Se Removal Research Articles

Phytoextraction of arsenic, nickel, selenium and zinc from sewage sludge: from laboratory to pilot scale

AimsThe present study aimed at: (i) verifying the suitability of pure sewage sludge (SS) as growing medium for the hyperaccumulator species (Pteris vittata, Odontarrhena chalcidica, Astragalus bisulcatus and Noccaea caerulescens); (ii) evaluating the removal of As, Ni, Se and Zn operated by the chosen species; (iii) estimating the potential metal yields (bio-ore production) and connected monetary rewards in a small-scale field experiment.MethodsHyperaccumulator plants were first tested under controlled conditions, on three different SS (P1, P2, P3) characterized by the presence of one or more contaminants among As, Ni, Se and Zn. P1 sludge was then chosen for a small-scale field experiment. Hyperaccumulator seedlings were transferred on SS and cultivated for 16 weeks before harvesting.ResultsAll hyperaccumulator species grew healthy on P1 SS, with A. bisulcatus and O. chalcidica reaching an average biomass of 40.2 and 21.5 g DW/plant. Trace metal concentrations in aerial parts were: As (P. vittata) 380 mg/kg DW, Ni (O. chalcidica) 683 mg/kg DW, Se (A. bisulcatus) 165 mg/kg DW, Zn (N. caerulescens) 461 mg/kg DW. The total removal of As, Ni, Se and Zn from SS due to phytoextraction was 5.8, 19, 18, 29% respectively.ConclusionsThis study demonstrated that phytoextraction can be applied to SS for the removal contaminants while recovering valuable metals. Se and As were identified as the most promising target element, while Ni and Zn removal was poorly efficient under the present experimental conditions.

Efficient adsorptive and reductive removal of U(VI) and Se(IV) using porous hexagonal boron nitride supported nanoscale iron sulfide: Performance and mechanism

The removal of U(VI) and Se(IV) in an aqueous solution was investigated by batch experiments and characterized by spectroscopy techniques such as FTIR, XRD, SEM, TEM, XPS, using [email protected] nanocomposite which was synthesized by hexagonal BN (h-BN) as the stabilizer anchored onto FeS nanoparticles to address the agglomeration of the FeS. The effects of pH, adsorbent concentration, contact time, and initial concentration of U(VI) and Se(IV) on [email protected] adsorption U(VI) and Se(IV) were studied. Results showed that [email protected] nanocomposite showed an excellent decontamination performance due to the large surface area and surface potential. A pseudo-second-order kinetic model well reflected the kinetic adsorption of U(VI) and Se(IV) which indicated chemical interaction mainly contributed to U(VI) and Se(IV) adsorption on [email protected] The adsorption process of removing U(VI) fitted Freundlich and D-R models well which presented multilayer adsorption on the nanocomposite surface. The Langmuir model fitted well with sorption isotherm data of Se(IV) removal displaying a single monolayer reaction between Se(IV) and [email protected] The adsorption of U(VI) and Se(IV) was high pH-dependent since pH affected the [email protected] nanocomposite surface potential and U(VI) and Se(IV) speciation. The maximum sorption capacity of U(VI) and Se(IV) reached 163.11 and 196.39 mg/g, respectively. These results reveal that [email protected] nanocomposite could be promising for the effective decontamination of U(VI) and Se(IV).

Insights into the transformation mechanism of Se in sized ash particles arising from coal combustion: Model vs. experiment

One major challenge on Se emission control in power plants is the relatively low capture efficiency of the fly ash while with large fluctuations in the proportion of unstable physically adsorbed Se. In this study, a comprehensive transformation model of Se during coal combustion is developed and compared to field tests for validation. Results show three transformation stages of Se: remain SeO2 vapor (> 750 °C), chemical adsorption dominates (350–750 °C) and physical adsorption dominates (< 350 °C). The condensation of Se is hardly occurred in each stage due to the low partial pressure of SeO2(g). Se enrichment in small particles is reflected both by physical and chemical adsorption, and the particles of size <1 μm are the major host for the physically adsorbed Se. The gas-to-solid transformation of Se would be enhanced with increased fly ash particles and the inherent Ca/Fe fraction. The promotion effect of Fe is stronger than Ca partly due to the competition of SO2 in flue gas that leads to the fast consumption of CaO at >800 °C. These findings help better understand the partitioning mechanism of Se in sized ash particles and provide guidance on strengthened Se removal in power plants.

