Selenite Anions Research Articles

Removal of aqueous selenite anions from wastewater by electrodeposition and recycling used for catalyst of effective water splitting

Transforming toxic selenium in industrial wastewater into selenium resources is a significant challenge to realize the upgrading of valuable element resources and the removal of pollutants. Here, we chose copper, cobalt, and nickel foam as the electrode materials and used electrodeposition to capture selenite from selenium-containing wastewater. The effects of operating voltage, initial concentration, stirring rate and time on the removal efficiency of selenium were investigated. Among them, the removal efficiency of copper foam for 100 mg L−1 selenite could reach 91.2 % at −1.5 V operating voltage. The composition, morphology and structure of the products after electrodeposition were characterized by XPS, FESEM and TEM. The OER and HER properties of the electrodeposited products Cu2Se, CoSe2 and NiSe were evaluated by density functional theory calculations. It was proved that selenium could improve the electron transfer rate, and CoSe2 also had better HER performance than NiSe. The products formed after electrodeposition could be combined for overall water splitting to achieve efficient hydrogen production. This study proved the mechanism and resource utilization process of selenite removal through electrodeposition.

Removal and recycling of aqueous selenite anions using cobalt-based metal–organic-framework coated on multi-walled carbon nanotubes composite membrane

The utilization of selenium as a novel functional material is rapidly expanding, and the retrieval of selenium from waste containing selenium is gaining recognition in the industry. This study prepared a novel composite membrane coated with the cobalt-based metal–organic framework coated on multi-walled carbon nanotubes (Co-MOF@MWCNTs). The MWCNTs served as the skeleton to support the active components of Co-MOF, which enabled efficient removal and resource utilization of liquid selenite (SeO32−). The morphology, structure, and composition of the prepared membrane were characterized using field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc.. Applying a permeate flux of 67.08 L m−2 h−1, the SeO32− removal efficiency of the composite membrane reached up to 92.2%. The composite membrane containing CoSeO4 can be used as an electrocatalytic oxygen evolution catalyst. Density functional theory calculations and electrochemical analysis showed that the conversion from O* to OOH* was a rate-determining step. Under 1.0 M KOH conditions, the lowest overpotential for Co-MOF@MWCNTs-40 at 10 mA cm−2 was 360 mV. In this study, the process of selenium resource utilization and the mechanism of SeO32− removal by Co-MOF@MWCNTs are revealed. It demonstrates that membrane-based sequestration of SeO32− can provide a viable approach for SeO32− removal and utilization in wastewater.

Removal and recycling of selenite anions by iron-doped cobalt-based metal organic frameworks for oxygen evolution reaction

As the main form exists in selenium-containing wastewater, selenite (SeO32-) is often produced by human activities and is exceedingly difficult to be removed from wastewater. In this study, five iron-doped (Fe-doped) cobalt-based metal organic frameworks (Co/Fe-MOF) with different metal ratios were prepared to remove SeO32- anions. The prepared Co/Fe-MOF were confirmed by characterization and their adsorption properties experiments. They have excellent SeO32- removal performance at pH of 3–8 with a maximum adsorption capacity of 283.11 mg g−1 of Co-MOF. After uptaking SeO32- by Co/Fe-MOF, the used Co/Fe-MOF (U-Co/Fe) contains CoSeO4 and Fe2(SeO4)3 and can be used as electrocatalytic oxygen evolution catalysts. Their oxygen/selenium vacancies can reduce the overpotential of the oxygen evolution reaction (OER). In 1.0 M KOH, U-Co0.90Fe0.10 displayed the lowest overpotential 326 mV at 10 mA cm−2. This study reveals the mechanism and resource upgrading process of SeO32- removal by Co/Fe-MOF and demonstrates that a small amount of Fe doping could improve the performance of OER.

