Removal Of Uranyl Research Articles

Removal of Uranyl(VI) with Two–Dimensional Mg(OH)2-Based Heterojunctions: A Density Functional Theory Insight

Removal of Uranyl(VI) with Two–Dimensional Mg(OH)₂-Based Heterojunctions: A Density Functional Theory Insight

Open-Framework Vanadate as Efficient Ion Exchanger for Uranyl Removal.

The elimination of uranium from radioactive wastewater is crucial for the safe management and operation of environmental remediation. Here, we present a layered vanadate with high acid/base stability, [Me2NH2]V3O7, as an excellent ion exchanger capturing uranyl from highly complex aqueous solutions. The material possesses an indirect band gap, ferromagnetic characteristic and a flower-like morphology comprising parallel nanosheets. The layered structure of [Me2NH2]V3O7 is predominantly upheld by the H-bond interaction between anionic framework [V3O7]nn- and intercalated [Me2NH2]+. The [Me2NH2]+ within [Me2NH2]V3O7 can be readily exchanged with UO22+. [Me2NH2]V3O7 exhibits high exchange capacity (qm = 176.19 mg/g), fast kinetics (within 15 min), high removal efficiencies (>99%), and good selectivity against an excess of interfering ions. It also displays activity for UO22+ ion exchange over a wide pH range (2.00-7.12). More importantly, [Me2NH2]V3O7 has the capability to effectively remove low-concentration uranium, yielding a residual U concentration of 13 ppb, which falls below the EPA-defined acceptable limit of 30 ppb in typical drinking water. [Me2NH2]V3O7 can also efficiently separate UO22+ from Cs+ or Sr2+ achieving the highest separation factors (SFU/Cs of 589 and SFU/Sr of 227) to date. The BOMD and DFT calculations reveal that the driving force of ion exchange is dominated by the interaction between UO22+ and [V3O7]nn-, whereas the ion exchange rate is influenced by the mobility of UO22+ and [Me2NH2]+. Our experimental findings indicate that [Me2NH2]V3O7 can be considered as a promising uranium scavenger for environmental remediation. Additionally, the simulation results provide valuable mechanistic interpretations for ion exchange and serve as a reference for designing novel ion exchangers.

Novel chitosan-based derivative material loaded with the diethylenetriamine pentamethylene phosphonic acid for efficient adsorption of uranyl ions from weakly acidic wastewater

An ideal adsorption material capable of efficiently and selectively capture uranyl ions from radioactive wastewater remains a serious challenge. In this work, diethylenetriamine pentamethylene phosphonic acid (DTPMP), one of the common metal ion extractants with five negatively charged phosphate groups, was innovatively used to modify chitosan chains for better uranyl adsorption capacity. Two chitosan derivatives were designed, DTPMP protonated chitosan crosslinked with potassium tripolyphosphate (DTPP) and DTPMP reinforced potassium tripolyphosphate crosslinked chitosan (DCTPP), in which DCTPP possessed an excellent maximum adsorption capacity of up to 1316.82 mg/g for uranyl ions at 298 K. Compared to the 60 min taken-for 90 % by DTPP, the time taken to reach same percentage by DCTPP was only about 5 min, indicating its superior uranyl removal efficiency. Outstanding affinity and capture performance could be attributable to the remarkable mesoporous surfaces and abundant P-containing active sites. Influence of initial solution pH on the removal efficiency for uranyl was significantly attenuated due to the C-P bond. The fitting results of kinetic and isotherm models revealed that the uranyl adsorption mechanisms by as-prepared composites were physicochemical processes, mainly including surface complexation/chelation, chemisorption, and intra-particle diffusion. Theory calculations predicted potential binding modes and electrons transfer between the organophosphonic acid molecule and uranyl unit, validating the strong interaction and reduction of phosphorus-oxygen groups on uranyl ions. Furthermore, DCTPP showed great potentials to separate uranyl from simulated uranium-contaminated wastewater. Design and development of novel chitosan derivatives will provide theoretical support and technical reference for an effective treatment of weakly acidic radioactive wastewater.

