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Polluted environments often contain large amounts of toxic metals, such as cadmium, which pose a major threat to ecosystems and public health. Contamination by cadmium and its compounds is often observed in areas surrounding zinc mining sites and electroplating factories, and the control of cadmium pollution is essential for environmental safety and health. In this study, a highly efficient and straightforward separation strategy for K4Fe(CN)6@Fe3O4 nanocomposites is successfully developed to capture the Cd ions in the water environment. Batch adsorption experiments revealed that K4Fe(CN)6@Fe3O4 exhibited a high cadmium removal rate (greater than 98â¯%) at a pH level of 6.0 and solid-liquid ratio of 1.0â¯g/L at room temperature (298â¯K). Kinetic analysis revealed that the adsorption process followed a pseudo-second-order model and cadmium was rapidly removed in the first 10â¯min, with chemisorption dominating the capture of Cd2+ by K4Fe(CN)6@Fe3O4. Adsorption isotherms revealed a heterogeneous adsorption behavior, with a maximum adsorption capacity of 40.78â¯mg/g. The intrinsic adsorption of Cd2+ by K4Fe(CN)6@Fe3O4 occurring primarily through electrostatic interaction and ion exchange. In addition, K4Fe(CN)6@Fe3O4 exhibited an excellent regeneration capacity. Therefore, integrating Fe3O4 into the metal cyanide not only provided the composite material with excellent chemical stability and selective adsorption sites for Cd2+, but also facilitated subsequent sorbent collection and recovery. Overall, this study presents a simple and feasible approach for integrating Fe3O4 into potassium ferrocyanide frameworks for efficient cadmium removal from contaminated water.
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Cádmio , Ferrocianetos , Poluentes Químicos da Água , Cádmio/química , Cádmio/análise , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Adsorção , Ferrocianetos/química , Cinética , Purificação da Água/métodos , Concentração de Íons de Hidrogênio , Nanocompostos/químicaRESUMO
A sensitive and biocompatible N-rich probe for rapid visual uranium detection was constructed by grafting two trianiline groups to 2,6-bis(aminomethyl)pyridine. Possessing excellent aggregation-induced emission (AIE) property and the advantages to form multidentate chelate with U selectively, the probe has been applied successfully to visualize uranium in complex environmental water samples and living cells, demonstrating outstanding anti-interference ability against large equivalent of different ions over a wide effective pH range. A large linear range (1.0 × 10-7-9.0 × 10-7 mol/L) and low detection limit (72.6 nmol/L, 17.28 ppb) were achieved for the visual determination of uranium. The recognition mechanism, photophysical properties, analytical performance and cytotoxicity were systematically investigated, demonstrating high potential for fast risk assessment of uranium pollution in field and in vivo.
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Corantes Fluorescentes , Urânio , Urânio/análise , Urânio/química , Corantes Fluorescentes/química , Corantes Fluorescentes/toxicidade , Humanos , Limite de Detecção , Materiais Biocompatíveis/química , Células HeLa , Sobrevivência Celular/efeitos dos fármacos , Imagem Óptica , Compostos de Anilina/química , Compostos de Anilina/toxicidade , Piridinas/químicaRESUMO
Uranium [U(VI)] mining activity resulted in the discharge of uranium containing acid wastewater. It is necessary for immobilizing the uranium from wastewater to avoid its environmental pollution. In this work, a novel hydrothermal mineralization strategy is proposed for uranium stabilization. Three reaction systems such as Mg3(PO4)2 + UO22+, Mg2+ + PO43- + UO22+, and Mg2+ + PO43- + Mg3(PO4)2 + UO22+ were designed to investigate the uranium mineralization and stabilization performance. The consumed molar quantities of magnesium and phosphate were calculated to understand the mineralization mechanisms. The molar ratios of Mg/U and P/U in the experimental results were in agreement with those of thermodynamic calculation in the presence of dissolved Mg2+ and PO43- under the hydrothermal process. The calculated saturated index indicated the facile crystallization of uranium into the saleeite and chernikovite through hydrothermal mineralization at the pH value of 5 and 473 K. Crystallization into saleeite and chernikovite contributed to uranium stabilization, resulting in the negligible leaching rate of 5% due to the high crystallinity of 97.23%. Thus, hydrothermal mineralization of uranium crystallization into saleeite and chernikovite was promising for uranium stabilization with long-term stability.
