Evaluation of selective uptake of selenium (Se(IV) and Se(VI)) and antimony (Sb(III) and Sb(V)) species by baker's yeast cells (Saccharomyces cerevisiae)

An economical strategy towards the managing of selenium pollution from contaminated water: A current state-of-the-art review

During the last few decades, contamination of selenium (Se) in groundwater has turned out to be a major environmental concern to provide safe drinking water. The content of selenium in such contaminated water might range from 400 to 700 μg/L, where bringing it down to a safe level of 40 μg/L for municipal water supply employing appropriate methodologies is a major challenge for the global researcher communities. The current review focuses mostly on the governing selenium remediation technologies such as coagulation-flocculation, electrocoagulation, bioremediation, membrane-based approaches, adsorption, electro-kinetics, chemical precipitation, and reduction methods. This study emphasizes on the development of a variety of low-cost adsorbents and metal oxides for the selenium decontamination from groundwater as a cutting-edge technology development along with their applicability, and environmental concerns. Moreover, after the removal, the recovery methodologies using appropriate materials are analyzed which is the need of the hour for the reutilization of selenium in different processing industries for the generation of high valued products. From the literature survey, it has been found that hematite modified magnetic nanoparticles (MNP) efficiently adsorb Se (IV) (25.0 mg/g) from contaminated groundwater. MNP@hematite reduced Se (IV) concentration from 100 g/L to 10 g/L in 10 min at pH 4-9 using a dosage of 1 g/L. In 15 min, the magnetic adsorbent can be recycled and regenerated using a 10 mM NaOH solution. The adsorption and desorption efficiencies were over 97% and 82% for five consecutive cycles, respectively. To encourage the notion towards scale-up, a techno-economic evaluation with possible environmentally sensitive policy analysis has been introduced in this article to introspect the aspects of sustainability. This type of assessment is anticipated to be extremely encouraging to convey crucial recommendations to the scientific communities in order to produce high efficiency selenium elimination and further recovery from contaminated groundwater.

Mechanism analysis of selenium (VI) immobilization using alkaline-earth metal oxides and ferrous salt

The immobilization of selenate (SeO₄^2-) using metal oxides (CaO and MgO) and ferrous salt as the immobilization reagents were examined by the leaching test and solid-phase analysis via XRD, XAFS, TGA, and XPS. The results indicated that nearly all of SeO₄^2- was reduced to SeO₃^2- in the CaO-based reaction within 7 days. Then, the generated SeO₃^2- was mainly sorbed onto the iron-based minerals (Fe₂O₃ and FeOOH) through the formation of both bidentate mononuclear edge-sharing (¹E) and monodentate mononuclear corner-sharing (¹V) inner-sphere surface complexes, suggested by PHREEQC simulation and EXAFS analysis. Differently, less amount of SeO₄^2- (approximately 45.50%) was reduced to SeO₃^2- for the MgO-based reaction. However, if the curing time increases to a longer time (more than 7 days), the further reduction could occur because there are still Fe(II) species in the matrix. As for the associations of Se in the solid residue, most of the selenium (SeO₃^2- and SeO₄^2-) was preferentially distributed onto the Mg(OH)₂ through outer-sphere adsorption. Definitely, this research can provide a deep understanding of the immobilization of selenium using alkaline-earth metal oxide related materials and ferrous substances.

In Situ Selective Measurement of SeIV in Waters and Soils: Diffusive Gradients in Thin-Films with Bi-Functionalized Silica Nanoparticles

The speciation of selenium (Se) controls its fate and behavior, determining both its biological and environmental activities. However, in situ monitoring of Se^IV presents a significant challenge due to its sensitivity to redox change. A novel diffusive gradients in thin films (DGT) technique containing mercapto-, amino-bifunctionalized SBA15 mesoporous silica nanoparticles was developed and evaluated in a series of laboratory and field deployment tests. The SBA-DGT exhibited a linear accumulation of Se^IV ( r² > 0.997) over a 72 h deployment, with negligible accumulation of Se^VI(<5%). Consistent prediction of Se^IV occurred within ionic strength and pH ranges of 0.1-200 mmol L^-1 and 3.6-8, respectively. Limits of detection of the SBA-DGT were 0.03 μg Se^IV L^-1, which is suitable for natural waters. Moreover, the properties of the bifunctionalized SBA15 enable it to be fabricated within ultrathin (0.05 mm) gel layers for use in conjunction with O₂ planar optode imaging. This new sandwich sensor technology with SBA-DGT was validated by mapping the two-dimensional distribution of Se^IV and oxygen simultaneously in rice rhizospheres. This study shows that SBA-DGT provides a selective measurement of Se^IV in situ, demonstrating its potential for both environmental monitoring and as a research tool for improving our understanding of Se biogeochemical processes.

