A high-flux antibacterial poly(amidoxime)-polyacrylonitrile blend membrane for highly efficient uranium extraction from seawater.

Uranium is an important fuel for nuclear power, with 4.5 billion tons of it stored in the oceans, 1,000 times more than on land. Polymer membrane materials are widely used in the marine resources fields, due to their convenient collection, good separation and can work continuously. Herein, a poly(amidoxime)-polyacrylonitrile blend membrane (PCP) with high flux, excellent antibacterial properties and uranium adsorption performance has been prepared by using the phase inversion method, and the prepared membrane was used for highly efficient uranium extraction from seawater. In static adsorption experiments, the PCP membrane reached adsorption equilibrium after 48 h, and the adsorption capacity was 303.89 mg/g (C0 =50 mg/L). In dynamic adsorption experiments, it was found that the lower flow rate and higher number of membrane layers were favorable for dynamic adsorption. In addition, the water flux of the PCP membrane was 7.4 times higher than that of the PAN membrane. The adsorption mechanism can be attributed to the chelation between amino and hydroxyl groups in CS, amidoxime group in poly(amidoxime) and uranyl ions. The simple preparation process coupled with the excellent adsorption performance indicated that the PCP membrane would be a promising material for the uranium extraction from seawater.

Theory-Guided Design of a Method to Obtain Competitive Balance between U(VI) Adsorption and Swaying Zwitterion-Induced Fouling Resistance on Natural Hemp Fibers.

The competitive balance between uranium (VI) (U(VI)) adsorption and fouling resistance is of great significance in guaranteeing the full potential of U(VI) adsorbents in seawater, and it is faced with insufficient research. To fill the gap in this field, a molecular dynamics (MD) simulation was employed to explore the influence and to guide the design of mass-produced natural hemp fibers (HFs). Sulfobetaine (SB)- and carboxybetaine (CB)-type zwitterions containing soft side chains were constructed beside amidoxime (AO) groups on HFs (HFAS and HFAC) to form a hydration layer based on the terminal hydrophilic groups. The soft side chains were swayed by waves to form a hydration-layer area with fouling resistance and to simultaneously expel water molecules surrounding the AO groups. HFAS exhibited greater antifouling properties than that of HFAO and HFAC. The U(VI) adsorption capacity of HFAS was almost 10 times higher than that of HFAO, and the max mass rate of U:V was 4.3 after 35 days of immersion in marine water. This paper offers a theory-guided design of a method to the competitive balance between zwitterion-induced fouling resistance and seawater U(VI) adsorption on natural materials.

Mussel-inspired polydopamine microspheres self-adhered on natural hemp fibers for marine uranium harvesting and photothermal-enhanced antifouling properties.

The rapid development of nuclear energy and the accelerated consumption of uranium (U(VI)) ores have forced researchers to turn to marine U(VI) harvesting. However, the performance of marine U(VI) harvesting materials was challenged by the combination of ultralow concentrations of U(VI), high concentrations of various interfering ions and biofouling from abundant marine living organisms. Natural abundant hemp fibers (HFs) were adhered by mussel-inspired polydopamine microspheres (HFMPDA) during self-polymerization. Both HFs and PDA are derived from natural products with low-cost and eco-friendly properties to guarantee compatibility with biological marine environments. HFMPDA exhibits an outstanding distribution coefficient of 10.51 ± 0.51 L g-1 for U(VI) and great fouling resistance. The coordination forms between the U(VI) ion and HFMPDA were investigated by density functional theory (DFT), and the antifouling property was simulated by molecular dynamics (MD) calculations. The adsorption capacity of HFMPDA is 128.43 ± 3.26 µg g-1, which is 1.75 and 6.05 times higher than that of HFPDA (only covered by PDA) and V(V), respectively, after immersion for 34 days in the Yellow Sea, China. These polydopamine microspheres adhered to HF will be a photothermal marine U(VI) harvesting material with enhanced selectivity and fouling resistance.

Constructing an Amino-reinforced amidoxime swelling layer on a Polyacrylonitrile surface for enhanced uranium adsorption from seawater.

Polyacrylonitrile (PAN)-based materials have been studied for decades as uranium (U(VI)) adsorbents, because the further products of abundant nitrile groups, amidoxime (AO) groups, show great affinity for U(VI) ions. However, excessive amidoximation could cause the shrinkage of PAN fibers, resulting in decreased adsorption performance. Hence, an amino-reinforced amidoxime (ARAO) swelling layer was constructed on the PAN fiber surface (PAN-NH2-AO) by modification of the strongly hydrophilic amino group to prevent shrinkage. The molecular chains in the ARAO swelling layer would be swelled due to the adsorption of a large amount of water. Simultaneously, U(Ⅵ) ions can penetrate into the ARAO swelling layer with water molecules and coordinate with amino or AO groups, leading to increased adsorption performance. PAN-NH2-AO exhibited maximum U(VI) and water adsorption capacities of 492.61 mg g-1 and 20.32 g g-1 at 25 â„ƒ with a swelling ratio of 20.73%, respectively. The adsorption capacity of PAN-NH2-AO was 0.312 mg g-1 after a 91-day immersion in Yellow Sea, China. The study of the adsorption thermodynamics and kinetics of PAN-NH2-AO showed that the adsorption process was spontaneous homogeneous chemical adsorption. This paper proposes a novel method to obstruct amidoximation induced shrinkage and to maximize the potential application of PAN-based materials.

Swollen-layer constructed with polyamine on the surface of nano-polyacrylonitrile cloth used for extract uranium from seawater.

In this study, a swelling layer was constructed on the surface of the nano-polyacrylonitrile (PAN) fiber fabric prepared by electrospinning to enrich uranium (U (VI)) adsorption from seawater. The constructed swelling layer composes of a polyethyleneimine (PEI) containing a huge amount of amino groups and imino groups with strong hydrophilicity. The molecular chain swelled in an aqueous solution by forming a swelling layer on the PAN surface. In addition, p-aminobenzenesulfonic acid (SA) was used as the side chain end group grafted on the PAN surface, the benzene ring as the side chain can hinder the rotation of the PEI chain, thereby increasing the rigidity. The increasing of the rigidity leads to stretch the conformation of the PEI molecular chain, increasing the probability of collision with U (VI), which is beneficial for adsorption. The adsorption capacity of the prepared adsorbent in the adsorption experiment reached 215.25 mg g-1, and the adsorption capacity in the 8 ppm spiked simulated seawater reached 144.5 mg g-1. The adsorption mechanism of U (VI) was analyzed by XPS. The sulfonic acid group in SA as the terminal group and amino group in the swelling layer formed a coordination structure with U (VI). The swelling layer constructed on the surface of polyacrylonitrile fibers is used to effectively extract uranium from seawater.