Radioactive Wastewater Treatment Research Articles

Comparative study of silica-based porous materials in the purification of radioactive wastewater

A significant challenge in the treatment of low-level radioactive wastewater is the effective purification of low-concentration radionuclides. Silica-based adsorbents are advantageous for the deep-purification of low-concentration metal ions. This study investigates three primary types of silica-based adsorbents: functionalized mesoporous silica, various modified zeolites, and mesoporous calcium silicate hydrate (C-S-H). These adsorbents were synthesized and their deep-purification effects on heavy metals and radionuclides were compared. The results indicated that mesoporous silica showed relatively poor adsorption for most metal ions. Zeolites outperformed mesoporous silica, with Zn framework-modified zeolites showing enhanced adsorption for several metal ions. Notably, C-S-H displayed superior adsorption performance, achieving high adsorption capacities for various metal ions and radionuclides. Specifically, at a dose of 0.5 g/L, the adsorption efficiency of C-S-H for numerous radionuclides in nuclear power plant wastewater exceeded 92–99 %, highlighting its potential for practical applications. An in-depth analysis of the physical and chemical structure and the adsorption mechanisms of C-S-H revealed its large mesoporous structure and electrostatic attraction to cations across a wide pH range. Multivalent cations were removed through exchange with Ca2+ in C-S-H, whereas monovalent cations were removed through exchange with Na+ in C-S-H. The cyclic structure of silica-oxygen tetrahedra in C-S-H, which promotes large pore formation and provides abundant ion exchange sites, underpins its excellent adsorption properties. This study offers valuable insights for the selection and application of silica-based materials in radioactive wastewater treatment.

U(Ⅵ) sorption by porous sodium zirconium phosphate pellets from aqueous solution

Zirconium phosphate is the first artificially produced layered phosphate that can sorb a variety of nuclides from solutions. Sodium zirconium phosphate (NZP) was a type of α-zirconium phosphate (α-ZrP). The porous sodium zirconium phosphate pellets (p-NZP-P) with a diameter of more than ∼3 mm were prepared and used for uranium sorption. The p-NZP-P could be immersed in solutions for more than 5 days without dissolving and structurally collapsing. The sorption properties of U(Ⅵ) on p-NZP-P in solutions were investigated by both static and dynamic sorption tests. Synthetic p-NZP-P was analyzed in detail using various characterizations to investigate their character and structural changes. In the static sorption experiment, the equilibrium sorption capacity reached the 77.5 ± 1.5 mg·g−1 when the initial concentration of U(Ⅵ) was 100 mg/L, pHinitial = 4.5, T = 25 ℃. Uranium sorption increased by ∼69 % and ∼215 %, respectively, when the initial uranium concentration was increased from 100 to 300 mg·L−1 and the temperature was increased from 15 to 55 °C. Furthermore, uranium sorption increased by ∼541 % when the initial pH increased from 2.5 to 4.5, while it decreased by ∼39 % when the initial pH increased from 4.5 to 7.0. The sorption data corresponded to the pseudo-second-order kinetic model and the Langmuir isotherm model, as well as the theoretically predicted value of sorption capacity (∼199.9 mg·g−1). The results of the dynamic sorption experiment showed that decreasing the quality, increasing the flow rate and the initial U(Ⅵ) concentration would shorten the breakthrough time. The dynamic sorption data agreed well with the Thomas model. The characterization confirmed the porous properties, while the U(Ⅵ) sorption mechanisms relate to –OH coordination and ion exchange. A radioactive rare earth wastewater treatment test suggested that p-NZP-P could be the potential uranium sorbent due to its good stability and efficiency. This paper opened opportunities for the development of practical materials for treating radioactive wastewater in the application of actual scenarios.

