Treatment of model solutions and wastewater containing selected hazardous metal ions using a chitin/lignin hybrid material as an effective sorbent

Dual lignin-derived polymeric system for peptone removal from simulated wastewater

The long-term existence of peptone can breed a large number of bacteria and cause the eutrophication of municipal wastewater. Thus, removing peptone in the wastewater is a major challenge facing the current industry. This study used cationic and anionic lignin polymers, i.e., kraft lignin-[2-(methacryloyloxy)ethyl] trimethylammonium methyl sulfate (cationic lignin polymer, CLP) and kraft lignin-acrylic acid (anionic lignin polymer, ALP), as flocculants to eliminate peptone from model wastewater in the single and dual component systems. The affinity of peptone for ALP or CLP was assessed by quartz crystal microbalance with dissipation, X-ray photoelectron spectroscopy, contact angle, and vertical scan analyzer. Results illustrated that the adsorption effect of CLP for peptone was significantly superior to that of ALP owing to the stronger vital interaction between cationic polymer and peptone molecules. Based on destabilization and sedimentation analyses, introducing CLP triggered the preliminary flocculation of peptone via bridging action, as indicated by a considerable increment in the destabilization index (from 1.1 to 10.6). Moreover, peptone adsorbed more on the CLP coated surface than on the ALP coated one (14.8 vs 5.4 mg/m2), while ALP facilitated its further adsorption in the dual polymer system. This is because CLP adsorbed a part of peptone molecules on its surface. Then, ALP entrapped the unattached peptone onto the CLP coated surface through electrostatic interaction. Compared with the single polymer system, mixing ALP and CLP subsequently into the peptone solution in the dual system generated larger size aggregates (mean diameter of 6.1 μm) and made the system destabilization (Turbiscan stability index up to 58.1), thereby yielding more flocculation and sedimentation. Finally, peptone was removed successfully from simulated wastewater with a turbidity removal efficiency of 92.5%. These findings confirmed that the dual-component system containing two lignin-derived polymers with opposite charges could be viable for treating peptone wastewater.

Hydrothermal Synthesis of a Technical Lignin-Based Nanotube for the Efficient and Selective Removal of Cr(VI) from Aqueous Solution

Aminated lignin (AL) was obtained by modifying technical lignin (TL) with the Mannich reaction, and aminated lignin-based titanate nanotubes (AL-TiNTs) were successfully prepared based on the AL by a facile hydrothermal synthesis method. The characterization of AL-TiNTs showed that a Ti-O bond was introduced into the AL, and the layered and nanotubular structure was formed in the fabrication of the nanotubes. Results showed that the specific surface area increased significantly from 5.9 m2/g (TL) to 188.51 m2/g (AL-TiNTs), indicating the successful modification of TL. The AL-TiNTs quickly adsorbed 86.22% of Cr(VI) in 10 min, with 99.80% removal efficiency after equilibration. Under visible light, AL-TiNTs adsorbed and reduced Cr(VI) in one step, the Cr(III) production rate was 29.76%, and the amount of total chromium (Cr) removal by AL-TiNTs was 90.0 mg/g. AL-TiNTs showed excellent adsorption capacities of Zn2+ (63.78 mg/g), Cd2+ (59.20 mg/g), and Cu2+ (66.35 mg/g). After four cycles, the adsorption capacity of AL-TiNTs still exceeded 40 mg/g. AL-TiNTs showed a high Cr(VI) removal efficiency of 95.86% in simulated wastewater, suggesting a promising practical application in heavy metal removal from wastewater.

Cu(II) removal from water by trimercapto-s-triazine trisodium salt modified alkaline lignin