Biological selenate and selenite reduction by waste activated sludge using hydrogen as electron donor

Biological reduction of selenium oxyanions is widely used for selenium removal from wastewater. The process is, however, limited by the availability of a suitable, efficient and low cost electron donor. In this study, selenite and selenate reduction by waste activated sludge using hydrogen as the electron donor was investigated. Both selenite and selenate (80 mg/L) were completely removed using H2 within 8 days of incubation. In the presence of sulfate in the medium, the Se removal efficiency decreased to 77.8–95.4% (for selenite) and 88.2–99.4% (for selenate) at different temperatures and initial sulfate concentrations. Thermophilic conditions (50 °C) were better suited for both selenite and selenate reduction using H2 as electron donor with a 0.8–13.5% increase in overall Se removal. Similarly, sulfate reduction also increased from 69.1– 88% at 30 °C to 72–94.6% at 50 °C. Most of the H2 utilized was diverted towards Se and sulfate reduction with minimal production of byproducts such as methane (<0.32 mM) or volatile fatty acids (<0.92 mg/L). The elemental Se produced from selenite and selenate reduction ranged between 33.9 and 52.1 mg/L. The elemental selenium nanoparticles produced as a result of selenite and selenate reduction were characterized using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and dynamic light scattering (DLS) spectroscopy. Furthermore, characterization of the biomass using Fourier-transform infrared spectroscopy (FTIR) and excitation emission matrix (EEM) spectra of the extracellular polymeric substances (EPS) produced by the waste activated sludge were performed to elucidate the mechanism of selenium oxyanion reduction to elemental selenium nanoparticles.

High-yield recycling and recovery of copper, indium, and gallium from waste copper indium gallium selenide thin-film solar panels

A separation process for Cu, In, Ga, and Se (CIGS)-based thin-film solar panels is proposed in this study. Initially, the separation process, by peeling off the panels in a layer-by-layer manner, was achieved by utilizing the different thermal strains of materials inside the CIGS solar panels. Subsequently, the recovery process was performed by annealing the CIGS layers for the removal of Se, and then leaching was performed with nitric acid, followed by the individual extraction of valuable metals. The pH values, concentrations of extractant, stripping agents, organic-aqueous ratios, and reaction time were investigated in detail to optimize the separation conditions for Cu, In, and Ga. First, In was extracted using di-(2-ethylhexyl) phosphoric acid into the organic phase, while Cu and Ga remained in the aqueous phase, by controlling the extraction conditions. After the extraction of In, Ga was extracted using the same extraction agent under different conditions, and nearly pure Cu remained in the residual aqueous solution. Ammonium hydroxide was added to three solutions to form metal hydroxide precipitates. Under the optimal conditions, a recovery rate of >90% could be achieved for In, Ga, and Cu. Furthermore, all as-formed hydroxides were recycled and converted into metal oxides with a purity of >99% by calcination. These findings can provide a pathway for the effective recycling and recovery of Cu, In, and Ga from waste CIGS thin-film solar panels. • A facile and practical method to separate and recover valuable metals respectively from the real commercial thin-film solar panel was demonstrated. • A novel and low-cost physical separation process was induced to peer off the solar panel layer by layer via the extremely low-temperature liquid nitrogen treatment. • An extraction and stripping process was designed to separate Cu, In, and Ga from a complicated multi-element system individually. • Highly pure valuable metal oxides were recovered as the final products, establishing a possible curcular economy model for waste solar panel recycling and recovery.