Capture and recycling of toxic selenite anions by cobalt-based metal-organic-frameworks for electrocatalytic overall water splitting

A nanosheet-like cobalt-based metal-organic-framework (Co-MOF) is employed to uptake SeO32− anions, and the remove capacity of Co-MOF reaches a record of 280.0 mg g−1. After uptake SeO32− by Co-MOF, the recycling defect-rich CoSeO4 (R-CoSeO4) is used as an electrocatalyst for oxygen evolution reaction (OER), which displays an overpotential of 265 mV at 10 mA cm−2 in 1 M KOH. Furthermore, cobalt-cobalt selenide heterojunction nanoparticle (Co-Co0.85Se), a high-performance hydrogen evolution reaction (HER) electrocatalyst (overpotential of 97 mV at 10 mA cm−2 in 1 M KOH) is obtained by one-step calcining of R-CoSeO4. Series experiments and density functional theory calculations confirm the anion vacancy in R-CoSeO4 and heterojunction in Co-Co0.85Se can improve the OER and HER activity, respectively. Finally, two binder-free electrodes (R-CoSeO4/CC and Co-Co0.85Se/CC) are employed as anode and cathode, respectively, to construct a water electrolysis cell, which only needs 1.47 V to achieve 10 mA cm−2 in 1 M KOH.

Highly efficient sorption of selenate and selenite onto a cationic layered single hydroxide via anion exchange and inner-sphere complexation

• JU-111 is a cationic inorganic material and has exchangeable anions. • JU-111 has high sorption capacity and removal depth towards selenium anions. • Selenium anions can be effectively sorbed through inner-sphere complexation. Selenium is a double-edge sword element with a narrow dosage margin between as a nutrient and toxicant. Seeking efficient sorbents with high performance for reducing high content of selenium in wastewater is still highly desirable. In this work, we report a cationic layered single hydroxide that consists of only Al and O with free exchangeable Cl − in the interlayers with excellent sorption capability of selenate and selenite. The batch experiments including sorption isotherms, kinetics, selectivity, and desorption were systematically investigated. The maximum sorption capacities for selenate and selenite anions reached 164.7 mg Se/g and 190.3 ‍mg Se/g respectively, which represented one of the highest values among the existing inorganic materials. It also showed superior removal depth under simulated environmental conditions in the presence of multiple competing anions (Cl − , NO 3 – , CO 3 2– , SO 4 2− and PO 4 3− ). After close analysis by EXAFS and other characterization techniques, we fully revealed the sorption mechanism and found that the selenate and selenite anions were exchanged with Cl − in the interlayer space firstly and were immobilized onto the surface through inner-sphere complexation, resulting in such superior selenium removal performance.

Layered calcium hydrogen selenite chlorides Ca(HSeO3)Cl and Ca(HSeO3)Cl(H2O), the first halides obtained in СaCl2–H2SeO3–H2O system

Abstract Synthesis, crystal structures and IR spectra of the first representatives of calcium hydrogen selenite halides are reported. Colourless prismatic crystals of calcium hydrogen selenite chloride Ca(HSeO3)Cl and corresponding hydrated analogue Ca(HSeO3)Cl(H2O) were produced upon evaporation of aqueous solutions. Ca(HSeO3)Cl is monoclinic, P21/c, a = 7.0031(11) Å, b = 7.7336(12) Å, c = 8.5024(13) Å, β = 109.889(3)°, V = 433.02(12) Å3, R 1 = 0.039. Ca(HSeO3)Cl(H2O) is orthorhombic, Pbca, a = 6.222(4) Å, b = 10.413(7) Å, c = 16.875(10) Å, V = 1093.3 (12) Å3, R 1 = 0.041. Ca(HSeO3)Cl and Ca(HSeO3)Cl(H2O) represent new structure types. In both structures, Ca2+ cations adopt mixed-ligand environments formed by oxygen atoms of hydrogen selenite anions (and water molecules for Ca(HSeO3)Cl(H2O)) and chloride ions. Both structures are layered. The crystal structure of Ca(HSeO3)Cl(H2O) demonstrates a rare phenomenon of hydrogen-bonded assembly of water and chloride in the interlayer space.

