Interpenetrating polymer network hydrogels for removal of synthetic dyes: A comprehensive review

Machine Learning Enabled Reusable Adhesion, Entangled Network-Based Hydrogel for Long-Term, High-Fidelity EEG Recording and Attention Assessment

Due to their high mechanical compliance and excellent biocompatibility, conductive hydrogels exhibit significant potential for applications in flexible electronics. However, as the demand for high sensitivity, superior mechanical properties, and strong adhesion performance continues to grow, many conventional fabrication methods remain complex and costly. Herein, we propose a simple and efficient strategy to construct an entangled network hydrogel through a liquid-metal-induced cross-linking reaction, hydrogel demonstrates outstanding properties, including exceptional stretchability (1643%), high tensile strength (366.54 kPa), toughness (350.2 kJ m-3), and relatively low mechanical hysteresis. The hydrogel exhibits long-term stable reusable adhesion (104 kPa), enabling conformal and stable adhesion to human skin. This capability allows it to effectively capture high-quality epidermal electrophysiological signals with high signal-to-noise ratio (25.2 dB) and low impedance (310 ohms). Furthermore, by integrating advanced machine learning algorithms, achieving an attention classification accuracy of 91.38%, which will significantly impact fields like education, healthcare, and artificial intelligence.

Peroxymonosulfate activated M-MOF-74 (M = Co, Fe, Ni) visible light photocatalysts for methylene blue degradation enhancement

Persulphate-based advanced oxidation technology efficiently and cost-effectively removes organic dyes from water but designing stable photocatalytic systems and understanding their reaction mechanisms remain key challenges. Metal-organic frameworks (MOFs) have attracted considerable research attention for degrading organic pollutants owing to their high porosity, tunable structure, and ease of modification. In this study, a series of M-MOF-74 (M = Co, Fe, Ni) photocatalysts are synthesized by a hydrothermal method for methylene blue (MB) degradation. Among them, the Co-MOF-74 photocatalytic synergetic peroxymonosulfate system exhibits high catalytic activity after 30 min of visible light irradiation. MB degradation efficiency reaches 94.8%, and the reaction rate constant is 0.210 min-1, which is approximately 19.44 times higher than the reaction rate constant of the original Co-MOF-74. Compared with Fe-MOF-74 and Ni-MOF-74, Co-MOF-74 exhibits better photocatalytic performance due to the dynamic changes in the valence state of cobalt, which more effectively facilitate the activation of PMS. In addition, this study analyses the possible degradation pathways of MB in water and toxicological evaluations of intermediate products, providing new insights for the effective removal of dyes in water.

A comprehensive review of sustainable hydrogels from lignin for advanced wastewater solutions

Throughout the recent years, water bodies have been significantly contaminated via various industrial and pollution wastes posing threats to the living. To tackle the situation, Lignin-Based Hydrogels have appeared as a material with great potential for wastewater treatment. Biomass-derived polymers for wastewater treatment present a sustainable replacement to plastics based on petroleum owing to its biocompatibility, affordability, eco-friendliness and biodegradability. After cellulose the lignin is the second highest polyaromatic bio-polymer in plants. And serves as the Earth's primary renewable source for aromatic materials. Structurally, it is a cross-linked polymer enriched with hydrophilic functional groups like hydroxyls, methoxyls, carbonyls that makes it a promising precursor towards hydrogel development. This review focuses on hydrogels based on lignin, highlighting their synthesis, traits and potential functions in water treatment. It also examines various methods for extracting lignin from different raw materials. Challenges and limitations associated with real-world applications of LBHs are addressed and along with prospects for future research. Ultimately, this review provides valuable insights into developing sustainable hydrogels based on lignin for efficient elimination of aquatic contaminants.

Recent developments in conductive polysaccharide adsorbent formulations for environmental remediation: A review

Environmental remediation is crucial for human life and ecosystems, involving the cleanup of contaminated water to protect health and restore ecological balance. However, rapid industrialization and population growth have worsened pollution, particularly in water bodies, making effective wastewater treatment a key challenge in ensuring clean drinking water, and the adsorption of toxic gases for air treatment are the main strategies for environmental remediation. Among the various treatment methods, adsorption stands out for its high selectivity, low energy and chemical use, ease of operation, and cost-effectiveness. To date, innovative, highly efficient, non-toxic, engineered adsorbent materials have received potential interest from scientific and governmental communities. Conducting polymer-modified polysaccharide formulations are crucial in wastewater treatment due to their high surface area, adsorption efficiency, excellent stability, and eco-friendly, biodegradable properties. This review offers an extensive overview of recent progress in synthesizing conducting polymer-modified polysaccharide formulations (hydrogels, aerogels, nanofibers, and nanocomposites) for capturing toxic heavy metal ions, organic dyes, pharmaceuticals, phenols as well as adsorbing different toxic gases using various adsorption mechanisms. It also emphasizes the integration of different nanofillers, including carbon-based materials, Mxenes, nanoclay, metal/metal oxides, and hybrid nanomaterials, into conductive polysaccharide chains to improve their physicochemical properties and adsorption efficiency. The reported data showed that these engineered adsorbent materials based on conductive polysaccharide formulations have immense potential for wastewater treatment applications, offering more effective and sustainable solutions.