Assessment of electrochemical removal mechanisms of diverse transition metal dichalcogenides for caesium ion removal in wastewater treatment

Abstract Effective treatment of radioactive wastewater is crucial for broader nuclear energy adoption, with caesium radionuclides (most exist in the form of caesium chloride) presenting challenges due to their long half-life and biological hazards. Conventional adsorbents like zeolites and carbon-based materials, including graphene, face limitations in adsorption capacity due to the formation of electric double layers (EDL). This has led to the investigation of alternatives such as transition metal dichalcogenides (TMDs) e.g., MoS2, MoSe2, and WSe2, which offer promising galleries for caesium ion removal. Aside from extensively studied MoS2, there is limited research on the adsorption mechanisms and capacities of other TMDs like MoSe2 and WSe2. Here, we conduct a comparative study examining the removal mechanisms and capacities of exfoliated MoS2, MoSe2, and WSe2 nanosheets, alongside an evaluation of these properties in relation to graphene. Our investigation reveals distinct removal mechanisms and capacities among these three materials for capturing caesium ions in a variety of mechanisms. MoS2 nanosheets primarily utilise a pseudocapacitive charge storage mechanism via intercalation, as evidenced by a total charge storage of 0.78 C g1, with only 2.6% stored via EDL formation. In contrast, MoSe2 predominantly relies on EDL formation, with almost 60% of the total 0.54 C g1 charge storage attributed to this mechanism. Lastly, WSe2 exhibits a combination of both charge storage behaviours, with a total charge storage of 0.77 C g1, of which 14% is due to EDL formation. This research highlights the potential efficacy of TMDs as viable materials for caesium removal, offering an appealing alternative to conventional adsorbents and likely fostering advancements in water treatment technologies.

Enhanced cesium removal from wastewater using a potassium hexacyanoferrate/gelatin aerogel composite

In the wake of the 2011 Fukushima nuclear disaster, the presence of radioactive cesium (137Cs) in nuclear wastewater has posed a critical and enduring health risk. Addressing this challenge, we have synthesized a gelatin aerogel, denoted as KCuFC/GA, immobilized with potassium cupric ferrocyanide (KCuFC) through an in situ approach, aiming for the efficient extraction of 137Cs from aqueous environments. This novel aerogel's rich porous structure enhances the accessibility of adsorption sites, thereby significantly promoting the capture of Cs+. The adsorption of cesium onto KCuFC/GA was investigated under various experimental conditions, including initial solution pH, contact time, initial cesium concentration, and the presence of coexisting ions (K+, Na+, Ca2+, Mg2+, Sr2+). The results indicated that the adsorption performance was largely independent of pH, achieving a high cesium removal rate of 93.4 % within the first 5 minutes. The cesium adsorption data were well-described by the Langmuir adsorption model, indicating a maximum adsorption capacity of 222.22 mg·L−1. Furthermore, in the presence of various competing ions, KCuFC/GA has demonstrated unparalleled selectivity for Cs+, with a partition coefficient (Kd) of 2.49 × 105 mL·g−1, and has sustained its adsorptive properties across five cycles of use. Through systematic investigation, including X-ray photoelectron spectroscopy (XPS) analysis, we have elucidated the adsorption mechanism, highlighting the pivotal role of ion exchange between lattice K+ and Cs+. The straightforward fabrication process and the aerogel's robust cesium removal capabilities from complex solutions indicate that KCuFC/GA is a promising candidate for real-world applications in the treatment of radioactive wastewater.

Co/N-codoped carbon nanoplate array coated carbon fiber cathode for solar driven uranium extraction from complex radioactive wastewater

Organics bring great challenge on uranium reduction due to the formation of stubborn complexes between uranyl ions (UO22+) and organics. Herein, we developed an effective strategy to synchronously degrade organics and extract uranium from complicated radioactive wastewater, accompanied with electricity generation, by a novel self-driven photocatalytic fuel cell (NSPFC) system, in which a three-dimensional (3D) Co/N-doped carbon nanoplate array (Co-N-C/CF) decorated carbon fiber is employed as the cathode for highly efficient UO22+ reduction. Compared to pure CF, the optimized Co-N-C/CF cathode increases the rate constants (k) by 9 and 9.1 times for UO22+ and organic elimination, respectively, and improves electricity output by 2 times (Pmax, 1180 μW/cm2). This improvement should be ascribed to the 3D morphology of Co-N-C/CF that provided plenty of surface area for U(VI) reduction, and the doping of N and Co, which effectively increased the U(VI) adsorption sites and optimized the electron behavior on the cathode, respectively. These features endow the NSPFC system with excellent adaptability in treating complex radioactive wastewater with a wide range of pollutant concentration, pH, co-existed ions, pollutant organics and natural organic matters. Fascinating activity is also achieves in treating polluted seawater or under real sunlight illumination. This work not only provides a outstanding nanostructured cathode for uranium reduction but also suggests a charming system to resourcefully treatment of radioactive wastewater or polluted water bodies.

