Removal Of Sr Research Articles

Optimization of strontium removal by Tetraselmis chui grown in bubble column photobioreactors

Green microalgae of the class Chlorodendrophyceae have recently attracted the interest of researchers due to their ability to form micropearls (intracellular inclusions of amorphous calcium carbonate) highly enriched in Sr. The marine species Tetraselmis chui (included in the class Chlorodendrophyceae) shows high uptake of both stable and radioactive Sr isotopes and has been suggested as a potential candidate for the development of new bioremediation tools regarding radioactive 90Sr pollution. In this study, we optimized Sr removal from seawater by growing T. chui in 1-L bubble column photobioreactors (PBRs) with and without CO2 supply. Culturing T. chui in bubble column PBRs greatly improves cell production and Sr removal compared to previous studies. Furthermore, the addition of 10 mL L−1 h−1 CO2 further accelerates T. chui growth and results in better Sr removal rates. This study presents promising results for the development of new bioremediation methods to treat 90Sr pollution.

Partitioning of the high-level radioactive waste from the purex process by 40% TBF in isoparaffin using magnesium nitrate as a salting-out agent

Centrifugal contactor rig trials of the partitioning flowsheet were carried out using simulated and real high level waste solutions obtained by reprocessing of WWER-100 spent nuclear fuel with burn-up of 47 MW day/t. 40% TBP in Isopar M was used as a solvent with magnesium nitrate as a salting-out agent. Complete removal of Cs, Sr, Zr and Mo to raffinate was achieved. Rare earth elements, Am and Cm were totally concentrated in TPE and REE product. Comparison of the results of this work with previous trials with iron (III) nitrate as a salting-out agent [1] demonstrated that using magnesium nitrate as a salting-out agent resulted in higher decontamination factors of TPE and REE fraction from Cs (~10000) than using iron (III) nitrate (7500).

Rapid vitrification of Sr-loaded zeolite by microwave sintering for disposal of secondary radioactive wastes: Mechanism and performance

The rapid solidification of Sr-loaded zeolite, a potential secondary solid waste, is highly urgent for nuclear post-accident remediation. Microwave heating is first employed to dispose of spent Sr-loaded adsorbent. The adsorption kinetics and isotherm model of zeolite NaX for Sr(Ⅱ) was reported. Meanwhile, the effect of B2O3 additive on the phase evolution, microstructure, and chemical durability was systemically investigated. The results showed that the B2O3 addition could effectively lower the sintering temperature from 1200 ℃ to 1000 ℃ via microwave heating. The stable glass form was successfully obtained with sintering temperature of 1000 ℃, B2O3-doped amount of 25 wt.%, and dwell time of 40 min. The Sr was homogeneously distributed in the sintered matrix without substantial enrichment. Moreover, the leaching rate of Sr in the solidified form was about 1.19 × 10-5 g·m−2·d−1 after 42 days, demonstrating its excellent chemical stability. This study indicated rapid low-temperature vitrification of Sr-loaded zeolite by microwave heating was a promising approach for removal and immobilization of Sr in radioactive wastewater.

Comparison between synthetic and natural clinoptilolites for adsorptive removal of metal ions

The present work evaluated the removal performances of Ni2+, Cd2+, Sr2+, Mn2+, and Fe3+ from an aqueous solution using a comparison between synthetic clinoptilolite (SCP) and natural CP (NCP). Unlike previous demonstrations that treated each metal ion individually, these five metal ions and the used adsorbents were combined in a single treatment and explored via various characterizations, such as XRD patterns, SEM images, N2 sorption isotherms, ICP, and AAS analysis. The results revealed that the capacities of SCP at pH 3.0–8.0 and 25–75 °C were nearly 20 times higher than those of NCP, showing 2000, 1720, 1875, 1510, and 22 mg g−1, for Ni2+, Fe3+, Cd2+, Mn2+, and Sr2, respectively. The reason is mostly attributed to its purity and perfect crystal lattice. The kinetic behaviors in both cases indicated that the pseudo-2nd-order model provided a better description. Their adsorption behaviors exhibited a better fit with the Freundlich models on the removal of Ni2+, Cd2+, and Mn2+, the Langmuir equation on the removal of Fe3+, and both Freundlich and Langmuir on the removal of Sr2+, respectively. The thermodynamic findings indicated that the SCP was used to be faster, more spontaneous, and had a better favorable adsorption performance than the NCP. Additionally, five times recyclability and different stability tests further supported the dominant adsorbent nature of using SCP as an adsorbent.