Cellulose/Sodium Polyacrylate Interpenetrating Network Hydrogel with Intrinsic Anti-Freezing Property

Generally, small molecule alcohols and concentrated electrolyte ions can be introduced into the medium of hydrogels as anti-freezing agents to achieve significant anti-freezing properties. However, due to the exchange effect with the external environment, the anti-freezing agents may leak or change in composition causing contamination and unstable material performance during use. Here, cellulose and sodium polyacrylate (PAAS) were used to construct interpenetrating network hydrogels, with cellulose comprising up to 63% of the system. Sodium ions and carboxylic acid groups ionized from the polyacrylate network restricting the formation of water clusters through strong hydration and significantly reduced the ice crystal formation temperature. The rigid cellulose networks provided mechanical strength for the hydrogels. The new interpenetrating network hydrogels exhibited a low anti-freezing temperature (lowest at -56.12 °C), a high water content (over 82.5 wt%), and considerable toughness (up to 2.53 MJ m-3). The intrinsic anti-freezing hydrogel constructed in this work provides a new reference strategy for expanding the practicability of anti-freezing hydrogels.

New Trends in Preparation and Use of Hydrogels for Water Treatment

Hydrogel-based wastewater treatment technologies show certain outstanding features, which include exceptional efficiency, sustainability, reusability, and the precise targeting of specific contaminants. Moreover, it becomes possible to minimize the environmental impact when using these materials. Their flexibility, low energy consumption, and adaptability to meet specific requirements for different purposes offer significant advantages over traditional methods like activated carbon filtration, membrane filtration, and chemical treatments. Recent advancements in hydrogel technology, including new production methods and hybrid materials, enhance their ability to efficiently adsorb contaminants without altering their biocompatibility and biodegradability. Therefore, innovative materials that are ideal for sustainable water purification were developed. However, these materials also suffer from several limitations, mostly regarding the scalability, long-term stability in real-world systems, and the need for precise functionalization. Therefore, overcoming these issues remains a challenge. Additionally, improving the efficiency and cost-effectiveness of regeneration methods is essential for their practical use. Finally, assessing the environmental impact of hydrogel production, use, and disposal is crucial to ensure these technologies are beneficial in the long run. This review summarizes recent advancements in developing polymer-based hydrogels for wastewater treatment by adsorption processes to help us understand the progress made during recent years. In particular, the studies presented within this work are compared from the point of view of the synthesis method, raw materials used such as synthetic/natural or hybrid networks, and the targeted class of pollutants-dyes or heavy metal ions. In several sections of this paper, discussions regarding the most important properties of the newly emerged adsorbents, e.g., kinetics, the adsorption capacity, and reusability, are also discussed.

Sustainable bioactive hydrogels for organic contaminant elimination in wastewater

Immobilized enzyme bioremediation is a promising technique for eliminating pollutants to alleviate water scarcity pressure but is severely hindered by poor enzymatic activity and stability. An effective charge-assisted H-bonding approach is developed to achieve high laccase loading and enzymatic activity on bio(cellulose)-based hydrogels. Notably, this strategy can be readily extended to lipase and catalase. The bio-based hydrogels are synthesized by grafting deoxyribonucleic acid onto the cellulose backbone through a one-step structural regulation, achieving high mechanical strength, enzyme loading and contaminant capture for degradation. The biocompatible laccase-immobilized hydrogels exhibit significant removal and degradation performance for diverse organic micropollutants, including parent and substituted polycyclic aromatic hydrocarbons, per- and polyfluoroalkyl substances, antibiotics and organic dyes. Further testing focused on parent and substituted polycyclic aromatic hydrocarbons shows minimal influence of various co-existing interfering substances on performance of the laccase-immobilized bioactive hydrogel, with its contaminant removal and degradation efficiency in authentic wastewater being 93.0- and 64.3-fold that of commercial free laccase, respectively. This work provides an effective strategy for sustainable bioremediation of wastewater and other pollutant streams, while simultaneously enabling the development of innovative enzyme catalysts.

Floatable and magnetic MoS2/NiFe2O4/chitosan nanocomposite integrated melamine sponges with hybrid photothermal and photocatalytic enhancement for pollutant removal

Magnetic chitosan-based materials with good adsorption-photocatalysis and magnetic properties have great prospect in wastewater treatment. In this paper, a floating magnetic molybdenum disulfide/NiFe2O4/chitosan integrated melamine sponges (m-MoS2/CS@MS) was fabricated using chitosan as absorbent and adhesive, MoS2 and NiFe2O4 as photocatalysts, and melamine sponge as support material. The m-MoS2/CS@MS has a rich light-water-air-material interaction interface and can float on the water surface. The light absorbance of m-MoS2/CS@MS had dramatically increased by 55.77 % with the introduction of MoS2 and NiFe2O4 nanoparticles. The m-MoS2/CS@MS can effectively remove Congo red dye at pH = 2-10 under different coexisting inorganic salts (Cl-, SO42-) and water matrices (ultrapure water, tap water, Lake water, and mineral water). The m-MoS2/CS@MS had excellent photocatalytic degradation ability, reaching a degradation rate of 98.88 % under simulated solar light irradiation. Furthermore, the m-MoS2/CS@MS composite exhibited excellent stability, convenient magnetic recycling performance, reusability and its suitability for dye wastewater treatment under different conditions. This research provided a new insight into the practical application of sustainable and clean chitosan-based materials.

