Uranium Removal Efficiency Research Articles

Constructing Ce–OH groups on CeO2 for enhancing removal and recovery of uranium from wastewater and seawater

Efficient recovery of uranium from wastewater and seawater provides an important guarantee for the sustainable growth of nuclear energy. Herein, we skillfully use the alkali etching method to construct CeO2 hollow spheres rich in Ce–OH groups for the removal and recovery of uranium from water matrixes. It is found that the CeO2 exhibits fast adsorption kinetics (equilibrium time within 10 min) and moderate adsorption capacity (143.1 mg/g), and the removal efficiency of low concentration uranium (0.1 g/L and 1 g/L) reaches 100% within 1 min of adsorption. Moreover, the adsorption of uranium by CeO2 is almost unaffected by common anions and cations in the environment, even if the concentration of anions is 1000 times that of uranium. More importantly, the CeO2 can enrich uranium concentration in seawater by 167.9 times and the recovery rate reaches 83.9%. Mechanistic studies reveal that the adsorption of uranium by CeO2 is mainly attributed to the rich Ce–OH groups on the surface of CeO2, resulting in the rapid adsorption of U(VI) and mainly forms a single-bridge model. The findings of this study provide a green and efficient path for the removal and recovery of uranium from wastewater and seawater.

A synergistic bioelectrochemical-photocatalytic system for efficient uranium removal and recovery

Bioelectrochemical system (BES) is a promising technology for uranium recovery, which also enables simultaneous electricity generation. However, the bioelectrochemical recovery of uranium is hindered by its slow process due to the low reduction potential provided by microorganisms. Herein, we developed an innovative bioelectrochemical-photocatalytic system (BEPS) that combines the advantages of BES and photocatalysis, achieving enhanced uranium removal and recovery. The photogenerated electrons in BEPS possess a more negative reduction potential and stronger reduction capability than microbial electrons in BES, significantly accelerating uranium reduction and deposition on the electrode surface. Moreover, the electrons from the bioanode combine with photogenerated holes through the external circuit, effectively inhibiting the recombination of charge carriers. The BEPS significantly enhances uranium removal efficiency, kinetic, and electricity generation through a synergistic coupling mechanism between the bioanode and photocathode. Notably, the UO2 deposited on the electrode surface exhibited a recovery efficiency of 98.21 ± 1.37%, and the regenerated electrode sustained its photoelectric response and uranium removal capabilities. Our findings highlight the potential of the BEPS as an effective technology for uranium recovery and electricity generation.

The insight into behavior and mechanism of chitosan-embedded hydroxyapatite gel spheres used for efficient solidification of uranium in wastewater

In this work, hydroxyapatite (HAP), an environmentally friendly material was prepared with Phosphogypsum (PG) as calcium source, and uranium immobilization gel spheres were prepared by chitosan (CS) embedding, which would reduce HAP agglomeration while providing an abundance of uranium-loving groups, realizing “treating waste for waste”. The optimum pH for U(VI) removal was determined to be 4, the optimum dosage was 0.2 g/L, and qmax = 350.88 mg/g through batch experiments. When C0 = 10 mg/L, it was found that the removal rate of U(VI) by HAP-CS could be up to 99.92 %, and the residual uranium concentration was 0.008 mg/L, which meets the national emission standard. The removal rate of uranium can reach 95.92 % by applying it to high concentration uranium ore wastewater. CS was found to have good biocompatibility with HAP by SEM, FTIR, XRD, and XPS characterization. Meanwhile, we found that Ca, –OH, and P-O play a dominant role in the uranium removal process, and the main mechanism of uranium removal by Hydroxyapatite-Chitosan gel spheres (HAP-CS) is surface complexation, ion exchange, and dissolution–precipitation binding. The HAP-CS has high uranium removal efficiency, simple solid–liquid separation, and good biocompatibility, and can be used to treat actual uranium-containing wastewater.

