Recovery Of Se Research Articles

Volatilization and cleaning recovery of Pb, Se and Hg in acid sludge of copper smelting system during vacuum distillation

The high lead acid sludge, containing a small amount of selenium and mercury, is a hazardous waste product of the copper smelting system. Improper disposal of this waste can cause serious harm to the environment. In this study, the method of vacuum distillation was proposed for treating the high lead acid sludge. The study aimed to investigate the volatilization rule of selenium, mercury, and lead in the acid sludge during vacuum distillation, as well as to purify PbSe and metallic lead. The results indicated that under 5 Pa, Hg and Se commence volatilizing at 300 ℃, the content of Hg in volatile substances remains relatively constant after reaching 400 ℃, demonstrating nearly complete volatilization at this temperature with a ratio of 92.93 %. Similarly, selenium almost completely volatilizes at 800 ℃ with a ratio of 96.74 %, while lead does so at around 1000 ℃ with a ratio of approximately 99.27 %. Mercury at 400 ℃ can be recovered as mercury selenide. Lead selenide can be achieved at 800 ℃, while lead sulfate can be decomposed and purified at 1000 ℃ to obtain metallic lead with a purity higher than 99 %. The method can properly treat and recover mercury, selenium, lead and other elements in the acid sludge with short process and no pollution, which provides a new cleaning approach for high lead acid sludge.

Gradient Separation and Recovery of Pb, Se, Cu, and Hg from Acid Sludge by a Sustainable Hydrometallurgical Process

Gradient Separation and Recovery of Pb, Se, Cu, and Hg from Acid Sludge by a Sustainable Hydrometallurgical Process

Electrocatalytic Selenate Transformation to Tunable Products Using Affordable Catalysts

Anthropogenic selenium (Se) pollution has profound ecosystem and human health impacts. Compared to selenite or Se(IV), selenate or Se(VI) is chemically inert and more challenging for selective removal from the complex aquatic environment.1 Current Se(VI) removal efforts seek intensive resource and energy input to drive Se(VI) transformation, and are subject to environmental and operating conditions.2 The potential solution for sustainable Se(VI) transformation involves catalytic reduction of Se(VI). In current catalytic approaches, the reduction of Se(VI) is achieved using either abiotic photocatalysts (e.g., TiO2) or biotic enzymes (e.g., nitrate reductase).3 Here, we explored the opportunities of electrified Se(VI) transformation with functionalized catalysts to manage aquatic selenate pollution. Se(VI) can be removed through phase transformation into solid Se(0) that could cover reactive surfaces and prevent further catalysis, or gaseous Se(-II) that is toxic and needs to be captured. Alternatively, the reduction of Se(VI) into reactive Se(IV) allows exposure of active interfaces for continuous electrochemcial transformation. Therefore, a controlled reduction of Se(VI) to Se(IV) would be ideal in aquatic Se(VI) management and potential Se recovery. To the best of our knowledge, controlled Se(VI) transformation has not been fully achieved in the literature. In this study, we evaluated five affordable catalysts on graphite cathodes, including TiO2,3 underpotentially deposited Cu (UPD Cu),4 underpotentially deposited Cd (UPD Cd), Co, and CuFe nanoarrays.5 Among these five candidates, characteristic Se(VI) reduction peaks were identified for TiO2, UPD Cu, and UPD Cd through cyclic voltammetry. Less than 5% of 1-mM Se was removed using UPD Cu and UPD Cd, based on 24-hour chronoamperometry tests at corresponding potentials. Unfortunately, ppm-level Cu or Cd were detected in the treated effluent. In contrast, more than 90% of Se(VI) was removed using TiO2 as the catalyst after 24 hours. TiO2 was more robust and stable in electrocatalytic reactions with minimal catalyst dissolution and, therefore, was selected for further electrocatalytic Se(VI) reduction studies.During the TiO2-catalyzed reduction, Se(VI) would first transform into Se(IV) at a relatively positive potential. A maximum of 97% Se(VI) was found to be converted to Se(IV) in a 6-hour electrocatalytic Se(VI) reduction at -0.18 V. Decreasing electrode potential to -0.35 V, solid deposits of Se(0) appeared on a TiO2-modified graphite cathode. With a more negative electrode potential, further Se(0) reduction to Se(-II) was identified. The findings spotlight the opportunities to control Se(VI) transformation and harvest tunable products per removal demand and strategies. The effect of operational conditions was investigated at various TiO2 loading and solution pH. Higher TiO2 loading and lower solution pH favored the electrocatalytic Se(VI) transformation. The removal kinetics and performance were then studied under optimal operational conditions at -0.45 V, where Se(0) was dominant among Se(VI) reduction products, and -0.70 V, where Se(-II) was abundant. Kinetics analysis revealed that electrocatalytic Se(VI) reduction at -0.70 V was roughly four times faster as compared to that at -0.45 V. A total of 88.7 ± 2.3% of Se(VI) was removed after 24 hours of electrocatalysis at -0.70 V. In contrast, 48.2 ± 9.3% of Se(VI) was removed after 24 hours of electrocatalysis at -0.45 V. These results warrant further evaluation of the regenerability and lifespan of TiO2-modified graphite electrodes, an optimized electrode/reactor design, and an integrated Se removal/recovery system.

