Feather-weight cryostructured thiourea-chitosan aerogels for highly efficient removal of heavy metal ions and bacterial pathogens

Structural, mechanical, antioxidant and antibacterial properties of double cross-linked chitosan cryogels as hosts for thymol

The practical applications of essential oils (EOs) are limited by their hydrophobicity, volatility and instability. To overcome these drawbacks, the incorporation of EOs into porous materials is recommended. Chitosan (CS)-based composite cryogels as hosts for thymol as a volatile model terpenoid were developed using a double cross-linking of CS with glutaraldehyde (GA) and monochlorotriazinyl-β-cyclodextrin (MCT-β-CD), either in one-pot synthesis or through sequential cross-linking, first with GA and then with MCT-β-CD, resulting in CSCAV composites. Cross-linking with GA occurred under cryogelation conditions, while cross-linking with MCT-β-CD took place by heating at 60-80 °C. The composite cryogels were characterized by FTIR, 13C NMR, SEM, EDX, swelling kinetics, and uniaxial compressive tests. The mechanical, antioxidant, and antibacterial properties of composites were optimized by adjusting the concentrations of CS and GA, the initial CS to MCT-β-CD ratio, and the temperature regime. The novel CS-based biocomposites demonstrated sustained compression over 74 %, characteristic of porous materials obtained through cryogelation process. The antioxidant activity of the CSCAV composites revealed almost all composites exhibited over 85 % 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. The thymol-loaded composites displayed strong antibacterial effectiveness (up to 100 %) towards both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria, with greater inhibition activity observed against S. aureus.

Comprehensive insights into the application of graphene-based aerogels for metals removal from aqueous media: Surface chemistry, mechanisms, and key features

Efficient removal of heavy metals and other toxic metal pollutants from wastewater is essential to protect human health and the surrounding vulnerable ecosystems. Therefore, significant efforts have been invested in developing practical and sustainable tools to address this issue, including high-performance adsorbents. In this respect, within the last few years, graphene-based aerogels/xerogels/cryogels (GBAs) have emerged and drawn significant attention as excellent materials for removing and recovering harmful and valuable metals from different aqueous media. Such an upward trend is mainly due to the features of the aerogel materials combined with the properties of the graphene derivatives within the aerogel's network, including the GBAs' unique three-dimensional (3D) porous structure, high porosity, low density, large specific surface area, exceptional electron mobility, adjustable and rich surface chemistry, remarkable mechanical features, and tremendous stability. This review offers a comprehensive analysis of the fundamental and practical aspects and phenomena related to the application of GBAs for metals removal. Herein, we cover all types of (bottom-up) synthesized GBAs, including true microporous graphene-based aerogels as well as other 3D graphene-based open-cell interconnected mesoporous and macroporous aerogels, foams, and sponges. Indeed, we provide insights into the fundamental understanding of the GBAs' suitability for such an important application by revealing the mechanisms involved in metals removal and the factors inducing and controlling the highly selective behavior of these distinctive adsorbents. Besides conventional adsorptive pathways, we critically analyzed the ability of GBAs to electrochemically capture metal pollutants (i.e., electrosorption) as well as their efficiency in metals detoxification through reductive mechanisms (i.e., adsorption-reduction-readsorption). We also covered the reusability aspect of graphene aerogels (GAs)-based adsorbents, which is strongly linked to the GBAs' outstanding stability and efficient desorption of captured metals. Furthermore, in view of their numerous practical and environmental benefits, the development and application of magnetically recoverable GAs for metals removal is also highlighted. Moreover, we shed light on the potential practical and scalable implementation of GBAs by evaluating their performance in continuous metals removal processes while highlighting the GBAs' versatility demonstrated by their ability to remove multiple contaminants along with metal pollutants from wastewater media. Finally, this review provides readers with an accessible overview and critical discussion of major recent achievements regarding the development and applications of GAs-based adsorbents for metal ions removal. Along with our recommendations and suggestions for potential future work and new research directions and opportunities, this review aims to serve as a valuable resource for researchers in the field of wastewater treatment and inspire further progress towards developing next-generation high-performance GBAs and expanding their application.

