Lignin-based flame retardant via sequential purification-nanoparticle formation, and NP coupled chemical modification.

A nonhalogenated and ecofriendly flame-retarding material was developed using lignin, one of the main components of lignocellulosic biopolymers. Lignin was purified, dissolved, and formulated as nanoparticles and implemented after processing in an ecofriendly water-based γ-valerolactone (GVL) system at different concentrations. Nitrogen­phosphorus sequential chemical modification was performed using polyethyleneimine (PEI) and phytic acid (PA), The char residue increased by ≥10 % compared with lignin nanoparticles (LNPs). A 10 wt% lignin-based flame retardant (L-FR) based on the weight of cotton fabric was introduced using a simple dipping method. Compared to existing cotton fabrics, the combustion time of L-FR treated cotton fabrics was reduced by 6.8 s. The maximum flame height was reduced by 5.4 cm, and the charcoal residue increased by 25 %. The flame-retarding mechanism of L-FR involved low-temperature dehydration, thermal decomposition of cellulose by the phosphorus component of PA and generation of expansive gas by the nitrogen component of PEI. These results showed that lignin-based raw material processing, polymer processing, and chemical modification were biomass-based, suggesting that lignin could be converted into an ecofriendly flame retardant, highlighting the feasibility of high-value-added lignin.

Biodegradation in Composting Conditions of PBEAS Monofilaments for the Sustainable End-Use of Fishing Nets.

The development and utilization of biodegradable plastics is an effective way to overcome environmental pollution caused by the disposal of non-degradable plastics. Recently, polybutylene succinate co-butylene adipate co-ethylene succinate co-ethylene adipate, (PBEAS) a biodegradable polymer with excellent strength and elongation, was developed to replace conventional nylon-based non-degradable fishing nets. The biodegradable fishing gear developed in this way can greatly contribute to inhibiting ghost fishing that may occur at the fishing site. In addition, by collecting the products after use and disposing of them in composting conditions, the environmental problem such as the leakage of microplastics strongly can be prevented. In this study, the aerobic biodegradation of PBEAS fishing nets under composting conditions is evaluated and the resulting changes in physicochemical properties are analyzed. The PBEAS fishing gear exhibits a mineralization rate of 82% in a compost environment for 45 days. As a result of physicochemical analysis, PBEAS fibers show a representative decrease in molecular weight and mechanical properties under composting conditions. PBEAS fibers can be used as eco-friendly biodegradable fishing gear that can replace existing non-degradable nylon fibers, and in particular, fishing gear collected after use can be returned to nature through biodegradation under composting conditions.

pH-sensitive cellulose/chitin nanofibrillar hydrogel for dye pollutant removal.

In this study, a pH-sensitive smart hydrogel was successfully prepared by combining a polyelectrolyte complex using biopolymeric nanofibrils. By adding a green citric acid cross-linking agent to the formed chitin and cellulose-derived nanofibrillar polyelectrolytic complex, a hydrogel with excellent structural stability could be prepared even in a water environment, and all processes were conducted in an aqueous system. The prepared biopolymeric nanofibrillar hydrogel not only enables rapid conversion of swelling degree and surface charge according to pH but can also effectively remove ionic contaminants. The ionic dye removal capacity was 372.0 mg/g for anionic AO and 140.5 mg/g for cationic MB. The surface charge conversion ability according to pH could be easily applied to the desorption of the removed contaminants, and as a result, it showed an excellent contaminant removal efficiency of 95.1 % or more even in the repeated reuse process 5 times. Overall, the eco-friendly biopolymeric nanofibrillar pH-sensitive hydrogel shows potential for complex wastewater treatment and long-term use.

Effect of chemically modified lignin addition on the physicochemical properties of PCL nanofibers.

In this study, a chemically modified lignin additive was successfully prepared to improve the physicochemical properties of biodegradable polycaprolactone (PCL)-based nanofibers. The molecular weight and surface functional group characteristics of lignin were effectively controlled through a solvent fractionation process using ethanol. Then, PCL-g-lignin was successfully synthesized by using ethanol-fractionated lignin as a platform for the PCL grafting process. Finally, PCL/PCL-g-lignin composite nanofibers were simply prepared by adding PCL-g-lignin to the PCL doping solution and performing a solution blow spinning process. The addition of PCL-g-lignin could dramatically improve the physical and chemical properties of PCL nanofibers, and in particular, the tensile strength (0.28 MPa) increased by approximately 280 % compared to the conventional PCL. In addition, the lignin moiety present in PCL-g-lignin was able to impart UV blocking properties to PCL nanofibers, and as a result, it was possible to effectively suppress the photolysis phenomenon that occurred rapidly in existing PCL nanofibers. Therefore, PCL-g-lignin may be widely used not only as a reinforcing agent of existing biodegradable nanofibers but also as a functional additive for UV protection.

