High strength chitin/chitosan-based aerogel with 3D hierarchically macro-meso-microporous structure for high-efficiency adsorption of Cu(II) ions and Congo red

Acid-resistant chitosan/graphene oxide adsorbent for Cu2+ removal: The role of mixed cross-linking and amino-functionalized

Copper ions in wastewater pose a significant threat to human and ecological safety. Therefore, preparing macroscopic adsorbents with reusable and high adsorption performance is paramount. This paper used graphene oxide as the adsorbent and chitosan as the thickener. Additionally, a silane coupling agent was employed to enhance the acid resistance of chitosan, and amino-modification of graphene oxide was performed. Macroscopic adsorbents with high adsorption capacity were fabricated using 3D printing technology. The results show that all five proportions of inks exhibit good printability. Dissolution experiments revealed that all materials maintained structural integrity after 180 days across pH values. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) confirmed the successful preparation of the materials. Adsorption experiments showed that the best performing material ratio was 8 wt% graphene oxide and 7 wt% chitosan. Adsorption kinetics and isothermal adsorption experiments demonstrated that the adsorption process occurred via monolayer chemisorption. The adsorption process was attributed to strong electrostatic forces, van der Waals forces, and nitrogen/oxygen-containing functional group coordination. Cycling experiments showed that the material retained good adsorption performance after 6 cycles, suggesting its potential for practical heavy metal treatment applications.

Recent advances in chitosan-based nanocomposites for adsorption and removal of heavy metal ions

Due to the high concentration of various toxic and dangerous pollutants, industrial effluents have imposed increasing threats. Among the various processes for wastewater treatment, adsorption is widely used due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, and cost-effectiveness. Chitosan (CS) has received great attention as a pollutant adsorbent due to its low cost and many -OH and -NH2 functional groups that can bind heavy metal ions. However, weaknesses such as sensitivity to pH, low thermal stability and low mechanical strength, limit the application of CS in wastewater treatment. The modification of these functional groups can improve its performance via cross-linking and grafting agents. The porosity and specific surface area of CS in powder form are not ideal, so physical modification of CS via integration with other materials (e.g., metal oxide, zeolite, clay, etc.) leads to the creation of composite materials with improved absorption performance. This review provides reports on the application of CS and its nanocomposites (NCs) for the removal of various heavy metal ions. Synthesis strategy, adsorption mechanism and influencing factors on sorbents for heavy metals are discussed in detail.

Flexible cellulose nanofiber aerogel with enhanced porous structure and its applications in copper(II) removal

In order to achieve an aerogel with both rigid pore structures and desired flexibility, stiff carboxyl-functionalized cellulose nanofiber (CNFs) were introduced into a flexible polyvinyl alcohol-polyethyleneimine (PVA-PEI) crosslinking network, with 4-formylphenylboronic acid (4FPBA) bridging within the PVA-PEI network to enable dynamic boroxine and imine bond formation. The strong covalent bonds and hydrogen connections between CNF and the crosslinking network enhanced the wet stability of the aerogel while also contributed to its thermal stability. Importantly, the harmonious coordination between the stiff CNF and the flexible polymer chains not only facilitated aerogel flexibility but also enhanced its increased specific surface area by improving pore structure. Moreover, the inclusion of CNF enhanced the adsorption capacity of the aerogel, rendering it effective for removing heavy metal ions. The specific surface area and adsorption capacity for copper ions of the aerogel increased significantly with a 3 wt% addition CNF suspension, reaching 19.74 m2 g-1 and 60.28 mg g-1, respectively. These values represent a remarkable increase of 590.21 % and 213.96 %, respectively, compared to the blank aerogel. The CNF-enhanced aerogel in this study, characterized by its well-defined pore structures, and desired flexibility, demonstrates versatile applicability across multiple domains, including environmental protection, thermal insulation, electrode fabrication, and beyond.