Microbial removal of uranyl from aqueous solution by Leifsonia sp. in the presence of different forms of iron oxides

Immobilization of uranyl by indigenous microorganisms has been proposed as an economic and clean in-situ approach for removal of uranium, but the potential mechanisms of the process and the stability of precipitated uranium in the presence of widespread Fe(III) (hydr)oxides remain elusive. The potential of iron to serve as a reductant and/or an oxidant of uranium indicates that bioemediation strategies which mainly rely on the reduction of highly soluble U(VI) to poorly soluble U(IV) minerals to retard uranium transport in groundwater may be enhanced or hindered under different environmental conditions. This study purposes to determine the effect of ubiquitous Fe(III) (hydr)oxides (two-line ferrihydrite, hematite and goethite) on the removal of U(VI) by Leifsonia sp. isolated from an acidic tailings pond in China. The removal mechanism was elucidated via SEM-EDS, XPS and Mössbauer. The results show that the removal of U(VI) was retarded by Fe(III) (hydr)oxides when the initial concentration of U(VI) was 10 mg/L, pH was 6, temperature was 25 °C. Particularly, the retardatory effect of hematite on U(VI) removal was blindingly obvious. Also, it is worth noting that the U(VI) in the precipitate slow-released in the Fe(III) (hydrodr) oxide treatment groups, accompanied by an increase in Fe(II) concentration. SEM-EDS results demonstrated that the ferrihydrite converted to goethite may be the reason for U(VI) release in the process of 15 days culture. Mössbauer spectra fitting results further imply that the metastable iron oxides were transformed into stable Fe3O4 state. XPS measurements results showed that uranium product is most likely a mixture of Iron-U(IV) and Iron-U(VI), which indicated that the hexavalent uranium was converted into tetravalent uranium. These observations imply that the stability of the uranium in groundwater may be impacted on the prevailing environmental conditions, especially the solid-phase Fe(III) (hydr)oxide in groundwater or sediment.

Chemically functionalized poly(AAm-AMPSA) superadsorbent hydrogels for removal of uranyl from aqueous solutions

Chemically functionalized poly(AAm-AMPSA) superadsorbent hydrogels for removal of uranyl from aqueous solutions

Removal of aqueous uranyl ions using titania-supported mesoporous silica composite with the synergistic effect of coupled adsorption and photocatalytic reduction of U(VI)

The aim of this study is to determine and compare the adsorption capacities, kinetic and thermodynamic parameters of the adsorption process of uranyl ions from aqueous solution on nanotube titania impregnated mesoporous silica SBA-15 (TNT-SBA-15) and naked SBA-15 (nSBA-15) adsorbents. The TNT-SBA-15 composite containing various molar ratio of nanotube titania to silica (TNT-SBA-15(m:n)) in the matrix was synthesized by the sol–gel/impregnation method using sodium silicate as a silica precursor, sulphuric acid and nanotube titania. Batch adsorption experiments showed that the maximum adsorption capacity (qmax) of the TNT-SBA-15(m:n = 1:1) composite under indoor light be as high as 2.65 mMoleU g−1 that was 1.4 times higher than that of nSBA-15 under the same conditions. Under UV (300 W) illumination the qmax of TNT-SBA-15(1:1) adsorbent reached 3.49 mMoleU g−1 that was 2 times higher than the qmax in the dark. The increase in qmax of the TNT-SBA-15(1:1) composite in the two experiments was attributed to the synergistic effect of coupled sorption and photocatalytic reduction of U(VI) by titania following the deposition of uranium (IV) (hydr)oxide on the surface of the adsorbent. The adsorption process followed a pseudo-second kinetic model. The activation energy was found to be 160 and 135 kJ Mole−1 for the adsorption on nSBA-15 and TNT-SBA-15(1:1), respectively. The isotherm of the adsorption process follows the Langmuir as well as Freundlich models. The adsorption is an endothermic and spontaneous process. Adsorbed TNT-SBA-15 can be easily regenerated in 0.3 M HNO3 solution, and the qmax of the adsorbent was maintained at 95% the initial qmax after three consecutive adsorption–desorption cycles. These results revealed that, though TNT-SBA-15 made from inexpensive reagents could be an effective adsorbent for uranyl removal from wastewater.