Innovative potassium hexacyanoferrate intercalated into layered double hydroxide adsorbent for efficient cesium removal from seawater

Effective radioactive wastewater treatment technology is essential to ensure the sustainable development of nuclear energy. Here, the potassium ferrocyanide (HCF) intercalating with layered double hydroxide (LDH) (HCF@LDH) was successfully synthesized by coprecipitation method for selective cesium (Cs) removal from seawater. Characteristics of the adsorbent, and adsorption performance under different environmental conditions including Cs+ ion selectivity, and underlying adsorption mechanism were systematically investigated. The experimental results demonstrated that the adsorption capacity of HCF@LDH was 52.08 mg/g and it effectively removed 100 % of Cs+ from up to 200 mg/L Cs solution within 1 h under an optimal pH of 6.0–10.0. Moreover, the adsorbent displayed high selectivity towards Cs+ even in seawater and more than 90 % of Cs+ was removed from seawater and the highest cesium removal capacity from seawater was 44.64 mg/g. Both the Langmuir isotherm model (R2 = 0.997) and the pseudo-second-order kinetic model (R2 = 0.999) provided a good fit for the adsorption data signifying the adsorption process is homogeneous and formed monolayer through chemisorption. Furthermore, the reusability analysis exhibited this adsorbent was recycled and reused for at least 5 cycles without losing its original adsorption performance. The physicochemical analysis of the HCF@LDH proved that K4Fe (CN)6 successfully intercalated onto LDH and cation exchange between K+ and Cs+ played an important role in effective Cs adsorption. More specifically, the interstitial spaces of the hexacyanoferrate crystals facilitate the cation exchange process. The findings of this study demonstrate that HCF@LDH is a unique, highly effective, and selective adsorbent for Cs+ from complex seawater.

Effective removal and immobilization of radioactive iodate from aqueous solution by iron-gallic acid@palygorskite nanohybrid

Here, we developed a new low-cost and high-efficiency adsorbent, iron-gallic acid@palygorskite nanohybrid, for removing and immobilizing radioactive IO3- from wastewater. The results show that the key factor affecting the adsorption performance of the hybrid is the reaction time, which determines the degree of coating of GA-Fe(II) nanoparticles on the palygorskite. These nanoparticles are very randomly distributed on the surface of palygorskite rod-shaped crystals or combined with a large number of rod-shaped accumulations of palygorskite. In addition to the GA-Fe(II) complex formed at a molar ratio of 1:1, there are also iron elements in the hybrid that may be fixed to the surface and lattice of the palygorskite by ion exchange and isomorphic substitution. The adsorption process conforms to the pseudo-second-order kinetic model and Langmuir isotherm model, with a maximum adsorption capacity of 78.37 mg/g. It is also a spontaneous, endothermic, and disorder-increasing process. The extremely low desorption efficiencies confirm that the GA-Fe(II) complex exhibits strong chemical adsorption with the iodate, and the positively charged sites such as ferrous and iron ions presented in the palygorskite can also be fixed to the iodate through electrostatic attraction. Therefore, this adsorbent exhibits good application potential in the treatment of radioactive iodate wastewater.

Electrodeposition fabrication of graphene oxide/α-MnO2/polyaniline hierarchical porous electrodes with large hybrid specific capacitance for efficient U(VI) electrosorption

The radioactive pollution caused by the excessive discharge of uranium-containing wastewater generated from nuclear industry posed harmful effect to the ecological environment and human health. Herein, the electrodeposition of polyaniline on graphene oxide/α-MnO2 surface was conducted to fabricate novel hierarchical porous graphene oxide/α-MnO2/polyaniline (GMP) electrodes with large specific capacitance for U(VI) electrosorption through hybrid capacitance deionization (HCDI). As expected, the prepared GMP have high specific capacitance, small electrochemical impedance, and excellent electrosorption performance. Among the different GMP composites, GMP-2 presents the highest specific capacitance (303.85 F/g) and largest electrosorption capacity of U(VI) (330.41 mg/g at 0.9 V and pH4.0), indicating that its electrosorption capacity is closely related to the specific capacitance. Moreover, GMP-2 showed good selectivity for U(VI) electrosorption through pseudocapacitive mechanism. The XPS and FTIR characterization indicated that apart from hybrid capacitance (EDL and pseudocapacitance) mechanism, complexation and electrostatic interactions were also involved for U(VI) capture. The GMP-2 electrode is facile to fabricate and has excellent electrosorption performance, which could be used in HCDI for radioactive wastewater treatment.