Waste-treating-waste: Effective heavy metals removal from electroplating wastewater by ladle slag

Ladle slag, a by-product of steelmaking, presents a valuable strategy for waste reduction and valorization in wastewater treatment. This work demonstrates the successful simultaneous removal of Al(III), B(III), Ba(II), Cr(III), Mg(II), Sr(II), Pb(II), and Zn(II), from electroplating wastewater by ladle slag. First, Cr(III) and Pb(II) removals were evaluated in single synthetic systems by analyzing the influence of pH, temperature, and ladle slag dosage. Competitive removal was observed in binary batch experiments of Cr(III) – Pb(II), achieving 88% and 96% removal, respectively, with fast kinetics following a pseudo-second-order model. The findings of XRD, SEM, EDX, and FTIR of the slag after removal helped to elucidate the synergic removal mechanism involving ladle slag dissolution, precipitation, ion exchange, and adsorption in a tight relationship with the solution pH. Lastly, ladle slag was tested in real electroplating wastewater with the aforementioned ions at concentrations ranging from <1 to 1700 mg/L. The removal was performed in two steps, the first attained the following efficiencies: 73% for Al(III), 88% for B(III), 98% for Ba(II), 80% for Cr(III), 82% for Mg(II), 99% for Pb(II), 88% for Sr(II), and 88% for Zn(II). Visual MINTEQ simulation was utilized to identify the different species of ions present during the removal process. Furthermore, the leaching tests indicated a minimal environmental risk of secondary pollution in its application. The results promote an effective and sustainable approach to wastewater treatment within the circular economy.

Bioremediation of Crude Oil Contaminated Saline Soil Using a Bacterial Consortium and Different Carriers

AbstractBioremediation of crude‐oil‐contaminated soils is critical to supporting soil ecosystem health and functioning. Here, to explore the potential for different remediation strategies to restore soil microbial functioning and enhance remediation, three strains of bacteria, Bacillus toyonensis, Bacillus sp. and Bacillus cereus, were inoculated to saline, crude oil‐contaminated soil collected from Azadegan Oil Field, Iran. Bacteria were added using different carriers, including corn biochar, humic acid, chitosan and kaolin, and free bacteria as a control. Changes in soil metal concentrations and residual crude oil were determined after 60 days of incubation. Soil respiration, microbial biomass, and enzyme (dehydrogenase and catalase) activities were measured. The carriers accompanying a bacterial consortium were more efficient than free bacteria in removing crude oil and heavy metals from soil, and they performed better in removing n‐alkanes with carbon chains of C12–24. The oil removal rate and metal immobilization efficiencies were greatest in soils with chitosan‐bacteria treatment, with removal of crude oil, Al, Pb, Sr, and Cr (93%, 63%, 37%, 54%, and 15%, respectively) greater than for soils with free cells without treatment (61%, 54%, 9%, 50%, and 3%, respectively). Soil electrical conductivity decreased after application of bacterial mixtures with and without carriers. The inoculation of bacteria and application of soil amendments increased soil microbial biomass carbon and the activity of catalase and dehydrogenase. Overall, our results indicated the greatest potential remediation was achieved by applying immobilized microorganisms in chitosan to accelerate the biodegradation of crude oil and the removal of heavy metals.

