A lignin-based epoxy/TiO2 hybrid nanoparticle for multifunctional bio-based epoxy with improved mechanical, UV absorption and antibacterial properties

Preparation of uniform lignin/titanium dioxide nanoparticles by confined assembly: A multifunctional nanofiller for a waterborne polyurethane wood coating

We report a facile synthesis for lignin/titanium dioxide (TiO2) nanoparticles (LT NPs) at room temperature by confining assembly of lignin macromolecules. The LT NPs had a uniform nanosize distribution (average diameter ∼ 68 nm) and were directly employed as multifunctional nanofillers to reinforce a waterborne polyurethane wood coating (WBC). X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed the mechanism by which formed TiO2 confined lignin assembly. The LT NPs considerably increased the tensile strength of a WBC film from 16.3 MPa to 28.1 MPa. The WBC-LT NPs exhibited excellent ultraviolet (UV) A and UVB blocking performances of 87 % and 98 %, respectively, while maintaining 94 % transmittance in the visible region. Incorporating LT NPs into the WBC enhanced the coating performance (the hardness, adhesion, and abrasion resistance) on wood substrates. A quantitative color and texture analysis revealed that the LT NPs increased the decorativeness of actual wooden products. After nearly 1800 h of UV irradiation, wood coated with the WBC-LT NPs exhibited good color stability, where the original color remained unchanged or even became brighter. In this study, value-added valorization of lignin is enabled by using organic-inorganic nanofillers and insights are gained into developing multifunctional WBCs.

High capacity and selective adsorption of Congo red by cellulose-based aerogel with mesoporous structure: Adsorption properties and statistical data simulation

Large quantities of organic dyes are discharged into the environment, causing serious damage to the ecosystem. Therefore, it is urgent to develop inexpensive adsorbents to remove organic dyes. A novel cellulose-based aerogel (MPPA) with 3D porous structure was prepared by using cassava residue (cellulose) as basic construction blocks, doping ferroferric oxide (Fe3O4) for magnetic separation, and applying polyethyleneimine (PEI) as functional material for highly efficient and selective capture of Congo red (CR). MPPA exhibited porous network structure, numerous active capture sites, nontoxicity, high hydrophilicity, and excellent thermal stability. MPPA showed superior adsorption property for CR, with an equilibrium adsorption capacity of 2018.14 mg/g, and still had an adsorption property of 1189.31 mg/g after five recycling procedures. In addition, MPPA has excellent selectivity for CR in four binary dye systems. The adsorption behavior of MPPA on CR was further explored using a multilayer adsorption model, EDR-IDR hybrid model and AOAS model. Electrostatic potential and independent gradient models were used to further verify the possible interaction between MPPA and CR molecules. In conclusion, MPPA is a promising adsorbent in the field of treating anionic dyes.

Bio-based hyperbranched epoxy resins: synthesis and recycling

Epoxy resins (EPs), accounting for about 70% of the thermosetting resin market, have been recognized as the most widely used thermosetting resins in the world. Nowadays, 90% of the world's EPs are obtained from the bisphenol A (BPA)-based epoxide prepolymer. However, certain limitations severely impede further applications of this advanced material, such as limited fossil-based resources, skyrocketing oil prices, nondegradability, and a "seesaw" between toughness and strength. In recent years, more and more research has been devoted to the preparation of novel epoxy materials to overcome the compromise between toughness and strength and solve plastic waste problems. Among them, the development of bio-based hyperbranched epoxy resins (HERs) is unique and attractive. Bio-based HERs synthesized from bio-derived monomers can be used as a matrix resin or a toughener resulting in partially or fully bio-based epoxy thermosets. The introduction of a hyperbranched structure can balance the strength and toughness of epoxy thermosets. Here, we especially focused on the recent progress in the development of bio-based HERs, including the monomer design, synthesis approaches, mechanical properties, degradation, and recycling strategies. In addition, we advance the challenges and perspectives to engineering application of bio-based HERs in the future. Overall, this review presents an up-to-date overview of bio-based HERs and guidance for emerging research on the sustainable development of EPs in versatile high-tech fields.