Emerging Combination of Hydrogel and Electrochemical Biosensors

Electrochemical sensors are among the most promising technologies for biomarker research, with outstanding sensitivity, selectivity, and rapid response capabilities that make them important in medical diagnostics and prognosis. Recently, hydrogels have gained attention in the domain of electrochemical biosensors because of their superior biocompatibility, excellent adhesion, and ability to form conformal contact with diverse surfaces. These features provide distinct advantages, particularly in the advancement of wearable biosensors. This review examines the contemporary utilization of hydrogels in electrochemical sensing, explores strategies for optimization and prospective development trajectories, and highlights their distinctive advantages. The objective is to provide an exhaustive overview of the foundational principles of electrochemical sensing systems, analyze the compatibility of hydrogel properties with electrochemical methodologies, and propose potential healthcare applications to further illustrate their applicability. Despite significant advances in the development of hydrogel-based electrochemical biosensors, challenges persist, such as improving material fatigue resistance, interfacial adhesion, and maintaining balanced water content across various environments. Overall, hydrogels have immense potential in flexible biosensors and provide exciting opportunities. However, resolving the current obstacles will necessitate additional research and development efforts.

A review of methods for mitigating microplastic contamination in biosolids from wastewater treatment plants before agricultural soil application

Wastewater treatment plants (WWTP) are recognized as major sources of microplastic (MP) particles in terrestrial environments, particularly in agricultural soils through biosolids application. While many reviews have focused on the distribution, detection, and mitigation of MPs in wastewater effluent to limit their discharge into oceans, our understanding of methods to mitigate biosolid contamination remains limited. This review focuses on methods for mitigating MPs contamination in biosolids at various intervention points, including sources, WWTP including the primary and secondary treatment stages where sludge is generated, and post-contamination. These methods are categorized as physical, physicochemical, and biological approaches, and their advantages and limitations are discussed. For instance, physicochemical methods, especially froth flotation, are cost-effective but are hindered by contaminants and reagents. Physical methods like microfibre filtration devices (MFD) are safe but their efficiency depends on the filter pore size and design. Biological methods, particularly microbial degradation, are limited by the varying efficiencies of microorganisms in breaking down MPs and the extended time required for their effective degradation. Other physical methods including dissolved air flotation, and ultrasonication already exist in WWTPs but may require retrofitting or optimization to enhance MP removal from biosolids. As each method inherently has limitations, the key to achieving MP-free biosolids, and thus preventing their release into agricultural soil, lies in integrating these methods through multi-coupling strategies.

Biobased amphoteric aerogel with core-shell structure for the hierarchically efficient adsorption of anionic and cationic dyes

Efficient and simultaneous removal of anionic and cationic dyes from wastewater using low-cost and environmentally-friendly adsorbent is highly required. Herein, the carboxylated cellulose (carboxyl content: 2.97 mmol/g) derived from pomelo peel was extracted by a one-step H2O2/H2SO4-mediated oxidation method. Subsequently, a novel pomelo-peel cellulose/chitosan/sodium alginate (PCS) amphoteric aerogel with a specific core-shell structure was synthesized by multiple physical cross-linking strategies. The shell layer and core layer of the optimized P3CS0.75 aerogel can selectively adsorb cationic dyes and anionic dyes, in which, the theoretical maximum adsorption capacities were 888.27 mg/g and 1816.87 mg/g towards methylene blue (MB) and Congo red (CR), respectively. Especially, the aerogel's core/shell layer exhibited hierarchical adsorption behavior without overlapping sites even in the binary dye systems. The adsorption performance of obtained amphoteric aerogel remained effective in a wide pH range and under different practical water systems. Moreover, the removal efficiencies for MB and CR were slightly reduced from 90.76 % and 99.66 % to 88.08 % and 91.39 %, respectively, after 5 adsorption-desorption cycles, and the aerogel's structural integrity was also maintained due to its good compressive strength (487.16 KPa). In addition, the adsorption mechanism of PCS aerogel was investigated using adsorption kinetics, isotherm, thermodynamics, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was proved that the adsorption process was endothermic spontaneous-monolayer adsorption driven by electrostatic attraction and hydrogen bonding. Therefore, the prepared biobased aerogel was expected to be a prospective material for removing mixed dyes from wastewater.

Synergistic Effect Between 0D CQDs and 2D MXene to Enhance the Photothermal Conversion of Hydrogel Evaporators for Efficient Solar Water Evaporation, Photothermal Sensing and Electricity Generation

Solar-powered interfacial water evaporation is a promising technique for alleviating freshwater stress. However, the evaporation performance of solar evaporators is still constrained by low photothermal conversion efficiency and high water evaporation enthalpy. Herein, 0D carbon quantum dots (CQDs) are combined with 2D MXene to serve as a hybrid photothermal material to enhance the light absorption and photothermal conversion ability, meanwhile sodium carboxymethyl cellulose (CMC)/polyacrylamide (PAM) hydrogels are used as a substrate material for water transport to reduce the enthalpy of water evaporation. The synergistic effect in 0D CQDs/2D MXene hybrid photothermal materials accelerate the carrier transfer, inducing efficient localized surface plasmon resonance (LSPR) effect. This results in the enhanced photothermal conversion efficiency. The integrated hydrogel evaporators demonstrate a high evaporation rate (1.93 and 2.86 kg m-2 h-1 under 1 and 2 sunlights, respectively) and low evaporation enthalpy (1485 J g-1). In addition, the hydrogel evaporators are applied for photothermal sensing and temperature difference power generation (TEG). The TEG device presents an efficient output power density (230.7 mW m-2) under 1 sunlight. This work provides a feasible approach for regulating and controlling the evaporation performances of hydrogel evaporators, and gives a proof-of-concept for the design of multipurpose solar evaporation systems.