Extraction recovery and speciation of selenium in Se-enriched yeast.

The complete characterization of selenium-enriched yeast in terms of selenium species has been the goal of extensive research for the last three decades. This contribution addresses the two outstanding questions: the mass balance of the identified and reported selenium species and the possible presence of inorganic selenium. For this purpose, four procedures have been designed combining, in diverse order, the principal steps of selenium speciation analysis in Se-rich yeast: extraction of the Se-metabolome, derivatization of cysteine and Se-cysteine (SeCys) residues, proteolysis, and definitive Se recovery using SDS extraction, followed by mineralization. The recovery of selenium in each step and its speciation were controlled by ICP MS and by reversed-phase HPLC-ICP MS, respectively. The study, carried out for the SELM-1 reference material, demonstrated the presence of about 10% of inorganic selenium and a serious risk of losses of SeCys during derivatization and proteolysis. As result of our work, we postulate the following values for SELM-1: Se-metabolome fraction (SeMF) 14.8 ± 0.7%; total selenomethionine (SeMet) 66.2 ± 2.7% (including ca. 1.5% SeMet present in the SeMF); total SeCys 12.5 ± 1.5% (including 2% of SeCys present in the Se-MF); total inorganic selenium 9.7 ± 1.7%, accounting for > 99.8% of the selenium.

Foliar selenium biofortification of soybean: the potential for transformation of mineral selenium into organic forms.

Selenium (Se) deficiency, stemming from malnutrition in humans and animals, has the potential to disrupt many vital physiological processes, particularly those reliant on specific selenoproteins. Agronomic biofortification of crops through the application of Se-containing sprays provides an efficient method to enhance the Se content in the harvested biomass. An optimal candidate for systematic enrichment, guaranteeing a broad trophic impact, must meet several criteria: (i) efficient accumulation of Se without compromising crop yield, (ii) effective conversion of mineral Se fertilizer into usable organically bound Se forms (Seorg), (iii) acceptance of a Se-enriched crop as livestock feed, and (iv), interest from the food processing industry in utilization of Se-enriched outputs. Hence, priority should be given to high-protein leafy crops, such as soybean. A three-year study in the Czech Republic was conducted to investigate the response of field-grown soybean plants to foliar application of Na2SeO4 solutions (0, 15, 40, and 100 g/ha Se); measured outcomes included crop yield, Se distribution in aboveground biomass, and the chemical speciation of Se in seeds. Seed yield was unaffected by applied SeO4 2-, with Se content reaching levels as high as 16.2 mg/kg. The relationship between SeO4 2-dose and Se content in seeds followed a linear regression model. Notably, the soybeans demonstrated an impressive 73% average recovery of Se in seeds. Selenomethionine was identified as the predominant species of Se in enzymatic hydrolysates of soybean, constituting up to 95% of Seorg in seeds. Minor Se species, such as selenocystine, selenite, and selenate, were also detected. The timing of Se spraying influenced both plant SeO4 2- biotransformation and total content in seeds, emphasizing the critical importance of optimizing the biofortification protocol. Future research should explore the economic viability, long-term ecological sustainability, and the broad nutritional implications of incorporating Se-enriched soybeans into food for humans and animals.