Recent advancement in synthesizing bio-epoxy nanocomposites using lignin, plant oils, saccharides, polyphenols, and natural rubbers: A review

Due to environmental issues, production costs, and the low recycling capability of conventional epoxy polymers and their composites, many science groups have tried to develop a new type of epoxy polymers, which are compatible with the environment. Considering the precursors, these polymers can be produced from plant oils, saccharides, lignin, polyphenol, and natural resins. The appearance of these bio-polymers caused to introduce a new type of composites, namely bio-epoxy nanocomposites, which can be classified according to the synthesized bio-epoxy, the used nanomaterials, or both. Hence, in this work, various bio-epoxy resins, which have the proper potential for application as a matrix, are completely introduced with the synthesis viewpoint, and their characterized chemical structures are drawn. In the next steps, the bio-epoxy nanocomposites are classified based on the used nanomaterials, which are carbon nanoparticles (carbon nanotubes, graphene nanoplatelets, graphene oxide, reduced graphene oxide, etc.), nano-silica (mesoporous and spherical), cellulose (nanofibers and whiskers), nanoclay and so on. Also, the features of these bio-nanocomposites and their applications are introduced. This review study can be a proper guide for developing a new type of green nanocomposites in the near future.

Synergistic Effect of Nanoparticles: Enhanced Mechanical and Corrosion Protection Properties of Epoxy Coatings Incorporated with SiO2 and ZrO2

This research paper presents the fabrication of epoxy coatings along with the hybrid combination of SiO₂ and ZrO₂. The epoxy resin is incorporated with SiO₂ as the primary pigment and ZrO₂ as the synergist pigment. The study delves into the adhesion, barrier, and anti-corrosion properties of these coatings, enriched with silica and zirconium nanoparticles, and investigates their impact on the final properties of the epoxy coating. The epoxy resin, a Diglycidyl ether bisphenol-A (DGEBA) type, is cured with a polyamidoamine adduct-based curing agent. To evaluate the protective performance of silica SiO₂ and zirconia ZrO₂ nanoparticles in epoxy coatings, the coated samples were tested in a 3.5% NaCl solution. The experimental results clearly demonstrate a remarkable improvement in the ultimate tensile strength (UTS), yield strength (YS), and Elastic Modulus. In comparison to using SiO₂ separately, the incorporation of both ZrO₂ and SiO₂ resulted in a substantial increase of 43.5% in UTS, 74.2% in YS, and 8.2% in Elastic Modulus. The corrosion test results revealed that the combination of DGEBA, SiO₂, and ZrO₂ significantly enhanced the anti-corrosion efficiency of the organic coatings. Both these pigments exhibited superior anti-corrosion effects and mechanical properties compared to conventional epoxy coatings, leading to a substantial increase in the anti-corrosion efficiency of the developed coating. This research focuses the potential of SiO₂ and ZrO₂ in hybrid combination for applications, where mechanical, corrosion and higher adhesion to the substrates are of prime importance.

Structural Characteristics-Reactivity Relationships for Catalytic Depolymerization of Lignin into Aromatic Compounds: A Review

Developing renewable biomass resources is an urgent task to reduce climate change. Lignin, the only renewable aromatic feedstock present in nature, has attracted considerable global interest in its transformation and utilization. However, the complexity of lignin's structure, uncertain linkages, stability of side chain connection, and inevitable recondensation of reaction fragments make lignin depolymerization into biofuels or platform chemicals a daunting challenge. Therefore, understanding the structural characteristics and reactivity relationships is crucial for achieving high-value utilization of lignin. In this review, we summarize the key achievements in the field of lignin conversion with a focus on the effects of the β-O-4 content, S/G ratio, lignin sources, and an "ideal" lignin-catechyl lignin. We discuss how these characteristics influence the formation of lignin monomer products and provide an outlook on the future direction of lignin depolymerization.

Titanium dioxide nanoparticles functionalized chitosan toward bio-based antibacterial adsorbent for enhanced phosphate capture