Simultaneous removal of caesium and strontium using different removal mechanisms of probiotic bacteria

When radioactive materials are released into the environment due to nuclear power plant accidents, they may enter into the body, and exposing it to internal radiation for long periods of time. Although several agents have been developed that help excrete radioactive elements from the digestive tract, only one type of radioactive element can be removed using a single agent. Therefore, we considered the simultaneous removal of caesium (Cs) and strontium (Sr) by utilising the multiple metal removal mechanisms of probiotic bacteria. In this study, the Cs and Sr removal capacities of lactobacilli and bifidobacteria were investigated. Observation using an electron probe micro analyser suggested that Cs was accumulated within the bacterial cells. Since Sr was removed non metabolically, it is likely that it was removed by a mechanism different from that of Cs. The amount of Cs and Sr that the cells could simultaneously retain decreased when compared to that for each element alone, but some strains showed only a slight reduction in removal. For example, Bifidobacterium adolescentis JCM1275 could simultaneously retain 55.7 mg-Cs/g-dry cell and 8.1 mg-Sr/g-dry cell. These results demonstrated the potentials of utilizing complex biological system in simultaneous removal of multiple metal species.

Molten salt synthesis of MXene-derived hierarchical titanate for effective strontium removal

The removal and recovery of radioactive Sr(II) from wastewater and seawater has been of great concern due to the negative environmental impacts of nuclear energy development and the potential risk of nuclear accidents. Herein, a facile molten salt synthesis strategy was developed to systematically investigated the reaction of different types of MXenes with nitrates. Among the products, K+ intercalated hierarchical titanate nanostructures (K-HTNs) obtained from the direct chemical transformation of multilayered Ti3C2Tx exhibited unique layered structures, good physicochemical properties, and outstanding adsorption performance for Sr(II). The maximum adsorption capacity of Sr(II) by K-HTNs reached 204 mg·g−1 at ambient temperature, and the good regeneration and reusability of the titanate was also demonstrated. K-HTNs showed preferential selectivity for Sr(II) in different environmental media containing competing ions, and the removal efficiency of Sr(II) in real seawater was as high as 93.3 %. The removal mechanism was elaborated to be the exchange of Sr2+ with K+/H+ in the interlayers of K-HTNs, and the adsorbed Sr(II) had a strong interaction with Ti−O− termination on the titanate surface. Benefiting from the merits of rapid and scalable synthesis and excellent adsorption performance, MXene-derived K-HTNs have broad application prospects for the purification of 90Sr-contaminated wastewater and seawater.

Emulsion synthetic route of hierarchically porous zeolite-geopolymer composites for Sr2+ decontamination in fixed bed process

The decontamination of wastewater is an important issue for the nuclear industry. The removal of Sr2+, one of the most problematic radioelements, requires hierarchical materials suitable for fixed-bed processes. This article describes a patented emulsion-templating route for the synthesis of Linde Type A (LTA) zeolite-geopolymer composites with a multiscale porosity. By dispersing zeolite particles in an emulsion oil-in-water containing precursors of geopolymer, LTA zeolite–geopolymer composites can be obtained after curing and eliminating the oil phase. The zeolite particles alter the macroporous structure of the materials (replicating the oil droplets) as well as the size of the mesopores of the geopolymer binder. Moreover, zeolite contents higher than 30 wt% induce a crumbling of the material structure. The presence of LTA zeolite particles increases the selectivity of the composites for Sr2+ in very saline media, while the porous network of the material ensures rapid adsorption. The optimal composite prepared here outperformed a commercial sorbent for the Sr2+ decontamination of a saline wastewater through a packed column.

