RESUMEN
Aquatic selenium (Se) oxyanions have profound ecosystem and human health impacts, necessitating their conversion and immobilization into elemental Se(0) to mitigate the aquatic Se pollution. While thermodynamically favorable, this transformation encounters kinetic limitations, especially for selenate (SeO42-) or Se(VI). To lower the activation barrier, we investigated the electrocatalytic Se(VI) transformation using five affordable catalysts on graphite cathodes, including TiO2, underpotentially deposited Cu (UPD Cu), underpotentially deposited Cd (UPD Cd), Co, and CuFe. Among these five catalysts, we identified characteristic Se(VI) reduction peaks for TiO2 through cyclic voltammetry. Other catalysts removed less than 5% of 1-mM Se(VI) in 24-h chronoamperometry tests while leaching ppm-level metal cations in the treated water. In contrast, TiO2 as the electrocatalyst could remove more than 80% of 1-mM Se(VI) with negligible catalyst dissolution. Mechanistic investigations revealed a six-electron Se(VI)/Se(0) reduction pathway at -0.30 V (vs. Ag/AgCl), resulting in red Se(0) deposits on the TiO2-coated graphite cathode. Further potential decrease to more negative than -0.45 V led to Se(-II) formation, triggering cathodic Se(0) dissolution and surface regeneration. Electrochemical impedance spectroscopy indicated that Se(VI) reduction was optimal with a moderate TiO2 loading of 0.55 mg cm-2 and acidic environments (pH=1.0â¼2.5), achieving an optimized removal of 88.7 ± 2.3% under -0.70 V and an energy input of 3.6 kWh kg-1 Se. These findings lay the foundation for efficient selenate removal from impaired waters. Future efforts should evaluate catalyst performance over time and refine electrode and reactor designs to improve efficiency.
Asunto(s)
Ácido Selénico , Titanio , Contaminantes Químicos del Agua , Titanio/química , Catálisis , Contaminantes Químicos del Agua/química , Ácido Selénico/química , Purificación del Agua/métodos , Electrodos , Técnicas ElectroquímicasRESUMEN
Selenium is an essential inorganic compound in human and animal nutrition, involved in the proper functioning of the body. As a micronutrient, it actively contributes to the regulation of various metabolic activities, i.e., thyroid hormone, and protection against oxidative stress. However, Se exhibits a narrow concentration window between having a positive effect and exerting a toxic effect. In higher doses, it negatively affects living organisms and causes DNA damage through the formation of free radicals. Increased reactivity of Se anions can also disrupt the integrity and function of DNA-repairing proteins. As the permissible concentration of Se in drinking water is 10 µg/L, it is vital to develop sensitive and robust methods of Se detection in aqueous samples. In this study, for the first time, we proposed a selective aptamer for selenate ion detection, chosen following the SELEX process, and its application in the construction of an electrochemical aptasensor towards SeO42- ions. Measurement conditions such as the used redox marker and pH value of the measurement solution were chosen. The proposed aptasensor is characterized by good selectivity and an LOD of 1 nM. Conditions for biosensor regeneration and storage were also investigated in this research.
Asunto(s)
Aptámeros de Nucleótidos , Técnicas Biosensibles , Técnicas Electroquímicas , Ácido Selénico , Aptámeros de Nucleótidos/química , Ácido Selénico/química , Técnicas Biosensibles/métodos , Técnicas Electroquímicas/métodos , Iones , Técnica SELEX de Producción de Aptámeros/métodos , Humanos , Límite de DetecciónRESUMEN
Effects of aluminate and silicate species on the SeO42- immobilization using alkali-earth metal oxides and ferrous species have not been clearly elucidated. In the present study, Al and Si species were separately added into MgO/Fe(II) and CaO/Fe(II) reactions containing SeO42-, studied by toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray absorption fine structure (XAFS), and PHREEQC simulation. Approximately 42 % of SeO42- was reduced to SeO32- for MgO/Fe(II) reaction in the presence of Al species, being consistent with the case without Al species. The Al species only showed slight inhibition of Se leaching for the MgO/Fe(II) reaction. Most of Se oxyanions were adsorbed onto Mg(OH)2 through outer-sphere complexation. For CaO/Fe(II) reaction, all of SeO42- was reduced to SeO32- with or without Al species. However, the Se leaching amount (3 %) of sample added with Al species (CE3) is much lower than that (12 %) of sample without Al species (CE2). This is mainly because SeO32- can be sorbed onto the iron-based minerals through binuclear bidentate corner-sharing (2C) complexation instead of monodentate mononuclear corner-sharing (1V) complexation of the case without Al species. On the other hand, SeO42- was not reduced to SeO32- in the presence of silicate, and almost all of Se was leached out for silicate-contained samples except CaO/Fe(II) reaction with the addition of Al species. This is due to the polymerization of Al and Si species under a high-alkalinity environment, thereby stabilizing SeO42- in the amorphous silicon-aluminum structure and contributing to the decrease of Se leaching.
