Lingdi Shen

High recovery of lead ions from aminated polyacrylonitrile nanofibrous affinity membranes with micro/nano structure.

In this paper, highly porous polyacrylonitrile (PAN) nanofibrous membranes were successfully fabricated by wet-electrospinning technique from PAN and poly(vinyl pyrrolidone) (PVP) blended solution using hot water bath as extractor, and then aminated with diethylene triamine (DETA). The obtained aminated PAN (APAN) nanofibrous mats showed unique micro/nano structures and possessed extra high extraction capability for the removal of lead ions (Pb(2+)) from aqueous solution (maximum uptake capacity of Pb(2+) was up to 1520.0mg/g), and could maintain over 90% of its extraction capacity at the sixth cycle of extraction-dissociation. Interestingly, the hexagonal crystals of basic lead(II) carbonate (Pb3(CO3)2(OH)2) grown on micro/nano structured APAN nanofibers were observed when APAN membrane was immersed in Pb(II) ions aqueous solution. The results provided new insights for the removal of metal ions by metal crystal growth from wastewater with high recovery.

Electrospun Poly(acrylic acid)/Silica Hydrogel Nanofibers Scaffold for Highly Efficient Adsorption of Lanthanide Ions and Its Photoluminescence Performance

Combined with the features of electrospun nanofibers and the nature of hydrogel, a novel choreographed poly(acrylic acid)-silica hydrogel nanofibers (PAA-S HNFs) scaffold with excellent rare earth elements (REEs) recovery performance was fabricated by a facile route consisting of colloid-electrospinning of PAA/SiO2 precursor solution, moderate thermal cross-linking of PAA-S nanofiber matrix, and full swelling in water. The resultant PAA-S HNFs with a loose and spongy porous network structure exhibited a remarkable adsorption capacity of lanthanide ions (Ln(3+)) triggered by the penetration of Ln(3+) from the nanofiber surface to interior through the abundant water channels, which took full advantage of the internal adsorption sites of nanofibers. The effects of initial solution pH, concentration, and contact time on adsorption of Ln(3+) have been investigated comprehensively. The maximum equilibrium adsorption capacities for La(3+), Eu(3+), and Tb(3+) were 232.6, 268.8, and 250.0 mg/g, respectively, at pH 6, and the adsorption data were well-fitted to the Langmuir isotherm and pseudo-second-order models. The resultant PAA-S HNFs scaffolds could be regenerated successfully. Furthermore, the proposed adsorption mechanism of Ln(3+) on PAA-S HNFs scaffolds was the formation of bidentate carboxylates between carboxyl groups and Ln(3+) confirmed by FT-IR and XPS analysis. The well-designed PAA-S HNFs scaffold can be used as a promising alternative for effective REEs recovery. Moreover, benefiting from the unique features of Ln(3+), the Ln-PAA-S HNFs simultaneously exhibited versatile advantages including good photoluminescent performance, tunable emission color, and excellent flexibility and processability, which also hold great potential for applications in luminescent patterning, underwater fluorescent devices, sensors, and biomaterials, among others.

Low pressure UV-cured CS–PEO–PTEGDMA/PAN thin film nanofibrous composite nanofiltration membranes for anionic dye separation

Novel low pressure UV-cured chitosan–polyethylene oxide–polytriethylene glycol dimethacrylate/polyacrylonitrile (CS–PEO–PTEGDMA/PAN) thin film nanofibrous composite nanofiltration membranes for anionic dye separation are demonstrated. Firstly, a double-layer mat containing an ultrathin electrosprayed CS–PEO–triethylene glycol dimethacrylate (TEGDMA) hydrophilic nanobeaded top layer and an electrospun PAN nanofibrous substrate layer was manufactured. Then the hydrophilic top layer was acidic moist-cured followed by hot pressing to form an integrated barrier film on the supporting layer. Here, acidic moisture was utilized to soften the nanobeads and facilitate the CS melting process. Finally, the top layer was UV-cured to form CS–PEO–PTEGDMA semi-interpenetrating polymer networks to physically crosslink CS. Different conditions were selected to achieve an optimized integrated barrier layer on PAN nanofibrous substrate. The optimized membrane possessed high nanofiltration performance for anionic dye separation with superior permeate flux (∼117.5 L m−2 h−1) and high rejection (∼99.9%) to Direct Red 80 solutions under low applied pressure of 0.2 MPa for energy saving purposes. An adsorption-assisted nanofiltration process was proposed for the CS–PEO–PTEGDMA membranes to separate anionic dyes. Moreover, the resultant CS–PEO–PTEGDMA nanofiltration membranes exhibited excellent antifouling properties (the flux recovery ratio reached 96.0% after 3 runs for 18 h), and they also possessed good reusability over repeated operations with a simple regeneration process. This work may pave the way for other intriguing polymer materials and provide a practical feasibility for water purification.

