Release Of Se Research Articles

Calcium Phosphate Loaded with Curcumin Prodrug and Selenium Is Bifunctional in Osteosarcoma Treatments

Although SeO32− ions have been loaded onto calcium phosphate to treat a wide range of cancers, the quest to promote bone tissue regeneration is still ongoing. Curcumin (cur), an herbal extraction, can selectively inhibit tumor cells and promote osteogenesis. In this study, SeO32− ions were co-precipitated in biomimetic calcium phosphate (Se@BioCaP), and modified curcumin prodrug (mcur) was adsorbed on diverse Se@BioCaP surfaces (mcur-Se@BioCaP-Ads). Co-precipitation yielded Se@BioCaP with a significantly higher Se content and exhibited a tailorable micro-/nanostructure. The favorable pH-responsive release of Se and mcur from mcur-Se@BioCaP-Ads showed a synergistic anticancer efficiency in OS cells, enhancing OS cell inhibition more than a single dose of them, which might be associated with ROS production in OS cells. In addition, increased alkaline phosphatase activity and calcium nodule formation in MC3T3-E1 pre-osteoblasts were also verified. These results suggest this novel mcur-Se@BioCaP-Ads has promising and widespread potential in OS treatments.

Mesoporous Biosilica Beads for Controlled Selenium Nanoparticle Delivery from Collagen‐Chitosan Scaffolds: Promoting Bone Formation and Suppressing Prostate Cancer Growth

The controlled delivery of selenium nanoparticles (Se‐NPs) is promising for bone cancer treatment due to their dual benefits in bone regeneration and tumor inhibition, yet achieving an optimal dosing regimen remains challenging. Natural mesoporous biosilica (BS) beads have shown promise for drug delivery due to their microporous structure. This study explores incorporating BS beads into collagen‐chitosan (Coll‐CS) scaffolds, known for bone repair, to control Se‐NP delivery. Two approaches are compared: loading Se‐NPs into BS beads before integrating them into Coll‐CS scaffolds versus directly loading Se‐NPs into Coll‐CS scaffolds. The scaffold properties, Se release kinetics, cytocompatibility, and effects on mesenchymal stem cells (MSCs) and prostate cancer cells (LNCaP) are evaluated. BS bead‐loaded scaffolds provide controlled Se‐NP release and enhanced mechanical properties compared to directly loaded scaffolds. Higher Se‐NP concentrations in BS‐loaded scaffolds effectively promote MSC osteogenic differentiation and mineralisation while inhibiting LNCaP cell viability. In contrast, low Se‐NP concentrations not only induce early osteogenic differentiation but also promote cancer cell proliferation, underscoring the need for optimal Se‐NP concentration and release. These findings suggest that BS bead‐loaded Coll‐CS scaffolds are a promising strategy for controlled Se‐NP delivery, addressing the dual challenges of bone formation and cancer recurrence prevention in bone cancer treatment.

Se-incorporated polycaprolactone spherical polyhedron enhanced vitamin B2 loading and prolonged release for potential application in proliferative skin disorders

Development of novel drug vehicles for vitamin B2 (VitB2) delivery is very important for designing controllable release system to improve epidermal growth and bone metabolism. In this work, selenium (Se)-incorporated polycaprolactone (PCL) spherical polyhedrons are successfully synthesized via a single emulsion solvent evaporation method which is utilized to load VitB2 to fabricate cell-responsive Se-PCL@VitB2 delivery systems. Their physicochemical properties are characterized by DLS, SEM, XRD, FTIR, and TGA-DSC. The release kinetics of VitB2 or Se from the samples are investigated in PBS solution (pH = 2.0, 5.0, 7.4, 8.0 and 12.0). The cytocompatibilities are also evaluated with normal BMSC and epidermal HaCat cells. Results exhibit that Se-PCL@VitB2 particles presents spherical polyhedral morphology (approximately (3.25 ± 0.46) μm), negative surface charge (-(54.03 ± 2.94) mV), reduced crystallinity and good degradability. Stability experiments imply that both VitB2 and Se might be uniformly dispersed in PCL matrix. And the incorporation of Se facilely promotes the loading of VitB2. The encapsulation efficiency and loading capacity are (98.42 ± 1.06)% and (76.25 ± 1.27) for Se-PCL@VitB2 sample. Importantly, it exhibits more prolonged release of both VitB2 and Se in neutral PBS solution (pH = 7.4) than other pH conditions. Presumably, the electrostatic interaction between Se, VitB2 and PCL contribute to its release mode. Cell experiments show that Se-PCL@VitB2 presents strong cytotoxicity to HaCat cells mainly due to the cytotoxic effect of Se anions and PCL degradation products. However, it exhibits weak inhibitory effect on BMSC cells. These note that the synthesized Se-PCL@VitB2 particles can be promising drug vehicles for potential application in epidermal proliferative disorders.