Asunto(s)
Óxido de Magnesio , Óxidos , Adsorción , Álcalis , Aluminio , Compuestos Ferrosos/química , Hierro/química , Óxidos/química , Ácido Selénico/química , Silicatos , SilicioRESUMEN
Iron-based nanomaterials have high technological impacts on various pro-environmental applications, including wastewater treatment using the co-precipitation method. The purpose of this research was to identify the changes of iron nanomaterial's structure caused by the presence of selenium, a typical water contaminant, which might affect the removal when the iron co-precipitation method is used. Therefore, we have investigated the maturation of co-precipitated nanosized ferric oxyhydroxides under alkaline conditions and their thermal transformation into hematite in the presence of selenite and selenate with high concentrations. Since the association of selenium with precipitates surfaces has been proven to be weak, the mineralogy of the system was affected insignificantly, and the goethite was identified as an only ferric phase in all treatments. However, the morphology and the crystallinity of ferric oxyhydroxides was slightly altered. Selenium affected the structural order of precipitates, especially at the initial phase of co-precipitation. Still, the crystal integrity and homogeneity increased with time almost constantly, regardless of the treatment. The thermal transformation into well crystalized hematite was more pronounced in the presence of selenite, while selenate-treated and selenium-free samples indicated the presence of highly disordered fraction. This highlights that the aftermath of selenium release does not result in destabilization of ferric phases; however, since weak interactions of selenium are dominant at alkaline conditions with goethite's surfaces, it still poses a high risk for the environment. The findings of this study should be applicable in waters affected by mining and metallurgical operations.
Asunto(s)
Álcalis/química , Compuestos Férricos/química , Ácido Selénico/química , Ácido Selenioso/química , Precipitación Química , Cristalización , Hierro/química , Compuestos de Hierro/química , Minerales/química , Espectroscopía Infrarroja por Transformada de Fourier , Espectroscopía de Mossbauer , TemperaturaRESUMEN
The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals.
Asunto(s)
Biofortificación , Ácido Selénico/metabolismo , Selenio/metabolismo , Selenoproteínas/metabolismo , Animales , Antioxidantes/química , Antioxidantes/metabolismo , Humanos , Plantas/metabolismo , Ácido Selénico/química , Selenio/química , Selenocisteína/química , Selenocisteína/metabolismo , Selenometionina/química , Selenometionina/metabolismo , Selenoproteínas/biosíntesis , Suelo/químicaRESUMEN
This study attempted to address molecular, developmental, and physiological responses of tomato plants to foliar applications of selenium nanoparticles (nSe) at 0, 3, and 10 mgl-1 or corresponding doses of sodium selenate (BSe). The BSe/nSe treatment at 3 mgl-1 increased shoot and root biomass, while at 10 mgl-1 moderately reduced biomass accumulation. Foliar application of BSe/nSe, especially the latter, at the lower dose enhanced fruit production, and postharvest longevity, while at the higher dose induced moderate toxicity and restricted fruit production. In leaves, the BSe/nSe treatments transcriptionally upregulated miR172 (mean = 3.5-folds). The Se treatments stimulated the expression of the bZIP transcription factor (mean = 9.7-folds). Carotene isomerase (CRTISO) gene was transcriptionally induced in both leaves and fruits of the nSe-treated seedlings by an average of 5.5 folds. Both BSe or nSe at the higher concentration increased proline concentrations, H2O2 accumulation, and lipid peroxidation levels, suggesting oxidative stress and impaired membrane integrity. Both BSe or nSe treatments also led to the induction of enzymatic antioxidants (catalase and peroxidase), an increase in concentrations of ascorbate, non-protein thiols, and soluble phenols, as well as a rise in the activity of phenylalanine ammonia-lyase enzyme. Supplementation at 3 mgl-1 improved the concentration of mineral nutrients (Mg, Fe, and Zn) in fruits. The bioaccumulated Se contents in the nSe-treated plants were much higher than the corresponding concentration of selenate, implying a higher efficacy of the nanoform towards biofortification programs. Se at 10 mgl-1, especially in selenate form, reduced both size and density of pollen grains, indicating its potential toxicity at the higher doses. This study provides novel molecular and physiological insights into the nSe efficacy for improving plant productivity, fruit quality, and fruit post-harvest longevity.
