements in the Extraction, Characterization, and Bioactive Potential of Laminaran: A Review

Laminaran, a bioactive β-glucan derived from brown algae, has garnered significant attention due to its diverse pharmacological properties, including antioxidant, immunomodulatory, and mucosal protective effects. Despite promising research highlighting its potential applications in functional foods, nutraceuticals, and pharmaceuticals, the commercial utilization of laminaran remains limited, primarily due to challenges in extraction efficiency, structural complexity, and a lack of standardized methodologies. This review critically examines recent advancements in the extraction, purification, structural characterization, and biological evaluation of laminaran. Both conventional and emerging extraction methods-including ultrasound-assisted extraction, microwave-assisted extraction, and enzymatic techniques-are evaluated for their efficiency, scalability, and sustainability. Analytical tools, such as high-performance liquid chromatography, nuclear magnetic resonance, and mass spectrometry, are discussed for their roles in elucidating key structural features, such as molecular weight, degree of polymerization, and glycosidic linkage patterns, which are closely tied to laminaran's biological activity. Innovative extraction technologies have improved yield and purity, while structural insights have deepened the understanding of structure-function relationships. Interdisciplinary collaboration will be critical to advance laminaran from a marine-derived polysaccharide to a commercially viable bioactive compound for health, nutrition, and biomaterial applications.

Exploring Marine Biomineralization on the Al-Mg Alloy as a Natural Process for In Situ LDH Growth to Improve Corrosion Resistance

This study provides a detailed characterization of the AA5083 aluminum alloy, surface, and interface over 6 months of immersion in seawater, employing techniques such as SEM/EDX, GIXRD, μ-Raman and XPS. The purpose was to evaluate the evolution of the biomineralization process that occurs on the Al-Mg alloy. By investigating the specific conditions that favor the in situ growth of layered double hydroxide (LDH) during seawater immersion as a result of biomineralization, this research provides insights into marine biomineralization, highlighting its potential as an innovative and sustainable strategy for corrosion protection.

Enhancing Adsorption Performance of Ce(III) by Amine-Thiourea and Aniline-Modified Magnetic Chitosan Nanocomposites

To enhance the adsorption performance of chitosan for rare earth ions, two novel magnetic chitosan-based adsorbents were prepared by using chitosan-coated magnetic silica nanoparticles modified with amine-thiourea and aniline. The structure of copolymers was analyzed using characterization methods such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis, confirming the successful synthesis of modified magnetic chitosan nanocomposites. The investigation explored the influence of pH, contact time, dosage, initial concentration, and temperature on the adsorption performance. Comparative studies revealed a significantly enhanced adsorption performance after modification. The chitosan-coated magnetic silica nanoparticles modified with aniline (PAN-CS/Fe3O4@SiO2) reached adsorption saturation in about 120 min with a capacity of 136 mg/g, while the chitosan-coated magnetic silica nanoparticles modified with amine-thiourea (TSC-CS/Fe3O4@SiO2) exhibited a higher adsorption capacity of 156 mg/g for Ce(III). Both materials demonstrated strong agreement with the Langmuir isotherm model and pseudo-second-order kinetics. Thermodynamic analysis indicated that Ce(III) adsorption is both spontaneous and endothermic. Examination of the adsorption mechanisms suggested that the effective adsorption of Ce(III) is due to the strong synergistic effects of chelation and electrostatic interactions involving amino, carboxyl, and hydroxyl groups. This study demonstrates that chitosan modified with amine-thiourea and aniline is an effective approach to significantly enhance the rare earth ion adsorption by chitosan.