Ni‐Single‐Atom Mediated 2D Heterostructures for Highly Efficient Uranyl Photoreduction

AbstractSunlight‐driven photoreduction of the environmentally mobile uranyl (VI) to less soluble tetravalent uranium is of considerable value to environmental sustainability, yet the pursuit for high‐performance semiconductors is plagued by the current disadvantages of inferior charge separation/migration. This study reports that a nickel single atom isolated on a sulfur‐functionalized graphitic carbon nitride/reduced graphene oxide 2D heterostructure enables exceptional uranyl photoreduction. Under only 11 min of visible light irradiation, the single atom anchored semiconductor yields a high removal rate of 99.8% and a record‐high extraction capacity of 4144 mg g−1 in uranyl‐containing wastewater and seawater. Theoretical calculations confirm that the remarkable uranyl photoreduction originates from the synergetic effect of Ni single atoms and intimate heterojunction establishment that can not only promote the separation/migration of photoexcited carriers, but also greatly reduce the energy barrier of uranyl reduction. This study showcases the exciting potential of single atom semiconductors for efficient uranyl removal from uranium‐contaminated aqueous environments.

Modeling Uranyl Adsorption on MoS2/Mo2CTx Heterostructures Using DFT and BOMD Methods.

Uranium-bearing wastewaters exert a great threat to the ecological environment due to its high radiotoxicity level. The designing and fabrication of novel adsorption materials can be promoted for radionuclide elimination from wastewater. In this work, results from density functional theory and Born-Oppenheimer molecular dynamics simulations are reported for the uranyl adsorption behavior on the MoS2/Mo2CTx heterostructure in the gas phase and in an aqueous environment. Uranyl ions prefer to be adsorbed at deprotonated O sites on the Mo2COH surface and S sites on the MoS2 side of the heterojunctions, resulting in the formation of bidentate configurations. In addition to coordination interaction, H-bond and van der Waals interactions can also play an important role in binding configurations. More importantly, the oxidation state U(VI) can be reduced to U(V) and then to U(IV) caused by the strong reducibility of the Mo2COH surface at room temperature, whereas the uranyl complex can move freely on the MoS2 surface. However, the coordination number of U with respect to H2O in the first hydration shell on the Mo2COH surface remains unchanged and is found to be 3, which is similar to that on the MoS2 surface. This work provides novel nanosorbents for the removal of uranyl from wastewater. The present viewpoint provides valuable mechanistic interpretations for uranyl adsorption and will give a supplement to the experimental research.

CellUSorb: A high-performance, radiation functionalized cellulose based adsorbent for Uranium (VI) remediation in ground water

A state of the art, phosphate functionalized cotton cellulose based green U(VI) adsorbent has been synthesized via single step, 60Co gamma radiation mediated simultaneous irradiation grafting process, wherein bis(2-methacryloxyethyl) phosphate (B2MEP) was grafted onto cotton cellulose fabric. Samples were characterized using 13C NMR, FTIR, EDXRF, XRD and SEM techniques. Poly(B2MEP)-g-cellulose adsorbent (CellUSorb) was tested for removal of Uranyl (U(VI)) ions from water, adsorption capacities being 79.9 mg.g−1 and 135.9 mg.g−1 in batch and column modes, respectively. The equilibrium adsorption data were analyzed using Langmuir, Freundlich and Redlich-Peterson isotherm models, and kinetic data using pseudo first order, pseudo second order, intra-particle diffusion and Boyd’s models. The adsorbent viability was enhanced through regeneration achieved using ammonium oxalate as eluent, ensuring reusability for five cycles with < 20 % attrition loss/cycle. A standalone, portable water treatment set up, housing a ∼ 100 g CellUSorb cartridge (maximum theoretical U(VI) adsorption capacity ∼ 27,200L for [U(VI)] = 500 µg.L−1), has been conceptualized, fabricated and successfully tested for U(VI) removal to < 30 µg.L−1 (WHO permissible limit) from contaminated water. With potential upscaling for large scale, onsite U(VI) remediation, CellUSorb is a promising prospect that spotlights the role of cellulose in accomplishing UNO’s Sustainable Development Goal of “clean water for all” (SDG6).