Asunto(s)
Biofortificación/métodos , Nanopartículas/química , Ácido Selénico/farmacología , Selenio/farmacología , Solanum lycopersicum/metabolismo , Almacenamiento de Alimentos/métodos , Solanum lycopersicum/efectos de los fármacos , Solanum lycopersicum/crecimiento & desarrollo , Estrés Oxidativo , Fenilanina Amoníaco-Liasa/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ácido Selénico/efectos adversos , Ácido Selénico/química , Selenio/efectos adversos , Selenio/química , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , cis-trans-Isomerasas/genética , cis-trans-Isomerasas/metabolismoRESUMEN
The immobilization of selenate (SeO42-) using metal oxides (CaO and MgO) and ferrous salt as the immobilization reagents were examined by the leaching test and solid-phase analysis via XRD, XAFS, TGA, and XPS. The results indicated that nearly all of SeO42- was reduced to SeO32- in the CaO-based reaction within 7 days. Then, the generated SeO32- was mainly sorbed onto the iron-based minerals (Fe2O3 and FeOOH) through the formation of both bidentate mononuclear edge-sharing (1E) and monodentate mononuclear corner-sharing (1V) inner-sphere surface complexes, suggested by PHREEQC simulation and EXAFS analysis. Differently, less amount of SeO42- (approximately 45.50%) was reduced to SeO32- for the MgO-based reaction. However, if the curing time increases to a longer time (more than 7 days), the further reduction could occur because there are still Fe(II) species in the matrix. As for the associations of Se in the solid residue, most of the selenium (SeO32- and SeO42-) was preferentially distributed onto the Mg(OH)2 through outer-sphere adsorption. Definitely, this research can provide a deep understanding of the immobilization of selenium using alkaline-earth metal oxide related materials and ferrous substances.
Asunto(s)
Compuestos de Calcio/química , Contaminantes Ambientales/análisis , Compuestos Ferrosos/química , Óxido de Magnesio/química , Óxidos/química , Ácido Selénico/análisis , Adsorción , Contaminantes Ambientales/química , Modelos Teóricos , Ácido Selénico/química , Purificación del Agua/métodosRESUMEN
A general and simple metal-free protocol for expedient C-H functionalization leading to the regioselective generation of C-5 chalcogenated 8-aminoquinoline analogues in up to 90% yield at room temperature (25 °C) has been established. This methodology is an eco-friendly approach to the atom-economical utilization of diaryl/dialkyl chalcogenides for direct access to chalcogenated quinolines and is scalable to the gram scale without considerable decrease in the yield of the product. It represents a practical alternative to the existing metal-catalyzed functionalization of 8-aminoquinoline derivatives with broad functional group tolerance. The controlled experiments suggest that the reaction possibly proceeds through an ionic pathway at room temperature. Furthermore, the potentiality for the functionalization of free amines in chalcogenated-8-aminoquinolines provides an attractive perspective for further elaboration of the amine substituent through chemical manipulations. The applicability of the standardized method has been augmented through late-stage antimalarial drug diversification of primaquine analogues.