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The contamination of creek sediments near industrially nuclear dominated site presents significant environmental challenges, particularly in identifying and quantifying potentially toxic metal (loid)s (PTMs). This study aims to measure the extent of contamination and apportion related sources for nine PTMs in alpine creek sediments near a typical uranium tailing dam from China, including strontium (Sr), rubidium (Rb), manganese (Mn), lithium (Li), nickel (Ni), copper (Cu), vanadium (V), cadmium (Cd), zinc (Zn), using multivariate statistical approach and Sr isotopic compositions. The results show varying degrees of contamination in the sediments for some PTMs, i.e., Sr (16.1-39.6 mg/kg), Rb (171-675 mg/kg), Mn (224-2520 mg/kg), Li (11.6-78.8 mg/kg), Cd (0.31-1.38 mg/kg), and Zn (37.1-176 mg/kg). Multivariate statistical analyses indicate that Sr, Rb, Li, and Mn originated from the uranium tailing dam, while Cd and Zn were associated with abandoned agricultural activities, and Ni, Cu, and V were primarily linked to natural bedrock weathering. The Sr isotope fingerprint technique further suggests that 48.22-73.84% of Sr and associated PTMs in the sediments potentially derived from the uranium tailing dam. The combined use of multivariate statistical analysis and Sr isotopic fingerprint technique in alpine creek sediments enables more reliable insights into PTMs-induced pollution scenarios. The findings also offer unique perspectives for understanding and managing aqueous environments impacted by nuclear activities.
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Metais Pesados , Urânio , Cádmio , Zinco , Manganês , Níquel , Estrôncio , Lítio , Medição de Risco , China , Metais Pesados/análise , Monitoramento Ambiental/métodos , Sedimentos GeológicosRESUMO
The uranium (U) containing leachate from uranium tailings dam into the natural settings, may greatly affect the downstream environment. To reveal such relationship between uranium contamination and microbial communities in the most affected downstream environment under drought stress, a 180 cm downstream artificial reservoir depth sediment profile was collected, and the microbial communities and related genes were analyzed by 16S rDNA and metagenomics. Besides, the sequential extraction scheme was employed to shed light on the distinct role of U geochemical speciations in shaping microbial community structures. The results showed that U content ranged from 28.1 to 70.1 mg/kg, with an average content of 44.9 mg/kg, significantly exceeding the value of background sediments. Further, U in all the studied sediments was related to remarkably high portions of mobile fractions, and U was likely deposited layer by layer depending on the discharge/leachate inputs from uranium-involving anthoropogenic facilities/activities upstream. The nexus between U speciation, physico-chemical indicators and microbial composition showed that Fe, S, and N metabolism played a vital role in microbial adaptation to U-enriched environment; meanwhile, the fraction of Ureducible and the Fe and S contents had the most significant effects on microbial community composition in the sediments under drought stress.
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Urânio , Urânio/análise , Secas , Poluição Ambiental , Sedimentos Geológicos/químicaRESUMO
The extraction and utilization of uranium (U) ores have led to the release of significant amounts of potentially toxic metal(loid)s (PTMs) into the environment, constituting a grave threat to the ecosystem. However, research on the distribution and migration mechanism of U, chromium (Cr), and their accompanying PTMs in soil-plant system around U hydrometallurgical area remains insufficient and poorly understood. Herein, the distribution, migration, and risk level of PTMs were evaluated in soil and plant samples around U hydrometallurgical area, Northern Guangdong, China. The results demonstrated that the maximum content of U and Cr found in the analyzed soils were up to 84.2 and 238.9 mg/kg, respectively. These values far exceed the soil background values in China and other countries. The highest content of U (53.6 mg/kg) was detected in Colocasia antiquorum Schott, and the highest content of Cr (349.5 mg/kg) was observed in Pteridium aquilinum, both of which were enriched in their roots. The risk assessment of PTMs demonstrated that the study area suffered from severe pollution (PN > 3), especially from U, Cr, Th, and As, suggesting the non-negligible anthropogenic impacts. Hence, in light of the significant ecological hazard posed by the U hydrometallurgical area, it is imperative to implement appropriate restoration measures to ensure the human health and maintain the stability of the ecosystem.
