Recent advances in lignin-based porous materials for pollutants removal from wastewater

Emerging trends in cellulose and lignin-based nanomaterials for water treatment

Several industrial and agricultural practices contribute significantly to water contamination. These activities release several amount of pollutants, including pesticides, heavy metals, and organic compounds, into water sources, posing health risks and causing environmental damage. Industries such as mining, textiles, and pharmaceuticals discharge harmful toxins, further polluting water. Processes like ball-milling, adsorption, filtration, and flocculation are commonly used for wastewater treatment. Recent advancements have focused on the study of green nanomaterials (NMs), particularly cellulose-based and lignin-based NMs, due to their various properties, biodegradability, and low toxicity. This review covers the fabrication methods, modification techniques, and applications of cellulose-based and lignin-based NMs, such as cellulose nanofibers, nanocrystals, lignin-based aerogels, and hydrogels for wastewater treatment. The unique properties of lignin and cellulose, including their high surface area, functionalization, and biocompatibility, make them suitable for water purification. The paper also discusses a SWOT analysis, which will be useful for future researchers, highlighting both opportunities and challenges in this area. This paper aims to provide valuable insights into ongoing research and development in cellulose and lignin-based nanomaterials for next-generation water treatment solutions.

Lignin and Nanolignin: Next-Generation Sustainable Materials for Water Treatment

Water scarcity, contamination, and lack of sanitation are global issues that require innovations in chemistry, engineering, and materials science. To tackle the challenge of providing high-quality drinking water for a growing population, we need to develop high-performance and multifunctional materials to treat water on both small and large scales. As modern society and science prioritize more sustainable engineering practices, water treatment processes will need to use materials produced from sustainable resources via green chemical routes, combining multiple advanced properties such as high surface area and great affinity for contaminants. Lignin, one of the major components of plants and an abundant byproduct of the cellulose and bioethanol industries, offers a cost-effective and scalable platform for developing such materials, with a wide range of physicochemical properties that can be tailored to improve their performance for target water treatment applications. This review aims to bridge the current gap in the literature by exploring the use of lignin, both as solid bulk or solubilized macromolecules and nanolignin as multifunctional (nano)materials for sustainable water treatment processes. We address the application of lignin-based macro-, micro-, and nanostructured materials in adsorption, catalysis, flocculation, membrane filtration processes, and antimicrobial coatings and composites. Throughout the exploration of recent progress and trends in this field, we emphasize the importance of integrating principles of green chemistry and materials sustainability to advance sustainable water treatment technologies.

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.

Lignin and black liquor based composite hydrogels for the enhanced adsorption of malachite green dye from aqueous solutions: Kinetics, rheology and isotherm studies

Effluent from the textile industry, mainly dye wastewater, pollutes the water bodies and the environment. Mostly, malachite green has been used as a staining reagent in biological studies and a dye in the leather, textile, and aquaculture sectors. At present, research is moving towards developing sustainable adsorption-based dye removal systems. The aim of present study was to develop hydrogel from bio-waste for efficient removal of dye and cost effective. Towards this, black liquor (contains mainly lignin and hemicellulose macromolecules) was separated from the corncob through kraft-pulp process. Subsequently, the black liquor (BL) and sodium alginate (SA) were blended in different weight ratios (1:4, 1:2, 3:4 and 1:1) and cross-linked with calcium ion to form a composite hydrogel. The optimized weight ratio of Black liquor/Sodium alginate hydrogel was found to be 1:4 which exhibits maximum adsorption capacity (Qmax = 650 mg/g) for the dye concentration of 1500 mg/l. Furthermore, a comparison study was conducted with alkaline lignin (LN)/ sodium alginate (SA)-based composite hydrogel to validate the adsorption capability of black liquor-based hydrogel at a weight ratio of 1:4. The influence of parameters such as temperature, pH, adsorbent dosage, initial dye concentration was investigated on the malachite green dye removal and also optimized. Both the hydrogels (BL/SA and LN/SA) were further characterized using Field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller, X-ray diffraction, and Rheological techniques. The results showed that the maximum dye removal efficiency of 95.54 % and 94.06 % were observed for 0.25BL/SA and 0.25LN/SA hydrogels respectively in 12 min. The adsorption kinetics showed the pseudo-second-order fit and the adsorption isotherm established a high correlation with the Langmuir model. The reusability tests were performed on Black liquor/Sodium alginate and Alkaline Lignin/Sodium alginate hydrogels, which showed good regenerative performance up to four successive adsorption/desorption cycles. In addition, a thermodynamic study is carried out for adsorption of dye on hydrogel, which demonstrates that it is spontaneous and exothermic in nature. The synthesized composite bio-based hydrogels from this study showed fast and efficient removal of malachite green dye. This makes the hydrogel a potential candidate for the sustainable wastewater treatment.