A comparative study of electrocoagulation treatment with iron, aluminum and zinc electrodes for selenium removal from flour production wastewater

Electrocoagulation (EC) using iron (Fe), zinc (Zn) and aluminum (Al) electrodes was comparatively applied in the treatment of selenium (Se) in flour production (FP) wastewater. It was indicated that EC treatment with Fe anode obtained highest removal efficiency (79.1%) for Se in the 90 min treatment in the comparative study, which could be attributed to the superior adsorption capacity of in-situ generated iron flocs. Removal of Se resulted from electrodeposition and adsorption to in-situ generated flocs in EC treatment, and the operational conditions significantly influenced the Se removal performance in this work. The results showed the acidic condition and higher current density favored EC treatment on Se removal, EC removed up to 97.8% of Se at pH 4 under 15 mA cm−2, whereas it obtained 83.5% and 50.4% of removal efficiency at pH 7 and 10, respectively. There was competitive adsorption in the process of selenium removal, as the in-situ generated flocs effectively removed 35.6% of humic acid-like (HA-like) substance in FP wastewater after 90 min treatment. The FTIR results showed that HA-like substance mainly contained the protein water hydrogen bond, carboxylate COO antisymmetric stretching and other functional groups. Through the analysis of existence of Se in flocs and wastewater, it can be found that approximately 2.8%–3.92% of Se was removed by electrodeposition process. This study illustrated the Se removal mechanism and provided constructive suggestion for food manufacturing to the metal removal and utilization of advanced treatment.

Efficient removal of selenite in aqueous solution by MOF-801 and Fe3O4/MOF-801: Adsorptive behavior and mechanism study

Metal-organic framework materials (MOFs) and MOFs-based composite materials have been extensively applied to adsorb heavy metals due to their high specific surface area and high porosity. Herein, the MOF-801 and its complex Fe3O4/MOF-801 were respectively prepared and employed as adsorbents to capture the Se(IV) in an aqueous solution. And the Fe3O4/MOF-801 composite was post-synthesized from MOF-801 by a simple cryogenic hydrothermal process. The experimental results showed that the maximum adsorption capacity of MOF-801 and Fe3O4/MOF-801 was 101.2 and 206.6 mg/g under acidic conditions, respectively. The coexisting anions, except phosphate and sulfate ions, had negligible effect on the Se(IV) adsorption. The mechanism of Se(IV) removal by the two adsorbents was thoroughly analyzed by Zeta potential, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). And the results illustrates that the Se(IV) was captured on the surface hydroxyl sites of the MOF-801, while the Fe3O4/MOF-801 captured Se(IV) through electrostatic attraction, inner-sphere complexation, and the reduction effect. Furthermore, the existence of charge transfer in the Fe3O4/MOF-801, which facilitated the adsorption and reduction of Se(IV), was confirmed by the XPS analysis. This work provides a promising strategy to design high-performance magnetic MOFs composites for the removal of Se(IV) from wastewater.

Interplay between arsenic and selenium biomineralization in Shewanella sp. O23S

Bacteria play crucial roles in the biogeochemical cycle of arsenic (As) and selenium (Se) as these elements are metabolized via detoxification, energy generation (anaerobic respiration) and biosynthesis (e.g. selenocysteine) strategies. To date, arsenic and selenium biomineralization in bacteria were studied separately. In this study, the anaerobic metabolism of As and Se in Shewanella sp. O23S was investigated separately and mixed, with an emphasis put on the biomineralization products of this process. Multiple analytical techniques including ICP-MS, TEM-EDS, XRD, Micro-Raman, spectrophotometry and surface charge (zeta potential) were employed. Shewanella sp. O23S is capable of reducing selenate (SeO42−) and selenite (SeO32−) to red Se(-S)0, and arsenate (AsO43−) to arsenite (AsO33−). The release of H2S from cysteine led to the precipitation of AsS minerals: nanorod AsS and granular As2S3. When As and Se oxyanions were mixed, both As–S and Se(-S)0 biominerals were synthesized. All biominerals were extracellular, amorphous and presented a negative surface charge (−24 to −38 mV). Kinetic analysis indicated the following reduction yields: SeO32− (90%), AsO43− (60%), and SeO42− (<10%). The mix of SeO32− with AsO43− led to a decrease in As removal to 30%, while Se reduction yield was unaffected (88%). Interestingly, SeO42− incubated with AsO43− boosted the Se removal (71%). The exclusive extracellular formation of As and Se biominerals might indicate an extracellular respiratory process characteristic of various Shewanella species and strains. This is the first study documenting a complex interplay between As and Se oxyanions: selenite decreased arsenate reduction, whereas arsenate stimulated selenate reduction. Further investigation needs to clarify whether Shewanella sp. O23S employs multi-substrate respiratory enzymes or separate, high affinity enzymes for As and Se oxyanion respiration.

