Efficient adsorption of methylene blue and lead ions in aqueous solutions by 5-sulfosalicylic acid modified lignin

Lignin: A valuable and promising bio-based absorbent for dye removal applications

The importance of environmental issues and the existence of humans have led to the recognition of environmental concerns as the main risk to modern life. Notably, one major concern for protecting and managing the environment and human health is the presence of dyes in wastewater. Therefore, before discharging wastewater into mainstream water, it is crucial to remove dyes. Among all lignocellulosic materials, lignin is a highly fragrant biopolymer. Its abundant availability, complex structure, and numerous functional moieties, including hydroxyl, carboxyl, and phenolic, are used in different chemicals and applications. Based on this, lignin is a very useful green material for adsorption, specifically in removing both heavy metals and organic pollutants from wastewater. This article describes the use of lignin-based adsorbents as a recent breakthrough in the removal of dye from aqueous solutions. On the other hand, the review intends to encourage readers to study both established and novel avenues in lignin-based dye removal materials.

Non-destructive strategy to extract sustainable helix and high-strength Musa core fibers for rapid water conduction and evaporation

The reuse and development of natural waste resources is a hotspots and challenges in the research of new fiber materials and the resolution of environmental concern globally. Herein, this study aimed to develop a simple and direct manual extraction process to extract Musa core fibers (MCFs) for rapid water conduction and evaporation. Through simple processes such as ring cutting and stretching, this green and non-destructive inside-out extraction strategy enabled Musa fibers to be naturally and harmlessly degummed from natural Musa stems, with good maintenance of the fiber structure and highly helical morphology. The extracted fibers are composed of regularly and closely arranged cellulose nanofibrils in the shape of ribbon spirally arranged multi-filaments, and the single filament is about 2.65 μm. The high-purity fibers exhibit ultra-high tensile strength under a non-destructive extraction process, and the ultimate tensile strength in dry state is as high as 742.95 MPa. The tensile strength is affected by the number of fiber bundles, which shows that tensile strength and tensile modulus is higher than those of vascular bundle fibers in dry or wet condition. In addition, the MCFs membrane indicates good water conductivity, with a water absorption height of 50 mm for the sample in only 60 s. Moreover, the water evaporation rate of MCFs reaches 1.37 kg m-2 h-1 in 30 min, which shows that MCFs have excellent water conductivity and evaporation rate compared with ordinary cotton fibers. These results indicate that MCFs have great potential in replacing the use of chemical methods to extract fibers from vascular bundles, providing an effective way to achieve sustainability in quick-drying applications, as well as in the sustainable development of natural waste resources.

Selective adsorption of Cr(VI) by nitrogen-doped hydrothermal carbon in binary system

Selective adsorption of heavy metal ions from industrial effluent is important for healthy ecosystem development. However, the selective adsorption of heavy metal pollutants by biochar using lignin as raw material is still a challenge. In this paper, the lignin carbon material (N-BLC) was synthesized by a one-step hydrothermal carbonization method using paper black liquor (BL) as raw material and triethylene diamine (TEDA) as nitrogen source. N-BLC (2:1) showed excellent selectivity for Cr(VI) in the binary system, and the adsorption amounts of Cr(VI) in the binary system were all greater than 150 mg/g, but the adsorption amounts of Ca(II), Mg(II), and Zn(II) were only 19.3, 25.5, and 6.3 mg/g, respectively. The separation factor (SF) for Cr(VI) adsorption was as high as 120.0. Meanwhile, FTIR, elemental analysis and XPS proved that the surface of N-BLC (2:1) contained many N- and O- containing groups which were favorable for the removal of Cr(VI). The adsorption of N-BLC (2:1) followed the Langmuir model and its maximum theoretical adsorption amount was 618.4 mg/g. After 5th recycling, the adsorption amount of Cr(VI) by N-BLC (2:1) decreased about 15%, showing a good regeneration ability. Therefore, N-BLC (2:1) is a highly efficient, selective and reusable Cr(VI) adsorbent with wide application prospects.

Polymerized PEI-modified lignin polyphenolic materials by acid hydrolysis-phase separation for removal of Cr (VI) from industrial wastewater

Cr (VI) accumulates in an aqueous environment and exhibits huge harm to human health and the ecological system. Developed lignin biomass materials are complicated to prepare and have limited properties, and advances in lignin phenolic modification are lacking. Herein, an aminated poplar lignin-pyrogallol (PLP-PEI) with a simple design and adjustable phenolic hydroxyl content was developed using the acid hydrolysis-phase separation (AH-PS) method, and modified by the atom transfer radical polymerization (ATRP) strategy. Through diverse characterization analysis, the structural changes of PLP-PEI in the step-by-step synthesis process were monitored. An effective biomass capture system (Bio-Cap) was shown via systematically investigating the adsorption behaviors of Cr (VI) on PLP-PEI under various environmental conditions. Benefiting from introducing phenolic hydroxyl and amino groups, PLP-PEI demonstrated efficient adsorption capacity (598.80 mg/g for Cr (VI)). Additionally, the material also exhibited advantages, including monomeric chemisorption properties, strong reduction capability, and stable regeneration properties. Multiple driving forces were involved in the capture and removal process of Cr (VI), including complexation and electrostatic interaction. The low-cost natural biomass resources supported the industrial-scale synthesis and practical application of advanced aminated lignin polyphenol material, which showed outstanding advantages and enormous potential in the field of water environmental restoration.

