Uranium is a key resource for the development of the nuclear industry, and extracting uranium from the natural seawater is one of the most promising ways to address the shortage of uranium resources. Herein, a semiconducting covalent organic framework (named NDA‐TN‐AO) with excellent photocatalytic and photoelectric activities was synthesized. The excellent photocatalytic effect endowed NDA‐TN‐AO with a high anti‐biofouling activity by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed UVI to insoluble UIV, thereby increasing the uranium extraction capacity. Owing to the photoinduced effect, the adsorption capacity of NDA‐TN‐AO to uranium in seawater reaches 6.07 mg g−1, which is 1.33 times of that in dark. The NDA‐TN‐AO with enhanced adsorption capacity is a promising material for extracting uranium from the natural seawater.
The inherent features of covalent organic frameworks (COFs) make them highly attractive for uranium recovery applications. A key aspect yet to be explored is how to improve the selectivity and efficiency of COFs for recovering uranium from seawater. To achieve this goal, a series of robust and hydrophilic benzoxazole‐based COFs is developed (denoted as Tp‐DBD, Bd‐DBD, and Hb‐DBD) as efficient adsorbents for photo‐enhanced targeted uranium recovery. Benefiting from the hydroxyl groups and the formation of benzoxazole rings, the hydrophilic Tp‐DBD shows outstanding stability and chemical reduction properties. Meanwhile, the synergistic effect of the hydroxyl groups and the benzoxazole rings in the π‐conjugated frameworks significantly decrease the optical band gap, and improve the affinity and capacity to uranium recovery. In seawater, the adsorption capacity of uranium is 19.2× that of vanadium, a main interfering metal in uranium extraction.
The pronounced enrichment of surface-active compounds in the aerosols produced by bubble bursting plays a central role in the chemical transfer from the ocean into the atmosphere and has an important impact on the global Earth’s climate. However, the mechanism of chemical enrichment in bursting bubble aerosols remains poorly understood and controversial due to the high complexity and diversity of experimental behaviors. Contrary to the common belief, here we show that the major share of surfactants in the jet droplets produced by individually bursting bubbles at a calm solution surface is released directly from the bubble surface rather than from the solution surface or subsurface microlayer. We reveal that surfactants are accumulated at the surface of a rising bubble in solution following three successive stages with strongly distinct adsorption profiles: linear kinetic, mixed kinetic, and equilibrium. The magnitude of surfactant enrichment in the aerosol is directly determined by which adsorption mode is in control by the moment of the bubble bursting at solution surface. Our mechanistic description explains the diversity of experimental observations regarding the surfactant enrichment in aerosol droplets and lays the ground for understanding the more complex behaviors associated with collective effects at the solution surface (e.g., breaking waves).
Extracting uranium from seawater with a chemically stable adsorbent is one of the most promising strategies for challenges originating from sustainable nuclear energy industries. Covalent organic frameworks (COFs) featuring highly stable and regular porous network structures possess practical advantages compared to other adsorbents such as metal–organic frameworks. We are interested in designing rational monomers to achieve novel COFs and understanding structure–property relationships to improve the performance of natural seawater uranium extraction. In particular, biofouling is a critical issue for long-term uranium extraction in natural seawater, where it would cause a severe decrease in extraction capacity and high costs for adsorbent recycling. On the basis of the fully planar conjugated feature and photoelectric effect of triazine units, we successfully prepared a highly stable two-dimensional COF (named PT-BN-AO) that is based on triazine as central planar units and bridged by an olefin linkage with prominent antibiofouling activity and greatly enhanced uranium extraction capacity. On the basis of the superior photocatalytic performance of PT-BN-AO, it can generate biotoxic reactive oxygen species to sterilize bacteria effectively. Meanwhile, the photoelectric effect of PT-BN-AO promotes the reduction of U(VI) to U(IV) by photoelectrons, thus greatly improving the adsorption capacity of uranium. On the basis of the excellent photocatalytic and photoelectric properties, the extraction capacity of PT-BN-AO for uranium in natural seawater reached 5.78 mg g–1, which is 1.42 times that without light irradiation. The excellent performance of PT-BN-AO makes it an advanced material for the practical extraction of uranium from seawater.
Rapid quantitative determination of bulk molecular concentration in solid samples without sample pretreatment is demonstrated using the internal extractive electrospray ionization-mass spectrometry (iEESI-MS) analysis of six β-agonists, including salbutamol (Sal), clenbuterol (Cle), ractopamine (Rac), terbutaline (Ter), tulobuterol (Tul), brombuterol (Bro), in pork tissue samples. Single sample analysis only required 1 min. The linear range of detection was about 0.01-1000 μg/kg (R > 0.9994). The limit-of-detection (LOD) varied from 0.002 μg/kg for Sal to 0.006 μg/kg for Tul. Relative standard deviation (RSD) of quantitation was in the range 6.5-11.3%. The analytical results were validated by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-mass spectrometry (LC-MS), showing the accuracy rates of 92-105%. The current study extends the power of ambient MS as a method for the quantification of molecules at the surface of solid samples (e.g., in μg/cm units) toward the quantification of molecules in bulk sample volume (i.e., in μg/kg units), which is commonly required in food safety control, biomedical analysis, public security, and many other disciplines.
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