A review on carbon-based biowaste and organic polymer materials for sustainable treatment of sulfonamides from pharmaceutical wastewater

Frequent detection of sulfonamides (SAs) pharmaceuticals in wastewater has necessitated the discovery of suitable technology for their sustainable remediation. Adsorption has been widely investigated due to its effectiveness, simplicity, and availability of various adsorbent materials from natural and artificial sources. This review highlighted the potentials of carbon-based adsorbents derived from agricultural wastes such as lignocellulose, biochar, activated carbon, carbon nanotubes graphene materials as well as organic polymers such as chitosan, molecularly imprinted polymers, metal, and covalent frameworks for SAs removal from wastewater. The promising features of these materials including higher porosity, rich carbon-content, robustness, good stability as well as ease of modification have been emphasized. Thus, the materials have demonstrated excellent performance towards the SAs removal, attributed to their porous nature that provided sufficient active sites for the adsorption of SAs molecules. The modification of physico-chemical features of the materials have been discussed as efficient means for enhancing their adsorption and reusable performance. The article also proposed various interactive mechanisms for the SAs adsorption. Lastly, the prospects and challenges have been highlighted to expand the knowledge gap on the application of the materials for the sustainable removal of the SAs.

Sustainable triethylenetetramine modified sulfonated graphene oxide/chitosan composite for enhanced adsorption of Pb(II), Cd(II), and Ni(II) ions

A novel sulfonated group and triethylenetetramine modified GO/chitosan (GO-CS) adsorbent (T-SGO-CS) was successfully prepared and utilized for the adsorption of heavy metal ions from single-metal, binary-metal, and ternary-metal solutions. In a single system, the adsorption capacity was 312.28 mg/g for Pb2+, 260.52 mg/g for Cd2+, and 84.61 mg/g for Ni2+, whereas, Adsorption of Pb(II), Cd(II), and Ni(II) in binary and ternary systems was systematically studied. In tertiary systems, the effect of competitive adsorption was more pronounced. In addition, T-SGO-CS exhibited a high adsorption capacity and was recyclable for Pb2+, Cd2+, and Ni2+. T-SGO-CS is a novel and highly efficient adsorbent for omnidirectionally enhancing the adsorption of Pb2+, Cd2+, and Ni2+, as demonstrated by these results. Therefore, T-SGO-CS could be investigated as a potential new material for future applications in heavy metal removal.

Fabrication of maleic anhydride-acrylamide copolymer based sodium alginate hydrogel for elimination of metals ions and dyes contaminants from polluted water

The study explores the synergy of biobased polymers and hydrogels for water purification. Polymer nanomaterial's, synthesized by combining acrylamide copolymer with maleic anhydride, were integrated into sodium alginate biopolymer using an eco-friendly approach. Crosslinking agents, calcium chloride and glutaraladehyde, facilitated seamless integration, ensuring non-toxicity, high adsorption performance, and controlled capacity. This innovative combination presents a promising solution for clean and healthy water supplies, addressing the critical need for sustainable environmental practices in water purification. In addition, the polymer sodium alginate hydrogel (MAH@AA-P/SA/H) underwent characterization via the use of several analytical procedures, such as FTIR, XPS, SEM, EDX and XRD. Adsorption studies were conducted on metals and dyes in water, and pollutant removal methods were explored. We investigated several variables (such as pH, starting concentration, duration, and absorbent quantity) affect a material's capacity to be adsorbed. Moreover, the maximum adsorption towards Cu2+ is 754 mg/g while for Cr6+ metal ions are 738 mg/g, while the adsorption towards Congo Red and Methylene Blue dye are 685 mg/g and 653 mg/g correspondingly, within 240 min. Adsorption results were further analyzed using kinetic and isothermal models, which showed that MAH@AA-P/SA/H adsorption is governed by a chemisorption process. Hence, the polymer prepared from sodium alginate hydrogel (MAH@AA-P/SA/H) has remarkable properties as a versatile material for the significantly elimination of harmful contaminants from dirty water.