From leaching data to release estimates: Screening and scenario assessments of electric arc furnace (EAF) slag under unencapsulated use

Electric arc furnace (EAF) slag is the non-metallic byproduct of the primary U.S. steelmaking process. Much of the slag is marked for secondary uses as aggregates. EAF slags used as construction fill or residential groundcover are directly exposed to the environment, raising concerns of potential leaching impacts. Leaching data of EAF slags as function of eluate pH (Method 1313) and liquid-to-solid ratio (Method 1314) were used to refine an initial list of constituents of potential concern to those with potential to leach at concentrations greater than project thresholds, and to estimate release from EAF slags when used as unencapsulated groundcover. Screening assessment identified 11 of over 20 constituents requiring further assessment. Scenario-based assessments results showed that constituents with high available content and low leaching concentrations (Al, Cr, Co, Mn, Se) are persistent in contacting water over the assessment period while those with limited available content (As, Ba, Mo, V) were depleted. Aging decreased the release of Se while increasing Tl release, likely through a combination of hydration, carbonation, and cracking processes. Increasing fill depth and infiltration rates did not alter leaching concentrations; however, liquid-solid ratio for each assessment interval changed thereby impacting cumulative release.

Porous Se@SiO2 nanospheres alleviate diabetic retinopathy by inhibiting excess lipid peroxidation and inflammation

BackgroundLipid peroxidation is a characteristic metabolic manifestation of diabetic retinopathy (DR) that causes inflammation, eventually leading to severe retinal vascular abnormalities. Selenium (Se) can directly or indirectly scavenge intracellular free radicals. Due to the narrow distinction between Se’s effective and toxic doses, porous Se@SiO2 nanospheres have been developed to control the release of Se. They exert strong antioxidant and anti-inflammatory effects.MethodsThe effect of anti-lipid peroxidation and anti-inflammatory effects of porous Se@SiO2 nanospheres on diabetic mice were assessed by detecting the level of Malondialdehyde (MDA), glutathione peroxidase 4 (GPX4), decreased reduced/oxidized glutathione (GSH/GSSG) ratio, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL) -1β of the retina. To further examine the protective effect of porous Se@SiO2 nanospheres on the retinal vasculopathy of diabetic mice, retinal acellular capillary, the expression of tight junction proteins, and blood–retinal barrier destruction was observed. Finally, we validated the GPX4 as the target of porous Se@SiO2 nanospheres via decreased expression of GPX4 and detected the level of MDA, GSH/GSSG, TNF-α, IFN-γ, IL -1β, wound healing assay, and tube formation in high glucose (HG) cultured Human retinal microvascular endothelial cells (HRMECs).ResultsThe porous Se@SiO2 nanospheres reduced the level of MDA, TNF-α, IFN-γ, and IL -1β, while increasing the level of GPX4 and GSH/GSSG in diabetic mice. Therefore, porous Se@SiO2 nanospheres reduced the number of retinal acellular capillaries, depletion of tight junction proteins, and vascular leakage in diabetic mice. Further, we identified GPX4 as the target of porous Se@SiO2 nanospheres as GPX4 inhibition reduced the repression effect of anti-lipid peroxidation, anti-inflammatory, and protective effects of endothelial cell dysfunction of porous Se@SiO2 nanospheres in HG-cultured HRMECs.ConclusionPorous Se@SiO2 nanospheres effectively attenuated retinal vasculopathy in diabetic mice via inhibiting excess lipid peroxidation and inflammation by target GPX4, suggesting their potential as therapeutic agents for DR.