Recent advances in cellulose-based sustainable materials for wastewater treatment: An overview

Water pollution presents a significant challenge, impacting ecosystems and human health. The necessity for solutions to address water pollution arises from the critical need to preserve and protect the quality of water resources. Effective solutions are crucial to safeguarding ecosystems, human health, and ensuring sustainable access to clean water for current and future generations. Generally, cellulose and its derivatives are considered potential substrates for wastewater treatment. The various cellulose processing methods including acid, alkali, organic & inorganic components treatment, chemical treatment and spinning methods are highlighted. Additionally, we reviewed effective use of the cellulose derivatives (CD), including cellulose nanocrystals (CNCs), cellulose nano-fibrils (CNFs), CNPs, and bacterial nano-cellulose (BNC) on waste water (WW) treatment. The various cellulose processing methods, including spinning, mechanical, chemical, and biological approaches are also highlighted. Additionally, cellulose-based materials, including adsorbents, membranes and hydrogels are critically discussed. The review also highlighted the mechanism of adsorption, kinetics, thermodynamics, and sorption isotherm studies of adsorbents. The review concluded that the cellulose-derived materials are effective substrates for removing heavy metals, dyes, pathogenic microorganisms, and other pollutants from WW. Similarly, cellulose based materials are used for flocculants and water filtration membranes. Cellulose composites are widely used in the separation of oil and water emulsions as well as in removing dyes from wastewater. Cellulose's natural hydrophilicity makes it easier for it to interact with water molecules, making it appropriate for use in water treatment processes. Furthermore, the materials derived from cellulose have wider application in WW treatment due to their inexhaustible sources, low energy consumption, cost-effectiveness, sustainability, and renewable nature.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

Preparation, characterization, and adsorption performance of porous polyamine lignin microsphere

In this study, a porous polyamine lignin microsphere (PPALM) was prepared through the inverse suspension polymerization combined with freeze-drying, during which sodium lignosulfonate and polyetheramine (PEA) were crosslinked with epichlorohydrin (ECH) as the cross-linker. By adjusting the amount of ECH and PEA, the optimized PPALM exhibited suitable crosslinking degree, ensuring a balance of framework flexibility and rigidity, thereby facilitating the formation of abundant and fine pores. PPALM demonstrated good mechanical properties comparable to commercial sulfonated polystyrene cationic resin, with a porosity of 61.12 % and an average pore size of 283.51 nm. The saturation adsorption capacity of PPALM for Pb2+ was measured to be 156.82 mg/g, and it remained above 120 mg/g after five cycles of regeneration. Particularly, the concentration of 50 mg/L Pb2+ solution could be reduced to 0.98 mg/L after flowing through the PPALM packed bed, indicating the great potential of PPALM for application in wastewater treatment.

Separation of dye from aqueous solution by a new gravity compression and aeration system

Filtration is one of the important technologies for separating suspended particles. Under the condition of gravity compression, the filtration density can be increased and the separation effect of suspended particles can be improved. Considering the complex composition and the difficulty in degrading dye in industrial wastewater, a gravity compression aeration system with a modified polyester fibre ball (denoted as MPFB) was evaluated for the separation of dye from water. Congo red azo dye solution (0-40 mg/L) was selected as the model treatment compound. The MPFB was prepared by adjusting the concentrations of alkali (Quality score 0-25%), β-cyclodextrin (0∼80 g/L), reaction temperature (40-90°C), and silane coupler concentration (Concentration fractions 0-0.8%). We used Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) to characterise the MPFB. The separation was affected significantly by adsorption conditions such as MPFB dose and pH. The lower the MPFB dose, the higher the expected adsorption capacity. For the treatment of a dye solution at 500 mg/L, 100% removal was achieved with 48 g/L MPFB, at pH 8 during adsorption under non-circulation aeration. For 24 h of reaction, the system could reach the maximum adsorption capacity of 11.2 mg/g, which followed the pseudo-first order kinetics model and the intraparticle diffusion model. We discovered that circulation aeration provided the best adsorption and electrostatic and hydrogen bonding were the dominant components of adsorption. Overall, the system is a promising technology and has the potential to treat large volumes of dye wastewater.