CO2-Sourced Polymer Dyes for Dual Information Encryption

Large amounts of small molecule dyes leak into the ecosystems annually in harmful and unsustainable ways. Polymer dyes have attracted much attention because of their high migration resistance, excellent stability, and minimized leakage. However, the complex synthesis process, high cost, and poor degradability hinder their widespread application. Herein, green and sustainable polymer dyes are prepared using natural dye quercetin (Qc) and CO2 through a one-step process. The CO2-sourced polymer dyes show strong migration resistance, high stability, and can be degraded on demand. Additionally, the CO2-sourced polymer dyes showed unique responses to Zn2+, leading to significantly enhanced fluorescence, highlighting their potential for information encryption/decryption. The CO2-sourced polymer dyes can solve the environmental hazards caused by small molecule dye leakage and promote the carbon cycle process. Meanwhile, the one-step synthesis process is expected to achieve sustainable and widespread utilization of CO2-sourced polymer dyes.

Hydrogels and Their Functionalization-Analysis of the Possibility of Their Application in Post-Fire Water Treatment Processes

Increasingly intense changes in climatic conditions and the use of modified materials are causing fires, the consequences of which are increasingly serious for the environment. On one hand, there is the issue of access to water resources. On the other hand, there is the problem of post-fire wastewater, which often contains a mixture of simple inorganic compounds and complex organic molecules, making the removal of pollutants a difficult task requiring innovative approaches. Among these solutions, hydrogels stand out as a promising class of sorption materials. Depending on their synthesis or functionalization, hydrogels can effectively capture contaminants and facilitate the reduction or removal of specific pollutants. This study explores the functionalization of polymeric materials, specifically hydrogels, using microorganisms or bioactive substances to create materials capable of treating water contaminated with hazardous substances generated during firefighting incidents. The possibility of wastewater capture was also taken into account to retain pretreated water at the place of pollutant generation. The analysis covered the potential, conditions, and limitations of using hydrogels in post-fire operations for the effective management of contaminated waters. It was shown that hydrogels, depending on the modification, have the potential to capture wastewater and purify it from both organic and inorganic substances specific to post-fire wastewater. However, it is not possible for a given hydrogel to meet all desired expectations at the same time. Furthermore, modifications that facilitate the optimal performance of certain functionalities may render the others ineffective.

Modification of nickel ferrite nanoparticles by sodium docusate surfactant for superior crystal violet dye removal from aqueous solutions

In this study, nickel ferrite (NiFe2O4) nanoparticles were synthesized using the Pechini sol-gel method and modified with sodium docusate surfactant. The modified nanoparticles showed an enhanced adsorption capacity of 384.62 mg/g for crystal violet dye, compared to 237.53 mg/g for unmodified NiFe2O4. Characterization was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) techniques. The adsorption process was spontaneous, exothermic, and followed the Langmuir isotherm and pseudo-second-order kinetic model. Optimal conditions for maximum dye removal were achieved at pH 10, 50 min, and 298 K. Additionally, the synthesized adsorbents demonstrated excellent regeneration and reusability over five adsorption-desorption cycles with minimal efficiency loss.

Efficient removal of basic yellow 28 dye from water using facilely synthesized ZnO and Mg3B2O6 nanostructures

Basic yellow 28 dye, used extensively in the textile and leather industries, poses significant environmental and health risks, including allergic reactions, skin irritation, and respiratory problems. This study reports the Pechini sol-gel synthesis of novel ZnO/Mg3B2O6 nanostructures for the decontamination of basic yellow 28 dye from aqueous solutions. The nanostructures were synthesized by calcining at 650 and 850 °C for 5 h, producing ZM650 and ZM850, respectively. The average crystallite sizes were 39.28 nm for ZM650 and 51.03 nm for ZM850. BET surface areas were 70.71 m2/g for ZM650 and 48.13 m2/g for ZM850. FE-SEM and HR-TEM analyses revealed distinct morphological structures, with ZM650 exhibiting a dense aggregation of rod-like particles and ZM850 showing larger clusters. The maximum adsorption capacities were 381.68 mg/g for ZM650 and 303.03 mg/g for ZM850. The optimum adsorption was observed at a pH of 10, a contact time of 70 min, and a temperature of 298 K. Regeneration using a 6 M HCl solution demonstrated efficient reusability over five cycles. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm, indicating monolayer adsorption. Also, the adsorption process was found to be physical and exothermic.

Hemicellulose-Based Sensors: When Sustainability Meets Complexity

Hemicelluloses (HCs) are promising sustainable biopolymers with a great natural abundance, excellent biocompatibility, and biodegradability. Yet, their potential sensing applications remain limited due to intrinsic challenges in their heterogeneous chemical composition, structure, and physicochemical properties. Herein, recent advances in the development of HC-based sensors for different chemical analytes and physical stimuli using different transduction mechanisms are reviewed and discussed. HCs can be utilized as carbonaceous precursors, reducing, capping, and stabilizing agents, binders, and active components for sensing applications. In addition, different strategies to develop and improve the sensing capacity of HC-based sensors are also highlighted.