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Metais Pesados , Poluentes do Solo , Urânio , Humanos , Urânio/análise , Metais Pesados/análise , Cromo , Solo , Ecossistema , Monitoramento Ambiental/métodos , Poluentes do Solo/análise , China , Medição de RiscoRESUMO
Uranium contamination and remediation is a very important environmental research area. Removing radioactive and toxic uranium from contaminated media requires fundamental knowledge of targets and materials. To explore the-State-of-the-Art in uranium contamination control, we employed a statistical tool called CiteSpace to visualize and statistically analyze 4203 peer-reviewed papers on uranium treatment published between 2008 and 2022. The primary content presentations of visual analysis were co-authorships, co-citations, keyword co-occurrence analysis with cluster analysis, which could offer purposeful information of research hots and trends in the field of uranium removal. The statistical analysis results indicated that studies on uranium removal have focused on adsorption of uranium from aqueous solution. From 2008 to 2022, biochar and biological treatment were firstly used to sequester uranium, then adsorption for uranium removal dominates with adsorbents of graphene oxide, primary nanofiber magnetic polymers and metal-organic frameworks (MOFs). In recent years, photocatalysts and metal-organic frameworks are expected to be two of the most popular research topics. In addition, we further highlighted the characteristics and applications of MOFs and GOs in uranium removal. Overall, a statistical review was proposed to visualize and summarize the knowledge and research trends regarding uranium treatment.
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Estruturas Metalorgânicas , Urânio , Adsorção , Análise por Conglomerados , Temperatura AltaRESUMO
Uranium-containing wastewater is a common by-product of uranium mining. Phosphate and phosphate minerals can interact with uranyl ions [U(VI)], impeding the migration of these ions by forming relatively stable uranium-containing crystalline phase(s). In this study, hydroxyapatite microtubes (HAP-T) were fabricated to sequester uranyl ions from simulated radioactive wastewater. HAP-T had excellent adsorption and stability properties; over 98.76% of U(VI) could be sequestrated by 0.25 g/L HAP-T within 5 min at pH = 4.0. The isotherms and kinetics data could be suitably reflected by the Freundlich and the pseudo second-order kinetic models, respectively. The maximum adsorption capacity of HAP-T was 356.42 mg/g. The adsorption ability of HAP-T for U(VI) was inhibited when Mg2+ or SO42- ions or fulvic acid (FA) substances existed in the simulated radioactive wastewater. The inhibition by FA was attributed to its negative charges, which caused competition between FA and HAP-T for uranium sequestration. The primary mechanisms of U(VI) sequestration by HAP-T were electrostatic interactions and surface complexation. The effectiveness of HAP-T, HAP-B (bio-hydroxyapatite synthesized from fish bone), and HAP-C (commercially available synthesized hydroxyapatite) for uranium immobilization was compared; HAP-T was more effective than HAP-B or HAP-C in immobilizing uranium. HAP-T, which has a micron-sized tubular structure, is likely less mobile in groundwater than are HAP-B and HAP-C, which have nanoscale granular structures. In conclusion, HAP-T can be used to sequester and immobilize uranyl ions.