Agro-biofortification of maize with selenium for higher grain selenium contents and productivity

Selenium (Se) is a vital mineral nutrient for animal and human health, which can be supplemented through seed biofortification techniques. Present study determined the potential of improving Se content in maize grain via several Se fertilizer application methods to enhance the nutritional status of native populations. Field trials were conducted for two growing years with different Se application methods and application rates to evaluate grain Se content in maize, Se recovery, grain macro- and micro-nutrients and grain yield under rain-fed conditions. Results demonstrated that foliar and soil Se applications showed no significant impacts on maize biomass and grain yield as well as maize grain N, P, K, Ca, Mg, Fe, Mn, Cu and Zn contents. However, both foliar and soil Se application significantly enhanced the maize grain Se content. Foliar application of Se exhibited greater Se recoveries of 54 % and 108 % in the grain over soil Se fertilizer for the first and second growing seasons while the later was recorded with only 1.71 % and 0.97 % increase as compared to control. In conclusion, foliar Se application at silking stage at the rate of 8.85 µM enhanced the grain Se content in maize at minimum costs as compared to soil Se application.

Effects of Low-Level Inorganic Selenium on Selenium Bioaccumulation in Escherichia coli: A Bioanalytical Study Using Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

This study aimed to assess the bioaccumulation of selenite – Se(IV) – and selenate – Se(VI) – in Escherichia coli ATCC 11775 biomass. Escherichia coli cultures were exposed to low selenium concentrations (0.3–30.0 µM), and subsequent effects on growth and viability were evaluated. Selenium content in biomass was quantified using graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS), with Se recovery assessed through mass balance analysis. The average percentage of bioaccumulated Se exhibited variability depending on the Se species at different concentrations. At a concentration of 30.0 μM, elemental selenium formation emerged within the Se(IV) assay, leading to a significantly higher mean percentage of bioaccumulated selenium for Se(IV) (41.1%) compared to Se(VI) (15.8%). While the mean percentage of bioaccumulated selenium showed no significant variance across the Se(VI) concentrations, a significant difference was observed across the Se(IV) concentrations (ranging from 6.1% to 41.1%). Considering the percentage of Se recovered in the solid and liquid phases, the mass balance ranged from 82.1% to 94.5%. These findings underscore the ability of Escherichia coli ATCC 11775 to accumulate notable quantities of selenium, with the amount of bioaccumulated Se influenced by Se(IV) concentration but not by Se(VI). Furthermore, bacterial viability remained unaffected by selenium species and concentrations. This study contributes valuable insights into the bioaccumulation dynamics of Se(IV) and Se(VI) in non-genetically modified Escherichia coli, shedding light on factors governing selenium accumulation in bacterial biomass, particularly regarding natural biological representation, standardization, comparability, and applicability to environmental studies.

Partitioning of selenium from coal to fly ash: The key roles of Fe-bearing minerals and implications for Se potential recovery

The roles of Ca/Fe phases on selenium (Se) enrichment behavior in fly ash during coal combustion were investigated by examining the Ca/Fe mineralogy of various ash samples, exploring the binding forms of Se in fly ashes, and performing bench-scale adsorption experiments (150–1000 ℃). The results indicated that Se capture by fly ash is a function of flue gas temperature, particle size, and more importantly, the contents and form of Ca/Fe in combustion ash. Physical condensation/adsorption was mainly determined by temperature and particle size, contributing to less than 25% of total Se in fly ash. The remaining Se in fly ash was captured by chemical reactions of Se with ash components. Calcium in ash mostly was present as Ca-aluminosilicates, Ca-silicates, gypsum, or complex Ca-Al-Si-Fe-O mixed phases. Iron mainly occurred as Fe-silicates and some crystalline minerals including hematite, magnetite, and maghemite. Although adsorption experiments found that only CaO was able to capture SeO2 (g) at high temperature (> 900 ℃), the roles of lime as well as Fe2+-/Fe3+-silicates (conclusion from previous literature) can be excluded, as inferred from the small amount of CaO in ash and the lack of correlation between Fe-silicate and Se. Sequential extraction experiments and electron microscopy analysis revealed that Fe-bound Se was dominant and iron oxides might be the critical phase for Se retention. Simulated adsorption experiments demonstrated that magnetite had the best Se capture ability among the iron minerals. The extraction of Fe-bound Se from coal fly ash required more stringent conditions than that of physiosorbed-Se and Ca-bound Se. Therefore, pretreatment methods including magnetic separation, flotation, size segregation, etc. were suggested to be used prior to acid leaching. This study can provide scientific basis for developing high-efficiency Se recovery methods or Se emission control techniques for high-Se coal utilization in thermal power stations.