Porous chitosan quaternary ammonium salt hydrogel embedded with Cu, Ni and Pd nanoparticles for efficient coupled adsorption-catalytic reduction of methylene blue and 4-nitrophenol

Anthropogenic wastewater generation and water pollution can have negative impacts on public health and ecosystems. However, most materials do not have both adsorptive and catalytic properties, so the design and development of sustainable and multifunctional materials is essential for wastewater treatment. Herein, composite hydrogel (PHG) containing [2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) and chitosan quaternary ammonium salts (HACC) were prepared for wastewater treatment. The adsorption capacities of the PHG hydrogels for nickel (NiII), copper (CuII), and palladium (PdII) ions were 158.68, 182.99, and 229.78 mg/g, respectively. The adsorption process is consistent with the Langmuir adsorption model and quasi-secondary kinetics. For further application of adsorbed metal ions, NaBH4 was selected for in situ reduction to prepare hydrogel-based catalysts cemented with metal nanoparticles (Ni-, Cu- and Pd-NPs), respectively. The PHG-Pd catalysts demonstrated significant catalytic efficiency in reducing 4-nitrophenol and methylene blue, and Kapp were 0.307 and 0.365 min-1, respectively. Among them, the activation parameters for the reduction of 4-NP over PHG-Pd catalyst were calculated as Ea = 36.27 kJ/mol, ΔH# = 33.72 kJ/mol and ΔS# = -259.68 J/(mol·K). This study is expected to provide insights into the design of multifunctional adsorption catalysts for the removal of dyes and nitro compounds from wastewater.

Semi-IPN polysaccharide-based hydrogels for effective removal of heavy metal ions and dyes from wastewater: a comprehensive investigation of performance and adsorption mechanism

The escalating issue of environmental pollutants necessitates efficient, sustainable, and innovative wastewater treatment technologies. This review comprehensively analyzes the mechanisms and isotherms underlying the adsorption processes of semi-interpenetrating polymer network (semi-IPN) polysaccharide-based hydrogels to remove heavy metal ions and dyes from wastewater. Polysaccharides are extensively utilized in hydrogel synthesis due to their biocompatibility, cost-effectiveness, and non-toxic nature. The synthesis of these hydrogels as semi-IPNs enhances their mechanical and structural robustness and adsorption capacity. This review explores the key parameters affecting adsorption performance, including pH, temperature, contact time, and adsorbent dosage. Findings highlight that semi-IPN polysaccharide-based hydrogels exhibit remarkable adsorption capabilities through electrostatic interactions, ion exchange, and surface complexation. Furthermore, this review highlights the distinct advantages of semi-IPNs over other polymer networks. Semi-IPNs offer improved mechanical stability, higher adsorption efficiencies, and better reusability, making them a promising solution for wastewater treatment. Detailed isotherm models, including Langmuir and Freundlich isotherms, were studied to understand these hydrogels' adsorption behavior and capacity for different pollutants. This study highlights the potential of semi-IPN polysaccharide-based hydrogels as effective adsorbents for heavy metals and dyes and as a promising solution for mitigating environmental pollution. The insights provided herein contribute to developing advanced materials for environmental remediation, aligning with global sustainability goals, and advancing wastewater treatment technology.

Efficient removal of high concentration dyes from water by functionalized in-situ N-doped porous biochar derived from waste antibiotic fermentation residue

Using biochar for dye wastewater treatment is attracting interest due to its excellent adsorption properties and low costs. In this work, a novel biochar derived from oxytetracycline fermentation residue (functionalized OFR biochar, FOBC) was investigated as a efficient adsorbent for typical dyes removal. At 25 °C, the maximum adsorption capacity calculated by Langmuir model of FOBC-3-600 for methylene blue (MB), malachite green (MG), and methyl orange (MO) reached 643.97, 617.89, and 521.03 mg/g, respectively. The kinetics and isotherm model fitting showed that the chemisorption and physisorption both occurred during the adsorption process. Dyes were efficiently adsorbed through pore filling, electrostatic attraction, π-π interactions, and surface complexation. And the cycling experiment and environmental risk assessment indicated that the FOBC-3-600 had excellent recyclability and utilization safety. Overall, this study provides a practical method to simultaneously treat the dyeing wastewater and utilize the antibiotic fermentation residue.

Phytic acid-functionalized polyamidoxime/alginate hydrogel for targeted uranium extraction from acidic wastewater

Efficient removal of uranium from radioactive wastewater is crucial for both environmental protection and sustainable development of nuclear energy. However, selectively extracting uranium from acidic wastewater remains a significant challenge. Here we present a phytic acid-functionalized polyamidoxime/alginate hydrogel (PAG) via a facile one-step hydrothermal reaction. The PAG, leveraging the robust binding affinity of phytic acid and the selective coordination of amidoxime for U(VI), exhibited high efficiency and selectivity in adsorbing U(VI) from acidic uranium-containing wastewater. At pH 2.50, U(VI) adsorption equilibrium was achieved within 60 min, showcasing a maximum theoretical adsorption capacity of 218.34 mg/g. Additionally, the PAG demonstrated excellent reusability, maintaining a uranium removal rate exceeding 90 % over five adsorption-desorption cycles. Remarkably, the as-synthesized PAG removed 94.1 % of U(VI) from actual acidic uranium-contaminated groundwater with excellent anti-interference performance, reducing U(VI) concentration from 272.0 μg/L to 16.1 μg/L and making it meet the WHO drinking water standards (30 μg/L). The adsorption mechanism was elucidated through XPS and DFT calculation, revealing that the uranyl ion primarily coordinated with phosphate and amidoxime groups on phytic acid and polyamidoxime, respectively. These findings underscore the promising potential of PAG hydrogel for addressing acidic uranium-containing wastewater from uranium mining and metallurgy.

