Nuclear Effluents Research Articles

A four-fold interpenetrated MOF for efficient perrhenate/pertechnetate removal from alkaline nuclear effluents

The sequestration of 99Tc represents one of the most challenging tasks in nuclear waste decontamination. In the event of a radioactive waste leak, 99TcO4– (a main form of 99Tc) would spread into the groundwater, a scenario difficult to address with conventional anion exchange materials like resin and inorganic cationic sorbents. Herein, we present a nickel(II) metal-organic framework (MOF), TNU-143, featuring 3D four-fold interpenetrated networks. TNU-143 exhibits efficient ReO4– (a nonradioactive analogue of 99TcO4–) removal with fast anion exchange kinetics (<1 min), high sorption capacity (844 mg/g for ReO4–), and outstanding selectivity over common anions. More importantly, TNU-143 shows superior stability in alkaline solution and can remove 91.6% ReO4– from simulated alkaline high-level waste (HLW) streams with solid-liquid ratio of 40 g/L. The uptake mechanism is elucidated by the single-crystal structure of TNU-143(Re), showing that ReO4– anions are firmly coordinated to nickel cation to result in a 2D layered structures. Density functional theory (DFT) calculations confirm the transformation from TNU-143 to TNU-143(Re) is a thermodynamically favorable process. This work presents a new approach to the removal of ReO4–/99TcO4– from alkaline nulcear fuel using MOF sorbents.

Direct determination of 237Np in nuclear effluent by ICP-MS/MS

A new method for the rapid quantification of neptunium 237 in nuclear effluent was developed.

Biocarbon/polyaniline nanofiber electrodes with high hybrid capacitance and hierarchical porous structure for U(VI) electrosorption

The removal of U(VI) from nuclear effluents is significant for uranium resource recovery and environmental safety. Herein, polyaniline (PANI) was electrodeposited on porous biocarbon (cotton derived carbon, CC) to fabricate a high-performance composite electrode (CC/PANI) for U(VI) electrosorption. The CC/PANI electrode showed high specific capacitance and excellent cyclic stability, it also exhibited capacitive control characteristics for which the capacitance contribution has been quantified. The electrosorption results indicate that CC/PANI-2 has the highest specific capacitance among various CC/PANI electrodes, and also exhibits the highest electrosorption capacity for U(VI), reaching a maximum value of 282.2 mg/g at pH 4.0 and 0.9 V. The modeling results of electrosorption isotherms and kinetics for U(VI) indicated the good simulation by Langmuir and PFO models, respectively. The excellent electrosorption performance of CC/PANI-2 for U (VI) is attributed to its high hybrid capacitance, good conductivity, and improved hydrophilicity. The electrosorption mechanism for U(VI) removal is mainly ascribed to EDL and pseudocapacitive electrosorption, with possible contribution from U(VI) coordination by N atoms of CC/PANI. This work provides the strategy of incorporating PANI with biocarbon to fabricate a novel electrode for the efficient CDI treatment of radioactive nuclear wastewater.

Exciton dissociation and electron transfer behavior of a novel Donor-Acceptor g-C3N4 organic semiconductor photocatalytic separation of uranium

Photocatalytic uranium extraction from nuclear effluent is a promising method to avoid environmental damage and recover uranium resources. Here, the hollow tubular D-A organic semiconductor photocatalyst was fabricated by grafting 2,7-dibromo carbazole (Dbc) onto the g-C3N4 (TCN) framework. The intra-molecular D-A system promoted visible light absorption, enhanced charge transfer, and improved the separation of photogenerated electron-hole pairs. Additionally, the incorporation of the carbazole structure increased the volume separation and the surface separation, adjusted the electron excitation model, and reduced the energy required for exciton dissociation. The results showed that the removal rate of U(VI) by DCN3 reached 96.4% in 120 min and 93.3% removal of U(VI) under sunlight, and it was stable and reusable with little change under sunlight and after 5 consecutive cycles. Therefore, the D-A photocatalyst established a high photocatalytic uranium separation efficiency under sunlight and high concentrations of interfering anions and cations. This study provides insight and guidance for a deeper understanding of photocatalytic uranium separation.

