Facile fabrication and characterization of kraft lignin@Fe3O4 nanocomposites using pH driven precipitation: Effects on increasing lignin content

Superparamagnetic composites of lignin regenerated from ionic liquid solutions for the efficient and selective removal of cationic dyes

Magnetic lignin nanoparticles (MLNs) were prepared by inducing their self-assembly through lignin regeneration in the [N-methyl-2-pyrrolidone][C1-C4 carboxylic acid] ionic liquids ([NMP]ILs), which are low-cost protic ionic liquid. [NMP]ILs are self-assembling solvent that can enhance the adsorption capacity of MLNs to a greater degree than tetrahydrofuran or H2O. Additionally, the anion types of [NMP]IL greatly influence the physiochemical properties of MLNs. The MLNs prepared through self-assembly with [NMP][formate] (MLN/[NMP][For]) exhibited a higher maximum adsorption capacity (134.53 mg/g) than the [NMP]ILs of C2-C4 carboxylate anions. MLN/[NMP][For] demonstrated stable adsorption within a pH range of 6-10 or at high salt concentrations (0.01-0.5 mol/L), retaining over 80 % of its regeneration efficiency after 5 cycles. In addition, MLN/[NMP][For] selectively removed cationic dyes in mixed binary anionic-cationic dye solutions. This work demonstrated the feasibility of preparing magnetic biosorbents with good selectivity and stability though regeneration and by adjusting the anions of ionic liquids.

Electronic and magnetic properties of Au-doped diamond surfaces by first-principles calculation

The electronic and magnetic properties of the Au-doped diamond surface are investigated by first-principles calculation. After Au-doping, diamond shows surface p-type conductivity with an areal electron density of 6.34 × 1013 cm-2. Unlike the non-magnetic feature of intrinsic diamond, magnetism is induced for diamond (100), (110) and (111) surfaces as well as at different terminations (H, F, N and O). The magnetism originates from the s-p hybridization between the Au-6s state and the C-2p state, and the spin charge density and magnetic moments of Au-doped diamond originate mainly from the Au atoms and their surrounding C atoms. Further studies show that the magnetic properties still maintain under different doping concentrations (0.125-0.5 monolayer). Therefore, this study would provide great potential applications of diamond in novel magnetic semiconductors and transistors.

Selective adsorption of anionic dyes by a macropore magnetic lignin-chitosan adsorbent

Dyes pollution is well known for their hazardous impacts on human health and the environment. The removal of dyes from wastewater has become an important issue. In this study, magnetic micrometer-sized particles AL-CTS@MNPs were synthesized from alkaline lignin (AL) and chitosan (CTS) by "one-pot method". The adsorbent presented higher selectivity adsorption effect on anionic dyes than amphoteric and cationic dyes, and even no adsorption effect on cationic methylene blue (MB), which showed that the anionic dyes could be better separated from the other two types of dyes. The adsorption isotherms of the dyes were highly consistent with the Langmuir model, and the maximum adsorption capacity was 329.50 mg/g for methyl orange (MO) and 20.00 mg/g for rhodamine B (RhB). AL-CTS@MNPs showed good adsorption of anionic dyes (MO) in the pH range of 3-9. Meanwhile, the adsorbent AL-CTS@MNPs were also characterized, showing rough surface with specific surface areas of 37.38 m2/g, pore diameter of 95.8 nm and porosity of 17.62 %. The particle sizes were ranged from 800 μm to 1300 μm. The electrostatic attraction and π-π* electron donor-acceptor interactions were the main forces between the adsorbent and anionic dyes. While the electrostatic repulsive force between the adsorbent and the cationic dyes resulted in the non-absorption of MB by AL-CTS@MNPs. Subsequently, the adsorbent maintained a removal rate of >95 % after five adsorption-desorption cycles, demonstrating its excellent stability and recoverability. Ultimately, the prepared AL-CTS@MNPs illuminated good prospect on complex components dyes wastewater treatment.

Phospholipase D Immobilization on Lignin Nanoparticles for Enzymatic Transformation of Phospholipids

Lignin nanoparticles (LNPs) are promising components for various materials, given their controllable particle size and spherical shape. However, their origin from supramolecular aggregation has limited the applicability of LNPs as recoverable templates for immobilization of enzymes. In this study, we show that stabilized LNPs are highly promising for the immobilization of phospholipase D (PLD), the enzyme involved in the biocatalytic production of high-value polar head modified phospholipids of commercial interest, phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine. Starting from hydroxymethylated lignin, LNPs were prepared and successively hydrothermally treated to obtain c-HLNPs with high resistance to organic solvents and a wide range of pH values, covering the conditions for enzymatic reactions and enzyme recovery. The immobilization of PLD on c-HLNPs (PLD-c-HLNPs) was achieved through direct adsorption. We then successfully exploited this new enzymatic preparation in the preparation of pure polar head modified phospholipids with high yields (60-90 %). Furthermore, the high stability of PLD-c-HLNPs allows recycling for a number of reactions with appreciable maintenance of its catalytic activity. Thus, PLD-c-HLNPs can be regarded as a new, chemically stable, recyclable and user-friendly biocatalyst, based on a biobased inexpensive scaffold, to be employed in sustainable chemical processes for synthesis of value-added phospholipids.