Enhancing the uranium (VI) adsorption performance of phosphoric acid functionalized porous silica by controlled introduction of phosphoric acid group

The post-grafting of porous silica with organic group is a common method for the synthesis of organo-functionalized silica adsorbent. However, this method usually produces adsorbents with limited adsorption performances due to the pore blocking caused by the irregular introduction of organic group. In this work, we report the controllable synthesis of phosphoric acid functionalized porous silica adsorbent based on the co-condensation method for uranium (VI) adsorptive removal with enhanced adsorption performance. Characterizations of the obtained silica verify its porous structure and confirm the homogeneous distribution of phosphoric acid groups inside the silica. This silica is able to efficiently remove 98 % of uranium from a 100 mg/L uranium (VI) solution within 10 min at a dosage of 0.6 g/L and the maximum uranium (VI) adsorption amount reaches 509 mg/g. Both adsorption capacity and adsorption rate of this silica are superior than that of the silica synthesized based on conventional post-grafting method. Moreover, this silica can be reused for five times with uranium (VI) removal efficiency above 95 % and it is well applied in adsorption column for dynamically adsorptive removal of uranium (VI) from real nuclear wastewater. Mechanism-related investigations reveal that uranium (VI) adsorption on this silica proceeds by effective ion exchange of uranium (VI) ion with either phosphoric acid or silanol group and the formation of uranyl phosphonate or uranyl silicate complex. This work provides a feasible strategy to synthesize functionalized porous silica without significant pore blocking, and demonstrates the enhancement effect of regulating surface adsorption groups on the adsorption performances of porous silica. Besides, this work offers a promising adsorbent for efficient treatment of uranium-containing nuclear wastewater and reveals the mechanism of uranium adsorption on those silica adsorbent containing phosphoric acid, thiol or thioether group.

Adsorption performance and its mechanism of uranium using rod-like hydroxyapatite by one-step hydrothermal method

Rod-like Hydroxyapatite (HAP) was synthesized using a one-step hydrothermal method. The successful synthesis of HAP has been confirmed based on the results of XRD and EDS. TEM images show that the HAP synthesized through the one-step hydrothermal method exhibits a rod-like morphology with good dispersion and minimal stacking. There was no significant aggregation observed and the diameter is about 25 nm. Both single-factor experiments and orthogonal experiments were conducted to determine the optimal conditions for adsorbing uranium from wastewater with an initial concentration of 10 mg·l−1. The optimized parameters included a pH of 5.0, a HAP dosage of m = 0.01 g, a reaction time of t = 30 min, a temperature at room temperature, and an agitation speed of R = 120 r·min−1. Under these conditions, the uranium removal efficiency exceeded 98%. The impact of anions and cations in the solution on uranium adsorption by HAP was investigated, revealing that cations with higher valence and anions with higher charge density had a more pronounced effect on the adsorption process. The fitting results obtained using adsorption isotherm and kinetic models indicated that the primary mechanism of uranium adsorption was surface monolayer chemical adsorption. Thermodynamic parameters suggested that the adsorption of uranium onto HAP was a spontaneous, endothermic process driven by entropy. Characterization results from EDS, XRD, FTIR, and XPS techniques indicated that the mechanism of uranium adsorption by HAP involved electrostatic adsorption, dissolution–precipitation, and ion exchange processes.

Sol-gel transition effect based on konjac glucomannan thermosensitive hydrogel for photo-assisted uranium extraction

Exploiting the intelligent photocatalysts capable of phase separation provides a promising solution to the removal of uranium, which is expected to solve the difficulty in separation and the poor selectivity of traditional photocatalysts in carbonate-containing uranium wastewater. In this paper, the γ-FeOOH/konjac glucomannan grafted with phenolic hydroxyl groups/poly-N-isopropylacrylamide (γ-FeOOH/KGM(Ga)/PNIPAM) thermosensitive hydrogel is proposed as the photocatalysts for extracting uranium from carbonate-containing uranium wastewater. The dynamic phase transformation is demonstrated to confirm the arbitrary transition of γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel from a dispersed state with a high specific surface area at low temperatures to a stable aggregated state at high temperatures. Notably, the γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel achieves a remarkably high rate of 92.3% in the removal of uranium from the wastewater containing carbonates and maintains the efficiency of uranium removal from uranium mine wastewater at over 90%. Relying on electron spin resonance and free radical capture experiment, we reveal the adsorption-reduction-nucleation-crystallization mechanism of uranium on γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel. Overall, this strategy provides a promising solution to treating uranium-contaminated wastewater, showing a massive potential in water purification.

