Poly(amidoxime) functionalized MoS2 for efficient adsorption of uranium(VI) in aqueous solutions

Colorimetric sensing for the sensitive detection of UO22+via the phosphorylation functionalized mesoporous silica-based controlled release system

In this study, we developed a simple and sensitive colorimetric sensing method for the detection of UO22+, which was built to release MB from the molybdenum disulfide with a phosphate group (MoS2-PO4) gated mesoporous silica nanoparticles functionalized phosphate group (MSN-PO4) with UO22+ chelating. In the presence of UO22+, MoS2-PO4 can be effectively adsorbed onto the surface of MSN-PO4 based on the coordination chemistry for strong affinity between the P-O bond and UO22+. The adsorbed MoS2-PO4 was then utilized as an ideal gate material to control the release of signal molecules (MB) entrapped within the pores of MSN-PO4, resulting in a detectable decrease in the absorption peak at 663 nm. This colorimetric sensing demonstrated the advantages of simplicity and easy manipulation and exhibited a linear response to the concentration of UO22+ within the range of 0.02-0.2 μM. The detection limit of UO22+ was determined to be 0.85 nM, which was lower than the limit (130 nmol L-1) set by the US Environmental Protection Agency. Furthermore, the proposed colorimetric sensing method has been utilized to determine UO22+ in samples of Xiangjiang River and tap water, and a high recovery rate was achieved. This method shows promising potential in preventing and controlling environmental pollution.

Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions

Phytic acid-modified carboxymethyl cellulose (CMC-PA) has been investigated as a promising adsorbent for the removal of uranium from aqueous solutions. The synthesis of CMC-PA involves the hydrogen bonding interaction between CMC and PA, resulting in the incorporation of PA groups onto the cellulose backbone. The hydrophilicity, reusability and adsorption capacity of the prepared CMC-PA hydrogel have improved with the increase of PA content. Moreover, the adsorption experiments were conducted by varying parameters such as pH, initial uranium concentration, and contact time. The results showed that CMC-PA exhibited excellent uranium adsorption performance, with a theoretical maximum adsorption capacity of 436 mg/g. In addition, the material exhibits excellent reusability, and the reusability improves with the increase of crosslinking density, indicating that the crosslinking structure of the polymer gel can effectively enhance the structural stability of the material. Furthermore, CMC-PA also exhibits high selective adsorption performance towards uranium ions in the presence of various competing ions. Its high adsorption capacity, reusability, and selectivity make it a promising candidate for high-performance uranium ion adsorbents.

Ultra-fast uranium capture via the synergistic interaction of the intrinsic sulfur atoms and the phosphoric acid groups adhered to edge sulfur of MoS2

In order to deal with the sudden nuclear leakage event to suppress the spread of radioactive contaminants in a short period of time, it is extremely urgent needed to explore an adsorbent that could be capable of in-situ remedial actions to rapidly capture the leaked radionuclides in split second. An adsorbent was developed that MoS₂ via ultrasonic to expose more surface defects afterwards functionalized by phosphoric acid resulting in more active sites being endowed on the edge S atoms of Mo-vacancy defects, while simultaneously increased the hydrophilicity and interlayer spacing. Hence, an overwhelming fast adsorption rates (adsorption equilibrium within 30 s) are presented and place the MoS₂-PO₄ at the top of performing sorbent materials. Moreover, the maximum capacity calculated from Langmuir model is as high as 354.61 mg·g^-1, the selective adsorption capacity (S_U) achieving 71.2% in the multi-ion system and with more than 91% capacity retention after 5 cycles of recycling. Finally, XPS and DFT insight into the adsorption mechanism, which can be explained as interaction of UO₂²⁺ on the surface of MoS₂-PO₄ by forming U-O and U-S bonds. The successful fabrication of such a material may provide a promising solution for emergency treatment of radioactive wastewater during nuclear leakage events.

Highly efficient capture of uranium from seawater by layered double hydroxide composite with benzamidoxime

Through swelling/restoration reaction, benzamidoxime (BAO) is introduced into MgAl-LDH interlayers to assemble a new composite of MgAl-BAO-LDH (abbr. BAO-LDH). Wet samples of the BAO-LDH obtained by washing with diverse solvents are present in colloidal state, which facilitates the fabrication of thin film adsorbents convenient for actual application. After drying, the assembled sample exhibits floral morphology composed of thin nanosheets, much different from hexagonal morphology of NO₃^- intercalated MgAl-LDH precursor (NO₃-LDH), demonstrating a phenomenon rarely found in swelling/restoration. The BAO-LDH depicts an extremely large maximum sorption capacity (q_m^U) of 327 mg·g^-1 and ultra-high selectivity for U. At low U concentrations (5-10 ppm), nearly complete capture (~100%) is achieved in a wide pH range of 3-11, while at high U concentrations (110 ppm), quite high U removals (≥93.0%) are obtained at pH = 6-8, meaning perfect suitability for trapping U from seawater. For natural seawater containing trace amounts of U (3.93 ppb) coexisting with high concentration of competitive ions, the BAO-LDH displays significantly high U removal (87%). Complexation between interlayer BAO (N and O as ligands) with UO₂²⁺ and synergistic interactions of LDH layer hydroxyls with UO₂²⁺ contribute to the highly effective uranium capture. All results demonstrate the BAO-LDH is a promising adsorbent applied in seawater uranium extraction and nuclear wastewater disposal.

Transformation details of poly(acrylonitrile) to poly(amidoxime) during the amidoximation process

During the amidoximation process, transformation details of poly(acrylonitrile) (PAN) to poly(amidoxime) (PAO) is critical for optimizing amidoximation conditions, which determine the physicochemical properties and adsorption capabilities of PAO-based materials. Although the optimization of amidoximation conditions can be reported in the literature, a detailed research on the transformation is still missing. Herein, the effect of the amidoximation conditions (i.e. temperature, time, and NH₂OH concentration) on the physicochemical properties and adsorption capabilities of PAO was studied in detail. The results showed that the extent of amidoximation reaction increased with increasing temperature, time, and NH₂OH concentration. However, a considerably high temperature (>60 °C) and a considerably long time (>3 h) could result in the degradation and decomposition of PAO's surface topologies and functional groups, and then decrease its adsorption capability for U(vi). The optimal amidoximation condition was 3 h, 60 °C and 50 g L⁻¹ NH₂OH. At this condition, the PAO obtained presented the highest adsorption capability for U(vi) under experimental conditions. These results provide pivotal information on the transformation of PAO-based materials during the amidoximation process.

During the amidoximation process, transformation details of poly(acrylonitrile) (PAN) to poly(amidoxime) (PAO) is critical for optimizing amidoximation conditions, which determine the physicochemical properties and adsorption capabilities of PAO-based materials.