Exciton dissociation and transfer behavior and surface reaction mechanism in Donor–Acceptor organic semiconductor photocatalytic separation of uranium

Photocatalytic uranium extraction from nuclear effluent is a promising approach for avoiding environmental damage and recovering uranium resources. Here, a hollow tube-like D-A organic semiconductor photocatalyst consisting of triazine (Acceptor) and carbon ring (Donnor) was synthesized via two cheap monomers, sodium alginate and melamine. The incorporation of carbon ring structure could endow g-C3N4 with unique hollow hexagonal tube-like morphology, modulate the electronic excitation model, lower the energy for exciton dissociation, and promote the adsorption and activation of O2. Thus, the D-A photocatalyst established high efficiency of photocatalytic uranium separation under LED light and high concentration of anions and cations interference. More importantly, we propose a novel theory, that photocatalytic-induced-uranyl-coordination-reaction (PIUCR), and highlight that the formation rate and pathway of crystal nucleus is the most crucial step for the surface reaction of photocatalytic uranium separation. This study provides insights and guidelines for the in-depth understanding of the photocatalytic separation of uranium.

The Predicament and Outlet of Environmental Impact Assessment Mechanism from the Perspective of Risk Society: Taking Japan’s Accident-Type Nuclear Sewage Disposal as a Cut-In

As an important yardstick of social modernization, nuclear technology not only promotes the in-depth development of the national economy but also hangs a sword of Damocles in the field of the risk society. Against the background of the unrest of the nuclear leakage disaster at the Fukushima nuclear power plant, the Japanese government has announced its unilateral decision to discharge nuclear sewage into the sea, undoubtedly putting at least the Pacific Rim countries at huge potential risks. In order to maximize risk reduction and focus on preventive construction in advance, Japan's measures to discharge accident nuclear sewage into the sea have a legitimate basis for the application of an environmental impact assessment system. At the same time, in the process of operation, there are numerous risk dilemmas, such as lack of safety treatment standards, long follow-up disposal cycle and negative domestic supervision system, which need to be broken through one by one. The effective application of the environmental impact assessment system in the Japanese nuclear accident not only helps to reduce the environmental crisis caused by accidental nuclear effluent discharge to the sea but also has a positive and far-reaching international demonstration significance, which helps to better build a foundation of international trust and preventive guarantee system in advance for the possible accidental nuclear effluent treatment in the future.

Efficient removal of trace uranium from nuclear effluents using irradiation-functionalized fibrous adsorbents with very high salt tolerance

The extraction of uranium from nuclear effluents is both conducive to the recycling of nuclear fuel and reduces environmental pollution. Adsorbents are widely regarded as the most promising materials for trace uranium extraction; however, the adsorption of trace uranium from high-salinity environments is a challenge for adsorbents used to recover uranium from nuclear effluents. In this study, four different irradiation-functionalized adsorbents were fabricated and evaluated to screen suitable adsorbents for the removal of trace uranium from nuclear effluents. We found that the adsorbent with synergistic adsorption groups (NWF-g-PGMA-AO) exhibited the most distinctive trace uranium removal efficiency and robust stability in acidic, alkaline, and high-salinity environments. It was the synergistic involvement of hydroxyls in the coordination of amidoximes with uranium that enhanced the binding energy of uranium to NWF-g-PGMA-AO, thus improving its performance. In addition, the residual uranium concentration decreased to the maximum allowable emission concentration of 50 ppb over a wide pH range, with a minimum concentration of 9.35 ppb. Interestingly, nitrate, sulfate, phosphate, and chloride anions in the effluents did not decrease the uranium removal efficiency, whereas fluoride considerably reduced the efficiency, and the removal ratio was negatively correlated with fluoride concentration. This is attributed to the formation of [UO2Fn]2−n (n = 1, 2, 3, 4) species, which exhibit a decreasing affinity for adsorbents with increasing fluorine atoms as revealed by density functional theory calculations. This work makes a stride in designing superior adsorbents with synergistic adsorption groups for extracting trace uranium from nuclear effluents.