Natural Products of Licorice for Uranium Decorporation with Low Toxicity and High Efficiency.

The development and exploration of uranium decorporation agents with straightforward synthesis, high removal ability, and low toxicity are crucial guarantees for the safety of workers in the nuclear industry and the public. Herein, we report the use of traditional Chinese medicine licorice for uranium decorporation. Licorice has good adsorption performance and excellent selectivity for uranium in the simulated human environment. Glycyrrhizic acid (GL) has a high affinity for uranium (p(UO2) = 13.67) and will complex with uranium at the carbonyl site. Both licorice and GL exhibit lower cytotoxicity compared to the commercial clinical decorporation agent diethylenetriamine pentaacetate sodium salts (CaNa3-DTPA). Notably, at the cellular level, the uranium removal efficiency of GL is eight times higher than that of CaNa3-DTPA. Administration of GL by prophylactic intraperitoneal injection demonstrates that its uranium removal efficiency from kidneys and bones is 55.2 and 23.9%, while CaNa3-DTPA shows an insignificant effect. The density functional theory calculation of the bonding energy between GL and uranium demonstrates that GL exhibits a higher binding affinity (-2.01 vs -1.15 eV) to uranium compared to DTPA. These findings support the potential of licorice and its active ingredient, GL, as promising candidates for uranium decorporation agents.

Adsorptive removal of uranium(VI) from aqueous solutions by amino-functionalized montmorillonite@β-cyclodextrin composite

For economic and environmental security consideration, an amino-functionalized montmorillonite@β-cyclodextrin composite adsorbent (NH2-MMT@β-CD) was successfully synthesized to adsorb uranium(VI). NH2-MMT@β-CD performed excellent uranium(VI) removal performances with the uranium(VI) removal capacity of 469.4 mg/g, which was almost three times that of MMT. The reason for the improvement was that the introduction of 3-aminopropyltriethoxysilane and β-CD not only enhanced the d-spacing and surface roughness, but also brought abundant functional groups, like amino and hydroxyl groups, thus providing more useable active sites. Besides, NH2-MMT@β-CD also had good selectivity and favorable stability with the uranium(VI) removal efficiency of 90.4 % at the fifth cycle. Characterizations indicated that NH2-MMT@β-CD adsorbed uranium(VI) via electrostatic interaction, complexation, reduction reaction and ion-exchange. This work supplied a new idea for exploring novel clay-based adsorbents for selective and efficient removal and regeneration of uranium(VI) from aqueous solution.

Z-Scheme heterojunction Cu2(OH)3F/Bi2WO6 with improved photocatalytic activity for uranium removal from wastewater under air atmosphere

The proper treatment of uranium-contaminated nuclear wastewater is important for uranium resource recovery and environmental protection. Photocatalytic strategies have emerged as promising approaches for improving uranium removal efficiency. In this study, a Z-scheme heterojunction Cu2(OH)3F/Bi2WO6 (CFO/BWO) was synthesized by directly depositing CFO onto a BWO semiconductor for highly efficient photocatalytic removal of uranium from wastewater. The CFO semiconductor contains abundant O–H bonds and a high conduction band position, which can couple with BWO to form a heterojunction via interactions between the O and W atoms. Owing to the high electronegativity of CFO, electrons easily transfer from BWO to CFO, resulting in enhanced electron-hole separation and promoted electron transmission. Importantly, introducing CFO narrowed the bandgap of CFO/BWO compared to that of BWO, providing an appropriate band position, which is more conducive to the photocatalytic immobilization of uranium. Moreover, the mechanism of CFO/BWO heterojunction for photocatalytic immobilization of uranium revealed the formation of a stable crystalline phase of (UO2)O2·2H2O during the photocatalytic process. As a result, CFO/BWO could remove 91 % of uranium from simulated wastewater under an air atmosphere. The findings of this study provide a promising strategy by regulating the band position of heterojunctions for photocatalytic immobilization of uranium.