Lowered oral bioaccessibility of cadmium and selenium and associated health risk by co-digestion of rice and vegetables

Since foods are not ingested individually, co-digestion, in accordance with human daily diet conditions, should be stressed when assessing elements bioaccessibility and associated health risks. The oral bioaccessibility of cadmium (Cd) and selenium (Se) in 11 types of crops (rice, maize, pakchoi, eggplant, red pepper, towel gourd, kidney bean, soybean, cowpea, sweet potato, and taro) were determined, and the effects of co-digestion of 7 types of rice and vegetables on the bioaccessibility of Cd and Se were evaluated and validated with in vitro PBET method. The underlying mechanism was revealed by observing the surface morphological characteristics of digested substrates, and the exposure risk of Cd and Se were assessed. The results showed that the average bioaccessibility of Cd and Se in 11 types of crops varied from 58.7 % to 39.1 % and 48.4 % to 62.6 % from the gastric phase (GP) to the intestinal phase (IP). Interestingly, co-digestion of rice and vegetables reduced the bioaccessibility of Cd and Se to varying degrees compared to theoretical values. Great reduction in the bioaccessibility of Cd and Se in the GP (16.9–36.4 % and 9.9–23.2 %) than that in the IP (0.2–6.62 % and 0.23–12.3 %) were detected, which was attributed to the rice–vegetable aggregates formed during co-digestion. Rice–vegetable aggregates inhibited the release of Cd and Se, which was more pronounced in the GP than in the IP. Consequently, co-digestion of rice and vegetables reduced the oral exposure to Cd by 35.8 % and to Se by 19.6 %. The areas with higher non-carcinogenic risk of Cd and Se in the study region were reduced by 17 % and 10 %, respectively. Therefore, the role of co-digestion in assessing Cd and Se bioaccessibility and associated health risk cannot be neglected. This study has significant implications for investigating elements bioaccessibility and optimizing associated health risk assessment from a novel perspective.

Irrigation leads to new Se-toxicity paddy fields in and around typical Se-toxicity area

Although the issue has been of much concern and has subsequently been controlled for years, the environmental risk of excess selenium (Se) in farmlands still has not been eliminated in Se-toxicity areas. Different types of farmland utilization can change Se behavior in soil. Thus, located field monitoring and surveys of various farmland soils in and around typical Se-toxicity areas spanning eight years were conducted in the tillage layer and deeper soils. The source of new Se contamination in farmlands was traced along the irrigation and natural waterway. This research indicated that 22 % of paddy fields increased to Se-toxicity in surface soil led by irrigation with high-Se river water. Selenate is the dominant Se species in rivers (90 %) originating from geological background areas with high Se. Both soil organic matter (SOM) and amorphous iron content played important roles in the fixation of input Se. Thus, available Se was increased by more than twofold in paddy fields. The release of residual Se and eventual bounding by organic matter is commonly observed, thus suggesting that stable soil Se availability seems sustainable for a long time. This study is the first report in China that shows how new soil Se-toxicity farmland is caused by high-Se water irrigation. This research warns that external attention should be paid to the selection of irrigation water in high-Se geological background areas to avoid new Se contamination.

Selenium/sulfur-modified montmorillonite materials mitigate mercury pollution in farmland

Selenium (Se) amendment could reduce mercury (Hg) bioaccumulation in crops, but sometimes it could cause excessive Se accumulation in crops and potential Se exposure risks for humans. In this study, we designed and synthesized selenium and sulfur-modified montmorillonite materials (Se/S-Mont) to effectively reduce mercury levels and avoid excessive Se enrichment in plants. The results of pot experiments (1 g Se/S-Mont/100 g soil) and field microplot trials (0.3 g Se/S-Mont/100 g soil, 8 t/ha) showed that Se/S-Mont amendments significantly reduced the Hg concentrations in water spinach and hybrid Pennisetum by 28–68% and 57%–92% (P < 0.05), respectively, while they did not lead to excessive Se bioaccumulation in the plants. Se/S-Mont was more efficient in mitigating soil Hg pollution than adding raw materials (e.g., NaSeO₃) and their combinations, and they significantly reduced the available Se fraction in the soil and the Se levels in the plants (P < 0.05). The potential mechanisms revealed by X-ray absorption near-edge spectra (XANES) and pot experiments were the adsorption and slow release of Hg, S, and Se by Se/S-Mont, the high affinity between Hg and Se, competition between Se and S, and the formation of stable complexes containing Se–S–Hg. The Se/S-Mont immobilizer was easy to prepare and required the application of small amounts, and the remediation effect was relatively stable and exhibited few negative effects; therefore, the approach showed high environmental and economic potentials.

