Ultrathin
two-dimensional (2D) nanosheets with efficient light-driven
proton reduction activity were obtained through the exfoliation of
novel metal–organic frameworks (MOF), which were synthesized
by using a bis(4′-carboxy-2,2′:6′,2″-terpyridine)
ruthenium complex as a linker and 3d transition-metal
(Mn, Co, Ni, and Zn) anions as nodes. The nanosheet of the Ni2+ node exhibits a photocatalytic hydrogen evolution rate of
923 ± 40 μmol g–1 h–1 at pH = 4.0, without the presence of any cocatalyst or cosensitizer.
A combined experimental and theoretical study suggests a reductive
quenched pathway for the photocatalytic hydrogen evolution by the
nanosheet. The transition-metal nodes at the edge of the nanosheets
are proposed as the active sites. Density functional theory (DFT)
calculations attributed the different catalytic activities of the
nanosheets to the discrepancy of H adsorption free energy at various
transition-metal nodes.
Developing highly efficient adsorbents for uranium-contaminated
wastewater treatment has aroused tremendous attention due to the radioactive
feature and environmental hazards. Herein, the 3D vanadoborate framework
SUT-6 constructed from (VO)12O6B18O36(OH)6 clusters bridged by ZnO4(H2O) is evaluated for uranium removal, with a UO2
2+ adsorption capacity of up to 347.7 mg/g under
the optimal pH of 4.0. It exhibits high selectivity to UO2
2+ with the existence of various common interfering cations
and anions. In addition, the adsorption efficiency of SUT-6 is above
92% after the third round of the adsorption−desorption process.
Most importantly, SUT-6 retains great UO2
2+ adsorption
performance in uranium-contaminated environmentally relevant water
sources, including natural river water and groundwater. Comprehensive
characterization techniques were employed to probe the uranium speciation
and accurate atomic-scale position after adsorption, to determine
the adsorption mechanism. Results show that SUT-6 is promising for
UO2
2+ capture based on the unique crystalline
water coordination coupling with cation exchange and surface redox
chemistry mechanisms under complicated environmental water conditions.
This work provides new insights into designing highly efficient uranium
adsorbents for practical uranium capture.
Abstract. Based on analyzing the characteristics of the environment of low concentration uranium, the traditional processing method of low concentration uranium waste-water, such as adsorption method, chemical precipitation, evaporation-enrichment method were summarized. Then the principle, characteristics and scope of the latest processing technology such as Bentonite method, Zero-valent iron, biological adsorption method were summarized, and finally points out that the comprehensive utilization of various methods is an effective way to deal with low concentration uranium waste-water.
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