One-pot synthesis of novel polyvinylphosphonic acid hydrogels for efficient separation of low-enriched uranium in water

Uranium extraction from seawater and the treatment of radioactive wastewater has traditionally been a hot topic. Herein, p(VPA-AM)n solid hydrogels with high uranium extraction properties based on vinylphosphonic acid (VPA) were successfully prepared by one-step copolymerization for the first time. The batch adsorption experiments demonstrated that p(VPA-AM)n has strong uranium chelating ability, fast uranium adsorption kinetics (within 200 min) and high uranium adsorption capacity (644.67 mg/g), and its adsorption behavior conforms to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model, which is a spontaneous heat-absorbing chemical monolayer adsorption process. After 15 adsorption–desorption tests, the adsorption capacity was kept above 96 % of the original capacity, and the uranium extracted from the salt lake water achieved at 3.56 mg/g, which showed superb behavior in treating complex uranium systems. Mechanism studies revealed that the strong interaction between UO22 + and −PO43- dominated the adsorption and the robust complexation might have led to the electron transfer in the structure. The maximum uranium removal rate of p(VPA-AM)n in simulated seawater reached 90 %, and the simple in situ zinc oxide-modified p(VPA-AM)n hydrogel showed good anti-biosludge properties against three common bacteria (E. coli, B. subtilis and S. aureus), which has a great potential for application in seawater uranium extraction and uranium wastewater treatment.

Decoration of phosphoric acid groups onto Ti3C2Tx MXene for enhanced uranium removal

The construction of novel MXene-based composites with superb abilities through functionalization is an effective strategy to enhance the potential of this emerging inorganic lamellar material for environmental adsorption applications. The present work systematically investigated the adsorption performance of Ti3C2Tx MXene modified with phosphate functional groups that facilitate the capture of uranyl ions. After introducing phosphate groups via a two-step modification of 3-aminopropyltriethoxysilane (APTES) and phytic acid (PA), the synthesized Ti3C2-APTES-PA is significantly superior to pristine Ti3C2Tx nanosheets in terms of adsorption capacity, adsorption selectivity and reusability for uranium. The maximum uptake capacity of Ti3C2-APTES-PA at pH = 5 reaches 323 mg/g, which is 2.5 times higher than that of unmodified MXene. Furthermore, the large selectivity coefficient (SU/M > 16.2) declares that Ti3C2-APTES-PA preferentially adsorbs uranium among substantial competing ions. Ti3C2-APTES-PA also shows good cycling performance that its adsorption capacity remained 92.3 % after 6 cycles. When it comes to treating simulated uranium tailings pond leachate and radioactive wastewater from mines, high U(VI) removal rates of 88.9 % and 96.8 % can be achieved by our ternary composite at a dosage of 0.05 g/L. The underlying adsorption mechanism was unraveled by spectroscopic analysis to be the formation of coordination complexes of uranyl ions with phosphate groups on PA and hydroxyl groups on Ti3C2Tx substrate, as well as the reduction of a small amount of adsorbed U(VI) to U(IV) by MXene. The overall results imply that Ti3C2-APTES-PA is an effective uranium chelating scavenger for the treatment of environmental radioactive wastewater.

Ion-imprinted macroporous polyethyleneimine incorporated chitosan/layered hydrotalcite foams for the selective biosorption of U(VI) ions