Enhancement of CdS resistance to photocorrosion and photocatalytic removal of uranyl by complexation with N-deficient g-C3N4under aerobic conditions

The effect of oxygen on the reduction of uranyl and photocorrosion of CdS remains a pressing issue when CdS is used as a photocatalyst for the removal of uranyl in uranium-containing wastewater. In this study, composites (CdS/PCN) were prepared by designing N-deficient g-C3N4 composite with CdS for efficient photocatalytic reduction of uranyl under aerobic condition. Meanwhile, a series of characterizations of the CdS/PCN composites were carried out by XRD, FT-IR, XPS, EDS and UV–vis. Surprisingly, the CdS/PCN not only showed very high photocatalytic reduction activity for uranyl under aerobic condition, but also the photocorrosion of CdS by oxygen and h+ was inhibited. With a starting uranium (VI) concentration of 20 ppm, the uranium (VI) removal efficiency could reach 97.33% (dark: 30 min, light: 10 min). Interestingly, the removal efficiency was better in air condition than in pure nitrogen or 30% oxygen atmosphere, i.e. a proper amount of oxygen has accelerated the reduction reaction, while excess oxygen weakened the reduction. Finally, a new mechanism of reduction of uranyl by CdS/PCN photocatalyst was given under aerobic condit ions. This work presents a novel strategy for reduction of U(VI) by photocatalysis and the inhibition of photocorrosion of photocatalysts under aerobic conditions.

Modulating Uranium Extraction Performance of Multivariate Covalent Organic Frameworks through Donor-Acceptor Linkers and Amidoxime Nanotraps.

Covalent organic frameworks (COFs) can be designed to allow uranium extraction from seawater by incorporating photocatalytic linkers. However, often sacrificial reagents are required for separating photogenerated charges which limits their practical applications. Herein, we present a COF-based adsorption-photocatalysis strategy for selective removal of uranyl from seawater in the absence of sacrificial reagents. A series of ternary and quaternary COFs were synthesized containing the electron-rich linker 2,4,6-triformylphloroglucinol as the electron donor, the electron-deficient linker 4,4'-(thiazolo[5,4-d]thiazole-2,5-diyl)dibenzaldehyde as the acceptor, and amidoxime nanotraps for selective uranyl capture (with the quaternary COFs incorporating [2,2'-bipyridine-5,5'-diamine-Ru(Bp)2]Cl2 as a secondary photosensitizer). The ordered porous structure of the quaternary COFs ensured efficient mass transfer during the adsorption-photocatalysis capture of uranium from seawater samples, with photocatalytically generated electrons resulting in the reduction of adsorbed U(VI) to U(IV) in the form of UO2. A quaternary COF, denoted as COF 2-Ru-AO, possessed a high uranium uptake capacity of 2.45 mg/g/day in natural seawater and good anti-biofouling abilities, surpassing most adsorbents thus far. This work shows that multivariate COF adsorption-photocatalysts can be rationally engineered to work efficiently and stably without sacrificial electron donors, thus opening the pathway for the economic and efficient extraction of uranium from the earth's oceans.

All-Inorganic Open-Framework Chalcogenides, A3Ga5S9·xH2O (A = Rb and Cs), Exhibiting Ultrafast Uranyl Remediation and Illustrating a Novel Post-Synthetic Preparation of Open-Framework Oxychalcogenides

