Efficient Removal of Anionic Radioactive Pollutant from Water Using Ordered Urea-Functionalized Mesoporous Polymeric Nanoparticle

A urea-functionalized ordered mesoporous polymeric nanoparticle for removing the perrhenate anion ReO₄^- as the surrogate of the particularly intractable anion radioactive pollutant TcO₄^- was demonstrated in the present study. This nanomaterial (denoted as urea-MPN) was produced for the first time by a surfactant-directed urea-phenol-formaldehyde resol oligomers self-assembly protocol under hydrothermal condition. The obtained urea-MPN possessed the uniform nanosized spherical morphology with a 3D interconnected ordered cubic mesoporous structure. Also, the urea functional groups were succefully embedded in the polymer framework without the alteration of the molecular configuration. Meanwhile, it exhibited excellent β radiation resistance up to 200 kGy dose. We employed the perrhenate anion ReO₄^- to test its potential for the removal of anionic radioactive pollutant TcO₄^- from water. Interestingly, the optimized urea-MPN nanocomposite achieved the high removal efficiency at a low concentration of 0.25 mM within a short contact time of 30 min. The control experimental results revealed that the short nanoscale pore channels and the hydrophobic mesopore surface facilitated the hydrogen-bonding interaction between the charge-diffuse ReO₄^- tetrahedral oxoanion and the urea moieties in the framework of urea-MPN, accounting for the rapid and effective removal performance in pure water. Importantly, it can selectively capture ReO₄^- in the presence of different competitive anions including NO₃^-, CO₃^2-, SO₄^2-, and PO₄^3-. This attractive capability of this unique nanosized mesoporous polymeric sorbent will pave the way for the diverse applications in the decontamination of nuclear wastes in a more economical and sustainable manner.