In order to prevent uranium pollution and recovery uranium resources, it was necessary to find a highly efficient adsorbent for radioactive wastewater treatment. Herein, U(VI) imprinted polyethyleneimine (PEI) incorporated chitosan/layered hydrotalcite composite foam (IPCL) was synthesized by combining ion-imprinting and freeze-drying techniques. IPCL has a high amino/imino content and an ultralight macroporous structure, making it capable of efficiently adsorbing U(VI) and easy to separate; Especially after ion-imprinting, vacancies matching the size of uranyl ions were formed, significantly improving U(VI) selectivity. The adsorption isotherms and adsorption kinetics were in accordance with the Freundlich model and PSO model respectively, indicating that heterogeneous adsorption of U(VI) by the adsorbents. The adsorption capacity of IPCL-2 for U(VI) reached 278.8. mg/g (under the conditions of optimal pH 5.0, temperature of 298 K, contact time of 2 h, and adsorbent dosage of 0.2 g/L), which is almost double of that for the non-imprinted foam (PCL-2, 138.2 mg/g), indicating that IPCL-2 can intelligently recognize U(VI). The heterogeneous adsorption mechanism of U(VI) by IPCL-2 involves complexation, ion-exchange and isomorphic substitution. The adsorption of U(VI) by IPCL-2 is spontaneous and endothermic. IPCL-2 has excellent adsorption performance for U(VI), and is a promising adsorbent for radioactive pollution control.

Reverse osmosis membrane with crown ethers decoration for enhanced radionuclides sieving

Reverse osmosis (RO) membranes have been widely applied in the increasingly discharged radioactive wastewater treatment. However, conventional RO membranes suffer from the issues of the limited nuclides rejections and the relatively low water permeance. In this work, a new type of RO membrane with decoration of crown ethers (15C5 and 18C6) was prepared via an interfacial polymerization process to remove the radionuclide-contaminated components. Due to the special hollow structure of crown ethers (CEs) and the hydrogen bonding within the amidogen, the obtained MPD@15C5-TMC and MPD@18C6-TMC membranes exhibited smoother surfaces and thinner polyamide active layers than the pristine MPD-TMC membrane. The optimized MPD@15C5-TMC and MPD@18C6-TMC RO membranes presented excellent pure water permeances up to 2.16 and 2.91 L m−2 h−1 bar−1, and maintained high rejections towards Cs+, Sr2+ and Co2+, respectively. Furthermore, the membrane possessed a remarkable operational stability and an excellent anti-fouling property. These results confirmed the possibility of adopting crown ethers for RO membrane fabrication and verified their great potential for the practical application in removing radioactive elements from wastewater.

Practical applications of inorganic adsorbents for radioactive waste water treatment at NARI. Part I: Laboratory scale tests

BackgroundSeveral varieties of radioactive waste water, such as Mo-99, laundry, process and waste ethylene glycol waste water, were stored at NARI and needed for further treatment. Radionuclides, which mainly be Cs-137, Sr-90 and Co-60, should be removed from waste water before discharge. MethodsPractical adsorption by commercial (Cs-Treat, Sr-Treat, DT-30, DT-30A, A-51 and NRW 160) and customized (ACCs and AC-Sr) inorganic adsorbents for on-site radioactive waste water treatment in the laboratory scale were investigated. Treatment equipment, procedures, consumption volumes and capacities of adsorbents are described and discussed as well. Significant FindingsCapacities and performance of commercial and customized adsorbents for various radionuclides (Cs-137, Sr-90 and Co-60) were investigated. Two inorganic adsorbents, ACCs and AC-Sr, were developed by NARI for specific radionuclides (Cs-137 and Sr-90) adsorption. Adsorption capacities of ACCs for Cs-137, where the removal rate was more than 95 % within 10 days applied in process waste water, was equivalent with commercial adsorbents, DT-30 and DT-30A. The removal rate of Gross β, Cs-137 and Sr-90 applied by AC-Sr had maintained more than 95 % for 50 days of laundry waste water treatment.

Construction of novel phytic acid-based lignin for highly efficient treatment of low-level radioactive wastewater: Synthesis, performance, and mechanistic insights