Asunto(s)
Aminoquinolinas/síntesis química , Aminas/química , Catálisis , Yodo/química , Estructura Molecular , Oxidación-Reducción , Ácido Selénico/química , Solventes/química , Estereoisomerismo , Ácidos Sulfénicos/químicaRESUMEN
Methane oxidation coupled to selenate reduction has been suggested as a promising technology to bio-remediate selenium contaminated environments. However, the effect of dissolved oxygen (DO) on this process remained unclear. Here, we investigate the feasibility of selenate removal at two distinct DO concentrations. A membrane biofilm reactor (MBfR) was initially fed with â¼5â¯mg Se/L and then lowered to â¼1â¯mg Se/L of selenate, under anoxic condition containing â¼0.2â¯mg/L of influent DO. Selenate removal reached approximately 90% without selenite accumulation after one-month operation. Then 6-7â¯mg/L of DO was introduced and showed no apparent effect on selenate reduction in the subsequent operation. Electron microscopy suggested elevated oxygen exposure did not affect microbial shapes. 16S rDNA sequencing showed the aerobic methanotroph Methylocystis increased, while possible selenate reducers, Ignavibacterium and Bradyrhizobium, maintained stable after oxygen boost. Gene analysis indicated that nitrate/nitrite reductases positively correlated with selenate removal flux and were not remarkably affected by oxygen addition. Reversely, enzymes related with aerobic methane oxidation were obviously improved. This study provides a potential technology for selenate removal from oxygenated environments in a methane-based MBfR.
Asunto(s)
Metano/química , Oxígeno/farmacología , Ácido Selénico/química , Bacterias/enzimología , Bacterias/aislamiento & purificación , Biopelículas , Reactores Biológicos/microbiología , Membranas Artificiales , Nitratos/metabolismo , Nitritos/metabolismo , Oxidación-Reducción , Ácido Selénico/aislamiento & purificaciónRESUMEN
Selenate (Se(VI)) and selenite (Se(IV)) are common soluble wastewater pollutants in natural and anthropogenic systems. We evaluated the reduction efficiency and removal of low (0.02 and 2 mg/L) and high (20 and 200 mg/L) Se(IV)(aq) and Se(VI)(aq) concentrations to elemental (Se0) via the use of ascorbic acid (AA), thiourea (TH), and a 50-50% mixture. The reduction efficiency of AA with Se(IV)(aq) to nano- and micro-crystalline Se0 was ≥ 95%, but ≤ 5% of Se(VI)(aq) was reduced to Se(IV)(aq) with no Se0. Thiourea was able to reduce ≤ 75% of Se(IV)(aq) to bulk Se0 at lower concentrations but was more effective (≥ 90%) at higher concentrations. Reduction of Se(VI)(aq)âSe (IV)(aq) with TH was ≤ 75% at trace concentrations which steadily declined as the concentrations increased, and the products formed were elemental sulfur (S0) and SnSe8-n phases. The reduction efficiency of Se(IV)(aq) to bulk Se0 upon the addition of AA+TH was ≤ 81% at low concentrations and ≥ 90% at higher concentrations. An inverse relation to what was observed with Se(IV)(aq) was found upon the addition of AA+TH with Se(VI)(aq). At low Se(VI)(aq) concentrations, AA+TH was able to reduce more effectively (≤ 61%) Se(VI)(aq)âSe(IV)(aq)âSe0, while at higher concentrations, it was ineffective (≤ 11%) and Se0, S0, and SnSe8-n formed. This work helps to guide the removal, reduction effectiveness, and products formed from AA, TH, and a 50-50% mixture on Se(IV)(aq) and Se(VI)(aq) to Se0 under acidic conditions and environmentally relevant concentrations possibly found in acidic natural waters, hydrometallurgical chloride processing operations, and acid mine drainage/acid rock drainage tailings. Graphical Abstract á .
