Green Synthesis of Size-Controllable Polyfurfuryl Alcohol Nanospheres as Novel Bio-adsorbents

Nanomaterials derived from biomass preparation exhibit potential applications in the field of environmental protection. However, the synthesis methods still have some problems, including being a time-consuming and complex process and causing secondary pollution. In this work, polyfurfuryl alcohol (PFA) nanospheres are synthesized via a green method that uses water as the solvent, sodium dodecyl sulfate as the stabilizer, and p-benzenesulfonic acid monohydrate as the acid catalyst. In addition, the filtrate remained capable of preparing uniform nanospheres in five subsequent runs. Moreover, the size of PFA nanospheres could be regulated from 40 to 800 nm. The small PFA nanospheres provide a large surface area, suggesting more adsorption sites. PFA nanospheres are used first as novel bio-adsorbents for cationic dye (methylene blue) removal because of their abundant oxygen-containing functional groups and negative potential. Synthesis parameters and adsorption conditions affecting cationic dye removal, sorption mechanisms, and kinetics were studied. Results suggest that the synergistic effect of electrostatic attraction, π–π interactions, and hydrogen bonding contributes to the maximum adsorption capacity as high as 343.3 mg/g. Furthermore, the PFA nanospheres exhibited good regenerative properties. This work paves the way for the green and sustainable preparation of biomass furfuryl alcohol nanospheres

Positively Charged Polyamine Nanofiltration Membrane for Precise Ion–Ion Separation

Positively charged nanofiltration (NF) membranes offer enormous potential for lithium–magnesium separation, hard water softening, and heavy metal removal. However, fundamental performance limitations for these applications exist in conventional polyamide-based NF membranes due to the negatively charged surface and low ion–ion selectivity. We hereby innovatively develop an advanced positively charged polyamine-based NF membrane built by the nucleophilic substitution of bromine and amine groups for precise ion–ion separation. Specifically, polyethylenimine (PEI) and 1,3,5-tris(bromomethyl)benzene (TBB) are interfacially polymerized to generate an amine-linked PEI-TBB selective layer with an ultrathin thickness of ∼95 nm, an effective pore size of 6.5 Å, and a strong positively charged surface with a zeta potential of +20.9 mV at pH 7. The PEI-TBB composite membrane achieves a water permeance of 4.2 L·m–2·h–1·bar–1, various divalent salt rejections above 90%, and separation factors above 15 for NaCl/MgCl2 and LiCl/MgCl2 mixed solutions. A three-stage NF process is implemented to achieve a Mg2+/Li+ mass ratio sharply decreasing from 50 to 0.11 with a total separation factor (SLi,Mg) of 455. Furthermore, the polyamine-based NF membrane exhibits excellent operational stability under continuous filtration and high operational pressure, demonstrating great application potential for precise ion–ion separation

High-Performance Multilayer Composite Membranes with Mussel-Inspired Polydopamine as a Versatile Molecular Bridge for CO₂ Separation

It is desirable to develop high-performance composite membranes for efficient CO₂ separation in CO₂ capture process. Introduction of a highly permeable polydimethylsiloxane (PDMS) intermediate layer between a selective layer and a porous support has been considered as a simple but efficient way to enhance gas permeance while maintaining high gas selectivity, because the introduced intermediate layer could benefit the formation of an ultrathin defect-free selective layer owing to the circumvention of pore penetration phenomenon. However, the selection of selective layer materials is unfavorably restricted because of the low surface energy of PDMS. Various highly hydrophilic membrane materials such as amino group-rich polyvinylamine (PVAm), a representative facilitated transport membrane material for CO₂ separation, could not be facilely coated over the surface of the hydrophobic PDMS intermediate layer uniformly. Inspired by the hydrophilic nature and strong adhesive ability of polydopamine (PDA), PDA was therefore selected as a versatile molecular bridge between hydrophobic PDMS and hydrophilic PVAm. The PDA coating endows a highly compatible interface between both components with a large surface energy difference via multiple-site cooperative interactions. The resulting multilayer composite membrane with a thin facilitated transport PVAm selective layer exhibits a notably enhanced CO₂ permeance (1887 GPU) combined with a slightly improved CO₂/N₂ selectivity (83), as well as superior structural stability. Similarly, the multilayer composite membrane with a hydrophilic CO₂-philic Pebax 1657 selective layer was also developed for enhanced CO₂ separation performance

Microstructure and Flight Behaviors of Droplet and its Solidification in Twin-Wire Arc Sprayed Ni-Al Composite Coatings

<div><p>Droplet flight and solidification behaviors during twin-wire arc sprayed (TWAS) composite coatings were systematically investigated. Both theoretical model and numerical method were established for calculating the droplet deformation, breakup and solidification process in air flow based on the volume of fluid (VOF) dual-phase flow model jointed with the standard k-ε model. The experimental simulation results indicate that TWAS droplet is broken through explosion or two steps breaking process. The calculation of TWAS gas flight dynamics demonstrates that the TWAS particles are accelerated at first and then slowed down. Microstructure of the TWAS prepared Ni-5wt.%Al and Ni-20wt.%Al composite coating was accordingly characterized by XRD, SEM and TEM, so the phase compositions of the Ni-Al composite coatings were obtained. TEM analysis also showed that an amorphous phase was formed according to the characteristic of diffraction ring in Ni matrix solid solution at an original state.</p></div

Microstructure and Flight Behaviors of Droplet and its Solidification in Twin-Wire Arc Sprayed Ni-Al Composite Coatings

<div><p>Droplet flight and solidification behaviors during twin-wire arc sprayed (TWAS) composite coatings were systematically investigated. Both theoretical model and numerical method were established for calculating the droplet deformation, breakup and solidification process in air flow based on the volume of fluid (VOF) dual-phase flow model jointed with the standard k-ε model. The experimental simulation results indicate that TWAS droplet is broken through explosion or two steps breaking process. The calculation of TWAS gas flight dynamics demonstrates that the TWAS particles are accelerated at first and then slowed down. Microstructure of the TWAS prepared Ni-5wt.%Al and Ni-20wt.%Al composite coating was accordingly characterized by XRD, SEM and TEM, so the phase compositions of the Ni-Al composite coatings were obtained. TEM analysis also showed that an amorphous phase was formed according to the characteristic of diffraction ring in Ni matrix solid solution at an original state.</p></div