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Durapatita , Urânio , Durapatita/química , Urânio/análise , Águas Residuárias , Adsorção , CinéticaRESUMO
Batch and column leaching tests were used to study thallium's release and migration behaviour and evaluate its potential toxicity risks in soil. The results indicated that leaching concentrations of Tl using TCLP and SWLP were much higher than the threshold, indicating a high risk of thallium pollution in the soil. Furthermore, the intermittent leaching rate of Tl by Ca2+ and HCl reached its maximum value, demonstrating the easy release of Tl. After HCl leaching, the form of Tl in the soil has changed, and ammonium sulfate has increased its extractability. Additionally, the extensive application of calcium promoted the release of Tl, increasing its potential ecological risk. Spectral analysis showed that Tl was mainly present in minerals such as Kaolinite and Jarosite, and exhibited significant adsorption capacity for Tl. HCl and Ca2+ damaged the crystal structure of the soil, greatly enhancing the migration and mobility of Tl in the environment. More importantly, XPS analysis confirmed that the release of Tl (I) in the soil was the leading cause of increased mobility and bioavailability. Therefore, the results revealed the risk of Tl release in the soil, providing theoretical guidance for its pollution prevention and control.
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A kind of high yield and recyclable Cobalt-Carbon composite (Zn1Co5/PnC) was prepared by carbothermal reduction process, in which the cobalt acetate and zinc acetate were considered as Zn and Co precursors, and the polyester waste was evolved as the carbon precursor. The morphology, structure and composition of the composite were characterized using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results showed that evaporation of zinc contributed to the formation of porous carbon structure, and the Co nanoparticles were wrapped and protected by the porous carbon matrix. The Zn1Co5/PnC activated peroxymonosulfate (PMS) system (Zn1Co5/PnC/PMS) was constructed to degrade the levofloxacin (LEV). The activity and mechanism of LEV degradation was understood. The LEV degradation efficiency was high to 96.60% within 90 min in the presence of Zn1Co5/P4C. Moreover, the Zn1Co5/P4C still maintained favorable PMS activation performance after five-cycle runs. The results show that the Zn1Co5/P4C played positive role in activating the PMS, it may be due to the facts that the polyester derived carbon could supported the Co while the evaporated Zn could increase the surface area of Zn1Co5/P4C, leading to the increased activity. The possible degradation pathways were proposed by identifying the intermediate products through liquid chromatography-mass spectrometry analysis. This study put forward a promising method to use polyester waste to synthesize high yield cobalt-carbon composite for degrading the antibiotic in wastewater.
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Cobalto , Levofloxacino , Cobalto/química , Peróxidos/química , Carbono/químicaRESUMO
In a Co-HAP/PMS system, catalytic degradation process of RhB was accompanied by the gradual leaching of cobalt ion. The results of additional experiments showed that leached cobalt ion indeed contributed to active PMS for RhB degradation, which was not addressed in the previous study. The finding of the contribution from leached cobalt ion to PMS activation was reported due to the valuable comments of Zuo et al., what will be concerned in the future work. Importantly, Co-HAP still showed a significant contribution to PMS activation for RhB degradation at the initial stage. Fortunately, the release of Co2+ from Co-HAP was slow, the secondary pollution could not be addressed due to the slightly release of Co2+ ion that the Co2+ concentration is lower than the standard of the discharge wastewater. Furthermore, the mechanism of non-radical reaction in the Co-HAP/PMS system was reported to confirm the heterogeneous catalysis of a Co-HAP/PMS system.
