Lignin Nanospheres Research Articles

Modified lignin nanosphere adsorbent for lead and copper ions

Heavy metal ions in wastewater have negative effects on humans and the environment. In this paper, the adsorption of lead and copper ions by modified eucalyptus lignin nanosphere (ECLNPs) was studied. The spherical alkali-lignin particles had a diameter of 50 nm, abundant carboxyl groups of 0.66 mmol/g, and relatively high adsorption performance. The equilibrium adsorption capacities of Pb(II) and Cu(II) by ECLNPs were 126.0 mg/g and 54.4 mg/g, respectively. Both Pb(II) and Cu(II) adsorptive processes fitted a pseudo-second-order kinetics model. In the simultaneous adsorption process of Pb(II) and Cu(II), ECLNPs had higher adsorptive selectivity for Pb(II) than Cu(II), and there was a competitive adsorption process between Pb(II) and Cu(II). This resulted from the lower hydration heat of Pb(II) in water, which leads to easier separation from water ligands. ECLNPs also showed good recyclability, with 16.6% and 21.1% loss in Pb(II) and Cu(II) adsorption capacity, respectively, after three consecutive adsorption-desorption cycles, which provides a feasible technical direction for the utilization of biomass resources and the treatment of water contamination.

Facile synthesis of manganese oxide modified lignin nanocomposites from lignocellulosic biorefinery wastes for dye removal

In this study, a facile method to prepare MnO2 nanodots modified lignin nanocomposite (MnO2@LNP) was developed for efficient dye removal. The MnO2@LNP displayed hierarchical spherical nanostructures, where the MnO2 nanodots were evenly dispersed within the lignin nanosphere. Compared with lignin nanoparticles, the as-prepared MnO2@LNP exhibits higher surface area and can be separated after adsorption. It showed excellent adsorption capacity (806 mg/g) towards a typical cationic dye, methylene blue (MB), at a fast removal rate, where more than 80% of adsorption capacity was reached within 5 min at room temperature. The high adsorption capacity was contributed by the high surface area and negative charge on the adsorbent. The adsorption process is pH-responsive and exothermic, and the spent adsorbent can be reused for at least five cycles. This study displayed an efficient method to prepare MnO2@LNP for the high-value utilization of lignin-derived from lignocellulosic biorefinery.

Size-Controlled and Super Long-Term Stable Lignin Nanospheres through a Facile Self-Assembly Strategy from Kraft Lignin.

In diverse fields, much attention has been concentrated on the preparation of lignin nanospheres with various structures. Here we report a facile self-assembly strategy for preparing super long-term stable hollow and solid nanospheres based on lignin fractionation. We found that different lignins obtained at different pHs during fractionation can form nanospheres with different particle sizes and structures. The self-assembled and formation mechanisms of the nanospheres were surveyed by dynamic light scattering (DLS), elemental analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The analysis results showed that the phenolic hydroxyl groups and the intermolecular π-π interaction play a decisive effect in the formation of nanospheres. This study can not only facilitate the advance of lignin-based nanotechnologies but also provide a broad prospect for the use of black liquor.

Fabrication of lignin nanospheres by emulsification in a binary γ-valerolactone/glycerol system and their application as a bifunctional reducer and carrier for Pd nanoparticles with enhanced catalytic activity

Lignin nanosphere was prepared using green binary γ-valerolactone/glycerol system and then employed as a reducer and carrier for Pd nanoparticles.

Self-assembled lignin nanospheres with solid and hollow tunable structures

The fabrication of nanospheres with tailored structure has attracted much attention in material applications. Herein we found that the food additive, butylated hydroxytoluene (BHT), was able to adjust the solid and hollow structure of lignin nanospheres. At BHT concentrations greater than 0.3 mg/mL in tetrahydrofuran (THF), the obtained lignin nanospheres displayed a hollow structure due to phase separation between THF and water caused by BHT molecules, while the lignin nanospheres obtained without adding BHT exhibited a solid structure. BHT and lignin molecules containing a high content of the carboxy group did not participate in the formation of the nanospheres. Increases in the water stirring and dropping speeds reduced the diameter of the nanospheres, while increasing the initial concentration of lignin and BHT resulted in an increase in nanospheres diameters. Moreover, the shell wall thickness and single hole size could be controlled by employing the concentration of BHT and lignin. This work provides novel insights into the preparation of lignin nanospheres with tunable structures.

Enhancing the Broad-Spectrum Adsorption of Lignin through Methoxyl Activation, Grafting Modification, and Reverse Self-Assembly

Lignin nanospheres with broad-spectrum UV adsorption and excellent antioxidant properties were obtained by demethoxylation of alkali lignin (AL) and grafting the benzophenone moiety (UV-0) followed...

Preparation of a Novel Lignin Nanosphere Adsorbent for Enhancing Adsorption of Lead.

Carboxymethyl lignin nanospheres (CLNPs) were synthesized by a two-step method using microwave irradiation and antisolvent. The morphology and structure of CLNPs were characterized by 31P-NMR, FTIR, and SEM, and the results showed that they had an average diameter of 73.9 nm, a surface area of 8.63 m2 or 3.2 times larger than the original lignin, and abundant carboxyl functional groups of 1.8 mmol/g. The influence of dosage, pH, contact time, and concentration on the adsorption of metal ions onto CLNPs were analyzed, and the maximum adsorption capacity of CLNPs for Pb(II) was found to be 333.26 mg/g, which is significantly higher than other lignin-based adsorbents and conventional adsorbents. Adsorption kinetics and isotherms indicated that the adsorption of lead ions in water onto CLNPs followed the pseudo-second-order model based on monolayer chemisorption mechanism. The main chemical interaction between CLNPs and lead ions was chelation. CLNPs also showed an excellent recycling performance, with only 27.0% adsorption capacity loss after 10 consecutive adsorption–desorption cycles.