A novel and cost-effective synthesis of magnetic zeolite 4A using kaolinite and red mud for Sr(II) removal

A novel and cost-effective approach was successfully developed for synthesizing high-performance zeolite 4A encapsulating magnetic particles (magnetic zeolite 4A) using kaolinite and red mud as raw materials via one-step combined activation-reduction and subsequent hydrothermal synthesis. The concurrent reduction of iron compounds in red mud to magnetic particles mainly composed of Fe3O4 during the thermal activation of kaolinite eliminated the need for a distinct red mud reduction process, thereby streamlining the synthesis and maximizing efficiency. The resulting product comprised highly crystalline zeolite 4A encapsulating magnetic particles derived from the red mud, avoiding oxidation and corrosion of the magnetic material in acidic solutions. A series of magnetic zeolite 4A (MZ) were obtained by introducing varying percentages of red mud and kaolinite, and their morphological, structural, magnetic and adsorption properties were investigated. The BET specific surface area of the obtained MZ-20 is 13.6 m2/g. MZ-20 (red mud: kaolinite mass percentage is 20%) displayed the maximum adsorption capacity of 172 mg/g for Sr(II). Within 1 h, 96.4% of the Sr(II) was removed. The adsorption kinetics and isotherms followed the pseudo-second-order and Langmuir models, respectively. Using a mixed 0.1 M NaCl and 0.1 M HCl solution as eluent, the magnetic adsorbent maintained high desorption and regeneration ratios along with stable magnetic properties after four adsorption-desorption cycles. In summary, the MZ-20 adsorbent exhibited high adsorption capacity, recyclability and excellent magnetic properties, making it a decontamination candidate for removing Sr(II) from radioactive wastewater.

Removal of cesium and strontium ions with enhanced solid-liquid separation by combined ion exchange and BaSO4 co-precipitation

Treatment of cesium and strontium is critical in radioactive liquid waste management, where their ions are difficult to remove in single operations, owing to differences in valence state. Here, the efficacy of composite coagulants synthesised by combining fine clinoptilolite with co-precipitated barite (BaSO4) were investigated for the simultaneous removal of Cs+ and Sr2+ ions, producing aggregates with enhanced dewatering properties. Co-precipitated BaSO4 without clinoptilolite was found to be very effective in the removal of Sr2+ (>99 %) while only giving low-level Cs+ removal (~14 %) for solutions containing 25 ppm of Cs+ and Sr2. Conversely, pure clinoptilolite gave high Cs+ removal (>98 %) with rapid adsorption (<1 h) fitted to a Pseudo-Second Order (PSO) rate model. Composite coagulants were then produced using natural clinoptilolite combined with BaSO4 co-precipitation. Higher Sr2+ removal was obtained in all cases (>99.9 %), whereas Cs+ removal was reduced to <90 %, owing to exchange interactions with free Ba2+ ions. However, NaCl-preactivated clinoptilolite overcame low Cs+ removal efficiency, achieving >95 % removal. Their physical properties, sedimentation rates, and compressional yield stress were also studied to characterise the aggregates solid-liquid separation behaviour. The combined coagulates obtained settling rates almost twice that of pure BaSO4, and produced much greater consolidation, owing to increased aggregate density. Also, the combined systems had a higher gel point and lower specific compressive yield stress, suggesting less resistance to compression under centrifugal forces for dewatering. Overall, this study highlights that the use of composite coagulants can improve the removal efficiency of Cs+ and Sr2+ while also accelerating solid-liquid dewatering.

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.

A joint image super‐resolution network for multiple degradations removal via complementary transformer and convolutional neural network

AbstractWhile recent years have witnessed the unprecedented success of deep convolutional neural networks (CNNs) and vision transformers in single‐image super‐resolution (SISR), the degradation assumptions are simple and usually bicubic downsampling. Thus, their performances will drop dramatically when the actual degradation does not match this assumption, and they lack the capability to handle multiple degradations (e.g. Gaussian noise, bicubic downsizing, and salt &amp; pepper noise). To address the issues, in this paper, the authors propose a joint SR model (JIRSR) that can effectively handle multiple degradations in a single model. Specifically, the authors build the parallel Transformer and CNN branches that complement each other through bidirectional feature fusion. Moreover, the authors also adopt a random permutation of different kinds of noise and resizing operations to build the training datasets. Extensive experiments on classical SR, denoising, and multiple degradation removal demonstrate that the authors’ JIRSR achieves state‐of‐the‐art (SOTA) performance on public benchmarks. Concretely, the authors’ JIRSR outperforms the second‐best model by 0.23 to 0.74 dB for multiple degradations removal and is 0.20 to 0.36 dB higher than the SOTA methods on the Urban100 dataset under the ×4 SR task.