Cost-effective removal of toxic methylene blue dye from textile effluents by new integrated crosslinked chitosan/aspartic acid hydrogels

Chitosan/aspartic acid hydrogels were synthesized for MB dye removal from textile aqueous effluents with different ratios by gelation of chitosan with non-toxic gelling agent, crosslinker, glutaraldehyde (Glu). The obtained hydrogels were characterized by spectral and morphological techniques. The characterization techniques confirmed successful preparations and MB dye adsorption. Batch experiments were done to investigate the effects of adsorbent dose, pH, contact time, temperature, and initial MB dye concentration. The optimum conditions were: adsorbent dose 0.1 g, pH 5, contact time 30 min, and temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 1 (CSAA-HG1) and adsorbent dose 0.4 g, pH 2, contact time 60 min, temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 2 (CSAA-HG2). Adsorption capacity of newly hydrogels CSAA-HG1,2 was compared with each other. Adsorption efficiencies reached 99.85 % for CSAA-HG1 and 99.88 % for CSAA-HG2. MB dye adsorption on CSAA-HG1,2 followed Freundlich isotherm model (R2 = 0.94 and 0.92, respectively). Both adsorbents exhibited pseudo-second-order kinetics for MB dye adsorption (R2 = 1). The negative ΔHo indicated that the MB dye adsorption was exothermic, negative ΔGo confirmed that MB dye adsorption process was spontaneous and low values of ∆So indicated low degree of freedom, ordered MB dye molecules on CSAA-HG1,2 surfaces.

Polydopamine-modification of a magnetic composite constructed from citric acid-cross-linked cyclodextrin and graphene oxide for dye removal from waters

The effect of polydopamine (PDA) modification on aminated Fe₃O₄ nanoparticles (Fe₃O₄-NH₂)/graphite oxide (GO)/β-cyclodextrin polymer cross-linked by citric acid (CDP-CA) composites were studied for the removal of a cationic dye (methylene blue, MB) and an anionic dye (Congo red, CR) from waters. The micro-structural and magnetic characterizations confirmed the successful preparation of Fe₃O₄-NH₂/GO/CDP-CA and PDA/Fe₃O₄-NH₂/GO/CDP-CA composites. The maximum MB and CR adsorption capacities of Fe₃O₄-NH₂/GO/CDP-CA were 75 mg/g and 104 mg/g, respectively, while the corresponding amounts for PDA/Fe₃O4-NH₂/GO/CDP-CA composite were 195 mg/g and 64 mg/g, respectively. The dye sorption behaviors of these two composites were explained by their corresponding surface-charged properties according to the measured zeta potential results. Moreover, the high saturation magnetizations and the stable dye removal rate in the adsorption-desorption cycles indicated the good recyclability and reusability of the fabricated composites.

Biomass carbon mining to develop nature-inspired materials for a circular economy

A transition from a linear to a circular economy is the only alternative to reduce current pressures in natural resources. Our society must redefine our material sources, rethink our supply chains, improve our waste management, and redesign materials and products. Valorizing extensively available biomass wastes, as new carbon mines, and developing biobased materials that mimic nature's efficiency and wasteless procedures are the most promising avenues to achieve technical solutions for the global challenges ahead. Advances in materials processing, and characterization, as well as the rise of artificial intelligence, and machine learning, are supporting this transition to a new materials' mining. Location, cultural, and social aspects are also factors to consider. This perspective discusses new alternatives for carbon mining in biomass wastes, the valorization of biomass using available processing techniques, and the implementation of computational modeling, artificial intelligence, and machine learning to accelerate material's development and process engineering.

Preparation of a new gel-type lignin-based cationic adsorption resin for efficient removal of Ca2+ from aqueous solutions

Presently, most studies on modified lignin focused on the adsorption to heavy metal cations, but rarely to Ca²⁺ in hard water. Therefore, this work prepared a new gel-type lignin-based cationic adsorption resin (E-LSAF) through the crosslinking and curing of alkali lignin grafted by sodium sulfite sulfonated acetone to remove Ca²⁺ in water. Under the determined optimum synthesis conditions, E-LSAF with a highest sulfonic group content of 1.99 mmol/g was obtained. Structural and physicochemical measuring results showed E-LSAF was a gel-type resin, owning strong hydrophilicity, high mechanical strength, excellent thermal stability and acid-alkaline resistance. Adsorption results indicated the adsorption of E-LSAF to Ca²⁺ was well-fitted by Langmuir model, and the maximum adsorption capacity reached 45.8 mg/g. Pseudo-second-order model can describe this adsorption process well, suggesting it a chemisorption process. Dynamic column adsorption results showed E-LSAF could transform hard water into soft or even very soft water. The regeneration efficiency still maintained 80 % after 5 cycles. The adsorption mechanism was attributed to electrostatic attraction, ion exchange and complexation. This work provided a high-performance lignin-based cationic adsorption material with high adsorption capacity to Ca²⁺ and excellent acid-alkaline resistance, which filled the research gap of using modified sulfonated lignin to remove Ca²⁺ from water.