Unlocking the Potential of CO2 Capture: A Synergistic Hybridization Strategy for Polymeric Hydrogels with Tunable Physicochemical Properties

Unlocking CO2 capture potential remains a complex and challenging endeavor. Here, a blueprint is crafted for optimizing materials through CO2 capture and developing a synergistic hybridization strategy that involves synthesizing CO2-responsive hydrogels by integrating polymeric networks interpenetrated with polyethyleneimine (PEI) chains and inorganic CaCl2. Diverging from conventional CO2 absorbents, which typically serve a singular function in CO2 capture, these hybrid PEAC hydrogels additionally harness its presence to tune their optical and mechanical properties once interacting with CO2. Such synergistic functions entail two significant steps: (i) rapid CO2-fixing through PEI chains to generate abundant carbamic acid and carbamate species and (ii) mineralization via CaCl2 to induce the formation of CaCO3 micro-crystals within the hydrogel matrix. Due to the reversible bonding, the PEAC hydrogels enable the decoupling of CO2 through an acid fumigation treatment or a heating process, achieving dynamic CO2 capture-release cycles up to 8 times. Furthermore, the polyethyleneimine-acrylamide-calcium chloride (PEAC) hydrogel exhibits varying antibacterial attributes and high interfacial adhesive strength, which can be modulated by fine-tuning the compositions of PEI and CaCl2. This versatility underscores the promising potential of PEAC hydrogels, which not only unlocks CO2 capture capabilities but also offers opportunities in diverse biological and biomedical applications.

Exploring feasibility of citric acid infused lignocellulosic waste derived from chestnut and water melon peels for phytofiltration of Eosin yellow dye from water

The adsorption efficiency of cheap, ecofriendly, and easily available agro-waste, Trapa natans (Chestnut) and Citrullus lanatus (Watermelon) peels, has been investigated in their native forms (TNAT and CLAN) as well as citric acid impregnated forms (C-TNAT and C-CLAN), respectively, for the detoxification of toxic, deleterious, and carcinogenic Eosin yellow dye (EYD) from wastewater streams. Different operational parameters were optimized for the investigation of isothermal, kinetic and the thermodynamic models. R2 for sportive decontamination of Eosin by citric acid treated adsorbents were close to one, supporting the applicability of Langmuir, Temkin, and pseudo-second-order in this investigation. Maximum sorption capabilities were 222 and 667 mg/g for chemically treated bio-waste C-TNAT and C-CLAN, respectively, reflecting their efficient and promising performance, while Gibbs free energy revealed exothermic and spontaneous adsorption behavior. The kinetic statics for qe (cal) are quite close to qe (exp), indicating the viability and fitness of pseudo-second-order mechanisms. The present study suggests that both citric acid fabricated bio-waste C-TNAT and C-CLAN can be substantially employed to decontaminate persistent organic pollutants, like: Eosin yellow dye from wastewater using green approach to resolve socio-economic problems of developing countries.

Superabsorbent ZnO/rubber-based hydrogel composite for removal and photocatalytic degradation of methylene blue

A superabsorbent hydrogel was prepared by the free-radical copolymerization of natural rubber (NR) latex with poly(acrylic acid) (PAA) at NR loadings up to 50 wt%. An NR/PAA hydrogel containing 40 wt% of NR (NR-40) had a water absorption capacity of 214 g/g (21,400 %) of its dry weight. The compressive modulus increased 512 % and sample integrity was improved due to the physical entanglement of NR chains. NR-40 hydrogel removed 97 % of methylene blue (MB) from the aqueous solution in 1 h (at initial concentrations of 10-1000 mg/L) and produced a maximum removal of 1191 mg MB/g of hydrogel at an initial MB concentration of 4500 mg/L. The adsorption of MB was an endothermic process. Fourier transform infrared spectroscopy indicated that hydrogen bonding and electrostatic interaction drove the process. After the in-situ incorporation of ZnO into NR-40, absorbed energy from sunlight generated active species that could photocatalytically degrade adsorbed MB in the hydrogel matrix. The scavenger tests indicated that superoxide radical anions and hydroxyl radicals were the main species for this process. The hydrogel composite material showed good stability and could be regenerated and reused over 10 cycles, degrading >80 % of the adsorbed dye. This novel natural-based hydrogel provides double functions of adsorption and photodegradation of toxic dyes without the requirement of chemicals and a separation process.