3D Viologen-based covalent organic framework for selective and efficient adsorption of ReO4−/TcO4−

Due to the long half-life and high environmental mobility, the selective and efficient capture of TcO4− from nuclear effluents is very important, but it is still very challenging. Herein, we design and synthesize a novel three-dimensional (3D) cationic covalent organic framework (TFAM-BDNP) via Zincke reaction for selective capture of TcO4−/ReO4−. TFAM-BDNP exhibits high adsorption capacity (998 mg g−1) and extremely fast exchange kinetic (60 s) for ReO4− (the non-radioactive alternative to TcO4−), attributing to the open 3D hydrophobic channels, abundant active sites, and high chemical stability. More importantly, TFAM-BDNP shows good adsorption performance for ReO4− in the presence of significant excess competing anions with a wide pH value range of 2 to 12. Under complex simulated Hanford flow sample, TFAM-BDNP has outstanding removal efficiency of ReO4−. The adsorption mechanism of ReO4− is mainly caused by anion exchange process. This study provides a novel adsorbent for efficient capture of TcO4−/ReO4− in complex environmental systems and exploits an effective strategy for broadening the types of 3D COFs.

DGA-functionalized super-magnetic acid-stable sorbent for treatment of acidic rich nuclear effluent

An acid-stable magnetic nanoparticle coated with silica bound to diglycolamide (MNCSDGA) has been synthesised and its sorption behavior for UO22+, Th4+ and Eu3+ from mediums containing high concentrations (0.5–6.0 M) of nitric acid (HNO3) was examined.

Mechanistic studies of uranyl interaction with functionalized mesoporous chitosan-superparamagnetic nanocomposites for selective sorption: Characterization and sorption performance

Herein, two hybrid magnetic-chitosan nanocomposite core-shell were synthesized via subsequently heterogeneous nucleation immobilized with alanine/serine functionality for enhanced uranyl ions (UO 2 2+ ) sorption. The physiochemical characteristics of nanocomposites were determined by CHN, FTIR, XRD, BET, pHzpc, TEM, TGA, XPS and VSM studies. The synthesized mesoporous alanine (Ala) and serine (Ser) nanocomposites were found: superparamagnetic with saturation magnetization ( M S : 26.54 and 23.05 emu g -1 for Ala and Ser, respectively), large surface-to-volume ratio for Ser (61.1 m 2 g -1 to 0.41 cm 3 g -1 ), compared to Ala (60.4 m 2 g −1 to 0.36 cm 3 g −1 ), and amine content for Ala and Ser was (2.69 and 2.58 mmol N g -1 with density of ⁓13.42 and ⁓12.73 nm 2- , respectively. The sorption characteristics of uranyl ions were thoroughly examined and compared. At the optimal pH range of 3.5-5.0, Ala and Ser nanocomposites show maximum sorption capacities of 0.498 and 0.609 mmol U/g, respectively in sulfate medium, as well 0.583 and 0.742 mmol U/g in nitrate medium. The Langmuir model suits the sorption process well, and the pseudo-second-order rate equation (PSORE) enables single-layer chemical reactions. Small-size particles afford rapid sorption ⁓50 minutes with half-sorption-time (t 0.5 ) 3.9 and 4.2 min for Ser and Ala nanocomposite, respectively. The sorption is spontaneous, exothermic and regulated by entropy change. The sorption efficiency in various medium types can be arranged according to sorption capacity as follows: nitrate > chlorides >> sulphate medium. According to spectroscopic analyses (FTIR and XPS), the sorption sites are N/O functional groups, which adsorbed UO 2 2+ by anion-exchange, electrostatic attraction and chelation mechanisms. Elution and regeneration are successfully accomplished with using acidified urea solution achieving ⁓92%. Finally, both sorbents were tested and compared for the selectivity of UO 2 2+ from multicomponent simulated waste containing uranyl species. Both sorbents showed high sorption capacity, excellent selectivity, and good recyclability and reusability over multiples sorption cycles. • Alanine and serine efficiently functionalized the magnetic-chitosan nanocomposite core-shell, which were extensively characterized and tested for uranium sorption. • Sorbents have a high sorption capacity, great selectivity, and strong recyclability and reusability through numerous sorption cycles. • Nanocomposites show a high affinity for U(VI) and great selectivity from acidic simulated nuclear effluent. • Interaction mechanisms of nanocomposites with uranyl ions have been elucidated.