Selenium contamination, consequences and remediation techniques in water and soils: A review

Selenium (Se) contamination in surface and ground water in numerous river basins has become a critical problem worldwide in recent years. The exposure to Se, either direct consumption of Se or indirectly may be fatal to the human health because of its toxicity. The review begins with an introduction of Se chemistry, distribution and health threats, which are essential to the remediation techniques. Then, the review provides the recent and common removal techniques for Se, including reduction techniques, phytoremediation, bioremediation, coagulation-flocculation, electrocoagulation (EC), electrochemical methods, adsorption, coprecipitation, electrokinetics, membrance technology, and chemical precipitation. Removal techniques concentrate on the advantages, drawbacks and the recent achievements of each technique. The review also takes an overall consideration of experimental conditions, comparison criteria and economic aspects.

Efficient adsorption of Selenium(IV) from water by hematite modified magnetic nanoparticles

Selenium (Se) could enter the environment through different anthropogenic sources, posing potential health risk. The removal of trace Se(IV) from water by hematite coated magnetic nanoparticle (MNP@hematite) under different solution conditions was investigated through batch experiments. The adsorption capacity of Se(IV) by MNP@hematite was 25.0 mg/g.100 μg/L of Se(IV) could be rapidly decreased to below 10 μg/L by 0.1 g/L of MNP@hematite in 10 min. MNP@hematite could effectively remove Se(IV) in a wide pH range from 4 to 9. Se(IV) could form inner-sphere complex with MNP@hematite. Thus, the presence of chloride, nitrate, and sulfate (concentration of each anions <10 mM) did not affect the removal of Se(IV); whereas, carbonate (10 mM), silicate (1 mM), and phosphate (0.1 mM) yet reduced the adsorption efficiency by competing adsorption sites. Humic acid and alginate (up to 6 mg/L) did not have obviously influence on the removal of Se(IV). MNP@hematite particles were able to simultaneously remove Se(IV) and Sb(III) at trace level very efficiently in 10 min. The magnetic adsorbent can be easily recycled and regenerated in 10 mM NaOH for 15 min. In five consecutive cycles, the adsorption and desorption efficiencies were over 97% and 82%, respectively. MNP@hematite could be employed as effective adsorbent for Se(IV) removal from water.

Ultimate selenium(IV) monitoring and removal from water using a new class of organic ligand based composite adsorbent

This work reports the selenium (Se(IV)) detection and removal from water by ligand functionalized organic-inorganic based novel composite adsorbent. The composite adsorbent was prepared by direct immobilization of N,N'-di(3-carboxysalicylidene)-3,4-diamino-5-hydroxypyrazole onto the mesoporous silica monolith. The adsorbent exhibited distinct color change in the presence of various concentrations of Se(IV). This was characterized by UV-vis spectroscopy, and the color change was observed by naked-eye observation. The detection limit was determined to be 1.14 μg/L. The effect of solution pH, interferential metal ions, contact time, initial Se(IV) concentration, and adsorbent regeneration were evaluated. The maximum sorption capacity was determined based on the initial concentration. The data fitted well to the Langmuir isotherm model, and the maximum Se(IV) sorption capacity was 111.12 mg/g. The presence of diverse competing ions did not affect the Se(IV) sorption capacity, and the adsorbent had almost no sorption capacity for these coexisting ions, which suggests the high selectivity to Se(IV) ions. The adsorbed Se(IV) was eluted with suitable eluent (0.10 M NaOH) and simultaneously regenerated into the initial form for the next operation. The excellent reusability of the adsorbent was justified after eight consecutive sorption-elution-regeneration cycles. The proposed adsorbent is cost-effective and environmentally friendly and a potential candidate for treatment of water containing Se(IV).