Calcium-decorated biochar modified with phosphorus from wastewater to promote U(VI) removal: Adsorption behavior and mechanism

In this study, waste shrimp shell and phosphorous-containing wastewater were used to synthesize calcium-decorated biochar modified with phosphorus (Ca-BC-P) and utilized to remove uranium from aqueous solutions. The results from static adsorption experiment demonstrated that Ca-BC-P exhibited good U(VI) adsorption performance in acidic environments, with a maximum theoretical adsorption capacity of 1074.29 mg g−1. The adsorption behavior perfectly fit Langmuir isotherm and the pseudo-second-order kinetic models, which revealed the nature of monolayer chemical adsorption by Ca-BC-P. Thermodynamic analysis showed that this process was spontaneous and endothermic. Ca-BC-P also displayed excellent selectivity and could be reused for several times while keeping a high U(VI) removal efficiency. When treating simulated acidic uranium mine wastewater, the removal efficiency of uranium reached 99.9 % with Ca-BC-P. The U(VI) removal mechanism was attributed to the precipitation of Ca(UO2)2(PO4)2·6H2O and surface complexation, nHAP on the surface of Ca-BC-P played a pivotal role during the adsorption process. Therefore, Ca-BC-P could be prepared economically and showed great potential for efficiently remove uranium from mining wastewater.

Constructing amidoxime adsorption sites on the core-shell structured natural silk protein for uranium capture

Amidoxime-based fiber adsorbents hold significant promise for uranium extraction. However, a notable issue is that these adsorbents primarily originate from synthetic polymer materials, which, aside from providing good mechanical support, have no other functions. In recent study, we shifted our focus to silk fiber (SF), a natural protein fiber known for its unique core-shell structure and rich amino acids. The shell layer, due to its abundant functional groups, makes it easily modifiable, while the core layer provides excellent mechanical strength. Leveraging these inherent properties, an amidoxime-based fiber adsorbent was developed. This adsorbent utilizes amino and carboxyl groups for enhanced performance synergistically. This method involves establishing uranium affinity sites on the outer sericin layer of SF via chemical initiation of graft polymerization (CIGP) and amidoximation (SF-g-PAO). The water absorption ratio of SF-g-PAO is as high as 601.16 % (DG = 97.17 %). Besides, SF-g-PAO demonstrates an exceptional adsorption capacity of 15.69 mg/g in simulated seawater, achieving a remarkable removal rate of uranyl ions at 95.06 %. It can withstand a minimum of five adsorption-elution cycles. Over a 4-week period in natural seawater, SF-g-PAO displayed an adsorption capacity of 4.95 mg/g. Furthermore, SF-g-PAO also exhibits impressive uranium removal efficiency in real nuclear wastewater, with a removal rate of 63 % in just 15 min and a final removal rate of 90 %. It is hoped that this SF-g-PAO, prepared through this straightforward method and characterized by the synergistic action of amino and carboxyl groups, can offer innovative insights into the development of uranium extraction adsorbents.