Asunto(s)
Ácido Ascórbico/química , Modelos Químicos , Ácido Selénico/química , Ácido Selenioso/química , Tiourea/química , Ácido Ascórbico/análisis , Minería , Oxidación-Reducción , Ácido Selénico/análisis , Ácido Selenioso/análisis , Selenio/análisis , Compuestos de Selenio , Azufre , Tiourea/análisisRESUMEN
Soil dissolved organic matter (DOM) alters heavy metal availability, but whether straw amendment can manipulate soil selenium (Se) speciation and availability through DOM mineralization remains unclear. In this study, allochthonous maize straw and selenate were incubated together in four different soils for 1â¯y. The transformation and availability of DOM associated Se (DOM-Se) was investigated during aging. Results indicated that soil solution and soil particle surfaces were dominated by hexavalent hydrophilic acid-bound Se (Hy-Se). The amount of fulvic acid bound Se in soil solution (SOL-FA-Se) was higher than humic acid bound Se in soil solution (SOL-HA-Se), except in krasnozems, and mainly existed as hexavalent Se (Se(VI)). Tetravalent Se (Se(IV)) was the main valence state of FA-Se adsorbed on soil particle surfaces (EX-FA-Se) after 5â¯w of aging. The proportion of soil-available Se (SOLâ¯+â¯EX-Se) decreased with increasing straw rate. However, under an application rate of 7500â¯kg·hm-2, soluble Se fraction (SOL-Se) reduction was minimal in acidic soils (18.7%-34.7%), and the organic bound Se fraction (OM-Se) was maximally promoted in alkaline soils (18.2%-39.1%). FA and HON could enhance the availability of Se in the soil solution and on particle surfaces of acidic soil with high organic matter content. While Se incorporation with HA could accelerate the fixation of Se into the solid phase of soil. Three mechanisms were involved in DOM-Se aging: (1) Reduction, ligand adsorption, and inner/outer-sphere complexation associated with the functional groups of straw-derived DOM, including hydroxyls, carboxyl, methyl, and aromatic phenolic compounds; (2) interconnection of EX-FA-Se between non-residual and residual Se pools; and (3) promotion by soil electrical conductivity (EC), clay, OM, and straw application. The dual effect of DOM on Se aging was highly reliant on the characteristics of the materials and soil properties. In conclusion, straw amendment could return selenium in soil and reduce soluble Se loss.
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Restauración y Remediación Ambiental/métodos , Selenio/análisis , Suelo/química , Agricultura , Benzopiranos/química , China , Interacciones Hidrofóbicas e Hidrofílicas , Tallos de la Planta/química , Ácido Selénico/química , Selenio/química , Selenio/farmacocinética , Contaminantes del Suelo/análisis , Contaminantes del Suelo/farmacocinética , Espectroscopía Infrarroja por Transformada de Fourier , Factores de TiempoRESUMEN
Despite not being an essential element for plants, Se has been proved to reduce Cd accumulation and Cd-induced oxidative stress, although the underlying mechanisms are not fully understood. A pak choi hydroponic experiment was conducted to investigate the effects of Se on Cd accumulation, subcellular distribution, and Cd-induced oxidative stress at different growth stages. The results showed that on day 19 after germination, Cd content was significantly reduced by 32% by selenite, but was increased by 15% by selenate. Accordingly, selenite improved cell-wall Cd sequestration by 20%, whereas selenate caused enhanced translocation of Cd from the root to the shoot. However, the effects of selenite on the reduction in Cd accumulation and distribution in pak choi seedlings were completely dismissed on day 40. Nevertheless, both forms of Se enhanced antioxidative defense, as they both inhibited the accumulation of H2O2 and malondialdehyde. On day 19, ascorbate peroxidase and glutathione reductase activities were increased by more than 50% by selenite; additionally, superoxide dismutase, catalase, and peroxidase activities increased by up to 86%, 63%, and 24%, respectively, in the presence of selenite, when compared to Cd treatment alone. Activities of most of the antioxidants remained significantly unaffected by both forms of Se on day 40. Consequently, selenite and selenate affected Cd accumulation in pak choi seedlings by altering Cd subcellular distribution and by enhancing antioxidative defense, but such effects depended on the Se forms applied and the growth stage as well.