Removal of Antimony(III) from Aqueous Solution by Using Grey and Red Erzurum Clay and Application to the Gediz River Sample

The removal of Sb(III) from waste water is achieved in batch system by using grey and red Erzurum (Oltu) clay which are cheap and natural adsorbents. Adsorption experiments were studied. For this purpose, various important parameters such as contact time, pH, and temperature were examined on the adsorption of Sb(III) ions onto grey and red Erzurum (Oltu) clay. Decreasing amount of Sb(III) ions in the solutions by adsorption was determined with differential pulse anodic stripping voltammetry (DPASV) method. Langmuir and Freundlich isotherms for the adsorption processes were drawn. The adsorption was demonstrated in similarity with Langmuir model. The maximum adsorption capacity of red Erzurum clay for Sb(III) was found to be 9.15 mg/g. Also, surface of the adsorbent was characterized by using FTIR spectroscopy. Red Erzurum clay was applied on real sample (Gediz River), and 72.6% adsorption was obtained.

Changes in Sb speciation with waterlogging of shooting range soils and impacts on plant uptake

A pot experiment was conducted to investigate the solubility and redox species of antimony (Sb) in a relocated shooting range soil and its uptake by Lolium perenne L. and Holcus lanatus L. under different water regimes. After 1-week waterlogging, the total Sb concentration in soil solution decreased from ∼110 μg L(-1) to <20 μg L(-1), and slowly increased over the following 4 weeks, with the dissolution of Fe and Mn (hydr)oxides. In this process, half of the Sb in soil solution was reduced to Sb(III), which greatly affected the plant uptake of Sb. Waterlogging increased shoot Sb concentrations of L. perenne by ∼10 fold but decreased uptake in H. lanatus by 80%. Results indicate that Sb might primarily be taken up as Sb(III) by L. perenne and as Sb(V) by H. lanatus. Temporary waterlogging of soil may increase the risk of trace elements entering the food chain.

Biosorption: a new rise for elemental solid phase extraction methods

Biosorption is a term that usually describes the removal of heavy metals from an aqueous solution through their passive binding to a biomass. Bacteria, yeast, algae and fungi are microorganisms that have been immobilized and employed as sorbents in biosorption processes. The binding characteristics of microorganisms are attributed to functional groups on the surface providing some features to the biosorption process like selectivity, specificity and easy release. These characteristics turn the biosorption into an ideal process to be introduced in solid phase extraction systems for analytical approaches. This review encompasses the research carried out since 2000, focused on the employment of biosorption processes as an analytical tool to improve instrumental analysis. Since aminoacids and peptides as synthetic analogues of natural metallothioneins, proteins present in the cell wall of microorganisms, have been also immobilized on solid supports (controlled pore glass, carbon nanotubes, silica gel polyurethane foam, etc.) and introduced into solid phase extraction systems; a survey attending this issue will be developed as well in this review.

Preconcentration of by living bacteria immobilized on for microwave induced plasma optical emission spectrometry with continuous powder introduction

The analytical potential of living bacteria Lactobacillus plantarum for the preconcentration of selenium from mineral water and beer samples followed by the selenium determination by continuous powder introduction microwave induced plasma-optical emission spectrometry (CPI-MIP-OES) has been investigated. The use of the bacteria immobilized on silica permits on-column preconcentration of selenium with minimum sample pretreatment by the pH adjustment. Experimental conditions for the preconcentration were optimized and the mechanism of the biosorption was investigated. Results showed that the use of the preconcentration stage leads to the substantial lowering of the detection limit of selenium by OES. The detection limit of 52 ng g-1 by the CPI-MIP-OES was achieved which corresponds to 0.06 ng mL-1 in the sample solution regarding the preconcentration factor of 1000. Precision of 5 replicate measurements expressed as relative standard deviation was about 3%. The utility of the method was demonstrated in the determination of selenium in hard drinking water ERM-CA011a as well as in mineral water and beer samples.