Novel triazine-based cationic covalent organic polymers for highly efficient and selective removal of selenate from contaminated water

Selenium (Se) removal from contaminated water has become a major environmental problem in recent years. Designing efficient and selective materials for selenium adsorption is urgent and still represents a great challenge. Herein, two novel cationic covalent triazine frameworks (CTFS-Cl and CTFL-Cl) are developed for the first time and employed as a new class of Se adsorbents. The results from systematic adsorption experiments indicate that these materials can adsorb SeO42- in a wide range of pH values (2−11) with fast kinetics (5 min), outstanding adsorption capacity, and excellent selectivity over other competing anions. The maximum adsorption capacity achieved (149.3 mg/g by CTFS-Cl) constitutes one of the highest values among the organic polymeric materials. More importantly, after a single step adsorption, these materials can reduce the Se concentrations to lower than 10 μg/L, the lowest drinking water standard in the world. The adsorption mechanism was probed by XPS technique, EDS analysis, adsorption experiments, and DFT calculations, which reveals that anion exchange between Cl- and SeO42- is the main driving force for Se adsorption. Additionally, CTFS-Cl and CTFL-Cl perform well toward real contaminated river water sample with the residual Se being less than 8.49 μg/L. This work demonstrates the excellent performance of CTFs-based materials with great application prospect for Se removal in contaminated water treatment.

Anaerobic co-digestion of dissolved air floatation slurry and selenium rich wastewater for simultaneous methane production and selenium bioremediation

The energy potential of dissolved air floatation (DAF) slurry, a lipid-rich waste, is largely disregarded with the common practice of land spreading or landfilling. On the other hand, selenium (Se) contaminated wastewaters are perceived as unsuitable feedstocks because of their toxicity. This study aimed to evaluate the anaerobic co-digestion performance of a DAF slurry with Se rich wastewater using anaerobic granular sludge and waste activated sludge as the inocula. Anaerobic batch assays of DAF slurry supplemented with 0.05, 0.10, 0.25 and 0.50 mM selenate (SeO42−) and selenite (SeO32−), along with a control (without Se) were performed at 30 °C. Methanogenesis of the DAF slurry using anaerobic granular sludge was realised during co-digestion up to 0.50 mM SeO42−, whereas SeO32− was already toxic from 0.05 mM onwards. Co-digestion of the DAF slurry with 0.05 and 0.10 mM Se oxyanions (both selenate and selenite) containing wastewater using waste activated sludge achieved a similar cumulative methane yield of about 180 mL/g COD as that of mono-digestion (Se free DAF slurry) after 65 days of incubation. Simultaneously, more than 90% removal of Se was accomplished. The lag phase duration was, however, extended by 50 and 90% in the presence of 0.05 and 0.10 mM Se, respectively. The half maximal inhibitory concentration (IC50) for methane production using waste activated sludge was 0.08 mM for SeO42− and 0.07 mM for SeO32−. The IC50 amounted to 2.10 mM for SeO42− and 0.08 mM for SeO32− with anaerobic granular sludge. SeO42− and SeO32− were reduced to elemental Se nanoparticles, as shown by transmission electron microscopy. This study indicates the feasibility of methane production from a DAF slurry, codigested with wastewaters containing up to 0.10 mM SeO42− or SeO32−.

Cotton fabric decorated by a Zr4+ MOF for selective As(V) and Se(IV) removal from aqueous media

In this work we describe a new method for the fabrication of a bulk sorbent material composed of the metal-organic framework (MOF) [Zr6O4(OH)4(NH2BDC)6]·xH2O (MOR-1) supported on cotton textiles and demonstrate its ability to remove toxic oxyanions from the aquatic environment. The new sorbent shows exceptional capability for both individual and competitive sorption of As(V) and Se(IV) oxyanionic species from aqueous media, due to the strong binding of these species to the Zr4+ metal ions, the high permeability and large contact surface area of the fabric. The sorption capacities of MOR-1@cotton fabric for As(V) (459 mg g−1) and Se(IV) (325 mg g−1) largely exceed those of previous reported sorbents. In addition, MOR-1@cotton fabric showed excellent sorption efficiency in a wide pH range (3−7) as well as high selectivity for As(V) and Se(IV) against several competitive anionic species. Finally, the fabric sorbent was examined for its efficiency in the removal of As(V) and Se(IV) from genuine water samples (lake, river and well water) under realistic conditions with very satisfactory results. These data, along with the fact that the bulk MOR-1@cotton fabric can be easily retrieved from water after use (in contrast to sorbents being in powder form), pledges on the potential use of the material for real water treatment applications.