Selective Capture of Toxic Selenite Anions by Bismuth‐based Metal–Organic Frameworks

AbstractChemically durable and effective absorbent materials for selenite (SeO32−) remain highly desirable for contamination remediation. Now a bismuth‐based metal–organic framework (Bi‐MOF, CAU‐17) was used as adsorbent to capture SeO32− anions from aqueous solution with ultrahigh adsorption capacity of 255.3 mg g−1 and fast kinetics. Furthermore, the adsorbent showed excellent selectivity for SeO32− and was able to work steadily in a broad pH range of 4–11. Density functional theory (DFT) calculation, XANES modeling, and EXAFS fitting suggested that SeO32− anions were immobilized by forming Bi−O−Se bonds (T‐3 structural model) though splitting the O−Bi−O bond in the crystal structure, leading to a structural transformation of CAU‐17 in the solid state.

Selective Capture of Toxic Selenite Anions by Bismuth‐based Metal–Organic Frameworks

Chemically durable and effective absorbent materials for selenite (SeO32- ) remain highly desirable for contamination remediation. Now a bismuth-based metal-organic framework (Bi-MOF, CAU-17) was used as adsorbent to capture SeO32- anions from aqueous solution with ultrahigh adsorption capacity of 255.3 mg g-1 and fast kinetics. Furthermore, the adsorbent showed excellent selectivity for SeO32- and was able to work steadily in a broad pH range of 4-11. Density functional theory (DFT) calculation, XANES modeling, and EXAFS fitting suggested that SeO32- anions were immobilized by forming Bi-O-Se bonds (T-3 structural model) though splitting the O-Bi-O bond in the crystal structure, leading to a structural transformation of CAU-17 in the solid state.

Structural motifs in heteroleptic copper and cadmium selenites

Cu(II) cations in the presence of diamine ligands such as tetramethylethylendiamine (TMEDA) react with Na2SeO3 to produce the heteroleptic selenite copper compound of formula [Cu3(TMEDA)3(SeO3)2(H2O)4](NO3)2. In the cationic moiety two copper atoms are linked by two selenite anions through the O–Se–O bridge. One of the two bridging selenite anion coordinates to a third copper atom through the third oxygen atom. Reaction of Cd(CH3COO)2·2H2O with Na2SeO3 in the presence of ligand with softer character such as thiourea [(NH2)2CS; tu] or selenourea [(NH2)2CSe; tu] in aqueous solution afforded the complex [{Cd(tu)2SeO3}2], whose structure has been elucidated by X-ray diffraction analysis. It is the first reported example of a molecular cadmium selenite complex. Two cadmium cations stabilized by the coordination of four ancillary thiourea soft ligands, are linked together by two bridging selenite ions through O and O–Se–O bridges. A comparison between the coordination mode of the selenite ion in those cadmium and copper complexes and in inorganic extended CdSeO3 and hydrated CuSeO3 phases is also reported.

Substitutional Disorder of SeO32-/IO3- in the Crystalline Solid Matrix: Insights into the Fate of Radionuclides 79Se and 129I in the Environment.

As the crucial soluble species of long-lived radionuclides 129I and 79Se, iodate and selenite anions commonly share similar geometry of the trigonal pyramid XO3 (X = I, Se) but in different valence states. Although large amounts of investigations have been performed aiming at understanding the environmental behavior of these two anions individually, studies on cases when they coexist are extremely scarce. Structurally well-characterized natural/synthetic crystalline solids simultaneously incorporating these two anions as potential solubility-limiting products at the nuclear waste geological depository remain elusive. We report here a crystalline solid Th(IO3)2(SeO3) representing the first example of aliovalent substitution between IO3- and SeO32- sharing the same structural site, as demonstrated by single crystal X-ray diffraction, laser-ablation inductively coupled plasma mass spectrometry analysis, and spectroscopic techniques including infrared, Raman, and X-ray absorption spectroscopies. Sequentially, in the Eu(IO3)3 solid matrix, we demonstrated that the IO3- site can be sufficiently substituted by SeO32- in the presence of Th4+ via simultaneous incorporation of Th4+ and SeO32- in a charge-balancing mechanism. The obtained results provide insights into the environmental behavior of fission products 79Se and 129I: they may cocrystallize in one solid matrix and may be efficiently immobilized by incorporation into each other's solid phase through solid solution.

