Facile synthesis of silica-polymer monoliths using nonionic triblock copolymer surfactant for efficient removal of radioactive pollutants from contaminated seawater

Here, we introduce a highly porous functional mesoscopically silica-polymer composite based on silica monolith-conjugated thiourea/formaldehyde copolymer. The developed nanostructure enables selective and fast removal of the radioactive pollutants strontium (Sr[II]) and cesium (Cs[I]) ions from contaminated seawater. The silica/polymer composite was synthesized by introducing thiourea/formaldehyde solution into tetramethoxy orthosilicate/triblock copolymer emulsion. The chemical and textural features of the synthesized silica/thiourea-formaldehyde polymer composite (SiO₂-TUF) were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope, high-resolution transmission electron microscope, energy dispersive X-ray analysis, dynamic light scattering, thermal analysis, and N₂ adsorption/desorption measurements. The synthesized microporous SiO₂-TUF showed excellent cesium and strontium ions removal ability, reaching a maximum adsorption capacity of 78.2 and 40.3 mg g⁻¹ for Sr(II) and Cs(I), respectively. When tested with seawater contaminated with radioactive cesium and strontium, SiO₂-TUF was able to selectively target Sr(II) and Cs(I) ions. Among the different types of adsorption isotherms investigated, Sips isotherm showed the best fit with R² > 0.990. The kinetic studies showed that the pseudo-second-order model gave the best description of the uptake process.