Amidoxime Functional EVOH Nanofibers for Uranium Extraction from Seawater

Poly-(vinyl alcohol-co-ethylene) (EVOH) nanofibers (NFs) prepared by electrospinning technology were used as matrix material and then functionalized with the amidoxime (AO) group for uranium extraction from seawater (UES). During the modification process, acrylonitrile (AN) and cografted AN and acrylic acid (AA) were used as monomers to obtain EVOH-grafted poly AN (EVOH-g-PAN) NF and EVOH-cografted poly AN and poly AA (EVOH-g-PAN-PAA) NF mats with one-step chemically initiated graft polymerization (CIGP). Then, a series of NFs were modified into AO functional EVOH-g-PAO NFs and EVOH-g-PAO-PAA NFs by amidoximation and used for uranyl ion adsorption from their aqueous solution. The chemical structure, micromorphology, specific surface area, mechanical properties, hydrophilicity, etc., of NF mats before and after modification were investigated. Results showed that electrospinning and CIGP technology can successfully construct a highly controllable polyacrylonitrile (PAN) morphology on EVOH NFs. The use of electrospinning and CIGP in preparing EVOH NFs addressed challenges in UES materials, such as the AN grafting site, synthesis efficiency, mechanical strength of the adsorption material, and AO group utilization. Experiments showed that when adsorbed in 8 ppm uranium solution for 24 h, its adsorption capacity can reach up to 226.5 mg/g. Adsorption isotherm studies demonstrated a capacity of 704.2 mg/g, surpassing that of the majority of AO functional polymeric adsorbents. This study provides a new matrix material and synthesis method for the preparation of adsorbents for uranium extraction from seawater.