Removal of Uranium by Polymer Metal Oxide Nanofiber Composites: Enhanced Performance through Integration of Phthalic Acid

We developed polyacrylonitrile (PAN) nanofibers embedded with various commercially available metal oxide particles (Fe₂O₃, TiO₂, MnO₂, Co₃O₄, CoFe₂O₄, ZnFe₂O₄) via electrospinning for the removal of uranium (U-(VI)) from aqueous systems. We compared the performance of composites electrospun with and without the inclusion of phthalic acid (PTA), building on our prior evidence that PTA can promote particle dispersion in precursor sol-gels. Characterization using SEM, TEM, XPS, and BET confirmed that PTA results in improved metal oxide distribution within the polymer fiber, promotes enrichment of metal oxides on the nanofiber surface, and increases composite surface area and porosity. In batch sorption experiments, PTA-containing composites consistently exhibited greater U-(VI) uptake than those without PTA, producing more than 2- and 3-fold increases for top-performing Fe₂O₃ and TiO₂ composites, respectively. For Fe₂O₃ and TiO₂ composites with PTA, U-(VI) uptake increased from pH 2 to 7, suggesting a contribution from retained phthalic acid (as phthalate), and isotherm studies revealed sorption capacities exceeding ∼8 mg U/g (corresponding to >90% of U-(VI) removal) at environmentally relevant concentrations (∼1 μM). These composites are offer a simple, one-pot fabrication route to high-performing U-(VI) sorbents in which PTA improves metal oxide distribution, surface area and pore volume of the polymer-metal oxide composites while also contributing to U-(VI) uptake via cooperative binding with embedded metal oxides.