Loss of Selenium from Mollisol Paddy Wetlands of Cold Regions: Insights from Flow-through Reactor Experiments and Process-Based Modeling

Mollisols are critical agricultural resources for securing global food supply. Due to its health importance, selenium (Se) fate in the Mollisols attracts growing concerns. Land use change from conventional drylands to paddy wetlands impacts Se bioavailability in the vulnerable Mollisol agroecosystems. The underlying processes and mechanisms however remain elusive. Here, results of flow-through reactor experiments with paddy Mollisols from northern cold-region sites indicate that continuous flooding with surface water for 48 d induced redox zonation that facilitated the loss of Mollisol Se by up to 51%. Further process-based biogeochemical modeling suggests largest degradation rates of dissolved organic matter (DOM) in 30 cm deep Mollisols that contained the highest-level labile DOM and organic-bound Se. Electron shunting from degradation of Se-bearing DOM coupled to reductive dissolution of Se-adsorbed Fe oxides accounts mainly for Se(IV) release into the pore water. Consequent changes in DOM molecular composition make the reservoir of organic-bound Se vulnerable to flooding-induced redox zonation and likely enhance Se loss through destruction of thiolated Se and emission of gaseous Se from the Mollisol layer. This study highlights a neglected scenario where the speciation-driven loss of bioavailable Se from the paddy wetlands can be a significant consequence in the cold-region Mollisol agroecosystems.

The effect of wastewater components and operation conditions on selenium release during desulfurization wastewater evaporation: A lab-scale study

Rotary atomization evaporation technology is one of the effective technologies to achieve zero discharge of desulfurization wastewater. However, the migration and transformation mechanism of selenium during desulfurization wastewater evaporation is still unknown, hindering this technology's further application. Therefore, the effects of evaporation temperature, pH, Cl−, S2O2–8, SO2–4and Ca2+ on selenium release during evaporation were investigated in this work. The results showed that elevated temperature promoted the release of selenium, especially in the solid-phase pyrolysis stage. pH affected the release of selenium through influencing its initial species, and the release rate of Se(IV) increased with decreasing pH. The ionic compositions of the solution were also found to be a critical factor in the stability of selenium species during evaporation. Cl− would promote the release of Se(IV), while SO2–4 inhibited the release of selenium species, and Ca2+ had little effect on the final release rate of selenium species release. In addition, it was found that the presence of S2O2–8 would significantly enhance the conversion of Se(IV) to Se(VI) during the evaporation process. The results obtained in this work provided guidelines and suggestions for controlling the selenium release from desulfurization wastewater in power plants.

The fate of selenium in the desulfurization wastewater evaporation process: Migration mechanisms and risk analysis

Owing to the implementation of the zero wastewater discharge policy in China, stricter supervision and technical requirements have been imposed. Hot flue gas evaporation technology exhibits significant advantages in desulfurization wastewater treatment. However, volatile constituents (such as selenium, Se) present in wastewater may be released, thus disrupting the power plant's original Se balance. In this study, the evaporation of three desulfurization wastewater plants is performed. The release of Se mainly begins from the threshold at which wastewater is evaporated to dryness, and Se release rates of 21.5, 25.1, and 35.6% are detected. Furthermore, the key components and properties of wastewater for Se migration are identified through experiments and density functional theory calculations. Lower pH values and Cl− contents are not conducive to Se stability, and this tendency is more pronounced in selenite. The suspended solid content temporarily traps the Se in the initial evaporation process, as confirmed via a decrease in the Se release rate and a high binding energy (−307.7 kJ/mol). Moreover, results of risk assessment reveal that wastewater evaporation results in a negligible increase in Se concentration. This study evaluates the risk of Se release during wastewater evaporation and provides a basis for Se emission control strategies.