A functional lignin for heavy metal ions adsorption and wound care dressing

Recently, the application of lignin activation by demethylation to improve reactivity and enrich multiple functions has intensively attracted attention. However, it is still challenge up to now due to the low reactivity and complexity of lignin structure. Here, an effective demethylation way was explored by microwave-assisted method for substantially enhancing the hydroxyl (-OH) content and retaining the structure of lignin. Then, the optimum demethylated lignin was used to removal heavy metal ions and promote wound healing, respectively. In detail, for microwave-assisted demethylated poplar lignin (M-DPOL), the contents of phenolic (Ar-OH) and total hydroxyl (Tot-OH) groups reached the maximum for 60 min at 90 °C in DMF with 7.38 and 9.13 mmol/g, respectively. After demethylation, with this M-DPOL as lignin-based adsorbent, the maximum adsorption capacity (Q_max) for Pb²⁺ ions reached 104.16 mg/g. Based on the isotherm, kinetic and thermodynamic models analyses, the chemisorption occurred in monolayer on the surface of M-DPOL, and all adsorption processes were endothermic and spontaneous. Meanwhile, M-DPOL as a wound dressing had excellent antioxidant property, outstanding bactericidal activity and remarkable biocompatibility, suggesting that it did not interfere with cell proliferation. Besides, the wounded rats treated with M-DPOL significantly promoted its formation of re-epithelialization and wound healing of full-thickness skin defects. Overall, microwave-assisted method of demethylated lignin can offer great advantages for heavy metal ions removal and wound care dressing, which facilitates high value application of lignin.

Adsorption of heavy metal onto biomass-derived activated carbon: review

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Characterization and application of ligno-cellulosic fibers derived from Robinia Pseudoacacia for the bio-sorption of methylene blue from water

Ligno-cellulosic biomasses had been recognized for their potential use to produce chemicals and biomaterials. The current study focused on the use of a new cellulosic Robinia Pseudoacacia fiber and extracted lignin as adsorbents for methylene blue (a cationic dye). The biomaterials were analyzed using FT-IR spectroscopy, SEM, XRD, and TGA-DTA techniques. The surface of Robinia fibers was rough and porous. The crystallinity index (CrI) value for Robinia fibers was found to be 32%. The ability of the studied samples to remove methylene blue from water was assessed under the variation of time, pH, dye concentration, temperature, and NaCl concentration. The maximum adsorption capacity of methylene blue reached 191 mg/g for Robinia fibers and it achieved 22 mg/g for the extracted lignin (T = 20 °C, pH = 6, and time = 90 min). The adsorption data complied with the pseudo second-order kinetic model and both Langmuir and Freundlich isotherms. Based on these findings, the process suggested the occurrence of many physicochemical interactions between methylene blue molecules and the studied biomaterials. The adsorption mechanism was exothermic, non-spontaneous, and it was described by the decrease of the disorder. Adsorption results proved that Robinia fiber was an attractive candidate for the removal of cationic dyes from water.

Adsorption Study of Continuous Heavy Metal Ions (Pb2+, Cd2+, Ni2+) Removal Using Cocoa (Theobroma cacao L.) Pod Husks

The serious toxicological effects of heavy metal ions in aquatic ecosystems have motivated the search for alternatives to reduce contamination of water sources from industrial wastewater. In this work, continuous adsorption of nickel, cadmium, and lead was assessed using a packed bed column filled with Cocoa (Theobroma cacao L.) pod husks widely available in the northern region of Colombia. The physicochemical characterization of the agricultural biomass was performed to quantify its chemical composition by bromatological, FT-IR, and energy-dispersive X-ray spectroscopy (EDS). The breakthrough curves were constructed for all heavy metal ions with bed depth of 4 and 7.5 cm, taking aliquots at 10, 30, 60, 90, 120, 150, 180, 210, 240, and 270 min. Moreover, experimental data were fitted to adsorption models in continuous mode to predict adsorptive performance (Adams−Bohart, Thomas, and Yoon−Nelson). For the FT-IR analysis of biomass before and after adsorption, the most representative bands occur around 3200−3900 cm−1 attributed to the presence of hydroxyl groups, showing the destruction of the peaks of lignocellulosic materials. The breakthrough curves revealed that for a 7.5 cm bed, adsorption performance reported the following order of promising results: Pb2+ > Ni2+ > Cd2+; while for a 4 cm bed, Pb2+ > Ni2+. The mechanism of adsorption of the evaluated metals onto cocoa pod husk was attributed to cationic exchange and microprecipitation due to the presence of Ca, K, and Si in the structure of the bio-adsorbent. Finally, the continuous adsorption was modeled under the mathematical expressions of Adams−Bohart, Thomas, and Yoon−Nelson reporting good fitting with correlation coefficient above 0.95.

Development of Eggshell-Based Orange Peel Activated Carbon Film for Synergetic Adsorption of Cadmium (II) Ion

Heavy metal contamination has spread around the world, particularly in emerging countries. This study aimed to assess the effectiveness of starch/eggshell/orange peel-activated carbon-based composite films in removing cadmium (II) ions from water samples. X-ray diffraction and scanning electron microscopy were used to characterize the composite films. The effect of Cd²⁺ was studied using a UV-Vis spectrophotometer and atomic absorption spectroscopy. The morphology of the composite film reveals a highly porous and rough surface with more open channels and a non-uniform honeycomb, indicating that the film has a high potential to adsorb Cd²⁺. The diffraction peaks for this film were found to be at 13.74°, 17.45°, 18.4°, and 23.6°, indicating a typical crystalline A-type packing arrangement within the starch granules. The results indicate that crystalline structure was unaffected by the addition of eggshell powder and orange peel-activated carbon. In 0.5 mg L^-1 and 1.0 mg L^-1 Cd²⁺ ions, the composite film removed 100% and 99.7% of the Cd²⁺, respectively, while the maximum removal efficiency for methylene blue was 93.75%. Thus, the current study shows that starch/eggshell/orange peel activated carbon film has a high potential for commercial activated carbon as a low-cost adsorbent.