Agro-industrial waste 'wheat bran' for the biosorptive remediation of selenium through continuous up-flow fixed-bed column

Present study deals with the utilization of an agro-industrial waste wheat bran for the remediation of selenium species, Se(IV) and Se(VI) by continuous up-flow fixed-bed column system. Laboratory-scale column tests were performed to determine potentiality of wheat bran at various bed height, flow rates and initial metal ion concentration and it was found to be very potential biosorbent as it showed good sorption capacities of 72.54 microg/g and 62.51 microg/g for Se(IV) and Se(VI) respectively. Different models like Bed Depth Service Time (BDST), Thomas and Yoon-Nelson were applied to the experimental sorption data. The data showed very good fit to BDST model and sorption capacities (N(o)) computed using BDST model were 26,664 microg/L and 26,400 microg/L for Se(IV) and Se(VI) respectively. Also Yoon-Nelson model was found to show good agreement with the experimental kinetic results as compared to the Thomas model. Wheat bran was amenable to efficient regeneration with 10% NaOH. The biosorbent retained most of its original uptake capacity over three cycles of use. The excellent reusability of the biosorbent could lead to development of a viable metal remediation technology. Life factor calculation revealed that biosorbent bed will have sufficient capacity to avoid breakthrough at time t=0 up to 12.17 cycles for Se(IV) and 6.28 cycles for Se(VI) and bed would be completely exhausted after 56.89 cycles for Se(IV) and 18.73 cycles for Se(VI).

Heat-treated Saccharomyces cerevisiae for antimony speciation and antimony(III) preconcentration in water samples

An analytical method was developed for antimony speciation and antimony(III) preconcentration in water samples. The method is based on the selective retention of Sb(III) by modified Saccharomyces cerevisiae in the presence of Sb(V). Heat, caustic and solvent pretreatments of the biomass were investigated to improve the kinetics and thermodynamics of Sb(III) uptake process at room temperature. Heating for 30 min at 80 degrees C was defined as the optimal treatment. Antimony accumulation by the cells was independent of pH (5-10) and ionic strength (0.01-0.1 mol L(-1)). 140 mg of yeast and 2h of contact were necessary to ensure quantitative sequestration of Sb(III) up to 750 microg L(-1). In these conditions, Sb(V) was not retained. Sb(V) was quantified in sorption supernatant by inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectrometry (ICP-OES). Sb(III) was determined after elution with 40 mmol L(-1) thioglycolic acid at pH 10. A preconcentration factor close to nine was achieved for Sb(III) when 100mL of sample was processed. After preconcentration, the detection limits for Sb(III) and Sb(V) were 2 and 5 ng L(-1), respectively, using ICP-MS, 7 and 0.9 microg L(-1) using ICP-OES. The proposed method was successfully applied to the determination of Sb(III) and Sb(V) in spiked river and mineral water samples. The relative standard deviations (n=3) were in the 2-5% range at the tenth microg L(-1) level and less than 10% at the lowest Sb(III) and Sb(V) tested concentration (0.1 microg L(-1)). Corrected recoveries were in all cases close to 100%.

Biosorption of heavy metals by Saccharomyces cerevisiae: A review

Heavy metal pollution has become one of the most serious environmental problems today. Biosorption, using biomaterials such as bacteria, fungi, yeast and algae, is regarded as a cost-effective biotechnology for the treatment of high volume and low concentration complex wastewaters containing heavy metal(s) in the order of 1 to 100 mg/L. Among the promising biosorbents for heavy metal removal which have been researched during the past decades, Saccharomyces cerevisiae has received increasing attention due to the unique nature in spite of its mediocre capacity for metal uptake compared with other fungi. S. cerevisiae is widely used in food and beverage production, is easily cultivated using cheap media, is also a by-product in large quantity as a waste of the fermentation industry, and is easily manipulated at molecular level. The state of the art in the field of biosorption of heavy metals by S. cerevisiae not only in China, but also worldwide, is reviewed in this paper, based on a substantial number of relevant references published recently on the background of biosorption achievements and development. Characteristics of S. cerevisiae in heavy metal biosorption are extensively discussed. The yeast can be studied in various forms for different purposes. Metal-binding capacity for various heavy metals by S. cerevisiae under different conditions is compared. Lead and uranium, for instances, could be removed from dilute solutions more effectively in comparison with other metals. The yeast biosorption largely depends on parameters such as pH, the ratio of the initial metal ion and initial biomass concentration, culture conditions, presence of various ligands and competitive metal ions in solution and to a limited extent on temperature. An assessment of the isotherm equilibrium model, as well as kinetics was performed. The mechanisms of biosorption are understood only to a limited extent. Elucidation of the mechanism of metal uptake is a real challenge in the field of biosorption. Various mechanism assumptions of metal uptake by S. cerevisiae are summarized.