Optimizing soil remediation with multi-functional L-PH hydrogel: Enhancing water retention and heavy metal stabilization in farmland soil

Agricultural soils face severe challenges, including water scarcity and heavy metal contamination. Optimizing soil remediation efficiency while minimizing inputs is essential. This study assessed the water retention and heavy metal adsorption properties of L-PH hydrogel through aqueous experiments. Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) elucidated the adsorption mechanisms. The results showed that L-PH hydrogel exhibited high water absorption efficiency, with Zn2+ removed via electrostatic interactions and cation exchange, and Cd2+ and Cu2+ adsorbed through coordination complexation. Soil experiments tested water retention and heavy metal leaching under various application methods (M1 = 0-10 cm mixed, M2 = 10-20 cm mixed, T1 = 5-10 cm layered, T2 = 10-15 cm layered) and rates (NL = 0 %, L1 = 0.1 %, L2 = 0.2 %, L3 = 0.5 %). L-PH reduced water infiltration, enhanced soil water retention, and decreased heavy metal mobility across all treatments. The highest water retention was observed in the M1 method. Under M1L1, cumulative leaching of Cd2+, Cu2+, and Zn2+ decreased by 68.84 %, 33.44 %, and 83.60 %, respectively. Two-way ANOVA revealed that application rate had a greater effect on leaching than the method. FTIR and XRD analyses showed that at low concentrations (L1, L2), L-PH formed coordination bonds with Cd2+ and Cu2+, creating Cd(HCOO)2·2(NH2)2CO and Cu(HCOO)(OH) in the soil. Zn2+ was stabilized through adsorption and precipitation, forming Zn(OH)2, thereby reducing leaching. Higher concentrations of L-PH may have further interacted with Zn, leading to dissolution and adsorption/precipitation processes. Redundancy analysis (RDA) analysis suggests that an increase in organic carbon and moisture content in soil aggregates larger than 2 mm, along with a decrease in bioavailable heavy metals, may enhance heavy metal stabilization, reducing their movement and leaching. This study offers valuable insights into addressing the twin challenges of water scarcity and heavy metal pollution.

Lignin-Furanic Rigid Foams: Enhanced Methylene Blue Removal Capacity, Recyclability, and Flame Retardancy

Worldwide, populations face issues related to water and energy consumption. Water scarcity has intensified globally, particularly in arid and semiarid regions. Projections indicate that by 2030, global water demand will rise by 50%, leading to critical shortages, further intensified by the impacts of climate change. Moreover, wastewater treatment needs further development, given the presence of persistent organic pollutants, such as dyes and pharmaceuticals. In addition, the continuous increase in energy demand and rising prices directly impact households and businesses, highlighting the importance of energy savings through effective building insulation. In this regard, tannin-furanic foams are recognized as promising sustainable foams due to their fire resistance, low thermal conductivity, and high water and chemical stability. In this study, tannin and lignin rigid foams were explored not only for their traditional applications but also as versatile materials suitable for wastewater treatment. Furthermore, a systematic approach demonstrates the complete replacement of the tannin-furan foam phenol source with two lignins that mainly differ in molecular weight and pH, as well as how these parameters affect the rigid foam structure and methylene blue (MB) removal capacity. Alkali-lignin-based foams exhibited notable MB adsorption capacity (220 mg g-1), with kinetic and equilibrium data analysis suggesting a multilayer adsorption process. The prepared foams demonstrated the ability to be recycled for at least five adsorption-desorption cycles and exhibited effective flame retardant properties. When exposed to a butane flame for 5 min, the foams did not release smoke or ignite, nor did they contribute to flame propagation, with the red glow dissipating only 20 s after flame exposure.