Asunto(s)
Brassica/química , Cadmio/química , Ácido Selénico/química , Ácido Selenioso/química , Oxidación-Reducción , Estrés OxidativoRESUMEN
Cellulose-agar (CAB) composite hydrogel beads were generated for the uptake-release kinetics studies of Se(VI) and selenomethionine (SeMt) from water medium. The objective of this work is to analyze the surface structure, gel properties, thermal stability and chemical functionalities responsible for the adsorption of Se(VI) and SeMt. We propose here a possible mechanism for the adsorptions. Adsorption isotherms are in good agreement with the Freundlich model, yielding a high adsorption capacity for the CAB composite. Maximum adsorption capacity of Se(VI) and SeMt were found to be 7.083â¯mgâ¯g-1 and 34.639â¯mgâ¯g-1 respectively. The mean free energy of adsorption (E*) value was found to be 0.0423â¯kJâ¯mol-1 and 0.329â¯kJâ¯mol-1 of Se(VI) and SeMt respectively. 1â¯M HCl and 0.1â¯M HCl were able to desorb Se(VI) and SeMt respectively from CAB. The adsorption of Se(VI) was significantly reduced if As(III), Cr(III) and Hg(II) were present as complementary ions in the medium. Similar studies with pristine cellulose beads (CB) yielded insignificant uptake properties.
Asunto(s)
Agar/química , Celulosa/química , Hidrogeles/química , Ácido Selénico/química , Ácido Selénico/aislamiento & purificación , Selenometionina/química , Selenometionina/aislamiento & purificación , Adsorción , Concentración de Iones de Hidrógeno , Cinética , Termodinámica , Agua/química , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/aislamiento & purificaciónRESUMEN
Effects of sulfate on simultaneous nitrate and selenate removal in a hydrogen-based membrane biofilm reactor (MBfR) for groundwater treatment was identified with performance and biofilm microbial ecology. In whole operation, MBfR had almost 100% removal of nitration even with 50â¯mgâ¯mL-1 sulfate. Moreover, selenate degradation increased from 95% to approximate 100% with sulfate addition, indicating that sulfate had no obvious effects on nitrate degradation, and even partly promoted selenate removal. Short-term sulfate effect experiment further showed that Gibbs free energy of reduction (majority) and abiotic sulfide oxidation (especially between sulfate and selenate) contributed to degradable performance with sulfate. Microbial ecology showed that high percentage of Hydrogenophaga (≥75%) was one of the contributors for the stable and efficient nitrate degradation. Chemoheterotrophy (ratio>0.3) and dark hydrogen oxidation (ratio>0.3) were the majority of functional profile for biofilm in MBfR, and sulfate led to profiles of sulfate respiration and respiration of sulfur compounds in biofilm. Additionally, no special bacteria for selenate degradation was identified in biofilm microbial ecology, and selenate degradation was relied on Hydrogenophaga (75% of ecology percentage with sulfate addition) and Desulfovibrionaceae (4% of ecology percentage with sulfate addition). But with overloading sulfate, Desulfovibrionaceae was prior to sulfate degradation for energy supply and thus inhibited selenate removal.
Asunto(s)
Biopelículas/efectos de los fármacos , Reactores Biológicos/microbiología , Agua Subterránea/química , Hidrógeno/química , Nitratos/química , Ácido Selénico/química , Sulfatos/químicaRESUMEN
Selenium (Se) fertilisation in grazing systems can improve the quality of animal forage, but there are few studies addressing the influence of Se fertilisation on the chemical composition and ruminal degradability of forage fertilised with Se. The aim of this study was to evaluate the chemical composition and in vitro assays of truly degraded organic matter (TDOM), short-chain fatty acids (SCFA) total gas (GP) and methane (CH4 ) production of two harvests of Brachiaria brizantha cv. Marandu fertilised with urea coated with B, Cu and sodium selenate for 0, 10, 20, 40, 80 and 160 g/ha of Se. Selenium content in forage increased linearly with the different doses at 30 and 60 days after fertilisation. However, doses of 20 and 80 g/ha Se fertilisation yielded positive effects increasing Se content and truly degraded organic matter in vitro of Brachiaria brizantha cv. Marandu.