Fast and effective uranyl sequestration is of interest to the nuclear industry. Recently, layered chalcogenide materials have demonstrated fast, selective, and efficient sorption properties toward uranyl cations, and the development and investigation of new types of chalcogenide materials continues to be of interest and represents an intriguing option for uranyl remediation. Three new all-inorganic A3Ga5S9·xH2O (A = Rb, Rb/Cs, and Cs) open-framework chalcogenides were obtained via an in situ alkali carbonate to alkali sulfide conversion process achieved under mild hydrothermal conditions. The structures of the all-inorganic open-framework chalcogenides consist of a twofold interpenetrated diamond-like 3D framework containing pseudo-T3 [Ga10S20]10– supertetrahedra. Forty-eight percent of the structural volume is occupied by A+ cations and water species, as established by single-crystal X-ray diffraction (SCXRD), infrared (IR) spectroscopy, and energy-dispersive spectroscopy (EDS). The dynamic nature of the A+ cations and water molecules within the pores was investigated via SCXRD as well as by IR spectroscopy-monitored H2O-to-D2O exchange experiments. Framework stability was probed with post-synthetic treatment of A3Ga5S9·xH2O (A = Rb and Cs) samples in acidic solutions that resulted in the formation of the oxysulfide (A/H)3Ga5S9–yOy·xH2O (A = Rb and Cs; y = 0–1), as shown by SCXRD and IR. Ion-exchange studies on A3Ga5S9·xH2O (A = Rb and Cs) samples were carried out utilizing a uranyl acetate solution. The presence of the UO22+ species in the ion-exchange product was supported by IR spectroscopy and EDS. Batch method ion-exchange experiments on Cs3Ga5S9·xH2O powder demonstrated fast kinetics with 95% uranyl removal from the uranyl acetate solution during the first minute, a maximum uranyl uptake capacity of 15 mg/g, and the subsequent elution of uranyl species with KCl solution. The porous and dynamic nature of the A3Ga5S9·xH2O framework coupled with effective UO22+···S2– bonding interactions makes it a good potential sorbent for uranyl remediation from aqueous media.

Improving in vivo Uranyl Removal Efficacy of a Nano‐Metal Organic Framework by Interior Functionalization with 3‐Hydroxy‐2‐pyridinone

Comprehensive SummaryThe environmental contamination of uranium will occur in scenarios such as nuclear accidents and leakage from nuclear waste storage sites, which eventually leads to the internal uranium exposure of people, causing consequential injuries of renal failure, osteosarcoma, etc. The development of uranyl specific chelating agents that could sequester uranium in vivo is in urgent need and is important for the safe and efficient development of nuclear industry. Metal organic frameworks (MOFs) already serve as efficient uranium depletion materials in solutions of a wide range of pH and ionic strength for nuclear fuel recycling, uranium extraction from seawater, as well as environmental decontamination. Herein, a chromium‐based nano‐metal organic framework (nano‐MOF) functionalized interiorly with 3,2‐HOPO ligands, MIL‐101‐HOPO, is rationally synthesized. In vitro adsorption experiments show that MIL‐101‐HOPO exhibits high adsorption selectivity and fast adsorption kinetics for uranyl. The results of in vivo uranyl decorporation assays reveal that MIL‐101‐HOPO with the decoration of HOPO ligands on the interior wall exhibits significantly increased uranyl removal ratio in kidneys comparing to the pristine nMOFs, and is more effective than the clinically used ZnNa3‐DTPA. All those results corroborate the interior functionalization of MOFs as an efficient strategy to develop promising uranyl decorporation agents.

In Vivo Uranium Decorporation by a Tailor-Made Hexadentate Ligand.

The sequestration of uranium, particularly from the deposited bones, has been an incomplete task in chelation therapy for actinide decorporation. Part of the reason is that all previous decorporation ligands are not delicately designed to meet the coordination requirement of uranyl cations. Herein, guided by DFT calculation, we elaborately design a hexadentate ligand (TAM-2LI-MAM2), whose preorganized planar oxo-donor configuration perfectly matches the typical coordination geometry of the uranyl cation. This leads to an ultrahigh binding affinity to uranyl supported by an in vitro desorption experiment of uranyl phosphate. Administration of this ligand by prompt intraperitoneal injection demonstrates its uranyl removal efficiencies from the kidneys and bones are up to 95.4% and 81.2%, respectively, which notably exceeds all the tested chelating agents as well as the clinical drug ZnNa3-DTPA, setting a new record in uranyl decorporation efficacy.