Synthesis strategies, regeneration, cost analysis, challenges and future prospects of bacterial cellulose-based aerogels for water treatment: A review

Clean water is an integral part of industries, agricultural activities and human life, but water contamination by toxic dyes, heavy metals, and oil spills is increasingly serious in the world. Aerogels with unique properties such as highly porous and extremely low density, tunable surface modification, excellent reusability, and thermal stability can contribute to addressing these issues. Thanks to high purity, biocompatibility and biodegradability, bacterial cellulose can be an ideal precursor source to produce aerogels. Here, we review the modification, regeneration, and applications of bacterial cellulose-based aerogels for water treatment. The modification of bacterial cellulose-based aerogels undergoes coating of hydrophobic agents, carbonization, and incorporation with other materials, e.g., ZIF-67, graphene oxide, nanoparticles, polyaniline. We emphasized features of modified aerogels on porosity, hydrophobicity, density, surface chemistry, and regeneration. Although major limits are relevant to the use of toxic coating agents, difficulty in bacterial culture, and production cost, the bacterial cellulose aerogels can obtain high performance for water treatment, particularly, catastrophic oil spills.

Functional Bio-Based Polymeric Hydrogels for Wastewater Treatment: From Remediation to Sensing Applications

In recent years, many researchers have focused on designing hydrogels with specific functional groups that exhibit high affinity for various contaminants, such as heavy metals, organic pollutants, pathogens, or nutrients, or environmental parameters. Novel approaches, including cross-linking strategies and the use of nanomaterials, have been employed to enhance the structural integrity and performance of the desired hydrogels. The evolution of these hydrogels is further highlighted, with an emphasis on fine-tuning features, including water absorption capacity, environmental pollutant/factor sensing and selectivity, and recyclability. Furthermore, this review investigates the emerging topic of stimuli-responsive smart hydrogels, underscoring their potential in both sorption and detection of water pollutants. By critically assessing a wide range of studies, this review not only synthesizes existing knowledge, but also identifies advantages and limitations, and describes future research directions in the field of chemically engineered hydrogels for water purification and monitoring with a low environmental impact as an important resource for chemists and multidisciplinary researchers, leading to improvements in sustainable water management technology.

Enzymatic crosslinking of lignin nanoparticles and nanocellulose in cryogels improves adsorption of pharmaceutical pollutants

Pharmaceuticals, designed for treating diseases, ironically endanger humans and aquatic ecosystems as pollutants. Adsorption-based wastewater treatment could address this problem, however, creating efficient adsorbents remains a challenge. Recent efforts have shifted towards sustainable bio-based adsorbents. Here, cryogels from lignin-containing cellulose nanofibrils (LCNF) and lignin nanoparticles (LNPs) were explored as pharmaceuticals adsorbents. An enzyme-based approach using laccase was used for crosslinking instead of fossil-based chemical modification. The impact of laccase treatment on LNPs alone produced surface-crosslinked water-insoluble LNPs with preserved morphology and a hemicellulose-rich, water-soluble LNP fraction. The water-insoluble LNPs displayed a significant increase in adsorption capacity, up to 140 % and 400 % for neutral and cationic drugs, respectively. The crosslinked cryogel prepared by one-pot incubation of LNPs, LCNF and laccase showed significantly higher adsorption capacities for various pharmaceuticals in a multi-component system than pure LCNF or unmodified cryogels. The crosslinking minimized the leaching of LNPs in water, signifying enhanced binding between LNPs and LCNF. In real wastewater, the laccase-modified cryogel displayed 8-44 % removal for cationic pharmaceuticals. Overall, laccase treatment facilitated the production of bio-based adsorbents by improving the deposition of LNPs to LCNF. Finally, this work introduces a sustainable approach for engineering adsorbents, while aligning with global sustainability goals.

Lignin nanoparticles as a highly efficient adsorbent for the removal of methylene blue from aqueous media

This work demonstrated enhanced adsorption capabilities of lignin nanoparticles (LNPs) synthesized via a straightforward hydrotropic method compared to pristine lignin (PL) powder for removing methylene blue dye from aqueous solutions. Kraft lignin was used as a precursor and p-toluenesulfonic acid as the hydrotrope to produce spherical LNPs with ~ 200 nm diameter. Extensive characterization by SEM, AFM, DLS, zeta potential, and BET verified successful fabrication of microporous LNPs with fourfold higher specific surface area (14.9 m2/g) compared to PL (3.4 m2/g). Significantly reduced particle agglomeration and rearranged surface chemistry (zeta potential of -13.3 mV) arising from the self-assembly of lignin fractions under hydrotropic conditions enabled the application of LNPs and superior adsorbents compared to PL. Batch adsorption experiments exhibited up to 14 times higher methylene blue removal capacity, from 20.74 for PL to 127.91 mg/g for LNPs, and ultrafast equilibrium uptake within 3 min for LNPs compared to 10 min for PL. Kinetic modeling based on pseudo-first-order and pseudo-second-order equations revealed chemisorption as the predominant mechanism, with a rate constant of 0.032825 g/mg·h for LNPs-over an order of magnitude higher than PL (0.07125 g/mg·h). Isotherm modeling indicated Langmuir monolayer adsorption behavior on relatively uniform lignin surface functional groups. The substantially augmented adsorption performance of LNPs arose from the increased surface area and abundance of surface functional groups, providing greater accessibility of chemically active binding sites for rapid dye uptake. Overall, this work demonstrates that tailoring lignin nanoparticle structure and surface chemistry via scalable hydrotropic synthesis is a simple and sustainable approach for producing highly efficient lignin-based nano-adsorbents for organic dye removal from industrial wastewater.