Applying the Nernst Equation to Control ORP in Denitrification Process for Uranium-Containing Nuclear Effluent with High Loads of Nitrogen and COD

Several reviews of denitrification have shown it to be an efficient process for treating high nitrate-loaded effluents from nuclear industries. However, stressful conditions adversely affect biological kinetic parameters and performance. Additionally, actual nuclear effluents contain multiple pollutants and radioactive emissions that could render implementation difficult. The objective of this study was to treat and recycle water from nuclear industries by using a mixture of blended real nuclear wastewater (BRNW). The process was carried out under physicochemical parameters control in a biological model to established a technical setup and to model the denitrification process in a real nuclear wastewater effluent. Denitrification processes were carried out in the wastewater sample under controlled ORP conditions by the Hill model to establish the kinetic model. The results show a complete elimination of nitrate by the bacteria. Indicators of biochemical reactions were used to obtain a model based on Monod and controlled ORP. The good fit of the proposed model was verified under empirical and simulated conditions. To establish optimal performance, it was necessary to add 3% v/v of methanol, as a carbon source, to remove the nitrate in BRNW. Isolation techniques confirmed that Pseudomonas spp. was the dominant bacteria. Gene expression demonstrated the lack of inhibition of the NosZ gene responsible for the reduction in nitric oxide, a “greenhouse gas”. Finally, COD and uranium were removed from the liquid by precipitation. At the end of the process, the treated effluent could potentially be reused in industrial processes, recycling most of the wastewater effluents.

Removal of uranium from nuclear effluent using regenerated bleaching earth steeped in β‒naphthol

The intensification and adsorption of uranium on different adsorbents are considered an operative substitute technique for extraction from nuclear effluent. Many synthetic adsorbent materials have recently been developed for the removal of uranium from aqueous solution. Latterly, clay is a fundamental adsorbent to be considered in uranium recovery owing to the promising sorption properties. In this study, a spent bleaching earth from an edible oil manufacturing was remedied with a view to get rid of the edible oil remnants and then steeped in β‒naphthol to promote its adsorption characteristics. The clay is characterized by X‒ray Fluorescence (XRF), Fourier Transform Infrared Spectrometer (FTIR), surface area analyzer, Scanning Electron Microscope (SEM), and Energy-dispersive X‒ray spectroscopy (EDX). The experiments have been conducted upon adsorption efficiency of uranium to optimize the influence of pH value, agitation time, clay dosage, initial uranium ions concentration, and system temperature The uptake capacity of the new adsorbent is 175.10 mg g−1; it was been attained at pH 4.5, 60 min, and 25 °C. Both of the kinetic and isotherm of adsorption process were calculated and the data work in with pseudo‒first‒order kinetic model along with Langmuir‒Freundlich isotherm. Furthermore, the thermodynamic study implies the spontaneousness and exothermicity of the adsorption process of uranium ions. The negative value of ΔS° refers to the practicality of adsorption of uranium ions and the mitigation in randomness for the new adsorbent clay.

Resolving the conflict of nuclear wastewater discharging into the ocean based on the GMCR

PurposeJapan's decision to release nuclear wastewater into the Pacific Ocean in 2023 has sparked strong opposition at home and abroad. In this study, Graph Model for Conflict Resolution (GMCR) method is adopted to analyze the conflict problem, and reasonable equilibrium solutions are given to solve the conflict event.Design/methodology/approachIn this study, GMCR is adopted to solve the conflict problem. First, identify the key decision-makers (DMs) on the issue of nuclear effluent and the relevant options they might adopt. Second, the options of each DM are arranged and combined to form a set of feasible states. Thirdly, the graph model is constructed according to the change of DM's options, and the relative preference of each DM is determined. Finally, the conflict problem is solved according to the definition of GMCR equilibrium.FindingsDischarging nuclear wastewater into the ocean is not the right choice to solve the problem. Developing more space to store nuclear wastewater is more conducive to the protection of the ocean environment.Practical implicationsIt is undesirable for the Japanese government to unilaterally discharge nuclear wastewater into the ocean. Objectively assessing the radioactivity of nuclear wastewater and the cooperation of relevant stakeholders can better solve this conflict.Originality/valueThe problem arising from Japan's releasing plan is complicated because of a lack of information and the existence of multiple stakeholders, while GMCR can help us with a better view of the current circumstance in the conflict.