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Brachiaria/química , Fertilizantes/análisis , Ácido Selénico/metabolismo , Selenio/química , Alimentación Animal/análisis , Brachiaria/metabolismo , Metano/metabolismo , Valor Nutritivo , Hojas de la Planta/química , Proteínas de Plantas/metabolismo , Tallos de la Planta/química , Ácido Selénico/químicaRESUMEN
BACKGROUND: Foliar spraying of selenium (Se) has increasingly been applied to improve Se concentrations in grain crops, although little information is available about the properties of Se-enriched fruits. In the present study, selenium distribution in blueberry and Se effect on blueberry quality were investigated by foliar spraying selenite or selenate (200 g ha-1 ) on two blueberry cultivars (Bluecrop and Northland) during the young fruit or coloring stage. RESULTS: Selenium concentration in blueberry was mainly affected by cultivar and spray stage relative to the Se source. Northland was 1.3- to 1.5-fold higher than Bluecrop with respect to Se enrichment. Se treatment at the young fruit stage induced a 1.5- to 2.3-fold increase compared to that at the coloring stage with respect to the Se concentration of blueberry. Additionally, selenium was mainly stored in pomace, with an accumulative distribution ratio of 89.3-94.9%. The proportion of organic Se reached up to 77.0% in blueberry. Furthermore, the foliar application of Se significantly increased the anthocyanin concentration and the intact fruit rate of blueberry. CONCLUSION: Se-enriched blueberry can be used as a 'functional food'. Because Se was mainly accumulated in the pomace, the consumption of blueberries as fresh fruit, dried fruit and jam can improve the efficiency of Se supplement. © 2018 Society of Chemical Industry.
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Arándanos Azules (Planta)/crecimiento & desarrollo , Frutas/química , Ácido Selénico/metabolismo , Ácido Selenioso/metabolismo , Arándanos Azules (Planta)/química , Arándanos Azules (Planta)/metabolismo , Producción de Cultivos , Fertilizantes/análisis , Frutas/crecimiento & desarrollo , Frutas/metabolismo , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Ácido Selénico/química , Ácido Selenioso/químicaRESUMEN
This study examines selenite [Se(IV)] and selenate [Se(VI)] adsorption on two-line ferrihydrite in the presence and absence of two low-molecular-weight dissolved organic carbon (DOC) species, citric and salicylic acid. Ferrihydrite surface potential measurements were also examined to identify shifts in isoelectric points, which suggest possible adsorption mechanisms. Sorption was completed in batch reactor systems at environmentally relevant pH. Our results indicate citric acid suppressed both Se(IV) and Se(VI) sorption on ferrihydrite, which may be caused by competition. This was especially evident at pH 5 to 7 for Se(IV) and pH 5 to 6 for Se(VI). Little sorption suppression was observed for both Se species in the presence of salicylic acid. In the presence of Se(IV) and Se(VI), citric acid adsorption was reduced (pH 5-8). Salicylic acid sorption was almost completely suppressed in the presence of Se(IV) throughout the entire pH range examined, with minimal sorption occurring at pH 5. In the presence of Se(VI), the largest reduction in salicylic acid sorption occurred at pH 5 to 6. Small shifts in the surface potential of ferrihydrite at higher pH suggest that Se(VI) and salicylic acid form weak, outer-sphere complexes. However, at pH 5 and 6, there is a shift in the surface potential measurements to more negative values, indicating possible formation of stronger, inner-sphere complexes. Larger surface potential shifts for Se(IV) and citric acid suggest the formation of strong, inner-sphere complexes. This work demonstrates the ability of low-molecular-weight DOC species (particularly for citric acid) to increase Se(IV) and Se(VI) solubility through sorption suppression.
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Carbono/química , Ácido Selénico/química , Ácido Selenioso/química , Adsorción , Compuestos Férricos , Concentración de Iones de HidrógenoRESUMEN
Moderately halotolerant selenate- and tellurite-reducing bacteria were characterized for wastewater treatment applications. A selenate-reducing strain 9a was isolated from the biofilm of a leachate treatment plant at a sea-based waste disposal site. A tellurite-reducing strain Taa was isolated from an enrichment culture derived from brackish sediment. Both bacterial strains were Shewanella species. Strain 9a could anaerobically remove 45-70% of 1.0 mM selenate and selenite from water containing up to 3% NaCl within 4 days, while strain Taa could anaerobically and aerobically remove 70-90% of 0.4 mM tellurite from water containing up to 6% NaCl within 3 days. Globular particles of insoluble selenium were observed both outside and inside the cells of strain 9a. The insoluble tellurium formed by strain Taa was globular under microaerobic conditions but nanorod under aerobic conditions. These bacteria will yield a range of useful selenium and tellurium nanomaterials as well as wastewater treatment applications.