1 T@2H-phase MoS2 quantum dot-modified oxygen-rich vacant ZnO for the photo-reduction of uranium without sacrificial agents

Efficient and stable photocatalytic materials are urgently needed for the photo-reduction of uranium in wastewater treatment without the addition of external sacrificial agents under air conditions. Herein, we designed and synthesized 1 T@2H MoS2 QDs (MSQ) modified oxygen-rich defective ZnO photocatalysts 1 T@2H MoS2 QDs/OV-ZnO (MSQVZO) and systematically investigated its photocatalytic U(VI) activity in various matrices, which exhibited 97 % removal efficiency of uranium after 40 min of visible light irradiation under aerobic conditions, and the order of photocatalytic activity was MSQVZO > OV-ZnO > ZnO. XRD, ESR, XPS, and UV–vis were used for the characterization of the materials. In addition, it was argued using DFT analysis that the introduction of oxygen defects drove the OV-ZnO to interact with the intermediates of the oxygen evolution reaction (OER) reaction more readily than the ZnO, thus improving the activity of the OV-ZnO-based catalysts. More importantly, a new mechanism for photo-reduction of U(VI) was established. It provides an effective strategy for the photo-reduction of U(VI) without a sacrificial agent.

Efficient removal of uranium from acidic mining wastewater using magnetic phosphate composites

Uranium mining operations produce large volumes of acidic uranium mining wastewater, necessitating the development of environmentally friendly and recyclable materials for efficient uranium removal and recovery. The current study successfully produced hydroxyapatite (HAP-L) and magnetic phosphate composites (CaFeP-1, CaFeP-2, and FePO4) through a combination of mixing, ultrasonication, hydrothermal precipitation, and calcination methods. The research explores the influence of various parameters such as pH, solid–liquid ratio, contact time, initial uranium concentration, co-existing ions, and recyclability on the uranium removal efficiency of these materials. The findings indicate exceptional uranium adsorption capacities, with CaFeP-1 exhibiting the highest capacity among the materials, especially in acidic environments. Moreover, CaFeP-1 displays strong resistance to interference from other ions and can be recycled multiple times while maintaining high removal rates. Treatment of acidic uranium mining wastewater by CaFeP-1 results in pH adjustment and the reduction of uranium and other ion concentrations, making it a promising solution for comprehensive remediation of acidic uranium mining wastewater. The U(VI) removal mechanism by CaFeP-1 was validated through XRD, FT-IR, and XPS results. The U(VI) removal was attributed to processes such as dissolution-precipitation, surface complexation, and ion exchange. The formation of sodium uranyl phosphate hydrate was identified as a new product following U(VI) abatement by CaFeP-1. In summary, CaFeP-1 shows great potential for the effective treatment of acidic uranium mining wastewater.

Uranium removal in groundwater by Priestia sp. isolated from uranium-contaminated mining soil

Priestia sp. WW1 was isolated from a uranium-contaminated mining soil and identified. The uranium removal characteristics and mechanism of Priestia sp. WW1 were investigated. The results showed that the removal efficiency of uranium decreased with the increase of initial uranium concentration. When the uranium initial concentration was 5 mg/L, the uranium removal efficiency achieved 92.1%. The increase of temperature could promote the uranium removal. Carbon source could affect the removal rate of uranium, which was the fastest when the methanol was used as carbon source. The solution pH had significant effect on the uranium removal efficiency, which reached the maximum under solution pH 5.0. The experimental results and FTIR as well as XPS demonstrated that Priestia sp. WW1 could remove uranium via both adsorption and reduction. The common chloride ions, sulfate ions, Mn(II) and Cu(II) enhanced the uranium removal, while Fe(III) depressed the uranium removal. The Priestia sp. WW1 could effectively remove the uranium in the actual mining groundwater, and the increase of initial biomass could improve the removal efficiency of uranium in the actual mining groundwater. This study provided a promising bacterium for uranium remediation in the groundwater.

Enhancing Commercially Iron Powder Electron Transport by Surface Biosulfuration to Achieve Uranium Extraction from Uranium Ore Wastewater.

