In recent years, there is a strong interest to sequester uranium from seawater as a sustainable source of nuclear fuel. In this work, ethylene glycol methacrylate phosphate-grafted membrane adsorbers were synthesized using UV-initiated free-radical polymerization. The synthesized membranes were evaluated in DI water and synthetic seawater at different pH values in both batch and continuous modes of operation. A maximum capacity of 15.3 mg of U (g of the membrane)−1 was observed in synthetic seawater at pH 4.08. The membrane capacity was dependent on pH, swelling of the polymer network, and the ionic strength of the solution. During filtration, membranes with a lower degree of grafting recovered more uranium than membranes with a higher degree of grafting for a given feed condition. This work explores design considerations associated with the use of polymer-grafted membrane adsorbers to sequester uranium from seawater.

Phosphate ligands are widely used in ion-exchange and chelation separation materials (resins and membranes) to sequester heavy metals like lanthanides and actinides. In this work, the affinity, capacity, and kinetics of membranes functionalized with phosphate-containing copolymers for La3+ were characterized. In particular, the impact of the nonion complexing comonomers, 2-hydroxyethyl methacrylate (HEMA) and butyl methacrylate (BuMa), on the adsorption performance of ethylene glycol methacrylate phosphate EGMP was investigated. Membranes were coated with poly­(EGMP), poly­(EGMP-co-HEMA), or poly­(EGMP-co-BuMa) using thermally initiated free-radical polymerization and characterized using attenuated total reflectance Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and contact angle goniometry. Equilibrium adsorption data were modeled with the Langmuir isotherm and revealed several trends. At pH 4, the Langmuir constant (K L) which is an indicator of La3+ affinity is markedly higher when a non-H bonding “spacer” is present. Here, K L follows the trend: poly­(EGMP-co-BuMa) = 97 ± 18 mM–1 > poly­(EGMP-co-HEMA) = 6.0 ± 1.1 mM–1 > poly­(EGMP) = 2.3 ± 0.6 mM–1. Interestingly, the maximum capacity Q max (mmol La (mmol P)−1) follows a reverse trend: poly­(EGMP-co-HEMA) > poly­(EGMP) > poly­(EGMP-co-BuMA). Kinetic studies at pH 4 reveal that faster adsorption is observed for polymers with less intramolecular H-bonding. The impact of the spacing monomer on the affinity (K L) was pH-dependent where at pH 1, both poly­(EGMP-co-BuMA) and poly­(EGMP-co-HEMA) show the same K L. Furthermore, the polymer composition did not impact the adsorption kinetics at pH 1. Thus, the ability of the comonomer to serve as an H-bond donor did play a role at this pH. This work reveals the role of comonomers in polymeric adsorbents and suggests the ability to use them to tailor adsorbent performance.

Polymethacrylic acid (PMAA) and substituted polymethacrylic acid (PMAA/HQ) with para dihydroxy benzene (HQ) were synthesized via free radical polymerization and they were characterized using UV-vis, FT-IR, XRD spectral studies. The UV-vis spectrum of both PMAA and PMAA/HQ shows transitions due to π → π* at 218 and 306 nm respectively. The XRD analysis of PMAA shows semicrystalline, and the substituted PMAA shows amorphous. The morphology of the polymers determined from the SEM analysis exhibits fractured surface and cluster-like arrangement. The CV studies of PMAA/HQ and pristine HQ show that the redox behavior of HQ has changed in PMAA/HQ due to the polymeric effect. The corrosion inhibition efficiency of the resulting polymer was studied on aluminium in 0.3 M NaOH solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopic techniques, and their results were compared. The adsorption of synthesized polymer shows that the inhibition of aluminium in 0.3 M NaOH has been influenced by Langmuir adsorption isotherm. The anticorrosion and adsorption studies show that the corrosion inhibition potency of PMAA/HQ is more significant than PMAA.