Enhanced sequestration of Pb2+ and Cu2+ by Artemia cyst shell supported nano-Mg composite and the potential photocatalytic performance of carbonized exhausted-adsorbent

This study reported a new strategy for enhanced Pb2+ and Cu2+ sequestration by Artemia cyst shell (shell) supported nano-Mg from aqueous solutions and the carbonated exhausted-adsorbents sequenced potential application in photo-catalyst, which obtained two expected results. One is that the immobilization of nano-Mg onto Artemia cyst shell (shell-Mg) can greatly strengthen the adsorption effect of the neat cyst shell on Pb2+ and Cu2+. The adsorption capacities of shell-Mg for both metal ions reached to 622.01 and 313.91 mg/g, which was 10-15 and 30-50 times that of the neat shell respectively. And shell-Mg has strong selectivity, which was approximately 2-4 times that of shell. The shell-Mg can be used to retrieve Pb2+ and Cu2+ from aqueous solutions efficiently. Another is that the carbonated exhausted-adsorbents (C-shell-Mg-Pb and C-shell-Mg-Cu) showed their potential photocatalytic degradation effects on congo red under pH = 4 condition, the decolorization rate reached to 61.19% and 80.39% respectively. Reuse of exhausted adsorbents can avoid the secondary pollution caused by the regeneration, extend the utilization value of exhausted adsorbents, and provide a new viewpoint for the reuse of spent bio-nanomaterial adsorbents.

Synthesis of 2-amino-terephthalic acid crosslinked chitosan/bentonite hydrogel; an efficient adsorbent for anionic dyes and laccase

This research article presents the fabrication of NH2-terephthalic acid crosslinked chitosan-bentonite composite, which adopted a facile synthesis approach and offered efficient adsorption capacity for organic dyes. A novel hydrogel material named CB 5:1 demonstrated remarkable adsorption for anionic dyes (Congo red (CR) and brilliant blue (BB)) while showing a negligible affinity for cationic dyes. Adsorption isotherm studies revealed the adsorption capacity of 4950 mg/g and 2053 mg/g (per g of composite's dry weight) for CR and BB following the Langmuir adsorption model. Kinetics and thermodynamic studies were also conducted while the adsorption of anionic dyes in the presence of metal ions, cationic dyes, anionic dyes, and in simulated water remained unaffected. Laccase, an industrially important enzyme, was also immobilized on CB 5:1 to achieve enzyme stability and reusability, resulting in a staggering immobilization capacity (4782 mg/g) at pH 6.0. Laccase immobilized product was employed to perform dye degradation (> 90 % for CR and > 75 % for BB), and the reusability was tested. Overall, our crosslinked product proved appealing for removing high concentrations of anionic organic dyes from polluted water and could be envisaged for practical use.

Evaluation of ethanol-induced chitosan aerogels with human osteoblast cells

The following article provides an insight into the production of chitosan aerogels as potential materials for tissue engineering. Chitosan aerogels were prepared following two different protocols: formation in ethanol and formation in sodium hydroxide in an ethanol solution. The main objective was to apply a new route to obtain chitosan aerogels with no external cross-linkers and compare the mentioned preparation approaches. Forming chitosan aerogels in ethanol implies a simple, environmentally friendly, and efficient method. The prepared materials showed specific surface areas of up to 450 m2/g, highly porous networks and great mechanical properties. In vitro degradation studies revealed high stability for up to 10 weeks. The differences between the samples were significant. While the chitosan aerogels prepared in ethanol showed superior textural, morphological and mechanical properties, the chitosan aerogels prepared in the sodium hydroxide solution proved that a considerable influence on end properties could be made simply by adjusting the ageing medium. In vitro cell analysis with primary human osteoblasts showed good biocompatibility and pointed towards the potential use of these aerogels for orthopedic applications. This testing showed further that adjustments in structural properties by sodium hydroxide also come with a cost regarding their suitability to host bone cells.