Synthesis and characterization of Hf(SO4)2(H2O)4 and Hf(SeO3)(SeO4)(H2O)4

Using hydrothermal synthesis, Hf(SO4)2(H2O)4 and Hf(SeO3)(SeO4)(H2O)4 were obtained and characterized by X-ray, IR spectroscopy and thermo-gravimetric analysis. The experimental data from the IR spectra of the compounds showed characteristic absorption bands for the sulfate, selenite and selenate anions. The dehydration of the two complexes proceeded in two stages in which three and one water molecules were released, respectively. The decomposition up to 850 °C did not give HfO2, but lead to formation of intermediate phases Hf2O3(SO4) and Hf2O3(SeO3). The decomposition of the mixed valence selenite-selenate proceeds by two mechanisms, the first one resulting in the formation of intermediate HfO(SeO3) and the second one—its decomposition and formation of dihafnyl selenite Hf2O3(SeO3). The activation energy and the pre-exponential factor in the Arrhenius equations were determined for each process of dehydration and decomposition. These values were quite high for the decomposition of HfO(SeO3) due to the very strong bonds between the HfO2+ and SeO32− ions.

Explorations of New SHG Materials in the Alkali-Metal-Nb(5+)-Selenite System.

Standard high-temperature solid-state reactions of NaCl, Nb2O5, and SeO2 resulted in two new sodium selenites containing a second-order Jahn-Teller (SOJT) distorted Nb(5+) cation, namely, Na2Nb4O7(SeO3)4 (P1̅; 1) and NaNbO(SeO3)2 (Cmc21; 2). Compound 1 exhibits an unusual 3D [Nb4O7(SeO3)4](2-) anionic network composed of 2D [Nb4O11(SeO3)2](6-) layers which are further bridged by additional SeO3(2-) anions via corner sharing; the 2D [Nb4O11(SeO3)2](6-) layer is formed by unusual quadruple [Nb4O17](14-) niobium oxide chains of corner-sharing NbO6 octahedra being further interconnected by selenite anions via Nb-O-Se bridges. The polar compound 2 features a 1D [NbO(SeO3)2](-) anionic chain in which two neighboring Nb(5+) cations are bridged by one oxo and two selenite anions. The alignments of the polarizations from the NbO6 octahedra in 2 led to a strong SHG response of ∼7.8 × KDP (∼360 × α-SiO2), which is the largest among all phases found in metal-Nb(5+)-Se(4+)/metal-Nb(5+)-Te(4+)-O systems. Furthermore, the material is also type I phase matchable. The above experimental results are consistent with those based on DFT theoretical calculations. Thermal stabilities and optical properties for both compounds are also reported.

Nanomembrane Canister Architectures for the Visualization and Filtration of Oxyanion Toxins with One-Step Processing.

Nanomembrane canister-like architectures were fabricated by using hexagonal mesocylinder-shaped aluminosilica nanotubes (MNTs)-porous anodic alumina (PAA) hybrid nanochannels. The engineering pattern of the MNTs inside a 60 μm-long membrane channel enabled the creation of unique canister-like channel necks and cavities. The open-tubular canister architecture design provides controllable, reproducible, and one-step processing patterns of visual detection and rejection/permeation of oxyanion toxins such as selenite (SeO3(2-)) in aquatic environments (i.e., in ground and river water sources) in the Ibaraki Prefecture of Japan. The decoration of organic ligand moieties such as omega chrome black blue (OCG) into inorganic Al2O3@tubular SiO2/Al2O3 canister membrane channel cavities led to the fabrication of an optical nanomembrane sensor (ONS). The OCG ligand was not leached from the canister as observed in washing, sensing, and recovery assays of selenite anions in solution, which enabled its multiple reuse. The ONS makes a variety of alternate processing analyses of selective quantification, visual detection, rejection/permeation, and recovery of toxic selenite quick and simple without using complex instrumentation. Under optimal conditions, the ONS canister exhibited a high selectivity toward selenite anions relative to other ions and a low-level detection limit of 0.0093 μM. Real analytical data showed that approximately 96% of SeO3(2-) anions can be recovered from aquatic and wastewater samples. The ONS canister holds potential for field recovery applications of toxic selenite anions from water.