Uranyl extraction from aqueous solution by emulsion liquid membrane process

In this study, the elimination of Uranyl from aqueous solution is studied using an advanced technique of extraction; emulsion liquid membrane (ELM). Experimental results for the extraction of Uranyl are presented. The membrane phase consists of Kerosene as a diluent, Cyanex 302 as a carrier and sorbiton monooleate (Span 80) as a surfactant. Sulfuric acid solution as an internal aqueous phase. At the optimum conditions, the main variables studied which influenced the ELM extraction of Uranyl were the concentration of surfactant (3%), carrier (0.3%), internal phase (1 N H2SO4), types of internal phase (H2SO4 sulfuric acid), diluent (Kerosene), stirring speed (200 rpm), and the effect of volume ratios of the internal phase to the organic phase 1:1 (A/O) and of the emulsion to the feed solution 20/200 (Vemul/Vext). The results indicate that the removal percentage was obtained 100% in less than 20 min.This study also evaluated the effect of H2SO4 concentration in the internal aqueous phase on the stripping of Uranyl. The ELM treatment process represents a very interesting advanced separation process for the removal of Uranyl from aqueous solutions.

Hinokitiol, an Advanced Bidentate Ligand for Uranyl Decorporation.

Despite the critical role actinide decorporation agents play in the emergency treatment of people in nuclear accidents and other scenarios that may cause internal contamination of actinides, new ligands have seldom been reported in recent decades because the current inventory has been limited to only a handful of functional groups. Therefore, new functional groups are always being urgently sought for the introduction of advanced actinide decorporation agents. Herein, a tropolone derivative, 2-hydroxy-6-(propan-2-yl)cyclohepta-2,4,6-trien-1-one (Hinokitiol or Hino), is proposed to be a promising candidate for this purpose by virtue of its well-demonstrated high membrane permeability and high affinity for metal ions. The coordination stoichiometry of Hino with uranyl is demonstrated to be 3:1 both in an aqueous solution (pH 7.4) and in the solid state. The results of a liquid-liquid extraction experiment further show that Hino exhibits strong chelating ability and selectivity toward uranyl over biological essential metal ions (i.e., Mn2+, Zn2+, Co2+, and Ni2+) with an extraction efficiency of >90.0%. The in vivo uranyl removal efficacies of Hino in kidneys and bone of mice are demonstrated to be 67.0% and 32.3%, respectively. On the basis of the observations described above, it is highly possible that further modification of Hino will lead to a large family of multidentate agents with enhanced uranyl decorporation ability.

Synthesis and characterization of waste commercially available polyacrylonitrile fiber-based new composites for efficient removal of uranyl from U(VI)–CO3 solutions

The existing species of uranium determines the design of novel sorbents towards uranium extraction from the natural waters. Herein, three composites based on waste commercially available polyacrylonitrile fiber (WPANF), namely WPANF/TiO2·xH2O, WPANF/CTAB-bentonite, and WPANF/NZVI, were first prepared and employed for the removal of U(VI) from the carbonate coexisted aqueous solutions. Among them, the WPANF/TiO2·xH2O exhibited the optimum sorption capacity of ~40.6 mg·g−1 (pH 8.0, C0 = 50 mg·L−1, and [CO3]Total = 2 mmol·L−1), which is significantly greater than the WPANF/CTAB-bentonite (~12.6 mg·g−1) and WPANF/NZVI (~10.3 mg·g−1). All sorption capacities decreased with the increases of initial pH, [NaCl], and [CO3]Total, due to the species transformation from UO2(CO3)22− and (UO2)2CO3(OH)3− to UO2(CO3)34− that enhanced the electrostatic repulsion and the competitive sorption. The XPS analysis and DFT calculations indicated that in the composites, WPANF was a role in strengthening the mechanical properties of composites rather than the main sorption sites for uranyl carbonates. The sorption mechanisms were mainly involved in –OH group coordination, Br− anions exchanges, and redox reactions. Desorption, reusability and U(VI) sorption test in the simulated seawater demonstrated that WPANF/TiO2·xH2O could be an alternative candidate for acquiring uranium resource. This work has screened the potential composites for U(VI) extraction from the natural waters, especially based on the practical U(VI) speciation, and provides a novel research approach for the removal of U(VI) towards U(VI)–CO3 systems.

