Solubilization of lignin in copolymer micelles in aqueous solution

Critical Techniques for Overcoming the Diffusion Limitations in Heterogeneously Catalytic Depolymerization of Lignin

Heterogeneously catalyzed depolymerization of lignin to value-added chemicals is increasingly attractive but highly challengeable. Particularly, the diffusion limitation of lignin macromolecule to the solid catalyst surface is a big barrier, which significantly decreases the yield of monomer while increasing char formation. Therefore, for the potential industrial utilization of lignin, new knowledge focused on the size of lignin particles is of great importance to offer guidance for promoting lignin depolymerization and suppressing condensation in the heterogeneously catalytic systems. In this Review, the size of lignin particles and macromolecules are summarized. Previous approaches for improving the mass diffusion including enhancing the solubility of lignin and exploitation of hierarchical and "solubilized" materials are also discussed. Based on these, a constructive perspective is proposed. Thus, this work provides a new insight on the rational design of heterogeneous catalytic techniques for efficient utilization of the aromatic polymer of lignin.

Development of Lignin-Based Mesoporous Carbons for the Adsorption of Humic Acid

There is an increasing urge to make the transition toward biobased materials. Lignin, originating from lignocellulosic biomass, can be potentially valorized as humic acid (HA) adsorbents via lignin-based mesoporous carbon (MC). In this work, these materials were synthesized for the first time starting from modified lignin as the carbon precursor, using the soft-template methodology. The use of a novel synthetic approach, Claisen rearrangement of propargylated lignin, and a variety of surfactant templates (Pluronic, Kraton, and Solsperse) have been demonstrated to tune the properties of the resulting MCs. The obtained materials showed tunable properties (BET surface area: 95-367 m²/g, pore size: 3.3-36.6 nm, V _BJH pore volume: 0.05-0.33 m³/g, and carbon and oxygen content: 55.5-91.1 and 3.0-12.2%, respectively) and good performance in terms of one of the highest HA adsorption capacities reported for carbon adsorbents (up to 175 mg/g).

Electrospun lignin-PVP nanofibers and their ability for structuring oil

This work explores the electrospinnability of low-sulfonate Kraft lignin (LSL)/polyvinylpyrrolidone (PVP) solutions in N,N-dimethylformamide (DMF) and the ability of the different micro- and nano-architectures generated to structure castor oil. LSL/PVP solutions were prepared at different concentrations (8-15 wt%) and LSL:PVP ratios (90:10-0:100) and physico-chemically and rheologically characterized. The morphology of electrospun nanostructures mainly depends on the rheological properties of the solution. Electrosprayed nanoparticles or micro-sized particles connected by thin filaments were obtained from solutions with low LSL/PVP concentrations and/or high LSL:PVP ratios, whereas beaded or bead-free nanofibers were produced by increasing concentration and/or decreasing LSL:PVP ratio, due to enhanced extensional viscoelastic properties and non-Newtonian characteristics. Electrospun LSL/PVP nanofibers are able to form oleogels by simply dispersing them into castor oil at concentrations between 10 and 30 wt%. The rheological properties of the oleogels may be tailored by modifying the LSL:PVP ratio and nanofibers content. The potential application of these oleogels as bio-based lubricants was also explored in a tribological cell. Satisfactory friction and wear results are achieved when using oleogels structured by nanofibers mats with enhanced gel-like properties as lubricants. Overall, electrospinning of lignin/PVP solutions can be proposed as a simple and effective method to produce nanofibers for oil structuring.

Enhanced levofloxacin removal from water using zirconium (IV) loaded corn bracts

The presence of antibiotics in the environment has attracted considerable attention due to their toxicity. In this study, agricultural waste corn bracts (CBs) modified by zirconium cations were utilized to remove levofloxacin (LEV) from wastewater. Zr-modified CBs exhibited a strong adsorption capacity (Q_max = 73 mg/g), and their desorption rate could reach 89% by simply adjusting the pH to 11. FTIR and XPS analyses indicated that the mechanism of LEV adsorption included the complexation between the ketone/carboxyl groups of LEV and the Zr atoms and the π-π electron-donor-acceptor interaction. Zr-modified CBs are economic, effective and nontoxic adsorbents. This material not only removes antibiotics from wastewater but also enables recycling and reuse of agricultural waste.