A modified hyaluronic acid hydrogel with strong bacterial capture and killing capabilities for drug-resistant bacteria-infected diabetic wound healing

Management of diabetic wounds becomes increasingly challenging as bacterial infections intensify the inflammation. Employing polysaccharide hydrogels with inherent antibacterial qualities can significantly reduce the need for antibiotics to manage infections in diabetic wounds. The typical approach to achieving antibacterial outcomes with hydrogels relies on the penetration of bacteria into their porous architecture. Such penetration not only takes time but can also prolong inflammation, thus impeding the healing of wounds. Hence, the quick capture and eradication of bacteria are essential for optimizing the hydrogel's antibacterial performance. Herein, we introduce a multifunctional polysaccharide hydrogel dressing-designated as HAQ-created for managing bacterial infections in diabetic wounds. This dressing is based on hyaluronic acid, which is modified with methacrylic anhydride, and special functional groups are added to the modified hyaluronic acid matrix: phenylboronic acid for capturing bacteria and quaternary ammonium chitosan for bacterial destruction. As expected, the HAQ system exhibits robust antibacterial effectiveness against both methicillin-resistant Staphylococcus aureus and multidrug-resistant Pseudomonas aeruginosa in vitro and in vivo. Consequently, HAQ stands as a promising hydrogel dressing with intrinsic antibacterial capabilities and offers significant potential for managing diabetic wounds infected by drug-resistant bacteria.

Environmentally Benign Freeze-dried Biopolymer-Based Cryogels for Textile Wastewater Treatments: A review

Motivated by sustainability and environmental protection, great efforts have been paid towards water purification and attaining complete decolorization and detoxification of polluted water effluent. Textile effluent, the main participant in water pollution, is a complicated mixture of toxic pollutants which seriously impact human health and the entire ecosystem. Developing effective materials for potential removal of the water contaminants is urgent. Recently, cryogels have been applied in wastewater sectors due to their unique physiochemical attributes(e.g. high surface area, lightweight, porosity, swelling-deswelling, and high permeability). These features robustly affected the cryogel's performance, as adsorbent material, particularly in wastewater sectors. This review serves as a detailed reference to the cryogels derived from biopolymers and applied as adsorbents for the purification of textile drainage. We displayed an overview of: the existing contaminants in textile effluents (dyes and heavy metals), their sources, and toxicity; advantages and disadvantages of the most common treatment techniques (biodegradation, advanced chemical oxidation, membrane filtration, coagulation/flocculation, adsorption). A simple background about cryogels (definition, cryogelation technique, significant features as adsorbents, and the adsorption mechanisms) is also discussed. Finally, the bio-based cryogels dependent on biopolymers such as chitosan, xanthan, cellulose, PVA, and PVP, are fully discussed with evaluating their maximum adsorption capacity.

Highly Compressible, Superabsorbent, and Biocompatible Hybrid Cryogel Constructs Comprising Functionalized Chitosan and St. John's Wort Extract