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Bacterias/metabolismo , Ácido Selénico/química , Telurio/química , Bacterias/química , Bacterias Aerobias/química , Bacterias Anaerobias/química , Japón , Oxidación-Reducción , Aguas Salinas , Tolerancia a la SalRESUMEN
Iron-impregnated granular activated carbon (Fe-GAC) has been shown effective for selenite adsorptive removal from aqueous solutions, but similar effectiveness was not observed with selenate. This study examined the effects of background electrolytes and pH on selenate adsorption on to Fe-GAC, and surface bindings to elucidate the selenate adsorption mechanisms. The decrease magnitude of selenate adsorption capacity under three background electrolytes followed the order: LiCl > NaCl > KCl, as ionic strength increased from 0.01 to 0.1 M. Larger adsorption capacity differences among the three electrolytes were observed under the higher ionic strengths (0.05 and 0.1 M) than those under 0.01 M. Multiplet peak fittings of high resolution X-ray photoelectron spectra for O1s and Fe2p3/2 indicated the presence of iron (III) on adsorbent surface. pH variations during the adsorbent preparation within 3-8 in NaCl solutions did not cause appreciable changes in the iron redox state and composition. Raman spectra showed the formation of both monodentate and bidentate inner sphere complexes under pHs <7 and a mixture of outer sphere and inner sphere complexes at pH 8. These results explained the lower selenate adsorption under alkaline conditions. Mechanisms for monodentate and bidentate formations and a stable six-member ring structure were proposed. Two strategies were recommended for modifying Fe-GAC preparation procedure to enhance the selenate adsorption: (1) mixed-metal oxide coatings to increase the point of zero charge (pHzpc); and (2) ferrous iron coating to initially reduce selenate followed by selenite adsorption.
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Carbón Orgánico/química , Electrólitos , Ácido Selénico/química , Ácido Selenioso/aislamiento & purificación , Adsorción , Concentración de Iones de Hidrógeno , Hierro/química , Concentración Osmolar , Oxidación-Reducción , Óxidos , Contaminantes Químicos del Agua/química , Purificación del Agua/métodosRESUMEN
Dual ions substituted hydroxyapatite (HA) received attention from scientists and researchers in the biomedical field owing to their excellent biological properties. This paper presents a novel biomaterial, which holds potential for bone tissue applications. Herein, we have successfully incorporated ferric (Fe3+ )/selenate ( SeO42-) ions into the HA structure (Ca10-x-y Fey (PO4 )6-x (SeO4 )x (OH)2-x-y Oy ) (Fe-SeHA) through a microwave refluxing process. The Fe-SeHA materials were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and field emission scanning electron microscopy (FESEM). XRD and FTIR analyses revealed that Fe-SeHA samples were phase pure at 900°C. FESEM images showed that formation of rod-like shaped particles was inhibited dramatically with increasing Fe3+ amount. The Vickers hardness (HV) test showed that hardness values increased with increasing Fe3+ concentrations. Optical spectra of Fe-SeHA materials contained broadband over (200-600) nm. In vitro degradation and bioactivity tests were conducted in simulated body fluid (SBF). The incorporation of Fe3+ / SeO42- ions into the HA structure resulted in a remarkably higher degradation rate along with intense growth of apatite granules on the surface of the Fe-SeHA discs with Ca/P ratio of 1.35-1.47. In vitro protein adsorption assay was conducted in fetal bovine serum (FBS) and it was observed that the adsorption of serum proteins on Fe-SeHA samples significantly increased with increasing Fe3+ concentration. In vitro cytotoxicity tests were performed with human fetal osteoblast (hFOB) cell line and the results demonstrated that hFOB cells attached and proliferated faster on the Fe-SeHA materials compared to pure HA showing that Fe-SeHA materials were cytocompatible. ALP activity and intracellular calcium of hFOB cells on 1Fe-SeHA discs were statistically higher than pure HA, suggesting that presence of Fe3+ ion supported osteogenic differentiation of hFOB cells. Our results suggest that 1Fe-SeHA (0.2M Fe3+ /0.5M SeO42- co-doped HA) material could be considered as a promising candidate material for orthopedic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 340-352, 2018.