Selective separation and recovery of selenium and mercury from hazardous acid sludge obtained from the acid-making process of copper smelting plants

Acid sludge obtained from the acid-making process of copper smelting plants is a typical hazardous waste, and its mercury content is >40%. In addition to mercury, the material contains valuable metals such as copper and selenium. Thus, acid sludge treatment has both economic and environmental benefits. Unfortunately, current processes are constrained by complex procedures, severe pollution and difficulty in separating Se and Hg. There are few economically viable methods for the disposal or reuse of this waste. This study proposes a two-stage leaching process to separate and recover Se and Hg from acid sludge. In the first stage of the H2SO4 leaching selectively separated 94.5% of Cu from the toxic acid sludge, while only 0.89% of Se and 0.01% of Hg were leached. To further separate Hg and Se, a leaching system consisting of hydrogen peroxide and hydrochloric acid was adopted in the second leaching stage. During the reaction, selenide was converted into Se in the residue, while Hg was dissolved in solution as HgCl42−. >96% of Hg was leached with 146 g/L HCl and 21.8 g/L H2O2 under a liquid-to-solid (L/S) ratio of 10 at 70 °C for 30 min, resulting in significant Se enrichment in the residue. The Se purity in the obtained product was over 84.8%, while the contents of impurities were all lower than 4%. Moreover, the dissolved mercury could be effectively recovered by electrolysis. These findings demonstrate that high recoveries of Cu, Hg and Se from hazardous waste can be achieved with stepwise leaching followed by electrolysis. This treatment protocol for toxic acid sludge not only avoids potential environmental harm but also significantly improves the process economics.

Microbial community dynamics in a feedback-redox controlled bioreactor process that enabled sequential selenate, nitrate and sulfate removal, and elemental selenium recovery

Oxidation reduction potential (ORP) feedback-control by ethanol-dosing was recently proved effective in facilitating a two-stage fluidized bed reactor (FBR) process to remove selenate, nitrate, and sulfate from wastewater, and recover high-purity elemental Se without the formation of carcinogenic SeS. However, further optimization requires knowledge on the relationship between microbial community composition and process performance. Here, changes of microbial communities during the reduction of selenate and nitrate in the first FBR (FBR1) under various ORP conditions (−240 to −520 mV vs. Ag/AgCl), sulfate reduction in subsquent FBR (FBR2) and sulfide oxidation in sulfide oxidation reactor (SOR) were examined. Based on 16S rRNA gene sequencing, high ORP (stage i without sulfate: >−360 mV; stage ii with sulfate: >−440 mV) and elevated sulfate at ORP ≤ −480 mV (stage iii) in FBR1 altered the microbial communities both on fluidized carrier and bulk liquor. Selenate reducers (Geoalkalibacter and Geovibrio genera) were impacted at ORP > −360 mV (stage i) or >−440 mV (stage ii), when selenate removal in FBR1 declined. However, nitrate reducers (Caenispirillum and Paracoccus genera) were not affected in the FBR1, and facilitated ~100 % nitrate removal. At ORP ≤ −480 mV, selenate reducers were readily enriched in FBR1. In the FBR2, the major sulfate reducing genera were Desulfomicrobium, Desulfovibrio and Desulfuromonas, whereas the dominant sulfide-oxidating genera in SOR were Paracoccus, Thiobacillus and Acholeplasma. This study suggested that both nitrate- and selenate-reducing communities could remain active under elevated sulfate concentrations, enabling sequential oxyanions removal and elemental Se recovery from wastewater.

Rapid and sensitive determination of Se and heavy metals in foods using electrothermal vaporization inductively coupled plasma mass spectrometry with a novel transportation system.