High efficiency adsorption and removal of selenate and selenite from water using metal-organic frameworks.

A series of zirconium-based, metal-organic frameworks (MOFs) were tested for their ability to adsorb and remove selenate and selenite anions from aqueous solutions. MOFs were tested for adsorption capacity and uptake time at different concentrations. NU-1000 was shown to have the highest adsorption capacity, and fastest uptake rates for both selenate and selenite, of all zirconium-based MOFs studied here. Herein, the mechanism of selenate and selenite adsorption on NU-1000 is explored to determine the important features that make NU-1000 a superior adsorbent for this application.

Fe(Ⅲ)로 표면처리된 메조포러스 실리카에 의한 셀렌(Se), 비소(As), 불소(F) 인(P) 제거에 관한 연구

Fe(Ⅲ)로 표면처리된 메조포러스 실리카에 의한 셀렌(Se), 비소(As), 불소(F) 인(P) 제거에 관한 연구

Chemical and structural evolution in the Th-SeO3(2-)/SeO4(2-) system: from simple selenites to cluster-based selenate compounds.

While extensive success has been gained in the structural chemistry of the U-Se system, the synthesis and characterization of Th-based Se structures are widely unexplored. Here, four new Th-Se compounds, α-Th(SeO3)2, β-Th(SeO3)2, Th(Se2O5)2, and Th3O2(OH)2(SeO4)3, have been obtained from mild hydrothermal or low-temperature (180-220 °C) flux conditions and were subsequently structurally and spectroscopically characterized. The crystal structures of α-Th(SeO3)2 and β-Th(SeO3)2 are based on ThO8 and SeO3 polyhedra, respectively, featuring a three-dimensional (3D) network with selenite anions filling in the Th channels along the a axis. Th(Se2O5)2 is a 3D framework composed of isolated ThO8 polyhedra interconnected by [Se2O5](2-) dimers. Th3O2(OH)2(SeO4)3 is also a 3D framework constructed by octahedral hexathorium clusters [Th6(μ3-O)4(μ3-OH)4](12+), which are interlinked by selenate groups SeO4(2-). The positions of the vibrational modes associated with both Se(IV)O3(2-) and Se(VI)O4(2-) units, respectively, were determined for four compounds, and the Raman spectra of α- and β-Th(SeO3)2 are compared and discussed in detail.

Synthesis of Selenium Nanoparticles by Bacillus laterosporus Using Gamma Radiation

Aim: This study shows the possible synthesis of Selenium Nanoparticles (SeNPs) in aerobic optimized conditions using Bacillus laterosporus (B. laterosporus) bacterial strain.Methodology: B. laterosporus was used to reduce selenium ions (selenite anions) to SeNPs by fermentation in Luria-Bertani Enrichment (EM) medium. Optimization of fermentation conditions using two-level full factorial design was performed. SeNPs were further characterized by UV-Vis., DLS, TEM, FT-IR, EDX and XRD analysis. SeNPs synthesis by Gamma irradiated B. laterosporus cells at different radiation doses was reported. Evaluation the probability of B. laterosporus to synthesis SeNPs by fermentation in skimmed milk aerobically. A microtiterplate assay was used to evaluate the ability of SeNPs to inhibit the biofilm formation of Pseudomonas aeruginosa. Evaluating the antimicrobial activity of some antibiotic agents upon addition of SeNPs was performed.Results: B. laterosporus reduced the soluble, toxic, colorless selenium ions to the insoluble, non-toxic, red elemental SeNPs. Statistical analysis showed that the results were normally distributed. Temperature, incubation period and pH were significant factors in the fermentation process, in which the maximum SeNPs produced (8.37µmole/ml) was at temperature 37oC, incubation period 48hr, pH7. The Gamma radiation exposure dose 1.5kGy gave the maximum SeNPs produced (10.01 µmole/ml). A pink color appear in the fermented milk revealing the formation of SeNPs-enriched milk. SeNPs inhibit the biofilm formation of Pseudomonas aeruginosa with a percentage reduction of 99.7%. SeNPs increase the antibacterial activity of fucidic acid by 13.6% and 28.5% against Escherichia coli and Staphylococcus aureus respectively. But with Gentamycin sulphate, no change in the antibacterial activity.Conclusion: SeNPs can be synthesized aerobically by the probiotic B. laterosporus bacterial strain. SeNPs can be incorporated in nutraceuticals and functional foods like milk also can be used to inhibit the bacterial biofilm formation and can be added to some antibacterial creams to enhance their antimicrobial activity.