To overcome the poor removal ability of alkaline lignin (AL) toward heavy metals, trimercapto-s-triazine trisodium salt (TMT) was selected as the modifying agent to introduce reaction groups. The Fourier transform infrared (FT-IR) spectra and the scanning electron microscopy (SEM) suggested that -SNa, C-N, and C = N groups were successfully introduced. Copper (II) was applied to evaluate the uptake performance of the adsorbent (AL-TMT). Adsorbent dosage and solution pH were taken into account to study their effects in the batch experiments. The pseudo-second-order dynamics and Langmuir models better described the experimental data. Nitrogen (N) and carbon (C) functional groups in thiotriazinone carried by AL-TMT were determined to be the primary uptake sites through X-ray photoelectron spectroscopy (XPS), FT-IR, and electrostatic potential (ESP). The selective experiments of AL-TMT toward Cd(II), Cu(II), Pb(II), Zn(II), Co(II), and Mg(II) were performed. It showed that AL-TMT possessed better adsorption selectivity toward Cu(II) than others. Furthermore, the density functional theory (DFT) calculations of thiotriazinone in AL-TMT also exhibited the lowest binding energy toward Cu than toward others. This work may provide a theoretical basis to facilitate the extraction of specific heavy metals from water or wastewater by using such modified alkaline lignin.

Computational Design and Manufacturing of Sustainable Materials through First-Principles and Materiomics

Engineered materials are ubiquitous throughout society and are critical to the development of modern technology, yet many current material systems are inexorably tied to widespread deterioration of ecological processes. Next-generation material systems can address goals of environmental sustainability by providing alternatives to fossil fuel-based materials and by reducing destructive extraction processes, energy costs, and accumulation of solid waste. However, development of sustainable materials faces several key challenges including investigation, processing, and architecting of new feedstocks that are often relatively mechanically weak, complex, and difficult to characterize or standardize. In this review paper, we outline a framework for examining sustainability in material systems and discuss how recent developments in modeling, machine learning, and other computational tools can aid the discovery of novel sustainable materials. We consider these through the lens of materiomics, an approach that considers material systems holistically by incorporating perspectives of all relevant scales, beginning with first-principles approaches and extending through the macroscale to consider sustainable material design from the bottom-up. We follow with an examination of how computational methods are currently applied to select examples of sustainable material development, with particular emphasis on bioinspired and biobased materials, and conclude with perspectives on opportunities and open challenges.

Spirulina platensis Immobilized Alginate Beads for Removal of Pb(II) from Aqueous Solutions

Microalgae contain a diversity of functional groups that can be used as environmental adsorbents. Spirulina platensis is a blue-green microalga that comprises protein-N, which is advantageous for use in nitrogen-containing biomass as adsorbents. This study aimed to enhance the adsorption properties of alginate hydrogels by employing Spirulina platensis. Spirulina platensis was immobilized on sodium alginate (S.P@Ca-SA) via crosslinking. The results of field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy analyses of the N-containing functional groups indicated that Spirulina platensis was successfully immobilized on the alginate matrix. We evaluated the effects of pH, concentration, and contact time on Pb(II) adsorption by S.P@Ca-SA. The results demonstrated that S.P@Ca-SA could effectively eliminate Pb(II) at pH 5, reaching equilibrium within 6 h, and the maximum Pb(II) sorption capacity of S.P@Ca-SA was 87.9 mg/g. Our results indicated that S.P@Ca-SA fits well with the pseudo-second-order and Freundlich models. Compared with Spirulina platensis and blank alginate beads, S.P@Ca-SA exhibited an enhanced Pb(II) adsorption efficiency. The correlation implies that the amino groups act as adsorption sites facilitating the elimination of Pb(II).

Design, Synthesis and Adsorption Evaluation of Bio-Based Lignin/Chitosan Beads for Congo Red Removal

The morphology and intermolecular interaction are two of the most important factors in the design of highly efficient dye adsorbent in the industry. Millimeter-sized, bead-type, bio-based lignin/chitosan (Lig/CS) adsorbent was designed for the removal of Congo red (CR), based on the electrostatic attraction, π-π stacking, and hydrogen bonding, which were synthesized through the emulsification of the chitosan/lignin mixture followed by chemical cross-linking. The effects of the lignin/chitosan mass ratio, initial pH, temperature, concentration, and contact time on the adsorption were thoroughly investigated. The highest adsorption capacity (173 mg/g) was obtained for the 20 wt% Lig/CS beads, with a removal rate of 86.5%. To investigate the adsorption mechanism and recyclability, an evaluation of the kinetic model and an adsorption/desorption experiment were conducted. The adsorption of CR on Lig/CS beads followed the type 1 pseudo-second-order model, and the removal rate for CR was still above 90% at five cycles.