A Tool for Removing Metal Inclusions from the Surface of Paint and Varnish Car Coatings

In this article, we presents the synthesis and research of a tool for removing metal inclusions from the surface of car paint coatings. The optimal composition of the product was determined, which includes sodium laureth sulfate, citric acid, sulfosalicylic acid, hydrogen peroxide and water. As a result of the conducted studies, a connection was established between the composition and the physicochemical, surface-active properties of the developed agent. Approbation of this tool was carried out, which confirmed its effectiveness and showed that within 30–45 s after applying the developed tool, not only are metal inclusions on the surface of car paint coating removed but also mineral contaminants in the form of sand, earth, clay and other particles. The aim of the work was to develop and optimize a method for obtaining a low-toxicity, highly effective agent for removing metal inclusions from the surface of car paint coatings and to investigate its effectiveness, as well as its physicochemical, optical and surface-active properties.

Functionalized Alkaline Lignin for Removal of Lead in Aqueous Solution

Lignin, the second most abundant natural polymeric globally, is considered the source of the renewable aromatic compound. It serves as an alternative feedstock for the elaboration of chemicals and polymers. However, even until now, it is still primarily used as a low-value fuel for boilers. In the current research, alkaline lignin was modified and used as an adsorbent for removing lead (Pb) in an aqueous solution. The functionalized alkaline lignin (FAL) was prepared by a Mannich reaction with formaldehyde and dimethylamine, followed by esterification of carbon disulfide. The FAL was characterized using CHN elemental analysis, X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FT-IR) to observe the changes in composition, morphology, and chemical structure. The analysis revealed that alkaline lignin was successfully modified using amine and carbon disulfide. The adsorption study shows that the lead concentration reduced to 93.7% after 2 hours in contact with FAL. The FAL adsorption capacity could obtain 0.44 mmol/g of lead.

One-step synthesis of garlic peel derived biochar by concentrated sulfuric acid: Enhanced adsorption capacities for Enrofloxacin and interfacial interaction mechanisms

This study put forward a one-step carbonization method by concentrated sulfuric acid to prepare garlic peel derived biochar, and the synthetic conditions were optimized by L₁₆(4⁵) orthogonal experiments. Notably, in order to study the differences between the proposed synthetic method and the conventional pyrolysis method, the concentrated sulfuric acid carbonized garlic peels biochar (CSGPB) was compared with pyrolysis derived garlic peel biochar (HTGPB) in characterization and adsorption capacities for Enrofloxacin (ENR). Results showed that CSGPB exhibited more graphite-like structures with more active functional groups on the surface, and the equilibrium adsorption capacity of CSGPB (142.3 mg g^-1) was 13.7 times of HTGPB (10.4 mg g^-1) under identical conditions. Moreover, the adsorption behaviors including adsorption kinetics, isotherms and thermodynamics of CSGPB for ENR were fully investigated and discussed. Based on the above experiments, density functional theory (DFT) simulations were performed to reveal the interfacial interaction and adsorption mechanism. Results showed π-π interaction between quinolone moieties of ENR and graphite-like structures in CSGPB might be the dominant mechanism. As for the functional groups, the adsorption energies were -40.46, -15.21 and -5.96 kJ mol^-1 for -SO₃H, -OH and -COOH, respectively, which indicated -SO₃H was the most active functional groups on the surface of CSGPB. This study provided a new sustainable perspective for the design of efficient biochars, and explored the interfacial interaction mechanism of antibiotics removal on biochars.

Adsorptive removal of sulfosalicylic acid from aqueous medium by iron(III)-loaded magnetic chitosan/graphene oxide

In this study, an iron(III)-loaded magnetic chitosan/graphene oxide composite (Fe-MCG) was synthesized and applied for the adsorptive removal of sulfosalicylic acid (SSA) in aqueous solution. The results obtained from the application of various characterization techniques such as scanning electron microscopy (SEM), vibrating-sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS) prove the successful formation of the composite with enhanced microstructure and superparamagnetic properties. The adsorption capacity of Fe-MCG towards SSA via batch mode reaches up to 135 mg/g at 293 K. The adsorption of SSA onto Fe-MCG is driven by monolayer adsorption with the chemical and physical adsorption processes both playing active roles. The Langmuir isotherm and pseudo-second-order kinetic models were observed to best describe the equilibrium adsorption and kinetic processes, respectively. The values obtained for the associated thermodynamic parameters confirm that the adsorptive process is spontaneous, exothermic and entropy-increasing. The efficacy and reusability of the spent Fe-MCG was studied using 0.01 mol/L NaOH solution. The kinetic process for the desorption of SSA from Fe-MCG is well described by the pseudo-second-order kinetic model. Based on the experimental results and XPS analysis, the underlying mechanisms for the uptake of SSA onto Fe-MCG involve electrostatic forces, complexation, π-π stacking, and hydrogen bonding. Overall, the excellent features of Fe-MCG enhance its potential as an adsorbent for the sequestration of SSA in environmental media.

