Photothermal Properties and Solar Water Evaporation Performance of Lignin-Based Polyurethane Foam Composites.

Solar interfacial evaporation is the most promising route for desalination because it is highly efficient, affordable and offers green energy. Polyurethane foam (PUF) is an ideal substrate material for efficient solar water evaporation because of its low thermal conductivity, affordability, and high efficiency for continuous water transport. However, PUF exhibits poor mechanical properties after water absorption and expansion, and lacks the photothermal conversion effect. In this study, biorefinery lignin with efficient photothermal properties was introduced to prepare functional lignin-based PUF (LPUF), and the relationship between the molecular structure of fractioned lignin and the solar water evaporation performance was systematically investigated. The addition of lignin effectively enhanced the mechanical properties of LPUF after water absorption and swelling, and imparted the foam with a photothermal conversion effect. The water evaporation rate of LPUF was as high as 2.58 kg m-2 h-1 and could be further improved to more than 3.0 kg m-2 h-1 after loading polyaniline (PANI) on the surface of LPUF. LPUF-PANI exerted an excellent purification effect on dye wastewater with outstanding long-term stability, providing a potential solution for ecofriendly and sustainable economic production of fresh water. This study broadens the effective utilization of LPUF bulk materials in the fields of energy and environment.

Production of Lignin-Derived Functional Material for Efficient Electromagnetic Wave Absorption with an Ultralow Filler Ratio.

Industrial lignin, a by-product of pulping for papermaking fibers or of second-generation ethanol production, is primarily served as a low-grade combustible energy source. The fabrication of high-value-added functional materials with industrial lignin is still a challenge. Herein, a three-dimensional hierarchical lignin-derived porous carbon (HLPC) was prepared with lignosulfonate as the carbon source and MgCO3 as the template. The uniform mixing of precursor and template agent resulted in the construction of a three-dimensional hierarchical porous structure. HLPC presented excellent electromagnetic wave (EMW) absorption performance. With a low filler content of 7 wt%, HLPC showed a minimum reflection loss (RL) value of -41.8 dB (1.7 mm, 13.8 GHz), and a maximum effective absorption bandwidth (EAB) of 4.53 GHz (1.6 mm). In addition, the enhancement mechanism of HLPC for EMW absorption was also explored through comparing the morphology and electromagnetic parameters of lignin-derived carbon (LC) and lignin-derived porous carbon (LPC). The three-dimensional hierarchical porous structure endowed the carbon with a high pore volume, resulting in an abundant gas-solid interface between air and carbon for interfacial polarization. This structure also provided conductive networks for conduction loss. This work offers a strategy to synthesize biomass-based carbon for high-performance EMW absorption.

Effect of functional group and structure on hydrophobic properties of environment-friendly lignin-based composite coatings.

Hydrophobic coatings are widely used in a variety of materials surfaces. However, it remains a great challenge for the non-toxic and environmentally-friendly production of hydrophobic coatings. Herein, two nano-scale spherical lignin/SiO2 composite particles are synthesized based on the electrostatic interaction and the steric hindrance effect inspired by the self-protection of straw. Introduction of positively charged quaternary ammonium enhances the possibility of electrostatic self-assembly between lignin and SiO2 for QAL/SiO2, and access of super-long hydrophobic chains induces the formation of nano-sized particles for QALC12/SiO2. The coatings were fabricated by simply spraying on substrates and hydrophilic/hydrophobic properties were detected. The results show that the long hydrophobic chain can enhance the hydrophobic properties of lignin polymers (CA = 129°) and the spherical micro-nano structure is beneficial to improve the hydrophobic properties of the lignin/SiO2 composite (CA = 137°). Meanwhile, the hydrophobic coating has good self-cleaning performance. The excellent hydrophobic and self-cleaning properties are mainly benefited from the nano effect, reasonable hydrophilic/hydrophobic structure, and good dispersibility of spherical structure. This work not only provides a kind of lignin-based nano-scale waterproof coatings holding excellent properties in terms of cost, scalability, and robustness, but also has important significance for the high-value utilization of biomass resources.

Preparation and Performance of Lignin-Based Multifunctional Superhydrophobic Coating.

Superhydrophobic coatings have drawn much attention in recent years for their widespread potential applications. However, there are challenges to find a simple and cost-effective approach to prepare superhydrophobic materials and coatings using natural polymer. Herein, we prepared a kraft lignin-based superhydrophobic powder via modifying kraft lignin through 1H, 1H, 2H, 2H-perfluorodecyl-triethoxysilane (PFDTES) substitution reaction, and constructed superhydrophobic coatings by direct spraying the suspended PFDTES-Lignin powder on different substrates, including glass, wood, metal and paper. The prepared lignin-based coatings have excellent repellency to water, with a water contact angle of 164.7°, as well as good friction resistance, acid resistance, alkali resistance, salt resistance properties and quite good self-cleaning performance. After 30 cycles of sand friction or being stayed in 2 mol/L HCl, 0.25 mol/L NaOH and 2 mol/L NaCl solution for 30 min, the coatings still retain super hydrophobic capability, with contact angles higher than 150°. The superhydrophobic performance of PFDTES-Lignin coatings is mainly attributed to the constructed high surface roughness and the low surface energy afforded by modified lignin. This lignin-based polymer coating is low-cost, scalable, and has huge potential application in different fields, providing a simple way for the value-added utilization of kraft lignin.