Pivotal biological processes and proteins for selenite reduction and methylation in Ganoderma lucidum.

Microbial transformations, especially the reduction and methylation of Se oxyanion, have gained significance in recent years as effective detoxification methods. Ganoderma lucidum is a typical Se enrichment resource that can reduce selenite to elemental Se and volatile Se metabolites under high selenite conditions. However, the detailed biological processes and reduction mechanisms are unclear. In this study, G. lucidum reduced selenite to elemental Se and further aggregated it into Se nanoparticles with a diameter of <200nm, simultaneously accompanied by the production of pungent, odorous, and volatile methyl-selenium metabolites. Tandem mass tag-based quantitative proteomic analysis revealed thioredoxin 1, thioredoxin reductase (NADPH), glutathione reductase, 5-methyltetrahydropteroyltriglutamate-homocysteine methyltransferase, and cystathionine gamma-lyase as proteins involved in selenite reduction and methylation. Furthermore, the high expression of proteins associated with cell structures that prompted cell lysis may have facilitated Se release. The upregulation of proteins involved in the defense reactions was also detected, reflecting their roles in the self-defense mechanism. This study provides novel insights into the vital role of G. lucidum in mediating Se transformation in the biogeochemical Se cycle and contributes to the application of fungi in Se bioremediation.

Co-modified 3D printed β-tricalcium phosphate with magnesium and selenium promotes bone defect regeneration in ovariectomized rat

Magnesium (Mg) and Selenium (Se) are essential elements for bone health and have been studied extensively for its powerful osteogenesis and promoting bone regeneration. The purpose was to observe whether Co-modified 3D-printed β-tricalcium phosphate with Mg and Se could promote bone defect regeneration in an ovariectomized(OVX) rat model. The MC3T3-E1 cells were co-cultured with the leachate of β-TCP, Mg-TCP, and Mg/Se-TCP and induced to osteogenesis, and the cell viability, ROS, and osteogenic activity were observed by Cell Count Kit-8(CCK-8), fluorescent probe 2′, 7′-dichlorofluorescin diacetate, Alkaline phosphatase (ALP) staining, Alizarin Red(RES) staining, western blotting(WB), and immunofluorescence. Then the β-TCP, Mg-TCP, and Mg/Se-TCP were implanted into the femoral epiphysis bone defect model of OVX rats for 12 weeks. Micro-CT and histology analysis were used to observe the therapeutic effect. In vitro results show that the cell mineralization and osteogenic activity of the Mg/Se-TCP group is significantly higher than the β-TCP group and Mg-TCP group. Protein expressions such as FOxO1, SIRT1, SOD2, Runx-2, Cola1a, and OC of the Mg/Se-TCP group are significantly higher than the Con group and the β-TCP group. The results of intracellular ROS and SIRT1 and SOD2 immunofluorescence showed that Mg/Se-TCP can restore the oxidative stress balance of osteoblasts. Micro-CT and histology analysis showed that treatment with Mg/Se-TCP showed the largest amount of bone tissue in the defect area (p < 0.05), and exhibited lower values of residual biological material (p < 0.05), compared to that of the β-TCP group and Mg-TCP group. Our research results confirm that Mg/Se-TCP can improve the activity and function of osteoblasts and enhance bone regeneration mediated by reducing intracellular ROS in OVX rat models.Graphical The release of Mg and Se during the degradation of Mg/Se-TCP can improve the local bone repair ability. At the same time, it can also inhibit cell ROS, and ultimately greatly promote local bone repair.

Selenium-incorporated mesoporous silica nanoparticles for osteosarcoma therapy.