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In consideration of the severe hazards of radioactive uranium pollution and the growing demand of uranium resources, the novel sensor/adsorbent composite was creatively developed to integrate the dual functions for on-site detection of uranium contamination and efficient recovery of uranium resources. By hybridizing the luminescent 3D terbium (III) metal-organic framework (Tb-MOF) with sodium alginate (SA) gel using terbium (III) as cross-linker, the Tb-MOF/Tb-AG was fabricated with multi-luminescence centers and sufficient binding sites for uranium. Notably, the ultra-high sensitivity with detection limit as low as 1.2 ppt was achieved, which was 4 orders of magnitude lower than the uranium contamination standard in drinking water (USEPA) and even comparable to the sensitivity of the ICP-MS. Furthermore, the very wide quantification range (1.0 ×10-9-5.0 ×10-4 mol/L), remarkable adsorption capacity (549.0 mg/g) and outstanding anti-interference ability have been achieved without sophisticated sample preparation procedures. Applied in complex natural water samples from Uranium Tailings and the Pearl River, this method has shown good detection accuracy. The ultra high sensitivity and great adsorption capacity for uranium could be ascribed to the synergistic coordination, hydrogen bonding and ion exchange between uranium and Tb-MOF/Tb-AG. The mechanisms were explored by infrared spectroscopy, batch experiments, X-ray photoelectron studies and energy dispersive spectroscopic studies. In addition, the Tb-MOF/Tb-AG can be reused for uranium adsorption.
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The widespread adoption of nuclear energy has increased the amount of radioactive cesium (Cs) that is discharged into waste streams, which can have environmental risks. In this paper, we provide a comprehensive summary of current advances in aqueous Cs removal by employing a bibliometric analysis. We collected 1580 articles related to aqueous Cs treatment that were published on the Web of Science database between 2012 and 2022. By applying bibliometric analysis combined with network analysis, we revealed the research distribution, knowledge base, research hotspots, and cutting-edge technologies in the field of aqueous Cs removal. Our findings indicate that China, Japan, and South Korea are the most productive countries with respect to Cs removal research. In addition, both historic events and environmental threats might have contributed to research in Asian countries having a higher focus on Cs removal as well as strong international cooperation between Asian countries. A detailed keyword analysis reveals the main knowledge base for aqueous Cs removal and highlights the potential of the adsorption-based method for treating Cs contamination. Furthermore, the results reveal that exploration of functional materials is a popular research topic in the field of Cs removal. Since 2012, novel materials, including Prussian blue, graphene oxide, hydrogel and nanocomposites, have been widely investigated because of their high capacity for Cs removal. On the basis of the detailed information, we report the latest research trends on aqueous Cs removal, and propose future research directions and describe the challenges related to effective Cs treatment. This scientometric review provides insights into current research hotspots and cutting-edge trends in addition to contributing to the development of this crucial research field.
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Pyrite is a typical sulfide mineral which contains various potentially toxic metal(loid)s (PTMs). The pyrite smelting and subsequent industrial utilization activities usually release numerous amounts of PTMs into nearby ecosystem, which may be enriched in the nearby farmland soils and crops, leading to hidden but irreversible harm to human health via the food chain. Herein, the distribution pattern, source apportionment, and potential health risks of Pb, Zn, Cu, Cd and multiple seldom monitored PTMs (Ag, Bi, Sb, Sr, Th, U, W, and V) in the paddy soils and different organs of the rice plants from ten various sites in a typical industrial zone were investigated, where pyrite ores were used for the production of sulfuric acid and subsequent cement over several decades. The results showed that the contents of Cd, Pb and Zn in studied paddy soils generally exceeded the maximum permissible level (MPL) in China, and the contents of Sb and V were approaching the MPL. Moreover, the rice is easier to bioaccumulate Cd, Cu, and Zn than the other studied elements. The hazard quotient (HQ) calculations indicate that the rice containing such multiple elements may cause a high potential non-carcinogenic and carcinogenic health risk for residents, particularly for the senior group. The Pb isotope tracing method combined with PCA (principal component analysis) further uncovered that the pyrite industrial utilization contributed 18.58-55.41 % to the highly enriched PTMs in paddy soils. All these findings indicate that the paddy soil system has been contaminated by the pyrite industrial activities and certain distances or areas should be rigidly forbidden from rice cultivation in the proximity of the pyrite smelting and related industrial sites.