Dual lignin-derived polymeric systems for hazardous ion removals

The functionalization of lignin derivatives for ion removals is a promising method to expedite their use in treating industrial wastewater. In this work, kraft lignin (KL) was polymerized with [2-(methacryloyloxy)ethyl]trimethylammonium methyl sulfate (METAM) or acrylic acid (AA) in an acidic aqueous suspension system to produce cationic and anionic water-soluble lignin polymers with high molecular weights. Then, the interaction of soluble ions and KL-METAM and KL-AA was investigated using a Quartz crystal microbalance (QCM) and a vertical scan analyzer (VSA). The QCM, X-ray photoelectron spectroscopy (XPS) and contact angle measurement results showed that the adsorption efficiency of KL-AA was better than KL-METAM for ions due to the stronger electrostatic interaction, cationic π-interaction, and chelation between ions and KL-AA. Based on adsorption, sedimentation, and aggregate size analyses, the dual polymer systems of KL-AA/KL-METAM were more effective than KL-METAM/KL-AA in removing ions. Among Zn²⁺, Cu²⁺, and K⁺; Zn²⁺ interacted more effectively with polymers in all scenarios because it has higher reactivity for interacting with other elements. As the efficiency of ion removals was more remarkable than past reported findings, the system of KL-AA/KL-METAM may be a promising alternative for the removal of dissolved ions from solutions.

Removal of iron, zinc, and nickel-ions using nano bentonite and its applications on power station wastewater

Removal of high concentrations of toxic heavy metals from wastewater is very important within the environmental field because heavy metals pollution a serious environmental problem due to them being nonbiodegradable. This study shed some light on the use of Nano bentonite as an adsorbent for the elimination of Iron, Zinc, and Nickel ions from wastewater, and the optimum conditions were evaluated to find out thermodynamic and kinetic parameters and equilibrium adsorption models have been applied. The results showed that adsorption percentage increases with increasing temperature, speed of rotation, and volume of solution, but decreases with adsorbent dose and initial concentration increase. The adsorption process has fit pseudo-second-order kinetic model Langmuir and Freundlich adsorption isotherm models were applied to analyze adsorption data and both were found to apply to these adsorption processes. Thermodynamic parameters e.g., ΔG^o, ΔS^o, and ΔH^o of the adsorption process were found to be endothermic. Finally, the Nano bentonite was observed to be more powerful for the removal of Fe (III), Zn (II), and Ni (II) at the same experimental conditions.

Adsorption of Pb(II) from Aqueous Solution by Mussel Shell-Based Adsorbent: Preparation, Characterization, and Adsorption Performance

As a natural biological adsorbent, shell powder is inexpensive, highly efficient, and does not leave any chemical residue; thus, it can be used to remove contaminants from water. In this study, we used mussel shells as a raw material to prepare an adsorbent. Scanning electron microscopy was used to observe the surface morphology of the mussel shell powder before and after calcination, and X-ray diffraction measurements, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller measurements were performed to analyze the structure and composition of calcined mussel shell powder. Characterization of the shell powder before and after calcination revealed a change from calcium carbonate to calcium oxide, as well as the formation of a surface porous structure. Using Pb(II) as a representative contaminant, various factors affecting the adsorption were explored, and the adsorption mechanism was analyzed. It was found that the adsorption is consistent with the Freundlich adsorption isotherm and the pseudo second-order model. The calcined mussel shell powder exhibits excellent adsorption for Pb(II), with an adsorption capacity reaching 102.04 mg/g.

Excellent selectivity and high capacity of As (V) removal by a novel lignin-based adsorbent doped with N element and modified with Ca2

As one of the most significant natural polymer with the highest annual yield, lignin has been applied in the treatment of wastewater to remove heavy metal ions. However, there are still some shortages, such as low reactivity, difficulties in adsorbing oxyanions and low selectivity on specific oxyanions. To improve its adsorption properties, a novel lignin-based adsorbent was prepared in this study, doped with nitrogen by Mannich reaction, using triethylenetetramine (TETA) as N source, and further modified with Ca²⁺. The adsorption of Ca, N-co-doped lignin (Ca@N-Lig) for As (V), Cr (VI) and P (V) was studied. The Ca@N-Lig shows high capacity, excellent selectivity and prominent regeneration ability for As (V) adsorption. The adsorption of Ca@N-Lig for As (V) followed the Langmuir isotherm model and the pseudo-second-order kinetics model, yielding a maximum adsorption capacity of 681.59 mg·g^-1 and a fast adsorption equilibrium within 30 min. Ca@N-Lig has an excellent regeneration ability on the adsorption of As (V) with a decrease of about 15.60% after 5 adsorption/desorption cycles. This study offers an efficient way to remove As (V) from polluted water.