The zero-valent iron (ZVI) has attracted increasing attention due to the enhanced reactivity of ZVI to uranium wastewater. However, ZVI practical application is hampered due to its susceptibility to oxidation and the formation of passivation layers during storage and in situ restoration. To address these issues, we used a biosulfuration approach to modify ZVI for application in uranium ore wastewater treatment. A series of physicochemical characterization tools and photoelectronic analyses showed that BS-ZVI considerably increased carrier separation efficiency and visible light absorption capacity, resulting in a significant photoassisted enhancement effect on uranium extraction. Accordingly, the uranium removal efficiency of BS-ZVI reached 91% within 60 min, and its maximum adsorption capacity was 336.3 mg/g. By analyzing the mechanism, the improved U(VI) removal performance was mostly responsible on the dissolution of the passivation layer on the surface of ZVI, the generation of Fe(II) and FeS, and the important role of Shewanella putrefaciens extracellular polymers (EPS). Overall, the BS-ZVI biohybrid merges with the high activity of ZVI, bio-FeS, and self-regeneration ability of bacteria, expanding a promising new approach for sustainable treatment of uranium mine wastewater.

Perilla frutescens: A new strategy for uranium decorporation

Radionuclide uranium is a great threat to human health, due to its high chemical toxicity and radioactivity. Finding suitable uranium decorporation to reduce damage caused by uranium internal contamination is an important aspect of nuclear emergency response. However, the poor selectivity and/or high toxicity of the only excretory promoter approved by Food and Drug Administration (FDA) is an obvious disadvantage. Herein, we choose an edible natural product, the traditional Chinese medicine called Perilla frutescens (PF), which has wide sources and can be used as an excellent and effective uranyl decorporation. In vivo uranium decorporation assays illustrate the removal efficiency of uranium in kidney were 68.87% and 43.26%, in femur were 56.66% and 54.53%, by the test of prophylactic and immediate administration, respectively. Cell level experiments confirmed that it had better biocompatibility than CaNa3-DTPA (CaNa3-diethylenetriamine pentaacetate, a commercial actinide excretion agent). In vitro static adsorption experiments exhibited that its excellent selectivity sorption for uranyl. All those results findings would provide new research insights about natural product for uranyl decorporation.

Engineering layered double hydroxide with enzyme-mimicking antibiofouling ability for uranium capture

Materials capable of capturing environmentally mobile uranium from various sources, including nuclear waste and bio-aggressive seawater, are critical for energy and environmental sustainability. Unfortunately, the stability and reusability of existing absorbents is limited in seawater due to the ubiquitous and notorious biofouling, and therefore, developing high-performance materials with antibiofouling activity is of great importance for uranium capture. Here we report a tungstate exchanged layered double hydroxide composite (MgAl-LDH-NO3--WO42-) that exhibits a significant uranium removal efficiency of 98.8 % in 240 ppm uranium-containing wastewater and a maximum uptake capacity of 409.6 mg g−1. More importantly, MgAl-LDH-NO3--WO42- displays an excellent antibiofouling ability in bio-aggressive seawater by mimicking natural haloperoxidase in marine algae, enabling the excellent cyclic stability for uranium capture from seawater. This work provides an effective strategy to develop highly efficient LDH-based materials for uranium capture.

Development of granular composites based on laponite and Zr/Fe-alginate for effective removal of uranium (VI) from sulfate solutions

The object of research is granular composites based on zirconium-iron alginates and laponite. The task of research is to determine the influence of the Zr:Fe ratio on the structure of granular composites and efficiency of uranium (VI) removal from aqueous solutions. The influence of the zirconium and iron ratio on the parameters of the material's pore structure has been established, particularly on the change in the content of micropores within the matrix. The specific surface area of the materials ranges from 86 to 112 m²/g. The sorption properties of the composites regarding uranium (VI) have been investigated. The impact of the charge of surface groups and the form of uranium (VI) presence in sulfate solutions on their sorption characteristics has been demonstrated. The maximum adsorption capacity reaches 265.1 µmol/g at pH 6. It is shown that an elevated electrolyte content positively affects the efficiency of uranium (VI) removal in neutral and alkaline medium. It has been established that structural changes in the materials occur due to the intensive interaction of iron ions and alginate molecules, resulting in the formation of a dense gel-like structure. The mechanism of uranium (VI) removal is associated with the formation of surface complexes in the presence of electrolytes. The synthesized granulated composites exhibit improved removal efficiency of uranium (VI) under conditions of high mineralization of solutions, making them attractive for potential use as sorbents. The obtained results can be utilized in the development of effective methods for purifying water environments from uranium (VI) in high mineralization conditions, which is a relevant issue in the field of nuclear energy and the removal of radioactive substances from water systems