Effects of magnetic field on selenite removal by sulfidated zero valent iron under aerobic conditions

A novel strategy of sulfide modified zero valent iron (S-ZVI) coupled with the magnetic field (MF) is developed for selenite (Se(IV)) removal. The original ZVI particle size (30 μm), S/Fe ratio (1:80), solution pH (5), S-ZVI loading (0.75 g L−1), and MF intensity (20 mT) can exhibit the optimal enhancement effects of MF on Se(IV) removal by S-ZVI. Common corrosion promoters (Cl−, PO43−, SO42−, Mg2+, and Ca2+) and inhibitors (NO3−, SiO32−, and CO32−) show positive and negative effects on Se(IV) removal by S-ZVI, respectively. But MF can alleviate promoting or inhibiting effects of coexisting ions on Se(IV) removal by S-ZVI, and well preserve the reactivity of S-ZVI from background ions in water. Furthermore, MF can also enhance the reactivity of S-ZVI towards Se(IV) during consecutive experiments, the promotion factor (the ratio of kobs with MF to kobs without MF) increased from 2.57 to 5.83 with the increase of cycles. MF can not only improve the reactivity of ZVI covered with iron oxide or iron hydroxide but also effectively enhance the ability of ZVI covered with iron sulfide. S-ZVI exhibited good stability and recyclability in the presence of MF. XANES analysis of selenium species reveals that the reductive product of Se(IV) with or without MF is primarily Se(0), and Se(IV) removal by S-ZVI can be ascribed to adsorption and reduction. This work indicates that MF may widen the application of S-ZVI for pollutants removal in environmental remediation.

The removal of selenite and cadmium by immobilized biospheres: Efficiency, mechanisms and bacterial community

In this study, a complex bacterial consortium was enriched from a typical Pb–Zn mine area and immobilized by sodium alginate to form biospheres, which were used for treatment of selenite (Se(IV))- and cadmium (Cd(II))-containing wastewater without external carbon source. Batch experiments showed that the maximum Se(IV) removal efficiency was 92.36% under the optimal conditions of an initial pH of 5, dosage of 5 g/L, initial Se(IV) concentration of 7.9 mg/L and reaction time of 168 h. Subsequently, more than 99% of 11.2 mg/L Cd(II) was removed by the biospheres within 10 h. Physicochemical characterization showed that reduction and adsorption were the main mechanisms for Se(IV) and Cd(II) removal, respectively. During the removal process, selenium and CdSe nanoparticles were formed. Bacterial community analysis showed the dominant bacterial genera changed after treatment of Se(IV)- and Cd(II)-containing wastewater. Additionally, 16S rRNA gene function prediction results showed that amino acid transport, carbohydrate transport, ion transport and metabolism were the dominant gene functions. The present study provides a potential way for the biological treatment of Se(IV)- and Cd(II)-containing wastewater using immobilized biospheres without external carbon source in short-term.

Improved removal of selenium by calcite-derived CaO with porosity and anti-sintering in presence of acid gas

Ca-based sorbent injected into furnace is a promising technology for control emission of selenium. As commercially available CaO was easy to sintering under actual furnace temperature or in presence of CO2/SO2, calcite-derived CaO on removal of Se were tested by a gas-solid reaction system, which was designed to simulate process of gaseous trace elements in flue gas fast contacting with injected minerals, showing a simple, economical and practical method to improve anti-sintering. Results showed conspicuous superiority of calcite-derived CaO for its porosity and anti-sintering. Capture efficiency at 700–800 °C could reach to 80% basically, even to 90% as maximum, and chemisorption was dominance for capture by analysis of thermal desorption. Both CO2 and SO2 could affect capture, while their effects mechanisms on Se capture were quite different. The impact of CO2 depended on the adsorption temperature. Below 700 °C, existence of CO2 could inhibit Se capture due to formed CaCO3, so Se capture was suggested at above 700 °C after considering both capture efficiency and leachability. Effects of SO2 was relevant to content of CaSO4 formed. Se retention was promoted as low content of CaSO4 formed, but capture was inhibited by thickened product layer as high content formed.