Selenium (Se) compounds are promising chemotherapeutics due to their ability to inhibit cancer cell activity via the generation of reactive oxygen species (ROS). However, to circumvent adverse effects on bone healthy cells, new methods are needed to allow intracellular Se delivery. Mesoporous silica nanoparticles (MSNs) are promising carriers for therapeutic ion delivery due to their biocompability, rapid uptake via endocytosis, and ability to efficiently incorporate ions within their tunable structure. With the aim of selectively inhibiting cancer cells, here we developed three types of MSNs and investigated their ability to deliver Se. Specifically, MSNs containing SeO32- loaded on the surface and in the pores (MSN-SeL), SeO32- doped in the silica matrix (Se-MSNs) and Se nanoparticles (SeNP) coated with mesoporous silica (SeNP-MSNs), were successfully synthesized. All synthesized nanoparticles were stable in neutral conditions but showed rapid Se release in the presence of glutathione (GSH) and nicotinamide adenine dinucleotide phosphate (NADPH). Furthermore, all nanoparticles were cytotoxic towards SaoS-2 cells and showed significantly lower toxicity towards healthy osteoblasts, where Se doped MSNs showed lowest toxicity towards osteoblasts. We further show that the nanoparticles could induce ROS and cell apoptosis. Here we demonstrate MSNs as promising Se delivery carriers for osteosarcoma (OS) therapy.

Vertical distribution and major influencing factors of soil selenium in tropical climate: A case study of Chengmai County, Hainan Island

Soil selenium is of great significance to human health. Soil-forming parent rocks are the most critical factor that influences soil Se levels. Chengmai County, Hainan Island, has a tropical climate and diverse types of parent rocks, in which soil Se content is high. This study investigated the vertical distribution of soil Se from various parent rock substrates under tropical climatic conditions, and the factors that influence these soil Se contents, with 69 vertical soil profiles covering Chengmai County. The vertical distribution of soil Se and correlations with CIA (chemical alteration index), Al2O3, TFe2O3 (total iron oxide expressed as Fe2O3), total iodine, SOC (soil organic carbon), and pH were analysed. As per the results, the mean ± standard error of Se content in the A, B, and C horizons was 0.88 ± 0.13 mg/kg, 0.77 ± 0.08 mg/kg and 0.45 ± 0.05 mg/kg, respectively. The parent rock strictly controlled the horizon distribution of Se in the A-horizon. Soil Se showed A-B-horizons-enrichment in the vertical profile, especially in soil profiles overlying granite and basalt. It is hypothesised that the Se enriched in soils developed from the Tuolie Formation due to the release of Se from the weathering process of Se-rich rocks. Meanwhile, Se in soils developed from granite and basalt is more closely associated with exogenous input. Another crucial factor for the high level of Se in Chengmai County is the tropical climate, which has led the rocks to generally undergo intense chemical weathering. This results in soils rich in clay minerals and Fe/Al oxyhydroxides, which easily absorb and retain Se. Furthermore, the Se content of the B-horizon was generally higher than that of the A-horizon due to leaching. These results provide further knowledge and understanding of the geochemical behaviour of soil Se and guide the evaluation of Se-rich land resources under tropical climatic conditions.

Effect of phosphorus limitation on Se uptake efficiency in the microalga Nannochloropsis oceanica

Microalgae are considered an efficient accumulator and promising source of Se for feed additive purposes. This study aimed at investigating, for the first time, the effect of phosphorus limitation on Se accumulation and uptake efficiency in N.oceanica. A range of phosphorus concentrations (0–2470 µM) were tested in either the presence or absence of sodium selenite (0, 5, 30 µM). Se accumulation was increased up to 16-fold and Se uptake efficiency was increased up to 3.6-fold under phosphorus growth-limiting concentrations. N.oceanica was then cultivated in a 1.8L flat-panel photobioreactor in batch operation under two phosphorus growth-limiting concentrations (250 and 750 µM) where the accumulation of Se in the microalgal biomass, as well as its presence in the spent medium were analysed. This study is the first to investigate the effect of phosphorus limitation for increasing Se accumulation in microalgae, and to prevent the release of Se in wastewater.