Multifunctional carboxymethyl cellulose/graphene oxide/polyaniline hybrid thin film for adsorptive removal of Cu(II) and oxytetracycline antibiotic from wastewater

The antibiotics and metal ions in the contaminated water bodies must be removed using appropriate methods for sustainable development. In this study, the multifunctional carboxymethyl cellulose/graphene oxide/polyaniline (CMC/GO/PANI) hybrid thin film was synthesized and utilized for adsorptive scavenging of (Cu(II) and oxytetracycline (OTC) from wastewater. The prepared thin films' morphology, chemical compositions, functionality, and surface charge were analyzed by well-known physicochemical techniques. The adsorption process of the selected model pollutants was examined as a function of reaction time, Cu(II), and OTC solution pH, concentrations, and temperatures. Results showed that CMC/GO/PANI hybrid thin film had higher Cu(II) and OTC adsorption than CMC, GO/CMC, and PANI/CMP thin films due to the multifunctional synergetic effect. The adsorption kinetic data were fitted to the pseudo-second-order model. Redlich-Peterson isotherm model well interpreted Cu(II) and OTC scavenging equilibrium data. Energetically, the adsorption was spontaneous and endothermic for both pollutants. The multifunctional CMC/GO/PANI thin film was recycled and reused seven times during adsorption-desorption cycles. The study outcomes demonstrated that CMC/GO/PANI thin film could be reused multiple times for large-scale wastewater purification.

Surface modification of chitin nanofibers with dopamine as efficient nanosorbents for enhanced removal of dye pollution and metal ions

The development of environmentally friendly and low-cost adsorbents with high adsorption capacity remains a challenge. Herein, chitin nanofiber-polydopamine composite materials (CNDA) have been obtained by surface modification of chitin nanofiber using dopamine. According to the results of transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and X-ray photoelectron spectrometer (XPS), polydopamine have been successfully coated on the surface of chitin nanofiber (ChNF). The ability to remove methylene blue (MB) has been analyzed via standard adsorption experiments, indicating that the maximum adsorption capacity (qmax) can reach 196.6 mg/g at MB initial concentration of 50 mg/L. Most importantly, the adsorption kinetics, isotherm, and thermodynamics were used to investigate the MB adsorption mechanism on composites. This indicated that the polydopamine on the surface of chitin nanofiber (ChNF) plays an important role in the MB dye adsorption. Moreover, the removal ability of CNDA to metal ions has also been investigated, indicating high capacities for Fe3+, Mn2+, Cu2+, and Ni2+. Based on their biodegradability and good adsorption capacity, the CNDA composite material can be considered a promising adsorbent for wastewater treatment.

Synthesis and fabrication of segregative and durable MnO2@chitosan composite aerogel beads for uranium(VI) removal from wastewater

To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO2@chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO2 nanospheres but also significantly enhances the porous structure and surface area of MnO2@CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO2@CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO2@CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO2-based adsorbents. The chemisorption process of U(VI) on MnO2@CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO2@CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater.

Bio-based functionalized adsorptive polymers for sustainable water decontamination: A systematic review of challenges and real-world implementation

The overwhelming concerns of water pollution, industrial discharges and environmental deterioration by various organic and inorganic substances, including dyes, heavy metals, pesticides, pharmaceuticals, and detergents, intrinsically drive the search for urgent and efficacious decontamination techniques. This review illustrates the various approaches to remediation, their fundamentals, characteristics and demerits. In this manner, the advantageous implementation of nature-based adsorbents has been outlined and discussed. Different types of lignocellulosic compounds (cellulose, lignin, chitin, chitosan, starch) have been introduced, and the most used biopolymeric materials in bioremediation have been highlighted; their merits, synthesis methods, properties and performances in aqueous medium decontamination have been described. The literature assessment reveals the genuine interest and dependence of academic and industrial fields to valorize biopolymers in the adsorption of various hazardous substances. Yet, the full potential of this approach is still confined by certain constraints, such as the lack of reliable, substantial, and efficient extraction of biopolymers, as well as their modest and inconsistent physicochemical properties. The futuristic reliance on such biomaterials in all fields, rather than adsorption, is inherently reliable on in-depth investigations and understanding of their features and mechanisms, which can guarantee a real-world application and green technologies.