Pomelo peel derived phosphorus-doped biochar for efficient disposal of uranium-containing nuclear wastewater: Experimental and theoretical perspectives

The phosphoric acid activated biochar adsorbent is recognized as a good candidate for application in efficient disposal of uranium-containing nuclear wastewaters. However, the production of high-efficiency biochars with typical characteristics of large specific surface area, hierarchically porous structure and abundant adsorption group remains a challenge. In this work, we report a new hydrogelation-carbonization technique to facilely produce phosphorus-doped biochar from pomelo peel and meantime provide new sights into the interaction mechanism of phosphoric acid groups with uranium ion. An interesting hydrogelation phenomenon is found when simply mixing the phosphoric acid solution and pomelo peel powder. The resulted hydrogel readily undergo carbonization to produce desired biochar. The biochar exhibits good uranium removal efficiency (up to 99 %) with a maximum adsorption capacity of 603 mg/g at 313 K. The distribution coefficient of uranium (VI) attains 10.8 L/g. The biochar undergoes five desorption-adsorption cycles with desorption and adsorption efficiencies above 95 %. It can be applied in fix-bed column for dynamic adsorption of uranium from uranium-containing solutions and real nuclear wastewater with an adsorption capacity over 422 mg/g. Rather than direct interaction with uranium ion, our experimental and computational results reveal that the surface phosphoric acid groups initially undergo in-situ ionization to produce phosphonates and the complexation of phosphonate with uranium ion results in effective uranium adsorption. This work demonstrates the high efficiency of pomelo peel biochar for disposal of uranium-containing nuclear wastewater, and offers new insights into the mechanism of uranium adsorption on the adsorbents containing phosphoric acid and phosphonate groups.

Modulating conjugated microporous polymers via cyclization as a remarkable photo-enhanced uranium recovery platform

Uranium recovery is of great significance for managing environmental contamination, improving the utilization rate of uranium resources, reducing the pressure of nuclear fuel supply and building a closed-loop nuclear fuel cycle system. However, most of the current adsorbents are limited in practical application due to their poor selectivity in highly acidic environments (pH = 1). Here, we present a powerful uranium recovery strategy with combined ligand complexation, chemical reduction and photoreduction based on metal-free cyclization-modulated conjugated microporous polymers (CMPs). Our well-tailored CMP (CTATP-DHBA) is rich in pyridine and hydroquinone units, forming favorable six-membered chelation motifs to be well suited for selective loading and reduction of UVI, thus exhibiting remarkable uranium removal efficiency (ca. 83.27% removal in 200 ppm solutions, pH = 1). In the dark, CTATP-DHBA can effectively reduce pre-enriched UVI to UIV in situ via hydroquinone units on the skeleton, thus weakening the proton competition and achieving excellent uranium recovery efficiency. Meanwhile, the synergistic effect of the cyclized π-conjugated skeleton and the oxidized benzoquinone units significantly enhances the photocatalytic activity of CTATP-DHBA, and an additional UVI photocatalytic reduction can occur under visible light irradiation, enabling photo-enhanced uranium recovery. Environmental ImplicationThe mineralization of valence-variable radionuclides such as uranium could not only enhance the extraction performance and simplify the subsequent separation procedure, but also effectively weaken the competition of protons for selective sites in the acidic sample matrix. Thus, the construction of robust CMPs with excellent photoreduction activity and affinity may be an ideal material for the selective extraction and in-situ mineralization of strategic nuclide uranium from strongly acidic radioactive wastewater. Herein, a metal-free cyclization-modulated CMP with the favorable six-membered chelation motifs is tailor-made as an efficient platform for efficient extraction and in situ mineralization of valence-variable nuclide uranium.