Fast and Efficient Removal of Uranium onto a Magnetic Hydroxyapatite Composite: Mechanism and Process Evaluation

The exploration and rational design of easily separable and highly efficient sorbents with satisfactory capability of extracting radioactive uranium (U)-containing compound(s) are of paramount significance. In this study, a novel magnetic hydroxyapatite (HAP) composite (HAP@ CoFe2O4), which was coupled with cobalt ferrite (CoFe2O4), was rationally designed for uranium(VI) removal through a facile hydrothermal process. The U(VI) ions were rapidly removed using HAP@ CoFe2O4 within a short time (i.e., 10 min), and a maximum U(VI) removal efficiency of 93.7% was achieved. The maximum adsorption capacity (Qmax) of the HAP@CoFe2O4 was 338 mg/g, which demonstrated the potential of as-prepared HAP@CoFe2O4 in the purification of U(VI) ions from nuclear effluents. Autunite [Ca(UO2)2(PO4)2(H2O)6] was the main crystalline phase to retain uranium, wherein U(VI) was effectively extracted and immobilized in terms of a relatively stable mineral. Furthermore, the reacted HAP@CoFe2O4 can be magnetically recycled. The results of this study reveal that the suggested process using HAP@CoFe2O4 is a promising approach for the removal and immobilization of U(VI) released from nuclear effluents.

Nitrification Process in a Nuclear Wastewater with High Load of Nitrogen, Uranium and Organic Matter under ORP Controlled

To produce nuclear fuels, it is necessary to convert uranium′s ore into UO2-ceramic grade, using several quantities of kerosene, methanol, nitric acid, ammonia, and, in low level, tributyl phosphate (TBP). Thus, the effluent generated by nuclear industries is one of the most toxic since it contains high concentrations of dangerous compounds. This paper explores biological parameters on real nuclear wastewater by the Monod model in an ORP controlled predicting the specific ammonia oxidation. Thermodynamic parameters were established using the Nernst equation to monitor Oxiders/Reductors relationship to obtain a correlation of these parameters to controlling and monitoring; that would allow technical operators to have better control of the nitrification process. The real nuclear effluent is formed by a mixture of two different lines of discharges, one composed of a high load of nitrogen, around 11,000 mg/L (N-NH4+-N-NO3−) and 600 mg/L Uranium, a second one, proceeds from uranium purification, containing TBP and COD that have to be removed. Bioprocesses were operated on real wastewater samples over 120 days under controlled ORP, as described by Nernst equations, which proved to be a robust tool to operate nitrification for larger periods with a very high load of nitrogen, uranium, and COD.

Removal of hazardous metals from nuclear effluent using a process hybridisation technique

A process hybridisation has been conceptualised in a three-stage process (a) Complexation, (b) Ultrafiltration (UF), and (c) Resin bed treatment. The system demonstration with nuclear plant generated waste was performed effectively by using a 5 L lab scale experimental capacity set-up. In complexation stage, water soluble polymers viz., Polyethylene imine (0.1%), Polyvinyl alcohol (0.1%), were used as the complexing agents either individually or in combination and around 0.12% total metal ions [that includes Uranium 1000 ppm, and other metals, pH-5.6] has been passed through UF membrane unit followed by a polyacrylamidehydroxamate resin bed, where outlet concentration was found to be in BDL level.