Sustainable drug release from polycaprolactone coated chitin-lignin gel fibrous scaffolds

Non-healing wounds have placed an enormous stress on both patients and healthcare systems worldwide. Severe complications induced by these wounds can lead to limb amputation or even death and urgently require more effective treatments. Electrospun scaffolds have great potential for improving wound healing treatments by providing controlled drug delivery. Previously, we developed fibrous scaffolds from complex carbohydrate polymers [i.e. chitin-lignin (CL) gels]. However, their application was limited by solubility and undesirable burst drug release. Here, a coaxial electrospinning is applied to encapsulate the CL gels with polycaprolactone (PCL). Presence of a PCL shell layer thus provides longer shelf-life for the CL gels in a wet environment and sustainable drug release. Antibiotics loaded into core–shell fibrous platform effectively inhibit both gram-positive and -negative bacteria without inducting observable cytotoxicity. Therefore, PCL coated CL fibrous gel platforms appear to be good candidates for controlled drug release based wound dressing applications.

Ragauskas A. Recent Advances in the Application of Functionalized Lignin in Value-Added Polymeric Materials

The quest for converting lignin into high-value products has been continuously pursued in the past few decades. In its native form, lignin is a group of heterogeneous polymers comprised of phenylpropanoids. The major commercial lignin streams, including Kraft lignin, lignosulfonates, soda lignin and organosolv lignin, are produced from industrial processes including the paper and pulping industry and emerging lignocellulosic biorefineries. Although lignin has been viewed as a low-cost and renewable feedstock to replace petroleum-based materials, its utilization in polymeric materials has been suppressed due to the low reactivity and inherent physicochemical properties of lignin. Hence, various lignin modification strategies have been developed to overcome these problems. Herein, we review recent progress made in the utilization of functionalized lignins in commodity polymers including thermoset resins, blends/composites, grafted functionalized copolymers and carbon fiber precursors. In the synthesis of thermoset resins such as polyurethane, phenol-formaldehyde and epoxy, they are covalently incorporated into the polymer matrix, and the discussion is focused on chemical modifications improving the reactivity of technical lignins. In blends/composites, functionalization of technical lignins is based upon tuning the intermolecular forces between polymer components. In addition, grafted functional polymers have expanded the utilization of lignin-based copolymers to biomedical materials and value-added additives. Different modification approaches have also been applied to facilitate the application of lignin as carbon fiber precursors, heavy metal adsorbents and nanoparticles. These emerging fields will create new opportunities in cost-effectively integrating the lignin valorization into lignocellulosic biorefineries.

Ulvan dialdehyde-gelatin hydrogels for removal of heavy metals and methylene blue from aqueous solution

Hydrogels based on the polysaccharide ulvan from the green macroalgae Ulva fenestrata were synthesized and evaluated as an adsorbent for heavy metals ions and methylene blue. Ulvan was extracted from Ulva fenestrata using diluted hydrochloric acid and recovered by precipitation with EtOH. The extracted ulvan was converted into ulvan dialdehyde via periodate-oxidation and subsequently combined with gelatin yielding hydrogels. The hydrogels showed good water-uptake capacity with a maximum swelling degree of 2400 % in water and 900 % in PBS buffer. Adsorption tests of methylene blue showed a maximum adsorption capacity of 465 mg/g. The adsorption data of methylene blue followed the pseudo-second order kinetics and agreed with the Langmuir adsorption isotherm. The maximum adsorption capacity of heavy metal ions was 14 mg/g for Cu²⁺, 7 mg/g for Co²⁺and 6 mg/g for Ni²⁺and Zn²⁺ indicating that the hydrogels have a stronger affinity for Cu²⁺ than for Co²⁺, Ni²⁺, and Zn²⁺.