In-situ preparation of lignin/Fe3O4 magnetic spheres as bifunctional material for the efficient removal of metal ions and methylene blue

In this paper, magnetic composite of lignin/Fe3O4 spheres were synthesized via a straightforward one-step in-situ solvothermal method showing good capacity for adsorbing heavy metal ions and dyes. The physicochemical properties of lignin/Fe3O4 spheres are analyzed using a range of techniques such as SEM, XRD, FTIR, VSM, TG, and BET. Lignin/Fe3O4 spheres exhibited high adsorption capacities of 100.00, 353.36 and 223.71 and 180.18 mg/g for Cu (II), Ni (II) and Cr (VI) metal ions and methylene blue (MB) with equilibrium attained within 60 min. After the recycling experiments, lignin/Fe3O4 spheres still possesses excellent superparamagnetic properties and displays high adsorption capacity. The lignin/Fe3O4 spheres are an efficient and continuous adsorbent to remove heavy metal ions of Cu (II), Ni (II), Cr (VI) and cationic dyes of methylene blue in wastewater, which proves the great potential in practical pollutants treatment applications for water systems.

Recent advances and future perspective on lignocellulose-based materials as adsorbents in diverse water treatment applications

The growing shortage of non-renewable resources and the burden of toxic pollutants in water have gradually become stumbling blocks in the path of sustainable human development. To this end, there has been great interest in finding renewable and environmentally friendly materials to promote environmental sustainability and combat harmful pollutants in wastewater. Of the many options, lignocellulose, as an abundant, biocompatible and renewable material, is the most attractive candidate for water remediation due to the unique physical and chemical properties of its constituents. Herein, we review the latest research advances in lignocellulose-based adsorbents, focusing on lignocellulosic composition, material modification, application of adsorbents. The modification and preparation methods of lignin, cellulose and hemicellulose and their applications in the treatment of diverse contaminated water are systematically and comprehensively presented. Also, the detailed description of the adsorption model, the adsorption mechanism and the adsorbent regeneration technique provides an excellent reference for understanding the underlying adsorption mechanism and the adsorbent recycling. Finally, the challenges and limitations of lignocellulosic adsorbents are evaluated from a practical application perspective, and future developments in the related field are discussed. In summary, this review offers rational insights to develop lignocellulose-based environmentally-friendly reactive materials for the removal of hazardous aquatic contaminants.

Adsorptive properties and on-demand magnetic response of lignin@Fe3O4 nanoparticles at castor oil-water interfaces

Lignin@Fe₃O₄ nanoparticles adsorb at oil-water interfaces, form Pickering emulsions, induce on-demand magnetic responses to break emulsions, and can sequester oil from water. Lignin@Fe₃O₄ nanoparticles were prepared using a pH-induced precipitation method and were fully characterized. These were used to prepare Pickering emulsions with castor oil/Sudan red G dye and water at various oil/water volume ratios and nanoparticle concentrations. The stability and demulsification of the emulsions under different magnetic fields generated with permanent magnets (0-540 mT) were investigated using microscopy images and by visual inspection over time. The results showed that the Pickering emulsions were more stable at the castor oil/water ratio of 50/50 and above. Increasing the concentration of lignin@Fe₃O₄ improved the emulsion stability and demulsification rates with 540 mT applied magnetic field strength. The adsorption of lignin@Fe₃O₄ nanoparticles at the oil/water interface using 1-pentanol evaporation through Marangoni effects was demonstrated, and magnetic manipulation of a lignin@Fe₃O₄ stabilized castor oil spill in water was shown. Nanoparticle concentration and applied magnetic field strengths were analyzed for the recovery of spilled oil from water; it was observed that increasing the magnetic strength increased oil spill motion for a lignin@Fe₃O₄ concentration of up to 0.8 mg mL^-1 at 540 mT. Overall, this study demonstrates the potential of lignin-magnetite nanocomposites for rapid on-demand magnetic responses to externally induced stimuli.

Adsorption and Photo-Fenton Degradation of Methylene Blue Using Nanomagnetite/Potassium Carrageenan Bio-Composite Beads

The present study deals with the preparation of nanomagnetite (NM), potassium carrageenan (KC), and nanomagnetite/potassium carrageenan bio-composite beads (NC). Characterization of the prepared solid materials using different physicochemical techniques such as X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy-disperse X-ray spectroscopy (EDX), diffuse reflectance spectrophotometer (DRS), swelling ratio (SR%), N2 adsorption, pH of point of zero charges (pHPZC), and Fourier transform infrared spectroscopy (FTIR). Comparing between adsorption and photo-Fenton degradation process for methylene blue (MB) on the surface of the prepared solid materials. Nanomagnetite/potassium carrageenan bio-composite (NC) exhibited high specific surface area (406 m2/g), mesoporosity (pore radius, 3.64 nm), point of zero charge around pH6.0, and the occurrence of abundant oxygen-containing functional groups. Comparison between adsorption and photo-Fenton oxidation process for methylene blue (MB) was carried out under different application conditions. NC exhibited the maximum adsorption capacity with 374.50 mg/g at 40 °C after 24 h of shaking time while 96.9% of MB was completely degraded after 20 min of photo-Fenton process. Langmuir's adsorption model for MB onto the investigated solid materials is the best-fitted adsorption model based on the higher correlation coefficient values (0.9771–0.9999). Kinetic and thermodynamic measurements prove that adsorption follows PSO, endothermic, and spontaneous process, while photo-Fenton degradation of MB achieves PFO, nonspontaneous, and endothermic process. Photo-Fenton degradation is a fast and simple technique at a lower concentration of dye (< 40 mg/L) while at higher dye concentration, the adsorption process is preferred in the removal of that dye.

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.