Lignin-Containing Cellulose Nanofibril-Reinforced Polyvinyl Alcohol Hydrogels

Two lignin-containing cellulose nanofibril (LCNF) samples, produced from two unbleached kraft pulps with very different lignin contents, were used to produce reinforced polyvinyl alcohol (PVA) hydrogels. The effects of LCNF loading (0.25–2 wt %) and lignin content on the rheological and mechanical properties of the reinforced hydrogels were investigated. The 2 wt % LCNF-reinforced PVA hydrogels exhibited up to a 17-fold increase in storage modulus and a 4-fold increase in specific Young’s modulus over that of pure PVA hydrogel. Both the mechanical and rheological properties of LCNF-reinforced PVA hydrogels can be tuned by varying LCNF loading and LCNF lignin content. During LCNF production, lignin reduced cellulose depolymerization, resulting in LCNF with high aspect ratios that promoted entanglement and physical bridging of the hydrogel network. Free lignin particles generated during LCNF production acted as multifunctional nanospacers that increased porosity of the hydrogels. Because LCNFs were produced from unbleached chemical pulps, which have high yields and do not require bleaching, this study provides a more sustainable approach to utilize lignocelluloses to produce biomass-based hydrogels than by methods using commercial bleached pulps

Data for: A study of indoor air quality and passengers’ thermal comfort of metro transfer stations in Beijing

Field test data and experimental calculation data

Data for: A study of indoor air quality and passengers’ thermal comfort of metro transfer stations in Beijing

Field test data and experimental calculation data

Chiral Self-Assembly Behavior of Carboxylated Cellulose Nanocrystals Isolated by Recyclable Oxalic Acid from Degreasing Cotton

Carboxylated cellulose nanocrystals (OA-CNCs) isolated by aqueous recyclable oxalic acid hydrolysis from degreasing cotton were used to observe its self-assembly behavior and chiral nematic properties. The oxalic acid here served as the sole catalyst to esterify and hydrolyze the degreasing cotton. The results indicated that the obtained OA-CNC suspensions were spontaneously phase-separated into a chiral nematic mesophase above a critical concentration, and the occurrence of chiral self-assembly is highly dependent on the aspect ratio and the surface charge of the OA-CNC suspension. Scanning electron microscopy images of the cross section of OA-CNC solid films revealed a periodic ordered multilayer structure. The residual OA was easily recovered through simple re-crystallization method after reactions with a high recovery rate of at least 90%. The recycled OA (ROA) had excellent performance in terms of ROA-CNC yield even after reusing for five cycles. Moreover, the resultant ROA-CNCs from recycled OA could also form chiral nematic ordered phases with little change in the critical concentration and pitch, suggesting excellent suitability for sustainable OA-CNC production for photonics and other specialty applications

Phosphate-Functionalized Fibrous Adsorbent for Effectively Extracting Uranium from Seawater

Uranium is a basic and strategic resource related to national development and security. The uranium resources contained in the ocean are thousands of times that in the land, up to about 4.5 billion tons. However, it is still a severe challenge for the extraction of uranium from seawater as it contains trace amounts of uranium and a large number of cations. Herein, a new uranium extraction material, phosphate-functionalized collagen fibers, was prepared by a “covalent cross-linking” method by grafting the phosphate functional groups onto the surface of collagen fibers (CF) with a multihierarchy structure and multiple functional groups. The special structure of CF makes the adsorbent exhibit multistage kinetics and is controlled by chemisorption and layer diffusion. Through the introduction of amino and phosphoric acid functional groups, collagen fiber-alendronate sodium trihydrate (CF-AST) exhibits high-efficiency adsorption for uranium with the maximum adsorption reaching 277.78 mg g–1. In the extraction test from the East China Sea, CF-AST displayed a total uranium extraction mass of 29.61 μg after processing 10 L of seawater with an extraction rate of 89.69%. This adsorbent has shown superiorities in selectivity, kinetics, capacity, and reproducibility of uranium separation and enrichment from seawater, which is an economically viable and industrially scalable realistic uranium extraction material