Revealing the structural changes of lignin in Chinese quince (Chaenomeles sinensis) fruit as it matures

Chinese quince fruits (Chaenomeles sinensis) contain substantial amounts of lignin; however, the exact structure of lignin remains to be investigated. In this study, milled wood lignins (Milled wood lignin (MWL)-1, MWL-2, MWL-3, MWL-4, MWL-5, and MWL-6) were extracted from fruits harvested once a month from May to October 2019 to investigate their structural evolution during fruit growth. The samples were characterized via High-performance anion exchange chromatography (HPAEC), Fourier transform-infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermogravimetric (TGA), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and NMR (2D-heteronuclear single quantum coherence (HSQC) and 31P). The MWL samples in all fruit growth stages were GS-type lignin and lignin core undergoing minimal alterations during fruit development. The predominant linkage in the lignin structure was β-O-4', followed by β-β' and β-5'. Galactose and glucose were the main monosaccharides associated with MWL. In MWL-6, the lignin exhibited the highest homogeneity and thermal stability. As the fruit matured, a gradual increase in the β-O-4' proportion and the ratio of S/G was observed. The results provide comprehensive characterization of the cell wall lignin of quince fruit as it matures. This study could inspire innovative applications of quince fruit lignin and provide the optimal harvest time for lignin utilization.

Porous lignin-based composites for oil/water separation: A review

Frequent oceanic oil spill incidents and the discharge of industrial oily wastewaters have caused serious threats to environments, food chains and human beings. Lignin wastes with many reactive groups exist as the byproducts from bioethanol and pulping processing industries, and they are either discarded as wastes or directly consumed as a fuel. To make full use of lignin wastes and simultaneously deal with oily wastewaters, porous lignin-based composites have been rationally designed and prepared. In this review, recent advances in the preparation of porous lignin-based composites are summarized in terms of aerogels, sponges, foams, papers, and membranes, respectively. Then, the mechanisms and the application of porous lignin-based adsorbents and filtration materials for oil/water separation are discussed. Finally, the challenges and perspectives of porous lignin-based composites are proposed in the field of oil/water separation. The utilization of abundant lignin wastes can replace fossil resources, and meanwhile porous lignin-based composites can be used to efficiently treat with oily wastewaters. The above utilization strategy opens an avenue to the rational design and preparation of lignin wastes with high-added value, and gives a possible solution to use lignin wastes in a sustainable and environmentally friendly way.

Emerging environmentally friendly bio-based nanocomposites for the efficient removal of dyes and micropollutants from wastewater by adsorption: a comprehensive review

Water scarcity will worsen due to population growth, urbanization, and climate change. Addressing this issue requires developing energy-efficient and cost-effective water purification technologies. One approach is to use biomass to make bio-based materials (BBMs) with valuable attributes. This aligns with the goal of environmental conservation and waste management. Furthermore, the use of biomass is advantageous because it is readily available, economical, and has minimal secondary environmental impact. Biomass materials are ideal for water purification because they are abundant and contain important functional groups like hydroxyl, carboxyl, and amino groups. Functional groups are important for modifying and absorbing contaminants in water. Single-sourced biomass has limitations such as weak mechanical strength, limited adsorption capacity, and chemical instability. Investing in research and development is crucial for the development of efficient methods to produce BBMs and establish suitable water purification application models. This review covers BBM production, modification, functionalization, and their applications in wastewater treatment. These applications include oil-water separation, membrane filtration, micropollutant removal, and organic pollutant elimination. This review explores the production processes and properties of BBMs from biopolymers, highlighting their potential for water treatment applications. Furthermore, this review discusses the future prospects and challenges of developing BBMs for water treatment and usage. Finally, this review highlights the importance of BBMs in solving water purification challenges and encourages innovative solutions in this field.