Lignin Nanoparticles and Alginate Gel Beads: Preparation, Characterization and Removal of Methylene Blue

A novel and effective green system consisting of deep eutectic solvent (DES) was proposed to prepare lignin nanoparticles (LNPs) without any lignin modification. The LNPs are obtained through the dialysis of the kraft lignin-DES solution. The particle size distribution, Zeta potential and morphology of the LNPs are characterized by using dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average diameter of LNPs is in the range 123.6 to 140.7 nm, and the LNPs show good stability and dispersibility in water. The composite beads composed of LNPs and sodium alginate (SA) are highly efficient (97.1%) at removing methylene blue (MB) from the aqueous solution compared to 82.9% and 77.4% by the SA/bulk kraft lignin composite and pure SA, respectively. Overall, the LNPs-SA bio-nanocomposite with high adsorption capacity (258.5 mg/g) could be useful in improving water quality and other related applications.

Facile fabrication of composite cellulose fibrous materials for efficient and consecutive dyeing wastewater treatment

Fabricating dye adsorbents with efficient adsorption properties is of great significance in the treatment of printing and dyeing wastewater. Herein, composite materials of polydopamine decorated cellulose fibrous nonwovens (PDA@CF NWs) were fabricated by constructing a PDA functional layer on the surface of cellulose fibers via in situ polymerization. In addition, a three-dimensional adsorbent of 3D PDA@CF NWs with good hydrophilicity, structural stability, and compression resistance could be obtained using a facilely laminating and traditional loop bonding reinforcing technique. Attributed to the efficient and uniform loading of an active PDA functional layer, the resulting PDA@CF NWs exhibited a relatively large adsorption capacity of around 91 mg g⁻¹ towards the template dye of methylene blue within a fast equilibrium time of 2 h, which was superior to most of the fibrous adsorbents. In addition, the treatment column of 3D PDA@CF NWs exhibited a breakthrough capacity of 40.9 mg g⁻¹, reaching nearly 50% of the static saturated dye-binding capacity. More importantly, the 3D PDA@CF NWs column could effectively and continuously separate the mixture of different dyes under gravity, highlighting an excellent practical performance. Thus, the PDA@CF NWs are expected to provide a promising candidate for environment-friendly, large-scale and efficient treatment of industrial printing and dyeing wastewater.

Composite materials of polydopamine decorated cellulose fibrous nonwovens were fabricated for efficient and consecutive dyeing wastewater treatment.

Mixed biosorbent of agro waste and bacterial biomass for the separation of Pb(II) ions from water system

Adsorption of Pb(II) ions in aqueous systems by newly developed mixed biomass has been explored. Mixed biomass was prepared from agro-waste (raw Banyan tree bark, RBTB) and bacterial biomass (Pannonibacter phragmitetus). Chemical modification by sulphuric acid treatment of raw banyan tree bark (SMBTB) was accomplished for the effective separation of toxic Pb(II) ions from the aquatic system. FTIR, SEM and EDX analysis was utilized to deduce sorption characteristics of mixed biomass. Pb(II) ions maximal removal has occurred at pH-6.0, lead (II) ions concentration-25 mg/L, time and mixed biomass dosage (60 min and 3.5 g/L for RBTB - Pannonibacter phragmitetus; 30 min and 1.5 g/L for SMBTB - Pannonibacter phragmitetus) and temperature (30 °C). Data from equilibrium isotherm and kinetic analysis was best suited to the Langmuir model and pseudo-first-order kinetics. The spontaneous and exothermic nature of Pb(II) ions removal was described by thermodynamic parameters. The mixed biomass proved to be an effective and potential mixed biosorbent for toxic lead removal from solutions.

Development of functional lignin-based spherical particles for the removal of vanadium(V) from an aqueous system

A new type of functional lignin-based spherical particles (L-CTAB) prepared with the use of hexadecyltrimethylammonium bromide (CTAB) was applied as an effective biosorbent for removing vanadium(V) ions. The porous structure, characteristic functional groups, electrokinetic stability, morphology and size of the L-CTAB particles were examined. The conditions of removal were also investigated, including pH (2-12), sorbent mass (0.1-0.5 g), concentration (10-100 mg/dm3), phase contact time (1-240 min) and temperature (293-333 K). At pH 5.0 the maximum sorption percentage (%S) of V(V) was 45%, while at pH 2.0 it was 32%. The maximum sorption capacity of V(V) for L-CTAB was found to be 10.79 mg/g. The kinetic data indicate that the sorption followed the pseudo-second-order and film diffusion models. Sorption equilibrium for V(V) ions removal by L-CTAB was reached after 60 min at the initial concentrations 10 and 50 mg/dm³. It has been shown that the adsorption of V(V) ions on the surface of L-CTAB is a heterogeneous, endothermic and spontaneous reaction, as evidenced by the calculated values of thermodynamic parameters - free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) - for the tested systems at different temperatures. HCl solutions, used as an L-CTAB regeneration agent, quantitatively eluted V(V) ions.