Rapid, sensitive and simultaneous determination of trace multi-elements in various plant food samples such as grain, oilseed, vegetable and tea is always a challenge thus far. In this work, a rapid determination method for Se, Cd, As and Pb in food samples by inductively coupled plasma mass spectrometry (ICP-MS) using slurry sampling electrothermal vaporization (SS-ETV) was developed. To improve the analytical sensitivity and precision as well as eliminate the memory effect, a gas turbulator line and signal delay device (SDD) were for the first time designed for the graphite furnace (GF) ETV coupled with ICP-MS. The signal acquisition parameters of ICP-MS, ashing and vaporization conditions, and the flow rates of carrier gas and gas turbulator were investigated for Se, Cd, As and Pb in food samples. Under the optimized conditions, the limits of determination (LODs) for Se, Cd, As and Pb were 0.5 ng g-1, 0.3 ng g-1, 0.3 ng g-1 and 0.6 ng g-1, respectively; the limits of quantification (LOQs) for Se, Cd, As and Pb were 1.7 ng g-1, 1.0 ng g-1, 1.0 ng g-1 and 1.9 ng g-1, respectively; linearity (R2) in the range of 1 to 4,000 ng g-1 was >0.999 using the standard addition method. This method was used to analyze 5 CRMs including rice, tea and soybeans, and the concentrations detected by this method were within the range of the certified values. The recoveries of Se, Cd, As and Pb in plant food matrices including grain, oilseed, celery, spinach, carrot and tea samples were 86-118% compared to the microwave digestion ICP-MS method; and the relative standard deviations (RSDs) were 1.2-8.9% for real food sample analysis, proving a good precision and accuracy for the simultaneous determination of multi-elements. The analysis time was less than 3 min, slurry preparation time < 5 min without sample digestion process. The proposed direct slurry sampling ICP-MS method is thus suitable for rapid and sensitive determination of Se, Cd, As and Pb in food samples with advantages such as simplicity, green and safety, as well as with a promising application potential in detecting more elements to protect food safety and human health.

Selenium Biofortification of Grain Maize Through Foliar Application of Sodium Selenate: Selenium Accumulation and Recovery by the Grain

ABSTRACT The study was conducted to investigate the effects of sodium selenate foliar application on the biofortification of selenium (Se) compositions of grain maize (Zea mays L. cvs. DKC 5783 F1). The experiment was carried out in a randomized block design with three replications, and sodium selenate (Na2SeO4) was applied at eight different levels (0, 5, 10, 15, 25, 50, 75, 100 g Se ha−1) from the foliar when the maize plant reached 50–70 cm in height. Applications did not statistically affect yields and biomass, the contents of total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), boron (B), and molybdenum (Mo), but it affected Se content. The total Se levels varied between 27 and 523 µg kg−1, the highest value was obtained from 100 g Se ha−1 application. When the amount of foliar-applied Se was increased from 0 to 100 g Se ha−1, the Se content increased by 19.37-fold and Se accumulation increased by 19.30-fold. Se recovery showed no significant change across the Se rates with an average of 37.01%. Foliar selenium application showed a significantly greater potential for increasing the Se level in grain maize, with 1 g of Se ha−1 increasing the grains by 5.23 µg kg−1. In this study, the Se content of maize grain increased with foliar selenate application. For human Se nutrient, it would be necessary to consume more than 100 g of maize (dry weight) per day with the foliar selenate application to maize.

Uptake of Selenite by Rahnella aquatilis HX2 Involves the Aquaporin AqpZ and Na+/H+ Antiporter NhaA.

Microbial transformation of selenite [Se(IV)] to elemental selenium nanoparticles (SeNPs) is known to be an important process for removing toxic soluble selenium (Se) oxyanions and recovery of Se from the environment as valuable nanoparticles. However, the mechanism of selenite uptake by microorganisms, the first step through which Se exerts its cellular function, remains not well studied. In this study, the effects of selenite concentration, time, pH, metabolic inhibitors, and anionic analogues on selenite uptake in Rahnella aquatilis HX2 were investigated. Selenite uptake by R. aquatilis HX2 was concentration- and time-dependent, and its transport activity was significantly dependent on pH. In addition, selenite uptake in R. aquatilis HX2 was significantly inhibited by the aquaporin inhibitor AgNO3 and sulfite (SO32-), and partially inhibited by carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 2,4-dinitrophenol (2,4-DNP) treatments. Three mutants with in-frame deletions of aqpZ, glpF, and nhaA genes were constructed. The transport assay showed that the water channel protein AqpZ, and not GlpF, was a key channel of selenite uptake by R. aquatilis HX2, and sulfite and selenite had a common uptake pathway. In addition, the Na+/H+ antiporter NhaA is also involved in selenite uptake in R. aquatilis HX2.

A phosphonium ionic liquid conjugated magnetic graphitic carbon nitride nanocomposite: an effective sample pretreatment tool for selenium separation and determination.