Low-level radioactive wastewater exhibits a serious jeopardize to the ecology, natural environment, and human health. Hence, this study constructed a novel adsorbent (PA-EHL) via a simple grafting reaction by using enzymatic hydrolysis lignin waste (EHL) and phytic acid (PA) as raw materials. The adsorption capacity of PA-EHL was evaluated using Ce(III) and La(III) as the representative nuclides. PA grafting significantly promoted the formation of good textural properties, high crystalline stability, and abundant phosphorous/oxygen-containing functional groups on lignin surface, thus appreciably strengthening the adsorption performance. The PA-EHL exhibited high adsorption capacity for Ce(III) with 743.16 and for La(III) with 735.60 mg/g within 240 min. In addition, the efficient ability of PA-EHL for adsorbing Ce(III) and La(III) displayed superior anti-ions interference abilities, excellent reusability, and extremely low operational fees. The P-O on PA-EHL surface as the main active site, displayed strong binding affinity for Ce(III) and La(III) via electrostatic attraction-dominated physisorption and complexation-dominated chemisorption, respectively. In summary, the constructed PA-EHL addresses the drawback of conventional adsorbents in view of complicated fabrication process, low adsorption capacity, inferior anti-ions interference abilities, and expensive cost, which makes it as a potential adsorbent in industrial application for the highly efficient treatment of low-level radioactive wastewater.

Prediction of Uranium Adsorption Capacity in Radioactive Wastewater Treatment with Biochar.

Recently, Japan's discharge of wastewater from the Fukushima nuclear disaster into the ocean has attracted widespread attention. To effectively address the challenge of separating uranium, the focus is on finding a healthy and environmentally friendly way to adsorb uranium using biochar. In this paper, a BP neural network is combined with each of the four meta-heuristic algorithms, namely Particle Swarm Optimization (PSO), Differential Evolution (DE), Cheetah Optimization (CO) and Fick's Law Algorithm (FLA), to construct four prediction models for the uranium adsorption capacity in the treatment of radioactive wastewater with biochar: PSO-BP, DE-BP, CO-BP, FLA-BP. The coefficient of certainty (R2), error rate and CEC test set are used to judge the accuracy of the model based on the BP neural network. The results show that the Fick's Law Algorithm (FLA) has a better search ability and convergence speed than the other algorithms. The importance of the input parameters is quantitatively assessed and ranked using XGBoost in order to analyze which parameters have a greater impact on the predictions of the model, which indicates that the parameters with the greatest impact are the initial concentration of uranium (C0, mg/L) and the mass percentage of total carbon (C, %). To sum up, four prediction models can be applied to study the adsorption of uranium by biochar materials during actual experiments, and the advantage of Fick's Law Algorithm (FLA) is more obvious. The method of model prediction can significantly reduce the radiation risk caused by uranium to human health during the actual experiment and provide some reference for the efficient treatment of uranium wastewater by biochar.

Highly efficient and selective removal of 90Sr by the carboxylated COFs (Tp-DTA) from radionuclides-contaminated groundwater

In this study, a carboxyl-functionalized covalent organic framework (COF) rich in nitrogen (N) and oxygen (O) functional groups was prepared and characterized, which provided a new opportunity for the efficient and rapid treatment of radioactive contamination in nuclear wastewater. The synthesis of the COF (Tp-DTA) was constructed using 1,3,5-triformylphloroglucinol (TFP) and 2,5-diaminoterephthalic acid (DTA), providing a large specific surface area, mesoporous pore, and abundant coordination sites with high adsorption capacity and exceptional affinity for Sr2+. Batch adsorption experiments exhibited that Tp-DTA achieved a maximum adsorption capacity of 145.4 mg/g for Sr2+ in alkaline solutions, reaching adsorption equilibrium within 60 min. Tp-DTA exhibited rapid kinetics for 90Sr, with the amounts of 90Sr removed more than 95% within 3 min. In the presence of coexisting ions (Na+, K+, Cs+, Mg2+, and Ca2+), Tp-DTA displayed excellent preferential selectivity for Sr2+ and high removal efficiency. Even in simulated groundwater containing multiple complex ions, Tp-DTA demonstrated a strong affinity for Sr2+ and showed practical applicability with a nearly 100% removal efficiency for 90Sr. XPS and FTIR characterizations confirmed that the adsorption mechanism of Sr2+ involved chelation exchange between the carboxyl groups of Tp-DTA and Sr2+ in the solution. Furthermore, the desorption efficiency of HCl (>0.01 mol/L) can reach 95% and five cyclic desorption-adsorption experiments demonstrated the reusability of Tp-DTA, endowing the carboxyl-functional COF with great potential in the treatment of 90Sr-contaminated radioactive wastewater and environmental remediation.