Micro-nano structure nanofibrous p-sulfonatocalix[8]arene complex membranes for highly efficient and selective adsorption of lanthanum(III) ions in aqueous solution

In this study, micro-nano structured p-sulfonatocalix[8]arene (calix8) complex membranes prepared by electrostatic adsorbing anionic calix8 onto the cationic nanofibrous mats with micro-nano structure were utilized as an affinity membrane for the selective adsorption of lanthanum(III) ions, where the cationic nanofibrous mats were fabricated by wet-electrospinning technique from polyacrylonitrile (PAN) solution with the aid of pore-forming agent poly(vinyl pyrrolidone) (PVP) and followed by the amination with diethylene triamine (DETA). The as-prepared nanofibrous calix8 complex membranes were subject to selective adsorption of La(III) ions in aqueous solution and showed very high adsorption capacity and selectivity for La3+ from other metal ions such as Fe3+, Al3+, Cu2+, Ca2+, Mg2+ and K+. The resultant membranes adsorbed with La(III) ions could be desorbed and regenerated successfully without significantly affecting their adsorption capacity. The adsorption data at equilibrium were well fitted to Langmuir isotherm equation with a maximum adsorption capacity of 155.1 mg g−1 for La(III) ions. Furthermore, the possible adsorption mechanism of La(III) ions onto the calix8 membrane was discussed based on the FTIR and XPS data. This study demonstrated a facile route for highly efficient and selective separation of lanthanide ions from aqueous solutions.

Robust construction of a graphene oxide barrier layer on a nanofibrous substrate assisted by the flexible poly(vinylalcohol) for efficient pervaporation desalination

Here, a novel thin-film nanofibrous composite (TFNC) membrane consisting of an electrospun polyacrylonitrile (PAN) nanofibrous substrate and a robust graphene oxide barrier layer was developed through a facile vacuum filtration method for pervaporation desalination application. The exfoliated hydrophilic graphene oxide (GO) nanosheets were sturdily integrated together onto the PAN nanofibrous support with the aid of a flexible connector poly(vinylalcohol) (PVA) and a crosslinking agent glutaraldehyde (GA) via vacuum filtration. The hydrophilic PVA chains acting as the spacing bridges ensured that the stacked GO nanosheets were interlinked successfully with sufficient bonding by GA to provide adequate stability in a water environment. Benefiting from the superiority of an ultra-thin hydrophilic peculiar GO skin layer and a fully interconnected porous nanofibrous substrate, the resultant optimized robust GO/PAN TFNC membranes displayed an excellent permeate flux of 69.1 L m−2 h−1 and a stable high rejection (99.9%) over a testing period of 24 h from aqueous salt solution with NaCl concentrations of 35 g L−1 at 70 °C. This separation performance was superior to those of homogeneous membranes and composite membranes used in pervaporation desalination reported so far, indicating that this work may facilitate the development of pervaporation in practical desalination application.

High-performance nanofiltration membrane prepared by dopamine-assisted interfacial polymerization on PES nanofibrous scaffolds

AbstractThin-film nanofiltration composite (TFNC) membrane with high performance was demonstrated in this work. The membrane consisted of dopamine-modified polyethersulfone (PES) nanofibrous supporting layer and interfacially polymerized polyamide selective barrier layer. PES nanofibrous scaffold was modified with dopamine through self-polymerization. Here, dopamine was introduced to facilitate the formation of ultra-thin TFNC membrane on PES substrate with high performance and enhance the interfacial compatibility and structural stability of the composite membrane. An ultra-thin selective layer was generated by interfacial polymerization reaction between solutions of piperazine and trimesoyl chloride on the dopamine-modified porous PES membrane. Various parameters in interfacial polymerization, including monomer concentration, curing temperature, and curing time, were discussed and optimized to achieve high-performance composite nanofiltration membrane. The resulting TFNC membrane possessed relative high...