Cubically cage-shaped mesoporous ordered silica for simultaneous visual detection and removal of uranium ions from contaminated seawater

Abstract

There is an increasing interest in developing new technologies enabling the efficient detection and removal of radioactive pollution from seawater. Here, we report a dual-function organic-inorganic mesoporous structure for naked-eye detection and removal of uranyl ions from an aqueous environment. The mesoporous sensor/adsorbent is fabricated via direct template synthesis of highly ordered silica monolith (HOM) starting from a quaternary microemulsion liquid crystalline phase. The produced HOM is subjected to further modifications through growing an organic probe, Omega Chrome Black Blue G (OCBBG), in the cavities and on the outer surface of the silica structure. The spectral response for [HOM-OCBBG→U(VI)] complex shows a maximum reflectance at λmax = 548 nm within 1 min response time (tR); the LOD is close to 9.1 µg/L while the LOQ approaches 30.4 µg/L, this corresponds to the range of concentration where the signal is linear against U(VI) concentration (i.e., 5 to 1000 µg/L) at pH 3.4 with standard deviation(SD) of 0.079 (RSD% = 11.7 at n=10). Experiments and DFT calculations indicate the existence of strong binding energy between the organic probe and uranyl ions forming a complex with blue color that can be detected by naked eyes even at low uranium concentrations. With regard to the radioactive remediation, the new mesoporous sensor/captor is able to reach a maximum capacity of 95 mg/g within a few 2 minutes of the sorption process. The synthesized material can be regenerated using simple leaching and re-used several times without a significant decrease in capacity.

Engineered Sorbents for Selective Uranium Sequestration from Seawater

“…Inorganic materials, including graphene, mesoporous carbon and silica, have been thoroughly studied as efficient sorbents for U removal from aqueous solutions. − These materials have remarkable properties, such as strong durability, high surface area, affordability, and eco-friendliness. However, the limitations of inorganic compounds, particularly their poor selectivity, emphasize the need to explore functionalized materials with improved selectivity and sorption capabilities.…”

“…However, despite these advantages, the pure mSiO 2 still has limitations in terms of high U sorption capacity and selectivity due to the absence of active sites on its surface to sequester U from seawater. To overcome the limitations of pure mSiO 2 , various strategies have been explored to enhance its sorption performance. , One approach is the functionalization of mSiO 2 with organic moieties and by introducing active sites on its surface. In this section, we discuss and present some select studies encompassing the surface modification/functionalization of mesoporous silica(s) with different organic modifiers to enhance their applicability for U extraction from simulated and natural seawater.…”

“…Among several methods developed for UES, the synthesis and application of various sorbents using innovative strategies have been highly explored and put forward. − Over the time span of decades, several materials have been synthesized and tested for UES. Recently, the focus has been intensified toward the synthesis and application of porous materials such as metal–organic frameworks (MOFs), covalent organic frameworks (COFs), membranes, and hydrogels as suitable candidates for extraction of U from natural seawater. − Additionally, the researchers have reported synthesis and application of graphene- and silica-based (composite) sorbents for U extraction under the defined/optimized experimental conditions. − …”

Removal of Uranium from Aqueous Solution and Simulated Seawater Using a Mixed Matrix Membrane Fabricated by Cyclophosphazene and Triazine-Based Inorganic–Organic Hybrid Material

“…Although activated carbons are economically viable, they lack the crucial adsorption capacity and selectivity toward the adsorbate. Similarly, zeolites and other porous materials produced from metal frequently lack hydrothermal stability. − To address this issue, heteroatom-enriched metal-free porous materials are gaining more attention for the enhancement of removal efficiency and selectivity for uranium. , In some of the recent reports, sulfur, amidoxime, phosphate, and amine functionalization have shown high selectivity toward uranium. ,− In this direction, Wu et al reported a nitrogen and oxygen enriched g-C 3 N 4 /UiO-66 composite (CNUIO) for the selective removal of uranium ions from wastewater and groundwater . Recently, Cui et al reported a triazine-based COF (TFPT-BTAN-AO) with amidoxime functional groups for the selective removal and detection of uranium ions with a maximum adsorption capacity of 427 mg g –1 .…”

Simple one-pot synthesis of manganese dioxide modified bamboo-derived biochar composites for uranium(vi) removal

“…24–26 Carbon nanotubes, 27 graphene, 28 and other emerging carbonaceous materials have highly efficient adsorption properties for U( vi ). 29 However, these new carbonaceous materials are still restricted for practical application because of their high production cost. As a type of carbonaceous material, biochar formed by thermochemical decomposition of biomass materials at high temperatures is expected to solve the problem of high cost of carbon materials owing to its low price and simple preparation process.…”