Flexible fabrication chitosan-polyamidoamine aerogels by one-step method for efficient adsorption and separation of anionic dyes

Chitosan in situ grown polyamidoamine (CTS-Gx PAMAM (x = 0, 1, 2, 3)) aerogels were fabricated by a facile one-step freeze-drying method, with glutaraldehyde serving as a crosslinker. The three-dimensional skeletal structure of aerogel provided numerous adsorption sites and accelerated the effective mass transfer of pollutants. The adsorption kinetics and isotherm studies of the two anionic dyes were consistent with the pseudo-second-order and Langmuir models, indicating that the removal of rose bengal (RB) and sunset yellow (SY) was a monolayer chemisorption process. The maximum adsorption capacity of RB and SY reached 370.28 mg/g and 343.31 mg/g, respectively. After five adsorption-desorption cycles, the adsorption capacities of the two anionic dyes reached 81.10% and 84.06% of the initial adsorption capacities, respectively. The major mechanism between the aerogels and dyes was systematically investigated based on using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy analyses, confirming that electrostatic interaction, hydrogen bonding and van der Waals interactions were the main driving forces for the superior adsorption performance. Furthermore, the CTS-G2 PAMAM aerogel exhibited good filtration and separation performance. Overall, the novel aerogel adsorbent possesses excellent theoretical guidance and practical application potential for the purification of anionic dyes.

Preparation of DES lignin-chitosan aerogel and its adsorption performance for dyes, catechin and epicatechin

Herein, DES lignin was obtained by pretreatment of grapevine with a deep eutectic solvent (ChCl-LA). A novel chitosan-DES lignin composite aerogel material (CS-LIG aerogel) was prepared to adsorb methylene blue (MB), Congo red (CR), catechin (C), and epicatechin (EC). The CS-LIG aerogel was systematically characterized by modern technological instruments. It was demonstrated that the DES lignin was successfully incorporated and had an important effect on the morphological structure and adsorption of dyes and natural products in the aerogel. The adsorption kinetic models for both adsorbed CR and MB are pseudo-second-order models. Adsorption isotherms followed Langmuir for the adsorption of CR and Freundlich for the adsorption of MB. The π-π interaction and hydrogen bonding of DES lignin aromatic groups in CS-LIG aerogels were responsible for the adsorption of C and EC with 86.42 % and 90.85 % removal rates, respectively. This study opens a new avenue for the high-value utilization of DES lignin and the preparation of chitosan-based composites for the adsorption of dyes and purification of natural products.

Facile synthesis and characterization of Fe3O4/analcime nanocomposite for the efficient removal of Cu(II) and Cd(II) ions from aqueous media

In the water purification field, heavy metal pollution is a problem that causes severe risk aversion. This study aimed to examine the disposal of cadmium and copper ions from aqueous solutions by a novel Fe3O4/analcime nanocomposite. A field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction were used to characterize the synthesized products. The FE-SEM images showed that the analcime and Fe3O4 samples consist of polyhedral and quasi-spherical shapes with average diameters of 923.28 and 28.57 nm, respectively. Besides, the Fe3O4/analcime nanocomposite consists of polyhedral and quasi-spherical shapes with average diameters of 1100.00 nm. The greatest uptake capability of the Fe3O4/analcime nanocomposite toward the copper and cadmium ions is 176.68 and 203.67 mg/g, respectively. The pseudo-second-order kinetic model and Langmuir equilibrium isotherm best describe the uptake of copper and cadmium ions using the Fe3O4/analcime nanocomposite. The uptake of copper and cadmium ions using the Fe3O4/analcime nanocomposite is exothermic and chemical in nature.

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.