Efficient Removal of Methylene Blue Dye from Aqueous Media Using Facilely Synthesized Magnesium Borate/Magnesium Oxide Nanostructures

Methylene blue dye in water sources can pose health risks to humans, potentially causing methemoglobinemia, a condition that impairs the blood's ability to carry oxygen. Hence, the current study investigates the synthesis of novel magnesium borate/magnesium oxide (Mg3B2O6/MgO) nanostructures and their efficiency in removing methylene blue dye from aqueous media. The nanostructures were synthesized using the Pechini sol-gel method, which involves a reaction between magnesium nitrate hexahydrate and boric acid, with citric acid acting as a chelating agent and ethylene glycol as a crosslinker. This method helps in achieving a homogeneous mixture, which, upon calcination at 600 and 800 °C, yields Mg3B2O6/MgO novel nanostructures referred to as MB600 and MB800, respectively. The characterization of these nanostructures involved techniques like X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N2 gas analyzer, and field-emission scanning electron microscope (FE-SEM). These analyses confirmed the formation of orthorhombic Mg3B2O6 and cubic MgO phases with distinct features, influenced by the calcination temperature. The mean crystal size of the MB600 and MB800 samples was 64.57 and 79.20 nm, respectively. In addition, the BET surface area of the MB600 and MB800 samples was 74.63 and 64.82 m2/g, respectively. The results indicated that the MB600 sample, with its higher surface area, generally demonstrated better methylene blue dye removal performance (505.05 mg/g) than the MB800 sample (483.09 mg/g). The adsorption process followed the pseudo-second-order model, indicating dependency on available adsorption sites. Also, the adsorption process matched well with the Langmuir isotherm, confirming a homogeneous adsorbent surface. The thermodynamic parameters revealed that the adsorption process was physical, exothermic, and spontaneous. The MB600 and MB800 nanostructures could be effectively regenerated using 6 M HCl and reused across multiple cycles. These findings underscore the potential of these nanostructures as cost-effective and sustainable adsorbents for methylene blue dye removal.

Recent Advances in Preparation and Structure of Polyurethane Porous Materials for Sound Absorbing Application

Various acoustic materials are developed to resolve noise pollution problem in many industries. Especially, materials with porous structure are broadly used to absorb sound energy in civil construction and transportation area. Polyurethane (PU) porous materials possess excellent damping properties, good toughness, and well-developed pore structures, which have a broad application prospect in sound absorption field. This work aims to summarize the recent progress of fabrication and structure for PU porous materials in sound absorption application. The sound absorption mechanisms of porous materials are introduced. Different kinds of structure for typical PU porous materials in sound absorption application are covered and highlighted, which include PU foam, modified PU porous materials, aerogel, templated PU, and special PU porous materials. Finally, the development direction and existing problems of PU material in sound absorption application are briefly prospected. It can be expected that porous PU with high sound absorption coefficient can be obtained by using some facile methods. The design and accurate regulation of porous structures or construction of multilayer sound absorption structure is favorably recommended to fulfill the high demand of industrial and commercial applications in the future work.

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g-1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L-1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

Synergistically enhancing the selective adsorption of cationic dyes through copper impregnation and amino functionality into iron-based metal-organic frameworks

Dyes contaminating the sewages have seriously threatened the living beings and their separation from wastewater in terms of potential resource recovery is of high value. Herein, both of metal node doping and ligand group grafting were taken into account to enhance the adsorption selectivity of Fe-MOFs towards cationic dyes. The positive correlation between copper doping amount and selective coefficient (∂MOMB) for methylene blue (MB) over methyl orange (MO) within a certain range was mainly attributed to the increased surface negative charges via partial replacement of Fe(III) with Cu(II). Moreover, the amount of surface negative charges was further increased after amino functionalization and there was a synergism between Cu(II) and -NH2 in selectivity enhancement. As a result, Fe0.6Cu0.4-BDC-NH2 exhibited a 22.5-times increase in ∂MOMB and other cationic dyes including malachite green (MG) and rhodamine B (Rh. B) could also be selectively separated from binary and quaternary mixed dye systems. Moreover, Fe0.6Cu0.4-BDC-NH2 showed many superiorities like a wide pH range of 4.0-8.0, strong anti-interference ability over various inorganic ions, good recyclability, and stability. The adsorption kinetics and isotherm suggested that the MB adsorption process was a homogeneous single-layer chemisorption. Additionally, the thermodynamics manifested that the overall process was exothermic and spontaneous. According to the FT-IR and XPS spectra analysis, the electrostatic interaction and hydrogen bonding were determined as the main driving forces, and π-π interaction also contributed to the adsorption process.

Enhanced dye sequestration with natural polysaccharides-based hydrogels: A review

Due to the expansion of industrial activities, the concentration of dyes in water has been increasing. The dire need to remove these pollutants from water has been heavily discussed. This study focuses on the reproducible and sustainable solution for wastewater treatment and dye annihilation challenges. Adsorption has been rated the most practical way of the several decolorization procedures due to its minimal initial investment, convenient utility, and high-performance caliber. Hydrogels, which are three-dimensional polymer networks, are notable because of their potential to regenerate, biodegrade, absorb bulky amounts of water, respond to stimuli, and have unique morphologies. Natural polysaccharide hydrogels are chosen over synthetic ones because they are robust, bioresorbable, non-toxic, and cheaply accessible. This study has covered six biopolymers, including chitosan, cellulose, pectin, sodium alginate, guar gum, and starch, consisting of their chemical architecture, origins, characteristics, and uses. The next part describes these polysaccharide-based hydrogels, including their manufacturing techniques, chemical alterations, and adsorption effectiveness. It is deeply evaluated how size and shape affect the adsorption rate, which has not been addressed in any prior research. To assist the readers in identifying areas for further research in this subject, limitations of these hydrogels and future views are provided in the conclusion.