Synthesis of a Lignin-Fe/Mn Binary Oxide Blend Nanocomposite and Its Adsorption Capacity for Methylene Blue

A high-performance modified lignin adsorbent was prepared through coprecipitation of ferrous, ferric, and permanganate with lignin in sodium hydroxide solution. The structural characteristics of the synthesized lignin-Fe/Mn binary oxide blend nanocomposite (L-F/M) and its performance on the methylene blue (MB) removal from aqueous solution were evaluated. Influence factors of adsorption effects were analyzed including pH, contact time, dye concentration, temperature, and thermodynamics. The pseudo-second-order kinetic model well described the adsorption kinetics, and the adsorption isotherms best fitted the Langmuir model with a maximum adsorption capacity of 252.05 mg g-1 at 298 K. The adsorption mechanism showed that the L-F/M introduced the metallic element and negative charges to the lignin surface, which improved the adherence of MB via hydrogen bonding, electrostatic interaction, and coordination. Moreover, the removal ratio of MB maintained 81.2% after being used in five adsorption-desorption cycles. Results indicated that the L-F/M obtained was an efficient candidate for dye wastewater treatment.

Effects of cadmium stress on growth and physiological characteristics of sassafras seedlings

The effects of cadmium stress on the growth and physiological characteristics of Sassafras tzumu Hemsl. were studied in pot experiments. Five Cd levels were tested [CT(Control Treatment) : 0 mg/kg, Cd5: 5 mg/kg, Cd20: 20 mg/kg, Cd50: 50 mg/kg, and Cd100: 100 mg/kg]. The growth and physiological characteristics of the sassafras seedlings in each level were measured. The results showed that soil Cd had negative influences on sassafras growth and reduced the net growth of plant height and the biomass of leaf, branch and root. Significant reductions were recorded in root biomass by 18.18%(Cd5), 27.35%(Cd20), 27.57%(Cd50) and 28.95%(Cd100). The contents of hydrogen peroxide decreased first then increased while malondialdehyde showed the opposite trend with increasing cadmium concentration. Decreases were found in hydrogen peroxide contents by 10.96%(Cd5), 11.82%(Cd20) and 7.02%(Cd50); increases were found in malondialdehyde contents by 15.47%(Cd5), 16.07%(Cd20) and 7.85%(Cd50), indicating that cadmium stress had a certain effect on the peroxidation of the inner cell membranes in the seedlings that resulted in damage to the cell membrane structure. Superoxide dismutase activity decreased among treatments by 17.05%(Cd5), 10,68%(Cd20), 20.85%(Cd50) and 8.91%(Cd100), while peroxidase activity increased steadily with increasing cadmium concentration; these results suggest that peroxidase is likely the main protective enzyme involved in the reactive oxygen removal system in sassafras seedlings. Upward trends were observed in proline content by 90.76%(Cd5), 74.36%(Cd20), 99.73%(Cd50) and 126.01%(Cd100). The increase in proline content with increasing cadmium concentration indicated that cadmium stress induced proline synthesis to resist osmotic stress in the seedlings. Compared to that in CT, the soluble sugar content declined under the different treatments by 32.84%(Cd5), 5.85%(Cd20), 25.55%(Cd50) and 38.69%(Cd100). Increases were observed in the soluble protein content by 2.34%(Cd5), 21.36%(Cd20), 53.15%(Cd50) and 24.22%(Cd100). At different levels of cadmium stress, the chlorophyll content in the seedlings first increased and then decreased, and it was higher in the Cd5 and Cd20 treatments than that in the CT treatment. These results reflected that cadmium had photosynthesis-promoting effects at low concentrations and photosynthesis-suppressing effects at high concentrations. The photosynthetic gas exchange parameters and photosynthetic light-response parameters showed downward trends with increasing cadmium concentration compared with those in CT; these results reflected the negative effects of cadmium stress on photosynthesis in sassafras seedlings.

Lignin-derived (nano)materials for environmental pollution remediation: Current challenges and future perspectives

The supply of affordable drinking and sufficiently clean water for human consumption is one of the world's foremost environmental problems and a large number of scientific research works are addressing this issue Various hazardous/toxic environmental contaminants in water bodies, both inorganic and organic (specifically heavy metals and dyes), have become a serious global problem. Nowadays, extensive efforts have been made to search for novel, cost effective and practical biosorbents derived from biomass resources with special attention to value added, biomass-based renewable materials. Lignin and (nano)material adorned lignin derived entities can proficiently and cost effectively remove organic/inorganic contaminants from aqueous media. As low cost of preparation is crucial for their wide applications in water/wastewater treatment (particularly industrial water), future investigations must be devoted to refining and processing the economic viability of low cost, green lignin-derived (nano)materials. Production of functionalized lignin, lignin supported metal/metal oxide nanocomposites or hydrogels is one of the effective approaches in (nano)technology. This review outlines recent research progresses, trends/challenges and future prospects about lignin-derived (nano)materials and their sustainable applications in wastewater treatment/purification, specifically focusing on adsorption and/or catalytic reduction/(photo)degradation of a variety of pollutants.