Comprehensive Evaluation of Affordable Cathode Materials in Direct Electrochemical Selenite Reduction

Selenium (Se) is a naturally occurring metalloid that has been widely sourced for health care, clean energy technology development, and agricultural activities. These activities have accelerated Se release into the aquatic environment, urging engineered solutions to mitigate aquatic Se pollution and their ecological impact. Our lab previously demonstrated a direct electrochemical reduction approach to convert 97% of soluble selenite into elemental Se(0) on a gold cathode. This study builds upon our prior success in selenite separation to further explore alternative cathode materials to gold. Six economically competitive materials (Ni, graphite, Cu, Fe, stainless steel, and Ti) were evaluated for key performance parameters, including Se removal efficiency, Faradaic efficiency, energy consumption, and electrode durability. Preliminary cyclic voltammetry scans revealed that Ni and graphite could sustain Se(IV)/Se(0) reduction in diluted water matrices within their electrochemical window. The subsequent 24-h chronoamperometry (CA) test demonstrated 67% selenite removal using a Ni cathode, while graphite offered a better removal efficiency (92%). Separated selenite ions were primarily plated as elemental Se(0) on the cathode surface (Ni & graphite) or within the electrode structure (graphite). While graphite has better selenite removal than Ni, it demands more energy input and has lower Faradaic efficiency (C-3.7% vs. Ni-12.7%). Switching from a CA mode to a chronopotentiometry (CP) mode did not significantly impact selenite removal performance, and the energy consumption was increased by 15%. Continued exfoliation is observed on the graphite electrode surface, potentially due to the expansion of inner gas bubbles and the lattice destruction caused by Se(0) insertion. Our results suggest graphite offers comparable selenite separation performance to a gold cathode. Still, electrode exfoliation and higher energy input due to parasitic reactions must be appropriately addressed in future research efforts.

Synthesis, characterization, and evaluation of microwave-assisted fabricated selenylation Astragalus polysaccharides

Selenylation Astragalus polysaccharides (Se-APS) was fabricated by an optimized microwave-assisted method. Their physicochemical properties, antioxidant capacities and selenium (Se) release rate under gastrointestinal conditions were determined. Se-APS with the highest Se content (18.8 mg/g) was prepared in 0.4 % nitric acid, under the microwave conditions of 90 min and 80 °C. FTIR and XPS spectra indicated that Se was bound to the polysaccharide chain in the form of O-Se-O and O-H···Se, and most of Se+4 was reduced to Se0. Meanwhile, the micromorphology of Se-APS became clusters, loose and porous, which decreased its hydrodynamic particle size and negative surface charges. Besides, Se-APS displayed strong scavenging capacities towards ABTS and superoxide anion free radicals than Na2SeO3, and showed higher Se release rate (12.52 ± 0.31 %) under intestinal fluid comparing with gastric fluid (3.14 ± 0.38 %) during 8 h in vitro digestion. The results provided efficient preparation method references for selenylation polysaccharides, and broaden the application fields of APS.

A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant.

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge ‘membrane technology’, as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Effect of amino acids on the stability of anionic pollutants in fly ash blended cement

Fly ash has been used as a cementitious material for solid wastes immobilization. However, fly ash typically contains the hazardous elements Se, Cr, As, and B, and the leachability of these anions is a concern for its reuse. In this study, five amino acids were selected as models of simplified natural organic matter (NOM) in the pedosphere to modify the dissolution tests of Se, Cr, As, and B in ground fly ash blended cement. At the initial pH of 4.7, hydrocalumite and ettringite were easily dissolved, so Ca salt precipitates played an important role in immobilizing oxyanions. However, the stability of Ca salts was weakened by the ligand-promoted dissolution mechanism. In particular, the formation of complexes of H2Asp and HGly with Ca2+ promoted the release of Se, Cr, and As. H2Cys, on the other hand, acted as a reducing reagent to suppress Se and Cr mobility. At the initial pH of 12.0, the stable formation of hydrocalumite and ettringite effectively immobilized the anionic species. Under this condition, aside from the complexation of amino acids with Ca2+, the ion exchange between deprotonated amino acids and oxyanions in hydrocalumite interlayer may also threaten the stability of undesirable anionic species. However, the adsorption of amino acids on the surface of ettringite and hydrocalumite may inhibit their dissolution, resulting in a decrease in Se, Cr, As, and B release. This work provides a reference for understanding the stability of undesirable anionic pollutants in fly ash blended cement when they are exposed to geochemical environments.