We established an innovative and easy-to-use methodology for selenium (Se) extraction and determination from real water samples utilizing a magnetic nanocomposite adsorbent (MNC-SPE) aided by an inductively coupled plasma mass spectrometry (ICP-MS) approach. The MNC-SPE adsorbent was fabricated by hybridizing Fe3O4 nanoparticles on the surface of carbon nitride nanosheets (GCN NSs) that were coated with 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid (P-IL). A variety of techniques were used to thoroughly analyze the structural and chemical characteristics of MNC-SPE, and appear to have a great number of diverse active surface functional units (imidazole ring and -NH3+). In order to optimize the key factors affecting the Se extraction, parameters including the adsorbent dosage, contact time, eluent type, eluent volume, eluent time, and reusability of adsorbent were extensively studied. The proposed approach was validated under the optimal reaction conditions, and it showed good linearity between 0.15 and 100 pg μL-1 with a significant R2 value (R2 = 0.9994) toward Se metal. Besides, the Se limit of detection (LOD) and limit of quantification (LOQ) are 0.063 pg μL-1 and 0.147 pg μL-1, respectively. Further, by utilizing tap and river water samples, the applicability of the validated method was tested; the approach showed high Se recovery values in the range of 87.6-115.5% for the spiked real-world samples and the interday and intraday precision (RSD%) values of the approach were 4.8% (n = 6). The MNC-SPE can be regenerated and reused for four consecutive extraction-desorption cycles by employing 0.5 M NaOH eluent.

Fast and Sensitive Determination of Cadmium and Selenium in Rice by Direct Sampling Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry.

In this work, a direct solid sampling device based on modified graphite furnace electrothermal vaporization (GF-ETV) with inductively coupled plasma mass spectrometry (ICP-MS) was established for the simultaneous detection of trace selenium and cadmium in rice samples. A bypass gas was first designed in GF-ETV to improve the device’s analytical sensitivity and precision. The ashing and vaporization conditions, the flow rates of the Ar carrier and the bypass gases of ICP-MS were all investigated. Under the optimized conditions, the limits of detection (LODs) for Se and Cd were 0.5 μg kg−1 and 0.16 μg kg−1, respectively; the relative standard deviations (RSDs) of repeated measurements were within 8% (n = 6). The recoveries of Cd and Se in rice samples were in the range of 89−112% compared with the microwave digestion ICP-MS method, indicating good accuracy and precision for the simultaneous detection of Se and Cd in rice matrix. The whole analysis time is <3 min without the sample digestion process, fulfilling the fast detection of Se and Cd in rice samples to protect food safety.

Selenium and Tellurium Separation: Copper Cementation Evaluation Using Response Surface Methodology

In recent years, high demands for Se and Te in the solar panels and semiconductors industry have encouraged its extraction from primary and secondary sources. However, the two elements’ similar chemical and physical properties make pure element production, Se or Te, arduous. This work is aimed to investigate the significant factors of Se and/or Te recovery in the copper cementation process using the response surface methodology. The test was carried out in two series, for Te and Se, so that H2SO4, CuSO4, Te(or Se) concentration, and temperature are the factors of experimentation. According to response surface methodology (RSM) results for both test series (i. e. Se and Te), 50 g/L H2SO4, 15 g/L Cu, and 35 °C, 3000 mg/L Se (or 750 mg/L Te) was specified for higher Se recovery (97%), and the lowest Te extraction (2%) as an optimum condition, so that could make a suitable separation process. Hence, the cementation test was conducted in the simultaneous presence of Se and Te, so the separation index became 5291. Moreover, the cementation test was carried out in the pregnant leach solution of copper anode slime, and the separation factor was measured to be 606. On the other hand, the thermodynamic evaluation and XRD patterns of the process’s sediments confirm that Se is precipitated as Cu2Se and Cu1.8Se, whereas no Te components are detected in the sediments.

Selenium speciation in soils using flow injection hydride generation atomic absorption spectrometry with on-line removal of organic matter interferences

A method based on flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) with an on-line pre-reduction of Se(VI) to Se(IV) was developed and optimized to determine phosphate-extractable Se (0.1 M phosphate buffer KH2PO4/K2HPO4 at pH 7). The extracted fraction involves water-soluble Se (i.e. the most mobile Se fraction) and exchangeable Se (i.e. sorbed onto soil component surface). Kinetic discrimination mechanisms allowed the complete removal of interferences caused by organic matter due to the formation of humic substances (HS)–Se(IV) complexes observed when batch pre-reduction processes were used. Se(IV) and Se(VI) recoveries ranged 95–105% at a fortification level of 150 μg kg−1. The pre-reduction was efficiently carried out in 20 s in a 6 M HCl medium at 100 °C. Results from phosphate-extractable fractions were comparable to those obtained by ICP-MS. Se bound to organic matter was released digesting the remaining material from the phosphate buffer extraction with 0.1 M K2S2O8. Detection and quantification limits were 15 μg kg−1 Se and 50 μg kg−1 Se, respectively, in each fraction. The methodology was applied to 10 agricultural soils from Argentina with total Se concentration levels between 130 μg kg−1 and 419 μg kg−1.