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Oryza , Humanos , Solo , Chumbo , Ecossistema , Cádmio , Isótopos , Intoxicação por Metais Pesados , China , Cadeia AlimentarRESUMO
Cesium (Cs) is a byproduct of nuclear bombs, nuclear weapons testing, and nuclear fission in nuclear reactors. Cs can enter the human body through food or air and cause lasting damage. Highly efficient and selective removal of 137Cs from low-level radioactive effluents (LLREs), which contain many radionuclides and dissolved heavy metal species, is imperative for minimizing LLRE volume, and facilitating their final disposal. Prussian blue analogs (PBAs) have received much attention as materials for the removal of radioactive Cs because of their affinity for adsorbing Cs+. In this study, an inexpensive and readily available cyanide-based functional material (PBACu) exhibiting high efficiency and excellent selectivity toward Cs capture was designed through a facile low-temperature co-precipitation process. Nano-PBACu, crystallizing in the cubic space group (Fm-3m (225)), has an average pore size of 6.53 nm; consequently, PBACu can offer abundant atomic occupation sites for capturing and incorporating Cs. Here, the pseudo-second-order kinetic model and Langmuir model fitted well with the adsorption of Cs + on PBACu, with a maximum capture capacity of 95.75 mg/g within 5 min, confirming that PBACu could rapidly capture Cs ions. PBACu strongly and selectively interacted with Cs even in a simulant containing large Na+, NH4+, Ca2+, and Mg2+ ion concentrations in an aqueous solution. The process of Cs + adsorption by cyanide-based functional crystals was confirmed to involve the entry of Cs+ into cyanide-based functional crystals to replace K+ and finally achieve the lattice incorporation of Cs. The current results broaden the lattice theory of radionuclide Cs removal and provide a promising alternative for the immobilization of Cs from radioactive wastewater.
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Césio , Cianetos , Adsorção , Césio/química , Humanos , Concentração de Íons de Hidrogênio , Águas Residuárias/químicaRESUMO
As a type of useful solid waste, red mud (RM) should be reused to achieve waste-to-resource strategies. Additionally, the fast development of nuclear industry requires effective and reliable materials for treating uranium (U)-containing wastewater. This study attempted to remove uranyl ions [U(VI)] from mimic radioactive wastewater by various RM particles with different size fractions (e.g., >75, 45-75, 20-45, 10-20, 5-10, and <5-µm). Sorption data confirmed that the RM with a size fraction of <5-µm exhibited the largest adsorption capacity. The U removal behavior was favorably described by the pseudo-second-order model and Langmuir model. The mineral phases in the RM remarkably influenced U(VI) removal. Cancrinite, katoite, grossular, calcite, and calcium aluminum silicate phases made contributions to U(VI) adsorption. In addition, redox precipitation with iron-bearing minerals on RM surface also led to U(VI) adsorption. The findings of this work offer fundamental knowledge on the potential application of RM for clean-up of U(VI) from contaminated sites.
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Urânio , Poluentes Radioativos da Água , Adsorção , Carbonato de Cálcio , Concentração de Íons de Hidrogênio , Urânio/análise , Águas Residuárias , Poluentes Radioativos da Água/análiseRESUMO
The migration and transformation of uranyl [U (â ¥)] ions in the environment are quite dependent on the geological condition in particular with the site enriched in Fe. In this study, the interfacial interaction of U (â ¥) ions with maghemite (γ-Fe2O3) particles was studied and the interaction mechanism was explored as well. Batch experiments confirm that γ-Fe2O3 can effectively remove U (â ¥) from an aqueous solution within a relatively short reaction time (R% > 92.01% within 3 min) and has a considerable capacity for U (â ¥) uptake (qt: 87.35 mg/g). γ-Fe2O3 displays an excellent selectivity for U (â ¥) elimination. Results on the effects of natural organic matter such as humic acid (HA) indicated that HA could promote the interfacial interaction between γ-Fe2O3 and U (â ¥) under acidic conditions. Compared with other radionuclides (e.g., Sr(â ¡) and Cs(â )), U (â ¥) was more effectively removed by γ-Fe2O3. The U (â ¥) removal by γ-Fe2O3 is primarily due to electrostatic interactions and precipitation that result in the long-term retardation of uranium. γ-Fe2O3 not only can fast and selectively adsorb U (â ¥) but also can be magnetically recycled, demonstrating that γ-Fe2O3 is a cost-effective and promising material for the clean-up of uranyl ions from radioactive wastewater.