Impact of dissolved oxygen and pH on the removal of selenium from water by iron electrocoagulation

Removing dissolved selenium (i.e., selenate and selenite) from wastewater is a challenging issue for a range of industries. Iron electrocoagulation can produce Fe(II)-containing solids that can adsorb and chemically reduce dissolved Se. In a series of bench-scale experiments we investigated the effects of dissolved oxygen (fully oxic, partially oxic, and strictly anoxic) and pH (6 and 8) on the rate and extent of dissolved selenate and selenite removal by iron electrocoagulation. These studies combined measurements of the aqueous phase with the direct characterization of the resulting solids. Among the conditions studied the rate and extent of dissolved selenium (Se) removal were highest at pH 8 and strictly anoxic conditions. X-ray absorption spectroscopy demonstrated that in the absence of oxygen, Se was primarily transformed to elemental selenium (Se0) and selenide. Green rust that formed in the suspension during electrocoagulation played a key role as a reductant and sorbent of Se. At pH 6 dissolved oxygen did not affect the rates and extents of dissolved Se removal. Under all the conditions studied, dissolved Se removal was more effective with iron electrocoagulation than with the direct addition of pre-synthesized green rust or ferrous hydroxide. The most rapid and substantial dissolved Se removal was achieved by freshly-formed green rust and ferrous hydroxide, which are both Fe(II)-bearing solids. With an improved understanding of the products and mechanisms of the process, iron electrocoagulation can be optimized for removal of Se from wastewater.

Removal of dissolved selenium by siderite, pyrite, and sphalerite: Implications to selenium sequestration in water-saturated, anoxic coal waste rock

The mechanisms of abiotic sequestration of Se(VI) and Se(IV) on a sample of coal waste rock collected from the Elk Valley, Canada and on three pure mineral species (i.e., siderite, pyrite, and sphalerite) present in coal waste rock were assessed using sterile batch testing under water-saturated, anoxic conditions. Only siderite removed measurable Se(VI) from the test solutions with ~90% removal after 100 d attributed to initial adsorption to the siderite surface as Se(VI) and subsequent reduction to Se(IV) and Se(0). In contrast to Se(VI), all samples removed Se(IV) from the aqueous solutions. The rate of Se(IV) removal was pyrite > siderite > waste rock > sphalerite. The waste rock sample removed Se(IV) from solution in two stages: up to ~40% of the aqueous Se(IV) was rapidly removed (by day 1) followed by slower removal of Se(IV) with up to ~97% removal after 99 d. Se(IV) removal is attributed to the adsorption of Se(IV) and subsequent reduction to Se(0) onto the siderite and pyrite phases of the waste rock. The initial (1 d) removal of Se(IV) by waste rock was characterized using a distribution coefficient (Kd) of 15.5 L/kg. Longer-term Se(IV) removal was fitted with zero and first order removal rates. The removal of Se(IV) by sphalerite was minor and deemed to have a minimal effect on Se sequestration in the waste rock. Desorption tests on waste rock showed that the fraction of sequestered Se susceptible to desorption decreased with time as adsorbed Se(IV) was reduced to insoluble Se(0). These findings show that abiotic Se sequestration can occur in saturated, anoxic zones in coal waste rock dumps.

Removal of Se(IV) from water with biochar-supported nanoscale zero-valent iron: optimization of preparation conditions and adsorption characteristics

Removal of Se(IV) from water with biochar-supported nanoscale zero-valent iron: optimization of preparation conditions and adsorption characteristics

In situ synthesis of a porous ZrO2 coated fiber membrane for efficient static and dynamic removal of Se(iv)

High-performance static and dynamic removal of Se(iv) from environmental water was achieved by using a porous ZrO2 coated fiber membrane.

