Adsorption Of Uranium(?) From Aqueous Solution By Electro Spun PVA/PAA Based Nafiber Membrane

In the process of development and utilization of nuclear fuel,a lot of radioactive wastewater has been produced.In which,uranium could endanger the ecological environment and affects human health.Adsorption methods have high efficiency,easy operation and low cost have attracted increasing attention,become one of the main methods.Among the commonly used adsorbent materials,such as biomass,carbon-based,silicon-based and polymer,PVA/PAA have drawn enormous research interest mostly due to its super hydrophilicity,ductility and good mechanical properties.Combined with electrospinning technology,a nano-spun membrane with high porosity,large specific surface area and strong surface activity can be prepared and applied to remove U(?)in radioactive wastewater by simple functionalization.(1)Using PVA/PAA as matrix material and electrospinning technology,P-PVA/PAA,MnO₂-PVA/PAA and n ZVI-PVA/PAA were prepared by composite or in-situ synthesis methods.SEM,XPS,XRD,FT-IR and universal mechanical testing machine indicated that the micromorphology,physical and chemical properties of the four adsorbent materials,and the adsorption mechanism of U(?)was clarified.(2)The adsorption properties of four adsorbents for U(?)under different conditions were studied by the static adsorption method.The results show that the optimum p H values of PVA/PAA,P-PVA/PAA,n ZVI-PVA/PAA and Mn O₂-PVA/PAA for U(?)adsorption was 5.5,5.5,5.5 and 6.0,respectively,which are not affected by the ionic strength.The adsorption is mainly controlled by the inner-sphere surface complexation.The kinetic studies have shown that all of them are to the pseudo-second-order kinetic model,indicating that the adsorption is mainly controlled by chemical action.The isothermal studies have shown that all of them are to the Langmuir isothermal model,indicating monolayer adsorption,and the maximum adsorption capacities are 56.82 mg×g^-1,277.78 mg×g^-1 and 333.33 mg×g^-1,respectively.While The adsorption process of U(?)on n ZVI-PVA/PAA conforms to the pseudo-second-order kinetic model and Freundlich isothermal model,meaning the adsorption process was multi-layer adsorption.Thermodynamic functions?H>0,?S>0 and?G<0,indicated that the adsorption process of U(?)is spontaneous,endothermic and unreversible.The adsorbed P-PVA/PAA and Mn O₂-PVA/PAA can be eluted efficiently by 1.0 mol·L^-1 HCl solution,the elution rates was 97.25%and 97.58%,respectively.After five cycles,the reuse rate decrease from 96.75%and 95.82%to 86.25%and 83.67%.(3)The effect of p H on adsorption of P-PVA/PAA and Mn O₂-PVA/PAA for adsorption U(?)by full filtration technology.The optimum adsorption p H is 5.5 and 6.0.Furthermore,the effects of the injection rate and various ions(Na⁺,Mg²⁺,Ca²⁺,Cu²⁺,Cl^-,HCO^3-and NO₃^-)on the adsorption performance of Mn O₂-PVA/PAA for uranium were studied.The experimental results show that the adsorption performance decreases,and it has better adsorption selectivity for U(?)with increasing the injection rate of uranium solution.From the membrane breakthrough curve of Mn O₂-PVA/PAA,with increasing uranium concentration,the breakthrough point of Mn O₂-PVA/PAA decreases continuously.At the concentration of 10 mg L^-1,the penetration point of Mn O₂-PVA/PAA is about 56 L·m²,showing good adsorption performance for U(?).(4)The effects of soaking time of PVA/PAA,P-PVA/PAA and Mn O₂-PVA/PAA on tensile properties at p H 8 were studied.It is found that the strain of PVA/PAA,P-PVA/PAA and Mn O₂-PVA/PAA decreases from 23.6%,5.5%and 18.7%to 9.8%,5.5% and 8.8%respectively.Meanwhile,the stress decreases from 13.4 Mpa,9.7 Mpa and 11.4 Mpa to 5.3Mpa,4.2 Mpa and 6.5 Mpa,respectively.The results show that the strain and stress of PVA/PAA,P-PVA/PAA and Mn O₂-PVA/PAA decrease with increasing immersion time,and the tensile properties decrease.However,even after 30 days of immersion,the material still shows strong adsorption strength,which is expected to be applied to the separation and enrichment of uranium in seawater.Studies have shown that PVA/PAA,P-PVA/PAA,n ZVI-PVA/PAA and Mn O₂-PVA/PAA can effectively remove the U(?)from the radioactive wastewater,and can be used as a new adsorbent material to expand the application of nanofibers in the radioactive wastewater.