Process optimization of adsorptive phytoremediation of mutagenic brilliant green dye for health risk management using chemically activated Symplocos racemosa agro-waste

Textile industries use large amounts of water as well as dyes. These dyes containing water are then discharged into the water bodies causing a significant role in water pollution. Brilliant Green dye contributes to many harmful diseases related to the respiratory and gastrointestinal tract. In this study, Symplocos racemosa (SR) agro-waste was chemically treated with acid (SR-HCl) and base (SR-NaOH) and then used for removing Brilliant Green Dye (BGD) on the batch scale. They were characterized by SEM, EDX, FTIR, XRD, TGA and DSC. Optimized conditions were 30 °C temperature, pH 6, adsorbent dose of 0.10 g/25 ml dye solution, shaking speed of 100 revolutions per minute, initial dye concentration of 50 ppm and 35 min time for shaking adsorbent and dye solution. Adsorption data obtained were analyzed using isotherms. The experimental data was found to fit well with the Langmuir model and the maximum adsorption capacity (qmax) of BGD on the SR, SR-HCl, and SR-NaOH was revealed to be 62.90, 65.40, and 71 mg/g respectively. Kinetic data (pseudo-first-order and pseudo-second-order) were evaluated and adsorption tends to follow the pseudo-2nd-order, which indicated the chemisorption mechanism. The results revealed that Symplocos racemosa agro-waste can be considered as the potential biosorbent.

Synthesis and Applications of Hybrid Polymer Networks Based on Renewable Natural Macromolecules

Macromolecules obtained from renewable natural sources are gaining increasing attention as components for a vast variety of sustainable polymer-based materials. Natural raw materials can facilitate continuous-flow production due to their year-round availability and short replenishment period. They also open new opportunities for chemists and biologists to design and create "bioreplacement" and "bioadvantaged" polymers, where complex structures produced by nature are being modified, upgraded, and utilized to create novel materials. Bio-based macromonomers are expected not only to compete with but to replace some petroleum-based analogs, as well. The development of novel sustainable materials is an ongoing and very dynamic process. There are multiple strategies for transforming natural macromolecules into sophisticated value-added products. Some methods include chemical modification of macromolecules, while others include blending several components into one new system. One of the most promising approaches for incorporating renewable macromolecules into new products is the synthesis of hybrid networks based on one or more natural components. Each one has unique characteristics, so its incorporation into a network brings new sustainable materials with properties that can be tuned according to their end-use. This article reviews the current state-of-the-art and future potential of renewable natural macromolecules as sustainable building blocks for the synthesis and use of hybrid polymer networks. The most recent advancements and applications that involve polymers, such as cellulose, chitin, alginic acid, gellan gum, lignin, and their derivatives, are discussed.

Surface Modification of a Lignin-Derived Carbon-Supported Co-Based Metal/Oxide Nanostructure for Alkaline Water Splitting

Exploring low-cost and eco-friendly bifunctional electrocatalysts of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolytes is still highly desired, and is crucial for water electrolysis and sustainable hydrogen generation. In this work, we report a facile pyrolysis-oxidation strategy to convert by-product lignin into bifunctional OER/HER electrocatalysts (Co/Co3O4-NPC-400) composed of Co/Co3O4 anchored on N-doped carbon with a surface of rich oxygen vacancies and oxygen-containing groups. The co-pyrolysis of lignin and NH4Cl can achieve a N-doped carbon matrix with a hierarchical pore structure, while the air-annealing process can induce the formation of oxygen-containing groups and oxygen vacancies. Owing to its surface properties, hierarchical pore structure and multiple active components, the constructed Co/Co3O4-NPC-400 possesses bifunctional catalytic activity and superior stability for OER/HER, especially for unexpected OER activity with a high current density of about 320 mA∙cm-2 at a potential of 1.8 V (vs. RHE). Water electrolysis using Co/Co3O4-NPC-400 as both the anode and the cathode needs a cell voltage of 1.95 and 2.5 V to attain about 10 and 400 mA∙cm-2 in 1 M KOH. This work not only provides a general strategy for the preparation of carbon-supported electrocatalysts for water splitting, but also opens up a new avenue for the utilization of lignin.