Developing an eco-friendly, sustainable and antibacterial adsorbent is significant for actual water treatment. Herein, a new bio-based antibacterial adsorbent based on titanium dioxide (TiO₂) nanoparticles functionalized chitosan (CS) was prepared through an in-situ hydrolysis strategy using titanium oxysulfate as the source of TiO₂. The as-obtained CS/TiO₂ nanocomposite was characterized by a variety of analytical techniques. According to the Langmuir mode, the adsorption capacity of CS/TiO₂ reached 23.64 mg P g^-1, almost 8 times higher than that of CS. In addition, the normalized adsorption capacity (adsorption value per Ti) of CS/TiO₂ was calculated to be 102.68 mg P g^-1 Ti^-1, much higher than pure TiO₂ (60.11 mg P g^-1 Ti^-1). Moreover, CS/TiO₂ exhibited a highly selective capacity for phosphate removal in the presence of competing anions, and showed high stability in a wide pH range of 3.0-9.0. When the phosphate concentration was 2.0 mg P L^-1, the removal efficiency of phosphate reached 99.5 % and the residual concentration was only 10 μg P L^-1, which meets the USEPA standards for eutrophication prevention and control. In addition, after treatment by CS/TiO₂, the phosphate concentration of two sewage water samples decreased from 1.50 and 1.0 mg P L^-1 to <0.010 mg P L^-1, meeting the standard of level II water based on the Environmental Quality Standard of China (GB3838-2002). Ligand exchange and electrostatic interactions are mainly responsible for phosphate adsorption by CS/TiO₂. Furthermore, the CS/TiO₂ nanocomposites exhibited excellent antibacterial activity, which could avoid biofouling contamination caused by microorganisms. Benefiting from the above advantages, the as-designed CS/TiO₂ nanocomposite has great potential as a bio-based antibacterial adsorbent for phosphate removal or capture from wastewater.

Tailoring TiO2-lignin hybrid materials as a bio-filler for the synthesis of composites based on epoxy resin

In this publication, the functional TiO₂-lignin hybrid materials were designed and characterized. Based on elemental analysis and Fourier transform infrared spectroscopy, the efficiency of the mechanical method used to obtain systems was confirmed. Hybrid materials were also characterized by good electrokinetic stability, in particular in the inert and alkaline environments. The addition of TiO₂ improves thermal stability in the entire analyzed range of temperatures. Similarly, as the content of inorganic component increases, the homogeneity of the system and the occurrence of smaller nanometric particles increase. In addition, a novel synthesis method of cross-linked polymer composites based on a commercial epoxy resin and an amine cross-linker was described as a part of the article, where additionally newly designed hybrids were also used. Subsequently, the obtained composites were subjected to simulated tests of accelerated UV-aging, and then their properties were studied, including changes in wettability (using water, ethylene glycol, and diiodomethane as measurement liquids) and surface free energy by the Owens-Wendt-Eabel-Kealble method. Changes in the chemical structure of the composites were monitored by FTIR spectroscopy due to aging. Microscopic studies of surfaces were also carried out as well as measurements in the field of changes in color parameters in the CIE-Lab system.

A magnetically recyclable lignin-based bio-adsorbent for efficient removal of Congo red from aqueous solution

It has been always attractive to design a sustainable bio-derived adsorbent based on industrial waste lignin for removing organic dyes from water. However, existing adsorbent strategies often lead to the difficulties in adsorbent separation and recycling. Herein, we report a novel magnetically recyclable bio-adsorbent of Mg(OH)₂/Fe₃O₄/PEI functionalized enzymatic lignin (EL) composite (EL-PEI@Fe₃O₄-Mg) for removing Congo red (CR) by Mannish reaction and hydrolysis-precipitation. The Mg(OH)₂ and PEI functionalized EL on the surface act as active sites for the removal of CR, while the Fe₃O₄ allows for the easy separation under the help of a magnet. As-obtained EL-PEI@Fe₃O₄-Mg forms flower-like spheres and has a relatively lager surface area of 24.8 m² g^-1 which is 6 times that of EL. The EL-PEI@Fe₃O₄-Mg exhibits a relatively high CR adsorption capacity of 74.7 mg g^-1 which is 15 times that of EL when initial concentration is around 100 mg L^-1. And it can be easily separated from water by applying an external magnetic field. Moreover, EL-PEI@Fe₃O₄-Mg shows an excellent anti-interference capability according to the results of pH values and salt ions influences. Importantly, EL-PEI@Fe₃O₄-Mg possesses a good reusability and a removal efficiency of 92 % for CR remains after five consecutive cycles. It is illustrated that electrostatic attraction, π-π interaction and hydrogen binding are primary mechanisms for the removal of CR onto EL-PEI@Fe₃O₄-Mg. This work provides a novel sustainable strategy for the development of highly efficient, easy separable, recyclability bio-derived adsorbents for removing organic dyes, boosting the efficient utilization of industrial waste lignin.