Biobased porous hydrogels enriched with phytocompounds-rich herbal extracts have aroused great interest in recent years, especially in healthcare. In this study, new macroporous hybrid cryogel constructs comprising thiourea-containing chitosan (CSTU) derivative and a Hypericum perforatum L. extract (HYPE), commonly known as St John's wort, were prepared by a facile one-pot ice-templating strategy. Benefiting from the strong interactions between the functional groups of the CSTU matrix and those of polyphenols in HYPE, the hybrid cryogels possess excellent liquid absorption capacity, mechanical resilience, antioxidant performance, and a broad spectrum of antibacterial activity simultaneously. Thus, owing to their design, the hybrid constructs exhibit an interconnected porous architecture with the ability to absorb over 33 and 136 times their dry weight, respectively, when contacted with a phosphate buffer solution (pH 7.4) and an acidic aqueous solution (pH 2). These cryogel constructs have extremely high compressive strengths ranging from 839 to 1045 kPa and withstand elevated strains of over 70% without developing fractures. Moreover, the water-swollen hybrid cryogels with the highest HYPE content revealed a complete and instant shape recovery after uniaxial compression. The incorporation of HYPE into CSTU cryogels enabled substantial improvement in scavenging reactive oxygen species and an expanded antibacterial spectrum toward multiple pathogens, including Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and fungi (Candida albicans). Cell viability experiments demonstrated the cytocompatibility of the 3D cryogel constructs, which did not induce changes in the fibroblast morphology. This work showcases a simple and effective strategy to immobilize HYPE extracts on CSTU 3D networks, allowing the development of novel multifunctional platforms with promising potential in hemostasis, wound dressing, and dermal regeneration scaffolds.

Development and evaluation of thiosalicylic-modified/ion-imprinted chitosan for selective removal of cerium (III) ion

Chitosan was used in this study as the bio-based product for the development of microparticles for the specifically targeted removal of cerium ions (Ce3+) by ion-imprinting technology. A thiosalicylic hydrazide-modified chitosan (TSCS) is produced via cyanoacetylation of chitosan, followed by hydrazidine derivatization to finally introduce the thiosalicylate chelating units. Ion-imprinted Ce-TSCS sorbent microparticles were prepared by combining the synthesized TSCS with Ce3+, crosslinking the polymeric Ce3+/TSCS complex with glutaraldehyde, and releasing the chelated Ce3+ using an eluent solution containing a mixture of EDTA and HNO3. Ce-TSCS had a capacity of 164 ± 1 mg/g and better removal selectivity for Ce3+ because it was smart enough to figure out which target ions would fit into the holes made by Ce3+ during the imprinting process. The kinetic data were well suited to a pseudo-second-order model, and the isotherms were well described by the Langmuir model, both of which pointed to chemisorption and adsorption through Ce3+ chelation. XPS and FTIR analyses demonstrate that the predominant adsorption mechanism is the coordination of Ce3+ with the -NH-, -NH2, and -SH chelating units of the thiosalicylic hydrazidine. These findings provide fresh direction for the development of sorbent materials that can effectively and selectively remove Ce3+ from aqueous effluents.

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020-2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications.

Bio-Based Aerogels for the Removal of Heavy Metal Ions and Oils from Water: Novel Solutions for Environmental Remediation

Contamination of the aqueous environment caused by the presence of heavy metal ions and oils is a growing concern that must be addressed to reduce their detrimental impact on living organisms and safeguard the environment. Recent efficient and environmentally friendly remediation methods for the treatment of water are based on third-generation bioaerogels as emerging applications for the removal of heavy metal ions and oils from aqueous systems. The peculiarities of these materials are various, considering their high specific surface area and low density, together with a highly porous three-dimensional structure and tunable surface chemistry. This review illustrates the recent progress in aerogels developed from cellulose and chitosan as emerging materials in water treatment. The potential of aerogel-based adsorbents for wastewater treatment is reported in terms of adsorption efficacy and reusability. Despite various gaps affecting the manufacturing and production costs of aerogels that actually limit their successful implementation in the market, the research progress suggests that bio-based aerogels are ready to be used in water-treatment applications in the near future.