Enhancement of adsorption efficiency of crystal violet and chlorpyrifos onto pectin hydrogel@Fe3O4-bentonite as a versatile nanoadsorbent

The magnetic mesoporous hydrogel-based nanoadsornet was prepared by adding the ex situ prepared Fe₃O₄ magnetic nanoparticles (MNPs) and bentonite clay into the three-dimentional (3D) cross-linked pectin hydrogel substrate for the adsorption of organophosphorus chlorpyrifos (CPF) pesticide and crystal violet (CV) organic dye. Different analytical methods were utilized to confirm the structural features. Based on the obtained data, the zeta potential of the nanoadsorbent in deionized water with a pH of 7 was - 34.1 mV, and the surface area was measured to be 68.90 m²/g. The prepared hydrogel nanoadsorbent novelty owes to possessing a reactive functional group containing a heteroatom, a porous and cross-linked structure that aids convenient contaminants molecules diffusion and interactions between the nanoadsorbent and contaminants, viz., CPF and CV. The main driving forces in the adsorption by the Pectin hydrogel@Fe₃O₄-bentonite adsorbent are electrostatic and hydrogen-bond interactions, which resulted in a great adsorption capacity. To determine optimum adsorption conditions, effective factors on the adsorption capacity of the CV and CPF, including solution pH, adsorbent dosage, contact time, and initial concentration of pollutants, have been experimentally investigated. Thus, in optimum conditions, i.e., contact time (20 and 15 min), pH 7 and 8, adsorbent dosage (0.005 g), initial concentration (50 mg/L), T (298 K) for CPF and CV, respectively, the CPF and CV adsorption capacity were 833.333 mg/g and 909.091 mg/g. The prepared pectin hydrogel@Fe₃O₄-bentonite magnetic nanoadsorbent presented high porosity, enhanced surface area, and numerous reactive sites and was prepared using inexpensive and available materials. Moreover, the Freundlich isotherm has described the adsorption procedure, and the pseudo-second-order model explained the adsorption kinetics. The prepared novel nanoadsorbent was magnetically isolated and reused for three successive adsorption-desorption runs without a specific reduction in the adsorption efficiency. Therefore, the pectin hydrogel@Fe₃O₄-bentonite magnetic nanoadsorbent is a promising adsorption system for eliminating organophosphorus pesticides and organic dyes due to its remarkable adsorption capacity amounts.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Natural phenol-inspired porous polymers for efficient removal of tetracycline: Experimental and engineering analysis

Efficient and feasible removal of trace antibiotics from wastewater is extremely important due to its environmental persistence, bioaccumulation, and toxicity, but still remains a huge challenge. Herein, three natural phenol-inspired porous organic polymers were fabricated from natural phenolic-derived monomers (p-hydroxy benzaldehyde, 2,4-dihydroxy benzaldehyde and 2,4,6-trihydroxy benzaldehyde) and melamine via polycondensation reaction. Characterization highlighted that the increasing contents of hydroxyl groups in monomers induced an increase of the polymer total porosity and promoted the formation of a highly microporous structure. With mesopore-dominated pore (average pore diameter 9.6 nm) and large pore volume (1.78 cm³/g), p-hydroxy benzaldehyde-based porous polymer (1-HBPP) exhibited ultra-high maximum adsorption capacity (q_max) of 697.6 mg/g for tetracycline (TC) antibiotic. Meanwhile, the porous networks and plentiful active sites of 1-HBPP enabled fast adsorption kinetics (within 10 min) for TC removal, which could be well described by the pseudo-second-order model. Dynamic adsorption studies showed that 1-HBPP could be used in fixed-bed adsorption column (FBAC) with high removal efficiency (breakthrough volume per unit mass, 13.2 L/g) and dynamic adsorption capacity (201.6 mg/g), which were much higher than other reported adsorbents. The breakthrough curves both well matched with Thomas and Yoon-Nelson models in FBAC treatment. Moreover, removal mechanism analysis affirmed that pore-filling, hydrogen bonding, electrostatic interactions and π-π stacking interactions were main driving forces for TC adsorption. The prepared natural phenol-inspired porous adsorbents show great potential in antibiotics removal from wastewater, and this strategy would promote the sustainable and high-value utilization of natural phenolic compounds.