Tailored ultra-tough, antimicrobial and recyclable hydrogels based on chitosan and ionic liquid modified montmorillonite with different chain lengths for efficient adsorption of organic dyes in wastewater

Water pollution had exacerbated the global water crisis. Dye effluents posed a serious threat to the environment and human health, so there was an urgent need to develop sustainable methods to mitigate water pollution. In this work, sodium-based montmorillonite (MMT) was stripped using ionic liquids (ILs) with different chain lengths, and a pAAM/pAA/LMA/MMT@ILs-CS hydrogel adsorbent (MICHA) was prepared. The gel-based adsorbent was used to adsorb typical cationic (methylene blue: MB, rhodamine B: RhB) and anionic (methyl orange: MO, indigo carmine: IC) dyes from wastewater. The maximum adsorption capacities of MI16CHA for MB, MO, IC and RhB were 349.6817, 325.415, 316.0142 and 339.8154 mg/g, respectively. The adsorption kinetics and equilibrium data of MI16CHA for dyes were in accordance with the pseudo-first order and Langmuir isotherm models. The adsorption mechanism of MI16CHA on dyes were based on hydrogen bonding, electrostatic and π-π interaction. Thermodynamic studies showed that the adsorption of dyes on MI16CHA was spontaneous and heat-absorbing. The selective experiments demonstrated that MI16CHA has a promising application in real industrial conditions. Cyclic adsorption tests demonstrated the excellent recyclability of MI16CHA. In addition, MI16CHA had excellent antimicrobial and mechanical properties, which endowed the gel adsorbent with anti-pollution and durability.

Synergistic adsorption and photocatalysis reduction of uranium by UiO-66 (Ce)-CdS/PEI-modified chitosan composite sponge

Uranium is a critical element of the nuclear industry, and while extracting it from seawater is considered the most promising way to meet the growing demand for uranium, there are still some problems that still need to be solved. This work designed a UiO-66(Ce)-CdS/PEI-modified chitosan composite sponge (USPS) with an adsorption-photocatalytic synergistic effect to extract uranium efficiently. On the one hand, the drawback that the powder material is difficult to be recycled is solved. On the other hand, the uranium extraction capacity of the substrate sponge is improved. Compared with the unmodified PCS sponge, the uranium extraction capacity of the USPS-4 composite sponge is 1.63 fold higher than that of the PCS sponge. In addition, the USPS-4 composite sponge exhibits excellent selectivity and regenerability. The mechanism of uranium extraction can be summarized as the coordination chelation of uranium with active functional groups in the adsorption process and the reduction of hexavalent uranium by photogenerated electrons in the photocatalytic process. This study provides a new strategy for designing and preparing a novel material with high uranium extraction performance, easy separation, and recovery.

Separable alginate gel spheres encapsulated with La-Fe modified biochar for efficient adsorption of Sb(III) with high capacity

Sb and its compounds have been widely used in various industrial applications. Therefore, the preparation of Sb adsorbents with easy recovery and excellent adsorption levels is an urgent problem that must be resolved. By calcining and treating La/Fe metal-organic frameworks (MOF) biochar as a precursor, a loaded La-Fe-modified water hyacinth biochar was synthesised and used as a filler to synthesise iron alginate composite gel spheres, MBC/algFe. Through a series of static adsorption experiments, the effects of different filler addition ratios, solution pH, reaction time, coexisting ions, and other factors on the adsorption of Sb(III) were investigated. According to the Langmuir model, the maximum adsorption capacity of MBC/algFe at 25 ℃ was 277.8 mg·g-1. The adsorption mechanism mainly involved hydrogen bonding and metal-organic complexation interactions.

Polymeric Materials for Rare Earth Elements Recovery

Rare earth elements (REEs) play indispensable roles in various advanced technologies, from electronics to renewable energy. However, the heavy global REEs supply and the environmental impact of traditional mining practices have spurred the search for sustainable REEs recovery methods. Polymeric materials have emerged as promising candidates due to their selective adsorption capabilities, versatility, scalability, and regenerability. This paper provides an extensive overview of polymeric materials for REEs recovery, including polymeric resins, polymer membranes, cross-linked polymer networks, and nanocomposite polymers. Each category is examined for its advantages, challenges, and notable developments. Furthermore, we highlight the potential of polymeric materials to contribute to eco-friendly and efficient REEs recovery, while acknowledging the need to address challenges such as selectivity, stability, and scalability. The research in this field actively seeks innovative solutions to reduce reliance on hazardous chemicals and minimize waste generation. As the demand for REEs continues to rise, the development of sustainable REEs recovery technologies remains a critical area of investigation, with the collaboration between researchers and industry experts driving progress in this evolving field.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.