The effect of organic carbon form and concentration on fungal selenite reduction

Fungi are essential to the transformation of carbon (C) and are well-known for degrading recalcitrant plant material. They are also increasingly recognized for their bioremediation potential in contaminated environments. Some fungi transform selenium (Se), an essential nutrient and toxin of growing concern, from an aqueous bioavailable phase (Se(+IV, VI)) to solid or volatile phases (Se(0, -II)). We examined the effect of C on growth and Se transformation for several Ascomycota fungi, including Alternaria alternata SRC1lrK2f, Paraphaeosphaeria sporulosa AP3s5-JAC2a and Pyrenochaeta sp. DS3sAY3a, grown in 0–60 mmol C/L glucose or acetate with 0.1 mM Se(IV) over 23 days. Higher C concentrations coincided with more Se removal, but some species preferred certain C sources. A. alternata generally reduced the most Se regardless of C source, but Pyrenochaeta sp. reduced more with glucose. A. alternata predominantly solidified Se, whereas P. sporulosa mainly volatilized Se. Glucose and acetate concentrations in cultures with and without Se trended downward throughout the experiment, suggesting that carbon consumption continues despite Se presence. As biomass did not substantially increase throughout the experiment for any organism with Se(IV) but C consumption continued, it is likely that the fungi experienced a toxicity effect with Se(IV) as observed with increased pigment production, and predominantly consumed C for cell maintenance and repair purposes. This study helps discern the effect of C on fungal Se transformations, providing greater insight into the coupling between C and Se biogeochemical cycling as well as improving Se bioremediation strategies.

Enhanced simultaneous removal of toxic (SeO4)2− and metals Cr3+ and Cu2+ using polysulfide intercalated Layered double hydroxide

• Simultaneous removal of Se(VI) and metal cations. • More toxic Se(VI) reduced to nontoxic Se(IV) and Se(0) • Leached amount of Mo inhibited in the presence of metal cations. It is usually very difficult to remove (SeO 4 ) 2− (Se(VI) from aqueous solution due to its high stability and mobility. Here, it was found enhanced removal efficiency of Se(VI) in the presence of metals cations such as Cr(III) and Cu(II) using trimetallic LDH (FeMgAl-MoS 4 LDH) intercalated with MoS 4 2− which abbr. as S-LDH. The removal efficiency of Se(VI) was relatively poor (67.9%) when treated alone. However, in the presence of Cr(III) and Cu(II) cations the removal efficiency of Se(VI) was enhanced to 99.32% and 96.02%, respectively under similar experimental conditions. The metal cations were also simultaneously removed (>82%) and (>99.99%) for Cr(III) and Cu(II) cations, respectively. Moreover, secondary water pollution was also inhibited in the presence of the metal cations with Se(VI) since the amount of Mo leached from S-LDH into the solution was decreased from 19.82 to 1.13 ppm when 140 ppm Se(VI) initial sample was treated alone and in the presence of 20 ppm Cr(III), respectively. Similarly, the amount of Mo leached was decreased from 21.34 to 2.37 ppm when 140 ppm Se(VI) was treated alone and with 20 ppm Cu(II), respectively. This could be due to co-precipitation reaction of the leached MoS 4 2− with the cations in the solution. The pre- and post-adsorption characterization of S-LDH was conducted using XRD, FTIR, SEM-EDX, CHNS and XPS to determine the chemical structure and composition of the adsorbent as well as the reaction mechanisms. The reaction kinetics followed pseudo-second order which related with chemisorption and Langmuir reaction model was better fitted the isotherm data that indicated monolayer adsorption dominate in the reaction process. The evaluation of thermodynamic parameters with negative values of free energy, enthalpy and entropy indicated a spontaneous, exothermic and the solid/solution interface became less random and enthalpy driven processes. Based on the XPS result, the more toxic Se(VI) was mainly reduced to less toxic Se(IV) and Se(0) species due to the (-S-) 2− in MoS 4 2− and Fe(II) in the LDH while themselves oxidized to SO 4 2− and Fe(III), respectively. We believe that this strategy provides a new direction to find enhanced removal of the reluctant Se(VI) and retarding secondary water pollution when MoS 4 based LDHs used as sorbent materials.