Removal of the heavy metal ion nickel (II) via an adsorption method using flower globular magnesium hydroxide

To remove toxic Ni(II) ions from wastewater, a novel flower globular magnesium hydroxide (FGMH) was prepared by a gentle method using trisodium citrate as a crystal modifier. This material exhibited a high specific surface area. The synthesized products and adsorption mechanism for Ni(II) ions were examined by diverse characterization technologies and methods. FGMH was employed to remove Ni(II) ions by the adsorption method. The effects of various parameters, viz., the amount of adsorbent, contact time, temperature and pH, on the removal rate by the adsorbent were investigated in detail. The kinetic data fitted well with a pseudo-second-order model and experimental equilibrium adsorption data conformed to a Langmuir isotherm under optimized conditions. The optimal process parameters included 30 mg of FGMH, a 50 min contact time, pH values between 6.07 and 7.71 for the Ni(II) solution, and adsorption at room temperature for 50 mL of 80 mg/L Ni(II) solution. The percentage of removal efficiency was found to be above 92.64%, and the maximum adsorption capacity of MH was 287.11 mg/g under optimum adsorption conditions. The analyses indicated that the Ni(II) ions were chemisorbed on the FGMH surface.

Synthesis of recyclable carbon/lignin biocomposite sorbent for in-situ uptake of BTX contaminants from wastewater

In this work, both palm-date pits and pulping black liquor industrial wastes were recycled as low-cost starting materials for the production of three series of granule activated carbon (gAC)/Kraft lignin (KL) (gAC/KL_x, x = 33, 50 and 67%) biocomposites using a one-pot solid-state method. The gAC/KL_x biocomposites with defined characteristics were examined towards batch adsorption of BTX (Benzene, Toluene, and Xylene) in multi-solute salty wastewaters. Optimization of adsorption performances under different experimental conditions were carried out using high performance liquid chromatography (HPLC). Adsorption modeling versus contact time (0-12 h) and BTX concentrations (150-2250 mg/L) were examined using non-linear forms of nine kinetic and five isotherm equations to best understand gAC/KL_0.5 suitability for BTX sorption/recovery processing. Accordingly, the gAC/KL_x at KL blended ratio of 50% was found to be the topmost to achieve the highest BTX capacity even at broad ranges of water salinity (0-100 g/L) and pH (3-9) values. The adsorption mechanism found to best described by physico-sorption (E ≈ 0.12-1.38 kJ/mol) via the hydrophobic interaction and diffusion mechanisms. In respect to gAC/KL_0.5 affinities, the sorption capacity followed the descending sequence of X ≥ T > B. Particularly, the maximum theoretical BTX capacity using the best fitted Langmuir-Freundlich model (L-FM) for gAC/KL_0.5 was found to be slightly higher than obtained by gAC (363.9 and 360.1 mg/g, respectively), along with higher initial sorption (h) rate (≈742.47 mg/g.h) than of gAC (≈559.85 mg/g.h) and KL (≈22.22 mg/g.h). Batch BTX sorption/recovery processes and estimated cost suggested the effective utilization of gAC/KL_0.5 as a promising in-expensive sorbent (0.31 ± 0.05 US$/kg) for commercial decontamination of petroleum hazardous (BTX) pollutants from wastewaters up to five reuse cycles.

Lignin materials for adsorption: Current trend, perspectives and opportunities

Lignin is a highly aromatic low value biomass residue, which can be utilized for chemicals, fuels and materials production. In recent years significant attention has focused on adsorbent materials from lignin. However, only 5% of available lignin is exploited worldwide, thus significant opportunities still exist for materials development. This review summarizes recent research advances in lignin-based adsorbents, with a particular emphasis on lignin, its modification and carbon materials derived from this abundant feedstock. Lignin derived activated carbons have been utilized for air pollutant adsorption (e.g. CO₂, SO₂ and H₂S), while modified lignin materials have been developed for the removal of organic dyes and organics (like methylene blue, Procion Blue MX-R and phenols), heavy metals (such as Cu, Zn, Pb and Cd), or recovery of noble metals (e.g., Pd, Au and Pt). Future perspectives highlight how green chemistry approaches for developing lignin adsorbents can generate added value processes.