Towards single cell ICP-MS normalized quantitative experiments using certified selenized yeast

In the search for a normalized procedure to replicate and compare single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) experiments, SELM-1, a certified reference material containing selenium enriched yeast cells has been used. Selenium concentrations (both, intra- and extracellular) have been measured using either sequential or simultaneous procedures. Regarding quantitative results, the sequential procedure involving cell washing followed by freeze drying of the washed material and intracellular Se quantification using SC-ICP-MS provided best results. In this case, intracellular Se accounted for 1304 ± 48 mg kg−1 (corresponding to 64% of the certified Se content). The average mass of Se per yeast cell was 41.6 fg Se with a dispersion of 1.6–279 fg Se/cell. In the isolated extracellular Se fraction, the Se concentration accounted for 412 ± 48 mg kg−1 (about 21% of the total Se). Thus, the sequential procedure provided a total Se recovery of about 85% with respect to the certified value. The direct dilution and simultaneous measurement of intra- and extracellular Se by SC-ICP-MS provided results of 1024 ± 42 mg kg−1 for intracellular and 316 ± 30 mg kg−1 for extracellular Se representing a total recovery of about 66%. In both cases, an initial thorough characterization of the cell density per solid weighed material was conducted by flow cytometry and the cell integrity ensured using confocal microscopy. These results clearly demonstrated that with appropriate sample preparation, SC-ICP-MS is a unique tool, which is capable of providing quantitative information about intracellular and extracellular Se. In addition, SELM-1 seems the ideal tool to enable data normalization at the single cell level to replicate, benchmark, and improve new SC-ICP-MS studies by using the same material for data validation.

Recovery of Se, Zr, Pd, and Cs from simulated high‐level radioactive waste glass through phase separation

AbstractIn this study, elemental recovery was performed using phase separation from simulated high‐level radioactive waste (HLW) glass. To cause phase separation, SiO2 and B2O3 were added to the simulated HLW glass and adjusted the ratio of SiO2: B2O3: other oxides to 40:50:10. The phase separated glass was immersed in aqueous solutions of 0–3 mol/L of HNO3, H2SO4, and a 1:1 mixture of HCl–HNO3 at 363 K for 20 h, and the dissolution behavior of 17 elements was examined. The relationship between the dissolved mass fraction of each element and the acid concentration in the immersion liquid could be approximated by the modified sigmoid function. The recovery of stable nuclei Se, Zr, Pd, and Cs instead of long‐lived radioactive nuclei was tested using a four‐stage leaching process in which the sample was immersed sequentially in four aqueous solutions at 363 K of distilled water, HNO3, H2SO4, and a 1:1 mixture of HCl–HNO3 for 20 h. It was confirmed that Se, Zr, Pd, and Cs could be recovered selectively. Furthermore, the recovery result could be predicted based on the individual dissolution results described above.

Optimization of sample preparation of Brazilian honeys for TQ-ICP-MS analysis

Mass spectrometry-based techniques have been used to study the chemical profile of honeys to authenticate entomological, botanical and geographical origins. Sample preparation is a crucial step of the analysis to obtaining reliable data and minimizing interference owing to matrix effects. The present work studied the best sample digestion procedure for elemental analysis of Brazilian honeys from Tetragonisca angustula (Jataí) and Apis mellifera sp (Apis) by triple quadrupole inductively coupled plasma mass spectrometry (TQ-ICP-MS). A central composite design with 2² factorial and 3 center points considering different volumes of HNO3 and H2O2 was investigated. There was no statistically significant influence of the amounts of HNO3 and H2O2 on the recoveries of Ag, Al, As, Ba, Be, Ca, Cd, Ce, Co, Cr, Cs, Cu, K, La, Mg, Mn, Na, Ni, Pb, Rb, Se, Sr, Th, U, V and Zn mass fractions. Machine learning algorithms (Multilayer Perceptron, Random Forest and Support Vector Machine) allowed discriminating entomological origin of honeys based on chemical profile with a classification accuracy of 99%.