Chelating effect between uranyl and pyridine N containing covalent organic frameworks: A combined experimental and DFT approach

Covalent organic frameworks (COFs) are promising adsorbents for removing heavy metal ions, and have high crystallinity, a porous structure, and conjugated stability. N-containing functional groups are known to have great affinity for uranyl ions. In this work, to explore the peculiarity of the pyridine N structure as an efficient adsorbent, we chose 2,2′-dipyridine-5,5′-diamine (Bpy) and pyridine-2,5′-diamine (Py) as the core skeletons, and 1,3,5-triformylphloroglucinol (Tp) as the linker to synthesize two crystalline and stable N-containing COFs named TpBpy and TpPy, respectively, through a facile solvothermal method. Characterization results demonstrated that TpBpy and TpPy possessed regularly growing pore sizes, large specific surface areas and relatively strong thermal resistances. The results of batch experiments showed that both COF materials were capable of the effective removal of uranyl with uptake capacities of 115.45 mg g−1 and 291.79 mg g−1, respectively. In addition, density functional theory (DFT) simulations highlighted the beneficial chelation effect of the double N structure in pyridine monomers for removing uranyl ions. Combining systematic experimental and theoretical analyses, the adsorption process and interaction mode of porous COFs and UO22+ were revealed, to provide predictable support for the application of pyridine N-containing COFs in the field of environmental remediation.

Film-like chitin/polyethylenimine biosorbent for highly efficient removal of uranyl-carbonate compounds from water

Uranium contamination in groundwater has been increasingly reported, while biosorbents for the decontamination attracts growing attention because of their distinct advantages of abundant raw materials and eco-friendliness. Herein, a film-like chitin/polyethylenimine biosorbent (CH-PEI) was prepared and employed in the removal of uranyl-carbonate compounds from water. Fourier transform infrared spectra, element analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy, N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy were used to characterize the biosorbent. Besides, thermodynamic calculation and various batch experiments were conducted to investigate the adsorption performances of CH-PEI for uranyl removal from carbonate solution. The results showed that the biosorbent possessed a unique hierarchically porous structure and a high nitrogen content. The batch experiments exhibited that it obtained the maximum adsorption capacity at pH = 6. Notably, CH-PEI could reach sorption equilibrium within 4 h at the initial concentration of 50 mg/L. The maximum adsorption capacity were 247.04 mg/g and 1023.74 mg/g at the initial concentrations of 50 mg/L and 300 mg/L. The kinetics and isotherm data were well fitted by pseudo-second-order and Langmuir models. It could remove 98.9% of uranium in the simulated groundwater. The biosorbent showed fast regeneration, good structural stability and reusability in 5 cycles. Furthermore, the adsorption mechanism was confirmed to be anion exchange and electrostatic attraction between nitrogen species and uranyl-carbonate complexes through FT-IR and XPS analysis. Considering its low costs, high efficiency and easy collection, CH-PEI would be a promising biosorbent for uranium removal from groundwater. This study provides a potential technique for uranium removal using chitin-based adsorbents.

Modification of UiO-66 for removal of uranyl ion from aqueous solution by immobilization of tributyl phosphate

Two modified metal–organic frameworks (MOFs), were synthesized by immobilization of tributyl phosphate (TBP) on the UiO-66 and vacated UiO-66 (UiO-66-vac), and investigated for the removal of uranyl ion from aqueous solution. Characterization of MOFs was carried out by various techniques such as X-ray diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and BET surface area. FTIR confirmed efficient immobilizing of the TBP on the MOFs. Sorption results show that modification of MOFs enhances uranyl sorption capacity. Kinetics of sorption was investigated by pseudo-first-order and pseudo-second-order models. It is shown that at pH 5, sorption equilibrium for all MOFs, reaches a little more than 8 h. Equilibrium studies were done by Langmuir and Freundlich models and the sorption capacity of UiO-66, UiO-66-vac, UiO-66-TBP and UiO-66-vac-TBP obtained 177.1, 193.8, 201.9 and 203.5 mg g−1, respectively. Moreover, TBP immobilized MOFs, show more selectivity than UiO-66 and UiO-66-vac towards uranyl in wastewater containing cationic and anionic interferences. The effect of the contact time and pH for maximum removal of uranyl was studied. Two modified metal–organic frameworks (MOFs), were synthesized by immobilization of tributyl phosphate (TBP) on the UiO-66 and vacated UiO-66 (UiO-66-vac), and investigated for the removal of uranyl ion from aqueous solution.