Polymer Nanorings with Uranium Specific Clefts for Selective Recovery of Uranium from Acidic Effluents via Reductive Adsorption

Nanostructured polymeric materials, functionalized with an appropriate receptor, have opened up newer possibilities for designing a reagent that shows analyte-specific recognition and efficient scavenging of an analyte that has either a detrimental influence on human physiology and environment or on its recovery for further value addition. Higher active surface area, morphological diversity, synthetic tunability for desired surface functionalization, and the ease of regeneration of a nanostructured material for further use have provided such materials with a distinct edge over conventional reagents. The use of a biodegradable polymeric backbone has an added significance owing to the recent concern over the impact of polymers on the environment. Functionalization of biodegradable sodium alginate with AENA (6.85% grafting) as the receptor functionality led to a unique open framework nanoring (NNRG) morphology with a favorable spatial orientation for specific recognition and efficient binding to uranyl ions (U) in an aqueous medium over a varied pH range. Nanoring morphology was confirmed by transmission electron microscopy and atomic force microscopy images. The nanoscale design maximizes the surface area for the molecular scavenger. A combination of all these features along with the reversible binding phenomenon has made NNRG a superior reagent for specific, efficient uptake of UO22+ species from an acidic (pH 3-4) solution and compares better than all existing UO22+-scavengers reported till date. This could be utilized for the recovery of uranyl species from a synthetic acidic effluent of the nuclear power. The results of the U uptake experiments reveal a maximum adsorption capacity of 268 mg of U per g of NNRG in a synthetic nuclear effluent. X-ray photoelectron spectroscopy studies revealed a reductive complexation process and stabilization of U(IV)-species in adsorbed uranium species (U@NNRG).

An approach to model radionuclide concentration in lake environment under scarce data

ABSTRACT In present study, a fuzzy logic (FL)-based algorithm is developed to predict near field concentration of tritium (Bq/L) at different points in a lake system wherein nuclear effluents are disposed as point source from a nuclear power plant. The model is developed using five input variables, which affect the spatial distribution of tritium concentration within the chosen system. The proposed model is developed under scarce radionuclide data wherein the missing data were generated using random number concept. The simulated results from proposed fuzzy model are validated using independent data on tritium concentration, measured at different locations within the lake system. The model outputs (tritium concentration in Bq/L) have been found to be in agreement with their measured values at sampling locations within the error band of . The simulated results from proposed fuzzy model have been found to be in close agreement with those obtained from CFD (Computational fluid dynamics) model for identical flow conditions developed in the previous studies for the same system. The proposed model is simpler in predicting tritium concentration within the lake while knowing the blow down concentration of specific day with less computational efforts. The developed model could be useful in ascertaining the near-field tritium concentrations, in near future for assessing their impacts on biotic environment.

Adsorption of Sr(II) cations onto phosphated mesoporous titanium dioxide: Mechanism, isotherm and kinetics studies

In this work, phosphate-modified titanium dioxide nanoparticles with mesoporous structure were synthesized and utilised as an efficient nanoadsorbent for Sr(II) removal from aqueous environment. The globular titania particles with a 3–4 nm diameter with chemosorbed on their surfaces phosphate groups = Ti(O2POOH) have been obtained by liquid-phase synthesis. The characterization of titania nanoparticles were performed using XRD, TEM, IR-spectroscopy and Brunauer-Emmett-Teller analyses. The synthesized modified adsorbents exhibited SBET = 396–410 m2 g−1 and mesopore volume of 0.262 – 0.275сm3 g−1. The isotherm and kinetic models were used for the description of Sr(II) adsorption. The sample 4P-TiO2 showed the best adsorption ability for strontium ions removal. The adsorption capacity of Sr(II) onto modified 2P-TiO2, 4P-TiO2 and 8P-TiO2 samples was found to be 94.1, 172.5, 128.9 mg/g, respectively. An adsorption mechanism for Sr(II) removal was proposed. The adsorption/desorption studies were conducted to find the reusability of phosphated adsorbents. A titanium dioxide-based mesoporous material possesses a significant adsorption activity due to high content of surface acid sites. All the outcomes revealed that the phosphate modified titania showed great potential in Sr(II) removal from aqueous environment and nuclear effluents.

Hydrodynamic Modeling of Radionuclide Effluent in Moticher Lake, Kakrapar Atomic Power Station, India

AbstractRadioactive effluent is generated through a nuclear fuel cycle involving the use of radioactive materials in nuclear power plants. The concentration of the nuclear effluent is of concern if...