The role of alkalinity on metals removal from petroleum produced water by dolomite

Alkalinity is a critical parameter for describing the composition, pH buffer capacity, and precipitation potential of petroleum produced water (PW). Besides salinity, alkalinity and metal concentrations are generally greater in PW than in freshwater (FW) and seawater. This study presents batch reaction experimental and simulation results showing that the removal of Ba, Sr, and Cd from PW by dolomite is mostly due to sorption reactions, with sorption reactions and thus removal levels being higher for Cd than for Ba and Sr. In contrast, we found that the removal of Pb and As from PW by dolomite is largely due to precipitation and coprecipitation reactions of carbonate minerals on dolomite. Analyses of changes in the morphology as well as in the elemental and mineral composition of dolomite surface, along with pH, alkalinity, and Ba, Sr, Cd, Pb, and As removal measurements using synthetic PW and FW containing high concentrations (∼100 mg/L) of single and mixture toxic metals and metalloids (Ba, Sr, Cd, Pb, and As) at different initial alkalinity and pH conditions, indicate that in addition to salinity, alkalinity and pH generated from the dissolution of dolomite controls the removal of Ba, Sr, Cd, Pb, and As from PW by dolomite. However, we found that their impact is different for each metal in PW and FW. Ba, Sr, and Cd removal by dolomite is 10, 2, and 4 times smaller in PW than in freshwater (FW), respectively. Whereas As removal is practically the same regardless of salinity. Moreover, this study reveals the need of thermodynamic data of complex carbonate minerals formed from the precipitation of Ba, Sr, Cd, Pb, and As to capture the effect of alkalinity on their removal from PW by dolomite.

In-situ synthesis of potassium copper hexacyanoferrate−expanded graphite for effective removal of strontium from water

Radiostronium remediation is highly demanded for ecological conservation, nuclear energy sustainability, and human health. However, industrial applications of 90Sr removal adsorbents remain challenging due to the issues of efficient adsorbent exploitation and costly synthesis processes. Herein, we report a low-cost adsorbent for the removal of Sr2+ ions from water by in-situ synthesis and immobilization of potassium copper hexacyanoferrate (KCuHCF) onto expanded graphite (EG). The XRD, FTIR, SEM, and TEM results indicated that the nanoscale KCuHCF granules were homogenously distributed on EG interlayers. It showed excellent Sr2+ adsorption capacities of 6.05 mg·g−1 in water with ultralow Sr2+ concentrations and high selectivity even in the presence of various disturbing ions, including K+, Na+, Mg2+, and Ca2+ ions. The adsorption data were well-fitted by the pseudo-second-order kinetic model and the Langmuir isotherm model, suggesting the nature of heterogeneous monolayer chemisorption. Ion exchange between Sr2+ and lattice Fe2+ dominated the adsorption process. Compared with other state-of-the-art adsorbents that suffer the issues of complex and expensive synthesis processes, this work offers a facile and economical KCuHCF−EG adsorbent for the efficient removal of Sr2+ ions from radioactive wastewater.

Layered metal sulfides with MaSbc- framework (M = Sb, In, Sn) as ion exchangers for the removal of Cs(Ⅰ) and Sr(Ⅱ) from radioactive effluents: a review.

Nuclear power has emerged as a pivotal contributor to the global electricity supply owing to its high efficiency and low-carbon characteristics. However, the rapid expansion of the nuclear industry has resulted in the production of a significant amount of hazardous effluents that contain various radionuclides, such as 137Cs and 90Sr. Effectively removing 137Cs and 90Sr from radioactive effluents prior to discharge is a critical challenge. Layered metal sulfides exhibit significant potential as ion exchangers for the efficient uptake of Cs+ and Sr2+ from aqueous solutions owing to their open and exchangeable frameworks and the distinctive properties of their soft S2- ligands. This review provides a detailed account of layered metal sulfides with MaSb c- frameworks (M = Sb, In, Sn), including their synthesis methods, structural characteristics, and Cs+ and Sr2+ removal efficiencies. Furthermore, we highlight the advantages of layered metal sulfides, such as their relatively high ion exchange capacities, broad active pH ranges, and structural stability against acid and radiation, through a comparative evaluation with other conventional ion exchangers. Finally, we discuss the challenges regarding the practical application of layered metal sulfides in radionuclide scavenging.