A cellulose-based intelligent temperature-sensitive molecularly imprinted aerogel reactor for specific recognition and enrichment of ursolic acid

In this article, thermosensitive molecularly imprinted polymer and composite aerogel were combined for the first time to create an intelligent temperature-responsive aerogel reactor to effectively enrich ursolic acid (UA). Because aerogel carrier had a higher specific surface area and higher porosity compared to other carriers, the ursolic acid molecularly imprinted intelligent temperature responsive aerogel reactor (ITR&AR(G570)&UA-MIP) demonstrated a higher adsorption capacity for UA. More notably, ITR&AR(G570)&UA-MIP have the extraordinary capacity to spontaneously adsorb-desorb target molecule UA by regulating the reaction temperature. The ratio of the target molecule UA to the functional monomer and crosslinker in the grafting process and external influences had a major impact on how ITR&AR(G570)&UA-MIP were prepared overall. When the molar ratio of UA to 4-VP was 1:8, the weight ratio between ITR&AR(G570)&UA-MIP and EGDMA/DVB was 1:2:10, the reaction temperature was 60 °C, and the ambient pH = 6, the material showed the best adsorption capacity, reaching a peak of about 70 mg g-1. After researching the appropriate synthesis conditions, ITR&AR(G570)&UA-MIP were applied to lingonberry (Vaccinium Vitis-Idaea L.) berry extracts in this work. The outcomes show that this technique provides a new, intelligent, temperature-controlled adsorption material for the solid-phase extraction of triterpenoid acids in natural products, with good specific adsorption performance for the target molecule UA.

Cyclic desorption based efficacy of polyvinyl alcohol-chitosan variant resins for multi heavy-metal removal

The simultaneous removal of Cu, Pb and Fe from water bodies has been targeted in this work with polyvinyl alcohol (PVA) and chitosan (low, medium, and high molecular weight) derivative and with cyclic desorption efficacy target. For a varied range of adsorbent loading (0.2-2 g L^-1), initial concentration (187.7-563.1 mg L^-1 for Cu, 5.2-15.6 mg L^-1 for Pb, and 61.85-185.55 mg L^-1 for Fe), and resin contact time (5 to 720 min), batch adsorption-desorption studies were conducted. After first adsorption-desorption cycle, the optimum absorption capacity was 6.85 mg g^-1 for Pb, 243.90 mg g^-1 for Cu, and 87.72 mg g^-1 for Fe for the high molecular weight chitosan grafted polyvinyl alcohol resin (HCSPVA). The alternate kinetic and equilibrium models were analyzed along with the interaction mechanism between metal ions and functional groups. The cyclic desorption studies were carried out with simple eluent systems such as HCl, HNO₃, H₂SO₄, KOH, and NaOH. The experiments revealed that the HCSPVA derivative has been an impressive, reusable, and effective sorbent for the mitigation of Pb, Fe, and Cu in complex wastewater systems. This is due to its easy synthesis, excellent adsorption capacity, quick sorption rate, and remarkable regeneration capabilities.

Preparation of Nanocellulose-Based Aerogel and Its Research Progress in Wastewater Treatment

Nowadays, the fast expansion of the economy and industry results in a considerable volume of wastewater being released, severely affecting water quality and the environment. It has a significant influence on the biological environment, both terrestrial and aquatic plant and animal life, and human health. Therefore, wastewater treatment is a global issue of great concern. Nanocellulose's hydrophilicity, easy surface modification, rich functional groups, and biocompatibility make it a candidate material for the preparation of aerogels. The third generation of aerogel is a nanocellulose-based aerogel. It has unique advantages such as a high specific surface area, a three-dimensional structure, is biodegradable, has a low density, has high porosity, and is renewable. It has the opportunity to replace traditional adsorbents (activated carbon, activated zeolite, etc.). This paper reviews the fabrication of nanocellulose-based aerogels. The preparation process is divided into four main steps: the preparation of nanocellulose, gelation of nanocellulose, solvent replacement of nanocellulose wet gel, and drying of nanocellulose wet aerogel. Furthermore, the research progress of the application of nanocellulose-based aerogels in the adsorption of dyes, heavy metal ions, antibiotics, organic solvents, and oil-water separation is reviewed. Finally, the development prospects and future challenges of nanocellulose-based aerogels are discussed.