Amino-grafted Biochar as a Novel Photocatalyst for degradation of high concentration dye

Photocatalytic degradation of organic pollution by biochar was a sustainable strategy for waste water remediation, nevertheless, it still suffers drawbacks like low efficiency due to the poor photocatalytic properties of pristine biochar. Herein, amino groups were grafted on the edge sites/defects of biochar by Friedel-Crafts acylation to enhance the degradation of high concentration dye solutions. The results suggested that the amino groups played an important role in imparting photocatalytic properties to biochar. Owing to the strong Lewis basicity and electron-donating ability of amino groups, their interaction with oxygen-containing functional groups/aromatic structures in biochar was improved, which enhanced the electron exchange ability of biochar under visible light irradiation, resulting in excellent degradation performances of high concentration RhB (∼10 times faster than ungrafted biochar). In this work, amino-grafted garlic peel biochar delivered a new idea for the future direction of biochar-based photocatalysis in wastewater remediation.

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.

Efficient Photocatalytic Degradation of Congo Red Dye Using Facilely Synthesized and Characterized MgAl2O4 Nanoparticles

The discharge of congo red dye into water sources by factories has been associated with a range of health concerns, such as cancer, redness, skin irritation, and allergic reactions. As a result, this research focused on the cost-effective and straightforward production of MgAl2O4 nanoparticles by using the Pechini sol-gel process. Subsequently, these nanoparticles were employed for the successful photocatalytic decomposition of congo red dye. Moreover, extensive characterization of the fabricated MgAl2O4 nanoparticles was conducted through diverse methodologies, which included Fourier-transform infrared spectroscopy, ultraviolet-visible spectrophotometry, high-resolution transmission electron microscopy (HR-TEM), field-emission scanning electron microscopy (FE-SEM), and powder X-ray diffraction (XRD). Furthermore, the XRD analysis disclosed that the average crystal size of the produced MgAl2O4 nanoparticles is 10.36 nm, and their optical energy gap was determined to be 3.71 eV. The FE-SEM examination unveiled a combination of spherical and disorganized structures with a 0.14 μm average grain size. HR-TEM analysis, in turn, revealed that the fabricated MgAl2O4 nanoparticles were composed of minuscule spherical particles with an average diameter of 8.75 nm. The maximum degradation of 50 mL of congo red dye at a concentration of 25 mg/L reached 99.27% within 80 min at a pH of 3. Additionally, the findings confirmed the consistent decomposition activity toward congo red dye even after four cycles, thereby validating the effectiveness and reusability of the MgAl2O4 nanoparticles that were developed in this study.

Hemicelluloses hydrogel: Synthesis, characterization, and application in dye removal

Novel materials using biowaste as adsorbents in wastewater treatment have been allocated considerable interest. Herein, we present the synthesis of different hydrogels of crosslinked polyacrylamide in presence of hemicelluloses with/ without bentonite, using a soft reaction condition. The structure of new hydrogels was characterized by spectroscopic, thermal and microscopic experiments. The semi-interpenetrated network with hemicelluloses: 10 %; acrylamide 79 %; bentonite 10 %; N,N,N',N'-tetramethylethylenediamine: 1 % allows reducing 20 % the use of non-renewable acrylamide, without changing its decomposition temperatures and keeping its water absorption capacity. This hydrogel was applied to dye removals, such as rhodamine B, methylene red and methylene blue in aqueous solutions. In the case of methylene blue, highest removal is observed with maximum adsorption of qmax = 140.66 mg/g, compared to material without hemicelluloses that only a qmax = 88.495 mg/g. The adsorption kinetics and equilibrium adsorption isotherms are in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The developed hydrogel from hemicelluloses represents a potential alternative adsorbent for a sustainable system of sewage treatment.

Polymeric hydrogels-based materials for wastewater treatment

Low-cost and reliable wastewater treatment is a relevant issue worldwide to reduce the concentration of environmental pollutants. Industrial effluents containing dyes, heavy metals, and other inorganic and organic compounds can pollute water resources; therefore, novel technologies are required to mitigate and control their release into the environment. Adsorption is one of the simplest methods for treating contaminated water in which a wide spectrum of adsorbents can be used to remove emerging compounds. Hydrogels are interesting materials with high adsorption capacities that can be synthesized via green routes. These adsorbents are promising for large-scale industrial wastewater treatment applications; however, gaps still exist in achieving sustainable commercial implementation. This review focuses on the discussion and analysis of preparation, characterization, and adsorption properties of hydrogels for water purification. The advantages of these polymeric materials for water treatment were analyzed, including their performance in the removal of different organic and inorganic contaminants. Recent advances in the functionalization of hydrogels and the synthesis of novel composites have also been described. The adsorption capacities of hydrogel-based adsorbents are higher than 500 mg/g for different organic and inorganic pollutants, and can reach values of up to >2000 mg/g for organic compounds, significantly outperforming other materials reported for water cleaning. The main interactions involved in the adsorption of water pollutants using hydrogel-based adsorbents were described and explained to allow the interpretation of their removal mechanisms. The current challenges in the implementation of hydrogels for water purification in real-life operations are also highlighted. This review provides an updated picture of hydrogels as interesting materials to address water depollution worldwide.