Assembly of Thiometalate‐Based {Mo16} and {Mo36} Composite Clusters Combining [Mo2O2S2]2+ Cations and Selenite Anions

A new family of thiometalate-based composite molecular materials is synthesized and characterized. 1.6 and 1.9 nm-sized clusters are observed in the gas phase utilizing high-resolution ESI-MS. The diversity of the selenite anions as an inorganic ligand is demonstrated by the isolation of the highest nuclearity selenium-based oxothiometalate materials reported so far. The observed proton conductivity of the selenite based oxothiometalate species renders them as promising alternative materials for fuel-cell applications.

Controlling the Self‐Assembly of a Mixed‐Metal Mo/V–Selenite Family of Polyoxometalates

Five mixed-metal mixed-valence Mo/V polyoxoanions, templated by the pyramidal SeO(3)(2-) heteroanion have been isolated: K(10)[Mo(VI)(12)V(V)(10)O(58)(SeO(3))(8)]⋅18 H(2)O (1), K(7)[Mo(VI)(11)V(V)(5)V(IV)(2)O(52)(SeO(3))]⋅31 H(2)O (2), (NH(4))(7)K(3)[Mo(VI)(11)V(V)(5)V(IV)(2)O(52)(SeO(3))(Mo(V)(6)V(V)-O(22))]⋅40 H(2)O (3), (NH(4))(19)K(3)[Mo(VI)(20)V(V)(12)V(IV)(4)O(99)(SeO(3))(10)]⋅36 H(2)O (4) and [Na(3)(H(2)O)(5){Mo(18-x)V(x)O(52)(SeO(3))} {Mo(9-y)V(y)O(24)(SeO(3))(4)}] (5). All five compounds were characterised by single-crystal X-ray structure analysis, TGA, UV/Vis and FT-IR spectroscopy, redox titrations, and elemental and flame atomic absorption spectroscopy (FAAS) analysis. X-ray studies revealed two novel coordination modes for the selenite anion in compounds 1 and 4 showing η,μ and μ,μ coordination motifs. Compounds 1 and 2 were characterised in solution by using high-resolution ESI-MS. The ESI-MS spectra of these compounds revealed characteristic patterns showing distribution envelopes corresponding to 2- and 3- anionic charge states. Also, the isolation of these compounds shows that it may be possible to direct the self-assembly process of the mixed-metal systems by controlling the interplay between the cation "shrink-wrapping" effect, the non-conventional geometry of the selenite anion and fine adjustment of the experimental variables. Also a detailed IR spectroscopic analysis unveiled a simple way to identify the type of coordination mode of the selenite anions present in POM-based architectures.

New BaM2(SeO3)3·nH2O (M = Co, Ni, Mn, Mg; n ≈ 3) Zemannite‐Type Frameworks: Single‐Crystal Structures of BaCo2(SeO3)3·3H2O, BaMn2(SeO3)3·3H2O and BaMg2(SeO3)3·3H2O

AbstractThe syntheses and characterisation of a new family of isostructural mixed‐metal selenites based on the zemannite‐type framework are described. These BaM2(SeO3)3·3H2O phases are built up from three‐dimensional networks of MO6 (M = Co, Ni, Mn, Mg) octahedra and SeO3 pyramids. The octahedral groups form isolated M2O9 face‐sharing pairs, which are linked by the selenite anions into a three‐dimensional anionic framework. The framework encapsulates one‐dimensional 12‐ring channels occupied by the barium cations and water molecules. There are two types of channels: in one, the cations and water molecules are well ordered, and the channels are fully occupied; in the other, the same species are disordered, and the channels are partially occupied. There is little if any evidence of zeolitic reversible de/rehydration and cation ion‐exchange behaviour for these materials.