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Urânio , Poluentes Químicos da Água , Adsorção , Substâncias Húmicas/análise , Águas ResiduáriasRESUMO
Heterocyclic aromatic compounds such as malachite green can cause immense harm to the environment and mankind because of their toxic bio-accumulation and insufficient biodegradation. ZnFe2O4/TiO2 (ZF-T) has attracted attentions as a visible-light-driven catalyst because it can break and mineralize benzene through photolysis. Compared with TiO2, which photodegrades only 53.5% malachite green, anatase TiO2 loaded with ZnFe2O4 has greater photocatalytic activity and can degrade up to 90.1% malachite green. Furthermore, a photocatalytic efficiency above 80% can be obtained through five consecutive cycles with a duration of 4 h. In this study, ZF-T was characterized, and its photolytic parameters, including dosage, pH, time, and ionic strength, were optimized. The photolytic products of malachite green were analyzed by ultraviolet-visible spectroscopy and liquid chromatography-mass spectrometry, which confirmed that ZF-T can drive visible light to produce â¢O2- and H+ free radicals that can efficiently degrade heterocyclic aromatic hydrocarbons and cleave benzene rings. These outcomes deepen our understanding of the development and applications of visible-light-driven ZF-T composites in the field of wastewater purification.
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Benzeno , Titânio , Catálise , Luz , Corantes de Rosanilina , Titânio/químicaRESUMO
Uranium (U) immobilization from wastewater by zero valent iron (ZVI) was widely concerned through reduction and surface adsorption. Releasing of U due to re-oxidation of U(IV) into U(VI) limited the application of ZVI in U decontamination. In this work, a kind of biochar supported nano zero valent iron (Fe/BC(900)) was obtained by carbothermal reduction of starch mixed with ferric nitrate at 900 °C. U immobilization behavior by Fe/BC(900) in the presence of phosphate (P) was investigated. The U immobilization reaction was adjusted by controlling the sequence of U, Fe/BC(900) and P. U immobilization efficiency was enhanced to 99.9% in the presence of P. Reaction sequence of U, Fe/BC(900) and P influenced the U immobilization efficiency, which followed the order of (U-P)+Fe/BC(900)>(U- Fe/BC(900))+P>U+Fe/BC(900)>(P-Fe/BC(900))+U. P and nZVI both contributed to enhancing U immobilization through precipitation of uranyl-P and reductive co-precipitate (U(IV)) in a wide pH range. The released Fe ions could precipitate with uranyl and phosphate. Consumption of P and nZVI in the (P-Fe/BC(900))+U system limited U immobilization ability. The precipitate is highly dependent on U, P and Fe elements. U desorption in (U-P)+Fe/BC(900) system was not observed with stability.
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Urânio , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Ferro/análise , Fosfatos , Poluentes Químicos da Água/análiseRESUMO
Halloysite nanotubes (HNTs) are considered structurally promising adsorption materials, but their application is limited due to their poor native adsorption properties. Improving the adsorption capacity of HNTs for radioactive U(VI) is of great significance. By controlling the mass ratio of HNTs and dopamine (DA), composite adsorbents (HNTs@PDA) with different polydopamine (PDA) layer thicknesses were synthesized. Characterization of HNTs@PDA demonstrated that the original structure of the HNTs was maintained. Adsorption experiments verified that the adsorption capacity of HNTs@PDA for U(VI) was significantly improved. The effects of solution pH, temperature, and coexisting ions on the adsorption process were investigated. The removal efficiency was observed to be 75% after five repeated uses. The adsorption mechanism of U(VI) by HNTs@PDA can be explained by considering electrostatic interactions and the complexation of C-O, -NH- and C-N/CN in the PDA layer. This study provides some basic information for the application of HNTs for U(VI) removal.