Polyaniline-intercalated manganese dioxide Nanomaterial Composites for the Removal of Fe, Al and Sr

Polyaniline-intercalated manganese dioxide Nanomaterial Composites for the Removal of Fe, Al and Sr

Removal of Cs(I) and Sr(II) from Liquid Media with Crystalline Titanosilicates Prepared by Hydrothermal Synthesis

Removal of Cs(I) and Sr(II) from Liquid Media with Crystalline Titanosilicates Prepared by Hydrothermal Synthesis

Improving heavy metal removal efficiency from steel sludge: Application of the coupled ultrasonic-bioleaching treatment

&lt;p&gt;This study assessed the efficiency of Fe, Al, Ni and Sr removal from the steel sludge using the coupled bioleaching with Thiobacillus thiooxidans and ultrasonic waves. Growth conditions were optimized using the surface response method. The bacterium was adapted successively to three heavy metal-containing solutions with different concentrations of 100, 200, and 300 mg/ml. Samples were exposed to ultrasonic waves at frequencies of 30, 60 and 90 kHz and durations of 20, 30 and 40 min for two weeks. The highest Fe removal efficiency of 98.45% was obtained using the T. thiooxidation, wave frequency of 30 kHz for 40 min, and pulp density of 100 mg/ml. The maximum removal efficiency was found to be 99.74% for Al under a wave frequency of 90 kHz for 20 min and a pulp density of 300 mg/ml, approximately 100% for Ni under a wave frequency of 30 kHz for 20 min and a pulp density of 300 mg/ml, and 98.45% for Sr under a wave frequency of 90 kHz for 20 min and a pulp density of 300 mg/mL. Results showed that the removal efficiency of Ni and Al bioleaching improved significantly (P &amp;lt;0.05) under the ultrasonic irradiation while the removal efficiency of Fe and Sr remained statistically unchanged (P&amp;gt; 0.05) with and without the application of ultrasonic waves.&lt;/p&gt;&#x0D;

Phosphate (Bio)mineralization Remediation of 90Sr-Contaminated Groundwaters.

Historical operations at nuclear mega-facilities such as Hanford, USA, and Sellafield, UK have led to a legacy of radioactivity-contaminated land. Calcium phosphate phases (e.g., hydroxyapatite) can adsorb and/or incorporate radionuclides, including 90Sr. Past work has shown that aqueous injection of Ca-phosphate-generating solutions into the contaminated ground on both laboratory and field scales can reduce the amount of aqueous 90Sr in the systems. Here, two microbially mediated phosphate amendment techniques which precipitated Ca-phosphate, (i) Ca-citrate/Na-phosphate and (ii) glycerol phosphate, were tested in batch experiments alongside an abiotic treatment ((iii) polyphosphate), using stable Sr and site relevant groundwaters and sediments. All three amendments led to enhanced Sr removal from the solution compared to the sediment-only control. The Ca-citrate/Na-phosphate treatment removed 97%, glycerol phosphate 60%, and polyphosphate 55% of the initial Sr. At experimental end points, scanning electron microscopy showed that Sr-containing, Ca-phosphate phases were deposited on sediment grains, and XAS analyses of the sediments amended with Ca-citrate/Na-phosphate and glycerol phosphate confirmed Sr incorporation into Ca-phosphates occurred. Overall, Ca-phosphate-generating treatments have the potential to be applied in a range of nuclear sites and are a key option within the toolkit for 90Sr groundwater remediation.