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[Display omitted] • A novel Zr(IV)-based MOF with high-density free carboxylic groups was constructed. • The MOF demonstrates high stability and excellent uranium removal performance. • Dynamic sorption tests highlight its potential for treating radioactive wastewater. • The mechanism for its excellent ability to adsorb U(VI) was investigated. The extraction of uranium from aqueous environments, including the ocean and radioactive wastewater, represents a significant challenge with profound implications for energy resources and environmental remediation. This work presents the design and synthesis of a novel highly stable carboxylated metal–organic framework, BUT-12-3COOH, which achieves excellent U(VI) extraction ability from water. BUT-12-3COOH features high-density free carboxylic groups, exceptional chemical stability, fast kinetics, and high adsorption capacity for U(VI). Dynamic sorption experiments further demonstrated the potential of BUT-12-3COOH in treating real radioactive wastewater. The mechanisms for the U(VI) capture of BUT-12-3COOH are investigated through the combination of EDS, FT-IR, and XPS analysis. The results of this study underscore the promising utility of BUT-12-3COOH as an effective sorbent for extracting radionuclides from environmental specimens and liquid nuclear waste streams. [ABSTRACT FROM AUTHOR]

In this study, the inorganic-organic hybrid of PA/TNTs was synthesized and characterized by using multiple analysis techniques. Batch experiments were conducted to investigate the removal performance of PA/TNTs towards U(VI). The sorption kinetics procedure achieved equilibrium within 6 h. The maximum sorption capacity at 293 K and pH 5.0 was calculated to be 1.16 × 10 −3 mol/g. In addition, the PA/TNTs composite showed a higher sorption selectivity towards U(VI) over many other metal ions. The ionic strength experiments, desorption results, X-ray diffraction (XRD), solid fluorescence, extended X-ray adsorption fine structure (EXAFS) and Fourier transform infrared spectroscopy (FTIR) analysis suggested the predominant sorption mechanism was inner-sphere complexation rather than ion exchange or precipitation. Overall, the synthesized PA/TNTs composite could be utilized as a cost-effective material for the removal of U(VI) from wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • A three-step uranium oxide reduction recovery process has been developed. • The uranium recovered by this process achieved a purity of over 99.9% • The overall recovery rate of uranium reached 98.6%. • Heavy metal concentrations in wastewater meet WHO guidelines by this process. Resource utilization of uranium from the nuclear wastewater is of significance, and the facile strategy to recover high purity uranium oxide directly from wastewater is urgent to develop. Herein, a three-step uranium oxide reduction recovery process (URRP), that is integrated solid–liquid separation (SLS) and electrochemical purification (EP) together with solid-phase uranium re-recovery (SUR), is designed and applied for uranium reduction and purification. The SEM and ICP results were used to determine the carbonate system as the optimal separation system and the Ti electrode as the optimal electrochemical purification electrode. The single electron transfer process of uranyl ions in carbonate was established using cyclic voltammetry. Such three-step recovery process achieves a high-efficient recovery of uranium with a purity of over 99.9% in complex wastewater systems, and an improved return rate of uranium as high as 98.6%. Furthermore, the concentration of metal ions in wastewater is reduced to the standard set by the World Health Organization. Such a URRP offers a very promising solution for the treatment of wastewater and the recovery of high purity uranium. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Co LDO could be obtained by calcination of Ni-Co LDH. • The morphology of the Ni-Co LDO can be adjusted by the calcination temperature. • The Ni-Co LDO-500 prefer removing uranium to Ni-Co LDH. • Electrostatic attraction, surface complexation and memory effect contributed to U(VI) recovery. • Ni-Co LDO-500 showed good stability and excellent regeneration ability. The utilization and development of nuclear energy has resulted in the discharge of uranium-containing wastewater. Layer double hydroxides (LDHs) and oxides (LDOs) were reported for efficient extracting U(VI) from wastewater. In this work, nickel–cobalt layered double oxide (Ni-Co LDO-X, X represents the calcination temperature) with excellent electrostatic attraction and complexation was synthesized via calcination of nickel–cobalt layered double hydroxide (Ni-Co LDH) under air atmosphere for extracting U(VI) comparing to Ni-Co LDH. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential analysis were conducted to characterize the Ni-Co LDO-X. Batch adsorption experiments were carried out to investigate the U(VI) extraction properties. The U(VI) adsorption capacity on Ni-Co LDO-500 increased over 3 times compared to that of Ni-Co LDH. The process of uranium removed by Ni-Co LDO-500 conforms to the Langmuir model, the calculated maximum adsorption capacity is 707.91 mg/g. The results suggested that the excellent U(VI) adsorption ability on Ni-Co LDO-500 mainly dominated by the memory effect, electrostatic interaction, and complexation on the outer-sphere surface. Ni-Co LDO-500 has excellent regeneration ability in five adsorption/desorption experiments. The Ni-Co LDO-500 had favorable ability in removing uranium in actual wastewater with the residual concentration being lower than 0.05 mg/L. The above results highlight that the Ni-Co LDO-500 is promising to be used for the decontamination of uranium in actual uranium-containing wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZJU-X6 is a 3-fold interlocking cationic MOF and could capture 99TcO 4. • ZJU-X6 exhibited superior sorption ability and reusability toward 99TcO 4. • PDF and crystal structure clearly elucidated the sorption mechanism. Technetium-99 is one of most problematic radionuclides with a long half-life, high environmental mobility and solubility, which exists mainly in the form of anionic pertechnetate (99TcO 4 -). Searching for sorbents that hold efficient and selective elimination of radioactive 99TcO 4 - from aqueous solution is still a big challenge and further visualizing it in the sorbents is extremely difficult. Herein, we utilized an elongated organic neutral pyridyl ligand linked with Ni2+ to yield a novel 3-fold interlocking cationic metal–organic framework (ZJU-X6). Unexpectedly, the structure of ZJU-X6 held unique displaceable water pairs on the Ni2+ node in comparison to cationic metal–organic framework constructed by Ni2+. Attainable Ni2+ nodes distinctly improved the positive charge density of the framework, affording high sorption capacity, excellent selectivity, and removal depth toward 99TcO 4 -. Pair distribution functions (PDF) were applied to analyze the changes of atom distances in materials before and after capturing ReO 4 -, clearly showing that ReO 4 - entered into the body of ZJU-X6. More detailed sorption mechanism was atomically elucidated by obtaining the single crystal structure of 99TcO 4 --incorporated ZJU-X6. It is found that the water pairs were replaced by 99TcO 4 - and each Ni2+ coordinated with two 99TcO 4 - through oxygen atoms. In addition, each 99TcO 4 - engaged in multiple C–H...O hydrogen bonding with H atoms of aromatic rings that enhanced the trapping of 99TcO 4 -. [ABSTRACT FROM AUTHOR]