A simple environment-friendly process for preparing high-concentration alkali lignin nanospheres

Biomass nanomaterials based on aromatic ring monomers have broad application prospects in the fields of drug delivery, catalysis and environment. In this paper, based on the effective dissolution of commercial alkali lignin in imidazole ionic liquids, lignin nanospheres were rapidly prepared by adding anti-solvent of water. In the three imidazole ionic liquids (1-amyl-3-methylimidazolium acetate (C5mim][Ac]), 1-butyl-3methylimidazolium acetate ([Bmim][Ac]) and 1-ethyl-3-methylimidazolium acetate ([Emim][Ac])), lignin can dissolve well, and the dissolution rates are all >25%, which is much higher than other organic solvents. And the longer the alkyl chain in imidazole ring is, the lower the solubility of lignin is. The paper also studied the effects of lignin concentration, the addition rate of anti-solvent, stirring rate and pH on the size of lignin nanospheres. It was found that the lignin nanospheres prepared under suitable conditions have particle size in the range of 52–210 nm and have good stability for over two months. And, compared to other studied, the particle size of the nanospheres is much smaller and easier to control. Moreover, the quality of lignin nanospheres was elucidated by Fourier transform infrared spectroscopy (FT-IR), Gel permeation chromatography (GPC) and UV–vis spectroscopy (UV–Vis) measurements which found the molecular weight of lignin nanospheres was slightly lower the raw alkali lignin, and the main structure of the aromatic ring of lignin is preserved in the process of preparation of the nanospheres by ILs. The method of preparing lignin nanosphere from lignin-ionic liquids solution with water as anti-solvent is simple, rapid and environmentally friendly, and provides an efficient and feasible path for the high value utilization of lignin.

Lignin Nanosphere-Supported Cuprous Oxide as an Efficient Catalyst for Huisgen [3+2] Cycloadditions under Relatively Mild Conditions.

In this work, low-cost lignin nanospheres were fabricated and further applied as an efficient and sustainable support for preparing cuprous oxide (Cu2O) “green” catalyst by using electrospraying technology. The unalloyed lignin, a special three-dimensional molecular structure, was successfully processed into uniform nanospheres under an electrospraying condition. The synthesized lignin-supported Cu2O catalyst had a well-defined nanosphere structure, and Cu2O nanoparticles with sizes less than 30 nm were supported by exposed layers of lignin nanospheres. There were C–O–Cu bonds formed between the lignin nanospheres and the metallic nanoparticles. The lignin nanospheres and the lignin nanosphere-supported catalyst werfe characterized by utilizing XRD, SEM, TEM, XPS, EDS, and TGA. The immobilization of Cu2O nanoparticles on the lignin nanospheres was beneficial for dispersion of the Cu2O nanoparticles and preventing their aggregation, which could cause catalyst deactivation, which favored the Huisgen [3+2] cycloaddition reaction. The triazole synthesis results indicated that the lignin nanosphere-supported Cu2O catalyst had a high catalytic performance with 99% yield under solvent-free conditions. Furthermore, the as-synthesized catalyst could be recycled for four times without significantly losing its catalytic activity.

Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media

Dehydration reactions proceed readily in water-filled biological cells. Development of biocatalysts that mimic such compartmentalized reactions has been cumbersome due to the lack of low-cost nanomaterials and associated technologies. Here we show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts upon self-assembly and drying-driven aggregation in calcium alginate hydrogel. Spatially confined microbial cutinase and lipase retain 97% and 70% of their respective synthetic activities when the volume ratio of water to hexane increases from 1:1 to 9:1 in the reaction medium. The activity retention of industrially most frequently used acrylic resin-immobilized Candida antarctica lipase B is only 51% under similar test conditions. Overall, our findings enable fabrication of robust renewable biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse heterogeneous catalysts.

Preparation and formation mechanism of size-controlled lignin nanospheres by self-assembly

Lignin has recently attracted much attention due to their renewable nature. Here we focused on a simple self-assembly method for fabricating size and shape uniform enzymatic hydrolysis lignin (EHL) nanospheres, without chemical modification of lignin. EHL was dissolved in tetrahydrofuran at different initial concentrations and subsequently self-assembly with adding water under magnetic stirring for fabricating the nanospheres. The self-assembled structure, process parameters and formation mechanism of the nanospheres were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), fourier transform infrared spectroscopy (FTIR), and UV–vis absorption spectra. Results showed that the nanospheres were formed through a layer-by-layer self-assembly approach from inside to outside based on π–π interactions, which enabled the formation of nanospheres in the size range of 190–590nm. Increasing the pre-dropping EHL concentration resulted in an increase of the average diameter and yield of the nanospheres. The nanospheres have good stability, and their average diameters had no significant change after 30days. The chemical structural features of the nanospheres had not produced a significant change in the preparation process. High preparation temperature brought about the formation of the gaps at the surface of the nanospheres due to the effect of volatile speed of solvent. Moreover, the average diameter of the nanospheres decreased with an increase of stirring rate or the dropping speed of water. The proposed EHL nanospheres are eco-friendly, cost-effective and therefore a promising candidate for biomass based carrier.