Efficient and rapid capture of uranium(VI) in wastewater via multi-amine modified β-cyclodextrin porous polymer

Efficient and rapid capture of uranium(VI) in wastewater via multi-amine modified β-cyclodextrin porous polymer

Investigation of bentonite clay minerals as a natural adsorbents for Cs-137 real radioactive wastewater treatment

In this work, the removal of the radioactive element Cs-137 from actual radioactive wastewater was studied by batch adsorption studies. To lower the dangers of radioactive contamination, bentonite, a naturally occurring clay mineral, was used as an adsorbent. The bentonite clay mineral was characterized using chemical composition analyses, (XRD), (SEM), (EDX), (BET) surface area analysis, and (FT-IR). Experiments of batch adsorption were conducted to determine the optimal adsorbent. After two hours, equilibrium was attained with a bentonite Cs-137 removal effectiveness of 98%. The kinetics of Cs-137 adsorption on the bentonite clay surfaces was investigated. A good match was obtained for the bentonite kinetic data using the pseudo 2nd order kinetic model. As a result, it was found that bentonite was the good medium for adsorption. The findings provide helpful details on the ways in which bentonite clays adsorb radioactive Cs-137 and remediate pollution. The chosen of bentonite clay adsorbents was displayed to be hopeful adsorbent for the adsorption of the radioactive Cs-137 isotope because of effective material, very cheap, and available.

Highly-efficient uranium reduction, organic oxidation and electricity generation via a solar-driven wastewater resourceization system with a PANI/CF cathode

Co-existed organics bring great challenges for uranium recycling from water because of the formation of obstinate complexes with uranyl ions (UO22+), predominated species of uranium in water). Here, we proposed an effective strategy to simultaneously decompose organics and recycle uranium from complex radioactive wastewater, combined with electricity production, by a solar-driven wastewater resourcization system (SWRS), in which an electrodeposited polyaniline (PANI) decorated carbon fiber (CF-PANI) cathode was used for highly efficient UO22+ reduction based on the abundant –NH- groups and conductivity of PANI. Under sunlight illumination, a BiVO4 decorated WO3 nanoplate array (BVO/WNP) combined with a rear silicon cell (SC) was applied as the monolithic photoanode to generate oxidative holes and derived hydroxyl radicals for robust organic oxidation, and driven electrons to the CF-PANI cathode for uranium reduction and simultaneous electricity generation at external circuit. Compared to CF, the optimized CF-PANI improved the rate constants (k) by 6 and 6.7 times for UO22+ and organic removal, respectively, and enhanced power output by 2 times (Pmax, 1.12 mW/cm2). Additionally, near 100 % removal ratios for both UO22+ and organics accompanying with Pmax around 1 mW/cm2 were achieved by SWRS when treating model complex wastewater under wide conditions or even under real sunlight illumination. The fixed uranium on the CF-PANI cathode was mainly reduced into U(IV) species (95.8 %) and the repeated tests demonstrated the excellent stability of SWRS (without obvious decay after reusing 15 times). This work provides new insights on the resourceful treatment of radioactive wastewater and contaminated waters.

Developing a highly efficient, environmentally friendly and cost-effective copper sulfide semiconductor sponge for nuclear wastewater treatment under one sun

Solar-driven interfacial evaporation technology, as a green and low-energy water treatment method, finds widespread applications in desalination, power generation, and wastewater treatment systems. In this study, a three-dimensional sponge solar evaporator was prepared using hydrophilic compounds (konjac glucomannan, KGM) and a solar absorber (copper sulfide, CuS). In a single instance of solar irradiation, the sponge demonstrated swift evaporation rates at 1.58 kg m−2 h−1, coupled with an impressive interfacial water evaporation efficiency of 94.30%. Due to the characteristics of CuS and KGM, the sponge demonstrated photothermal properties, insulation, and rapid water transport. Even under radiation (1 kW/m2) and a wide range of pH conditions (pH∼2–12), the concentration of elements in radioactive wastewater could be reduced by a million times (from 1 g/L to 0.253 μg/L). Notably, during 20 cycles of testing, the sponge's evaporation efficiency only decreased by 1.13%. Furthermore, over an extended 5-hour evaporation period, it consistently sustained a steady evaporation rate of 1.577 kg m−2 h−1, showcasing its exceptional reproducibility and enduring resilience. Therefore, solar-driven interfacial evaporation technology exhibits significant potential for efficient treatment of radioactive wastewater.