One-pot preparation of magnetic nitrogen-doped porous carbon from lignin for efficient and selective adsorption of organic pollutants

Organic pollutants pose a serious threat to water environment, thus it is essential to develop high-performance adsorbent to remove them from wastewater. Herein, nitrogen-doped magnetic porous carbon (M-PLAC) with three-dimensional porous structure was synthesized from lignin to adsorb methylene blue (MB) and tetracycline (TC) in wastewater. The calculated equilibrium adsorption amount by M-PLAC for MB and TC was 645.52 and 1306.00 mg/g, respectively. The adsorption of MB and TC on M-PLAC conformed to the pseudo-second-order kinetic model. The removal of MB by M-PLAC showed fast and efficient characteristics and exhibited high selectivity for TC in a binary system. In addition, M-PLAC was suitable for a variety of complex water environments and had good regeneration performance, demonstrating potential advantages in practical wastewater treatment. The organic pollutant adsorption by M-PLAC was attributed to electrostatic interaction, hole filling effect, hydrogen bonding, and the π-π interaction.

Facile synthesis of Cu NPs@Fe3O4-lignosulfonate: Study of catalytic and antibacterial/antioxidant activities

Environmental pollution is one of the important concerns for human health. There are different types of pollutants and techniques to eliminate them from the environment. We hereby report an efficient method for the remediation of environmental contaminants through the catalytic reduction of the selected pollutants. A green method has been developed for the immobilization of copper nanoparticles on magnetic lignosulfonate (Cu NPs@Fe₃O₄-LS) using the aqueous extract of Filago arvensis L. as a non-toxic reducing and stabilizing agent. The characterization of the prepared Cu NPs@Fe₃O₄-LS was achieved by vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), scanning TEM (STEM), thermogravimetry-differential thermal analysis (TG/DTA), fast Fourier transform (FFT), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron (XPS) analyses. The synthesized Cu NPs@Fe₃O₄-LS was applied as a magnetic and green catalyst in the reduction of Congo Red (CR), 4-nitrophenol (4-NP), and methylene blue (MB). The progress of the reduction reactions was monitored by UV-Vis spectroscopy. Finally, the biological properties of the Cu NPs@Fe₃O₄-LS were investigated. The prepared catalyst demonstrated excellent catalytic efficiency in the reduction of CR, 4-NP, and MB in the presence of sodium borohydride (NaBH₄) as the reducing agent. The appropriate magnetism of Cu NPs@Fe₃O₄-LS made its recovery very simple. The advantages of this process include a simple reaction set-up, high and catalytic antibacterial/antioxidant activities, short reaction time, environmentally friendliness, high stability, and easy separation of the catalyst. In addition, the prepared Cu NPs@Fe₃O₄-LS could be reused for four cycles with no significant decline in performance.

Comparative Evaluation of the Adsorption Performance of Citric Acid-Treated Peels of Trapa natans and Citrullus lanatus for Cationic Dyes Degradation from Water

Various chemicals were explored in chemical combinations with two selected agrowastes in order to optimize, enhance, and improve their biosorption potential for the optimal and effective eradication of noxious, carcinogenic, and malignant cationic and basic dyes from wastewater. In this project, environmentally safe, economic, inexpensive, and widely available peels of Trapa natans (TP) and Citrullus lanatus (CP) were collected, dried, and pretreated with citric acid, revealing promising results. FT-IR and SEM characterizations of chemically changed biosorbents (C-TP and C-CP) have evidenced the presence of more secondary adsorption sites on their surfaces. These acid-modified biosorbents were employed to eliminate the hazardous and toxic basic dyes such as Rhodamine B (RAD) and Brilliant Green Dye (BLG) in batch mode processing. The Langmuir model was best fitted to equilibrium experimental data as compared to Freundlich and Temkin isothermal mathematical models with Qmax of 15.63 and 27.55 mg/g for RAD using C-TP and C-CP, respectively, whereas, for BLG on C-TP and C-CP, it was 128 and 189 mg/g, respectively. Therefore, the mechanism is related to chelation and ion exchange modes between adsorbate molecules and adsorbent surfaces, leading to homogeneous and monolayer adsorption and following pseudo-2nd-order kinetics in the best way. Thermodynamic parameters such as ΔG0, ΔS0, ΔH0, and ΔE0 are determined statistically for the adsorption performance of both novel chemically mutant biosorbents, which reflect that biosorption mechanisms are exothermic as well as spontaneous.