One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water

To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N₂ adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.

EDTAD-modified cassava stalks loaded with Fe3O4: highly efficient removal of Pb2+ and Zn2+ from aqueous solution

In this study, a novel magnetic cassava stalk composite (M-EMCS) was prepared through modification with ethylenediamine tetraacetic anhydride (EDTAD) and loading of Fe₃O₄. The surface morphology, molecular structure, and magnetic characteristics of the composite were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), vibrating-sample magnetometer (VSM), and X-ray diffraction (XRD). It was shown that EDTAD and Fe₃O₄ were successfully modified and loaded in cassava straw (CS), respectively. The capacity of M-EMCS to absorb heavy metals under different influencing factors was tested by atomic absorption spectroscopy. The adsorption processes of both Pb²⁺ and Zn²⁺ were suitably described by second-order kinetic models and Langmuir models, indicating monolayer chemisorption. M-EMCS had high adsorption rates and adsorption capacities for these two metal ions. The adsorption of Pb²⁺ and Zn²⁺ reached a plateau after 10 min, and the adsorption capacity of Pb²⁺ (163.93 mg/g) was higher than that of Zn²⁺ (84.74 mg/g). Thermodynamic analysis showed that the adsorption of two metals by M-EMCS was spontaneous, endothermic, and irreversible. XPS analysis showed that M-EMCS mainly removes Pb²⁺ and Zn²⁺ through ion exchange, chelation, and redox. Graphical abstract.

Adsorption of Methylene Blue Dye by Calix[6]Arene-Modified Lead Sulphide (Pbs): Optimisation Using Response Surface Methodology

Lead sulphide (PbS) modified with calix[6]arene was synthesised as an alternative and regenerative adsorbent for the adsorption of methylene blue (MB) dye. The prepared calix[6]arene-modified PbS was characterised via Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The response surface methodology (RSM) based on the central composite design (CCD) was employed to identify the most significant factors, such as the initial concentration, adsorbent dosage, pH, and temperature, and to optimise the effects of the factors on the adsorptive efficiency as its response. The optimised initial concentration, adsorbent dosage, pH, and temperature were 20.00 mg/L initial concentration, 44.00 mg calix[6]arene-modified PbS, pH 6, and a temperature of 31.00 °C. A good correlation between the values and well-fitted model was observed. The adsorption performance was evaluated based on the percentage removal of MB dye from the water system. The adsorption isotherm best fit the Langmuir isotherm model, and the adsorption rate was followed by a pseudo-second-order kinetic model, a single layer chemical adsorption with a maximum adsorption capacity (q_max) of 5.495 mg/g.

Application of gradient acid fractionation protocol to improve decolorization technology by lignin-based adsorbent

Wastewater contaminated with dyes is discharged by huge amount daily, and involved many hazardous materials. Thus, this study focused on introducing low cost, ecofriendly and available removal agent (lignin-based adsorbent). Three adsorbents, APKL-4, APKL-5 and APKL-6 were obtained using gradient acid precipitation technology and used for methylene blue (MB) removal. The samples were characterized by SEM, FT-IR and zeta potential analyzer. The results indicated that the three adsorbents exhibit significantly different adsorption behavior due to the structural differences caused by fractionation. The APKL-5 and APKL-6 have fewer hydrophilic groups in their molecules and thus have more adsorption active sites to load MB molecules. A pore structure inside of APKL-5 molecules is form in acid fractionation, which allows it to carry more MB molecules. The adsorption capacity of APKL-5 increased 3.8 times (from 345 to 1310 mg g^-1) in the alkaline solution which showing excellent pH responsiveness. This paper presents a new promising approach for preparing high efficiency, low cost and eco-friendly adsorbents and builds a foundation for developing further applications of lignin-based adsorbents.

Characterization and use of a lignin sample extracted from Eucalyptus grandis sawdust for the removal of methylene blue dye

A lignin sample was extracted from Eucalyptus grandis sawdust, by the Klason method, and used as adsorbent for the removal of methylene blue (MB) from aqueous solutions. By using a set of complementary analytical tools, the lignin appeared to be constituted of oxygenated functional groups and aromatic moieties, while showing a specific surface area of 20 m² g^-1 and polydisperse particles. Different experimental conditions with various solid to liquid ratio, pH, as well as other external experimental parameters were investigated for the removal of MB by the lignin sample. The experimental adsorption data at the equilibrium were properly fitted by Langmuir model, while adsorption kinetical isotherms were correctly adjusted by the pseudo-second order model. The MB removal by lignin was spontaneous involving physisorption mechanisms leading to a saturation of the adsorption sites with a maximum adsorbed amount of about 32 mg g^-1. The data acquired in this study also emphasized the interests to use lignin as potential adsorbent in the light of its properties for the removal of cationic dyes, including MB, with possible recycling and reuse cycles of lignin without any significant loss of its properties.