Biodegradable and hydrophobic nanofibrous membranes produced by solution blow spinning for efficient oil/water separation.

The development of nanofibrous oil-water separation materials is explosively progressing, but the remarkably low productivity is the main factor hindering their practical application. In this study, biodegradable polybutylene succinate (PBS) nanofibers with excellent productivity (27.0 g/h per nozzle) were successfully fabricated using the solution blow spinning (SBS) process, breaking away from the conventional electrospinning method. The prepared PBS nanofibers exhibited extremely thin fiber diameters (130 nm) with high porosity (97.4%). Without any chemical modification or inorganic/organic hybrid materialization, the PBS nanofibrous membrane showed excellent oil adsorption capacity (minimum: 18.7 g/g and maximum: 38.5 g/g) and separation efficiency; water and oil mixtures (99.4-99.98%) and emulsions (98.1-99.5%) compared to conventional organic polymer-based nanofibers. In terms of disposal after use, this biodegradable nanofibrous membrane was able to return to nature through hydrolysis and biodegradation processes.

Highly efficient Cr(VI) remediation by cationic functionalized nanocellulose beads.

Applications of nanocellulose as a water treatment material are being actively pursued based on its interesting properties, such as renewability, large specific surface area, hydrophilic surface chemistry, and biodegradability. This study used carboxymethyl cellulose nanofibrils (CMCNFs) to prepare a typical bead-type adsorbent with improved structural stability as an actual water treatment restoration material. In addition, a cationized nanocellulose adsorbent was prepared by introducing polyethyleneimine (PEI) on the surface of the CMCNF (P/CMCNF), the removal efficiency of Cr(VI) was evaluated, and its mechanism was elucidated. As a result, the P/CMCNF beads showed an excellent Cr(VI) removal capacity of 1302.3 mg/g, the best result among cellulose-based adsorption materials. Cr(VI) was effectively removed by electrostatic attractions combined with chemical reduction and chelation mechanisms. Furthermore, the macrobead fabrication and PEI surface modification process improved the underwater stability of the P/CMCNF, and it showed excellent reuse efficiency.

Eco-friendly alkaline lignin/cellulose nanofiber drying system for efficient redispersion behavior.

Although nanocellulose is an eco-friendly, high-performance raw material provided by nature, the agglomeration of nanocellulose that occurs during the drying process is the biggest obstacle to its advanced materialization and commercialization. In this study, a facile and simple nanocellulose drying system was designed using lignin, which is self-assembled together with cellulose in natural wood, as an eco-friendly additive. The addition of lignin not only minimized aggregation during the drying and dehydration process of nanocellulose but also ensured excellent redispersion kinetics and stability. In addition, the added lignin could be removed through a simple washing process. Through FTIR, XRD, TGA, tensile and swelling tests, it was confirmed that the addition of lignin enabled the reversible restitution of the nanocellulose physicochemical properties to the level of pristine never-dried nanocellulose in drying, redispersion, and polymer processing processes.

Cationic surface-modified regenerated nanocellulose hydrogel for efficient Cr(VI) remediation.

Because nanocellulose has a large specific surface area and abundant hydroxyl functional groups due to its unique nanomorphology, interest increases as an eco-friendly water treatment material. However, the distinctive properties of nanocellulose, which exists in a dispersion state, strongly hamper its usage in practical water treatment processes. Additionally, nanocellulose shows low performance in removing anionic pollutants because of its anionic characteristics. In an effort to address this challenge, regenerated cellulose (RC) hydrogel was fabricated through cellulose's dissolution and regeneration process using an eco-friendly aqueous solvent system. Subsequently, a crosslinking process was carried out to introduce the cationic functional groups to the RC surface PEI coating (P/RC). As a result, the PEI surface cationization process improved the mechanical rigidity of RC and showed an excellent Cr(VI) removal capacity of 578 mg/g. In addition, the prepared P/RC maintained more than 90% removal efficiency even after seven reuses.

Nano/Micro Hybrid Bamboo Fibrous Preforms for Robust Biodegradable Fiber Reinforced Plastics.

The focus on high-strength and functional natural fiber-based composite materials is growing as interest in developing eco-friendly plastics and sustainable materials increases. An eco-friendly fibrous composite with excellent mechanical properties was prepared by applying the bamboo-derived nano and microfiber multiscale hybridization phenomenon. As a result, the cellulose nanofibers simultaneously coated the micro-bamboo fiber surface and adhered between them. The multiscale hybrid phenomenon implemented between bamboo nano and microfibers improved the tensile strength, elongation, Young's modulus, and toughness of the fibrous composite. The enhancement of the fibrous preform mechanical properties also affected the reinforcement of biodegradable fiber-reinforced plastic (FRP). This eco-friendly nano/micro fibrous preform can be extensively utilized in reinforced preforms for FRPs and other green plastic industry applications.