Review of the Recent Advances in Electrospun Nanofibers Applications in Water Purification

Recently, nanofibers have come to be considered one of the sustainable routes with enormous applicability in different fields, such as wastewater treatment. Electrospun nanofibers can be fabricated from various materials, such as synthetic and natural polymers, and contribute to the synthesis of novel nanomaterials and nanocomposites. Therefore, they have promising properties, such as an interconnected porous structure, light weight, high porosity, and large surface area, and are easily modified with other polymeric materials or nanomaterials to enhance their suitability for specific applications. As such, this review surveys recent progress made in the use of electrospun nanofibers to purify polluted water, wherein the distinctive characteristics of this type of nanofiber are essential when using them to remove organic and inorganic pollutants from wastewater, as well as for oil/water (O/W) separation.

Recent Progress and Potential Biomedical Applications of Electrospun Nanofibers in Regeneration of Tissues and Organs

Electrospun techniques are promising and flexible technologies to fabricate ultrafine fiber/nanofiber materials from diverse materials with unique characteristics under optimum conditions. These fabricated fibers/nanofibers via electrospinning can be easily assembled into several shapes of three-dimensional (3D) structures and can be combined with other nanomaterials. Therefore, electrospun nanofibers, with their structural and functional advantages, have gained considerable attention from scientific communities as suitable candidates in biomedical fields, such as the regeneration of tissues and organs, where they can mimic the network structure of collagen fiber in its natural extracellular matrix(es). Due to these special features, electrospinning has been revolutionized as a successful technique to fabricate such nanomaterials from polymer media. Therefore, this review reports on recent progress in electrospun nanofibers and their applications in various biomedical fields, such as bone cell proliferation, nerve regeneration, and vascular tissue, and skin tissue, engineering. The functionalization of the fabricated electrospun nanofibers with different materials furnishes them with promising properties to enhance their employment in various fields of biomedical applications. Finally, we highlight the challenges and outlooks to improve and enhance the application of electrospun nanofibers in these applications.

Structural characterizations of lignins extracted under same severity using different acids

As the vital renewable feedstock originated from carbon-neutral resources, due to prominent aromaticity lignin owns the potential to produce high value-added products. Multi-functional lignin valorization demands efficient lignin extraction at milder conditions to keep its structure intact to substitute petroleum-based reactants. Lignin extraction severity (LES) is considered as the primary factor affecting the structure of extracted lignin and ultimately determines its applications. Except for the LES, the selection of suitable reagents for lignin extraction concerned with specific applications is crucially important. To explore the influence of different reagents, this study focused on lignin extraction employing the commonly used strong acids at the same LES. Four lignin preparations were extracted using 80% aqueous dioxane with the addition of H₂O (L1), HCl, H₂SO₄ and HNO₃ (pH = 1.30 ± 0.01 L2, L3 and L4, respectively). Analytical high-sensitive NMR (³¹P and 2D-HSQC) together with other characterizations (FTIR and GPC) were successfully employed and quantified while unveiling the structural heterogeneity among extracted lignin preparations. At the same LES, different reagents yielded lignin with varying structural characteristics and were potentially suitable for different applications.

Efficient and selective removal of Pb(ii) from aqueous solution by a thioether-functionalized lignin-based magnetic adsorbent

The effective and selective removal of heavy metal ions from sewage is a major challenge and is of great significance to the treatment and recovery of metal waste. Herein, a novel magnetic lignin-based adsorbent L@MNP was synthesized by a thiol-ene click reaction under ultraviolet (UV) light irradiation. Multiple characterization techniques, including Fourier transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), elemental analysis, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirmed the formed nano-morphology and structure of L@MNP. The effects of pH, contact time, initial metal concentration and temperature on the batch adsorption of Pb(ii) by L@MNP were investigated. Due to the existence of sulfur and oxygen-containing sites, the maximum adsorption capacity of L@MNP for Pb(ii) could reach 97.38 mg g^-1, while the adsorption equilibrium was achieved within 30 min. The adsorption kinetics and isotherms were well described by the pseudo-second-order model and Langmuir model, respectively, suggesting a chemical and monolayer adsorption process. In addition, L@MNP showed a high adsorption selectivity (k _Pb = 0.903) toward Pb(ii) in the presence of other co-existing metal ions. The experimental results also revealed that L@MNP displayed structural stability, ease of recovery under an external magnetic field, and acceptable recyclability after the fifth cycle. Considering its facile preparation, low cost and high adsorption efficiency, the developed L@MNP adsorbent demonstrated great potential in removing heavy metal ions from wastewater.