Selenium Removal Research Articles

Enhancing Selenium Removal Using Pre-Treated Natural Clay: Experimental Investigation and Predictive Modeling

Abstract A heat treatment methodology was adopted as a pretreatment strategy, altering the porous structure of the clay to minimize leaching for selenium adsorption in an aqueous system. Rigorous experiments were carried out in batch mode to determine optimal parameters across various variables, including contact time, adsorbent dosages, selenium concentrations, pH, temperature, and stirring speed during selenium removal using natural clay. Investigating several kinetic and isotherm models revealed the best fitting for the pseudo-second-order and the Langmuir isotherm. Endothermic and spontaneous characteristics of the adsorption process were shown during thermodynamic analysis. In this study, a predictive model for the efficiency of selenium separation was established using Response Surface Methodology (RSM). Additionally, an Artificial Neural Network (ANN), a data-driven model, was employed for comparative analysis. The predictive model exhibited a high degree of agreement with experimental data, demonstrated by a low relative error of <0.10, a high regression coefficient of >0.97), and a substantial Willmott-d index of >0.95. Moreover, the efficacy of pre-activated clay in selenium removal was assessed, revealing the superior performance of ANN models over RSM models in forecasting the efficiency of the adsorption process. This research significantly advances an effective and sustainable material for selenium removal, providing valuable insights into predictive modeling techniques applicable to similar contexts to boost scale-up confidence during industrial implementation in affected regions.

Selenocyanate removal using combined system of TiO2- photocatalysis and Fe(III)/SiO2 adsorption {UV-TiO2/[Fe(III)/SiO2]}: Complex destruction and simultaneous selenium species adsorption

Selenocyanate (SeCN‾) species, commonly found in industrial effluents from crude oil refineries and mining operations, present substantial health risks to humans and animals. This study investigates the treatment of selenocyanate-contaminated streams using a combination of TiO2 photocatalysis and Fe(III)/SiO2 binary oxide adsorption {UV-TiO2/[Fe(III)/SiO2]}. The Fe(III)/SiO2 binary oxide was synthesized and characterized using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. XRD analysis revealed non-crystalline Fe-oxide phases, while FTIR indicated the presence of various Fe and O functional groups on the Fe(III)/SiO2 surface. Adsorption studies using Fe(III)/SiO2 showed its selenocyanate uptake capacity ∼ 2.1 mg/g, with the respective data closely aligning with the Langmuir isotherm model. This Fe(III)/SiO2 adsorption feature was successfully combined in the {UV-TiO2/[Fe(III)/SiO2]} system in which the hydroxyl radicals (●OH) generated by the UV-TiO2 facilitated the breakdown of the selenocyanate complex, while the resulting selenite and selenate were simultaneously adsorbed by the Fe(III)/SiO2 within a 240-min reaction time. A mathematical model developed using a face-centered central composite design-response surface methodology (FCD-RSM) showed significant predictive capability with an insignificant lack of fit. Optimal conditions for selenium removal were determined to be 20 mg/L selenocyanate, 1 g/L TiO2, and 1 g/L Fe(III)/SiO2, at pH 5, within a 240-min reaction time. Kinetic analysis demonstrated that selenocyanate degradation followed pseudo-first-order kinetics, while total selenium removal adhered to pseudo-second-order kinetics, confirming the proposed selenium species removal mechanism. Overall, this integrated approach offers a promising solution for effective selenocyanate remediation in industrial wastewater.

Removal of selenate from wastewater using a bioelectrochemical reactor: The importance of measuring selenide and the role of competing anions

Removal of selenate (SeO42-) from selenate-contaminated wastewater is challenging due to the commonly co-existing and competing anions of sulfate (SO42-) and nitrate (NO3-). This study investigates SeO42− reduction to elemental selenium (Se0) in a cathode-based bioelectrochemical (BEC) reactor and a conventional biofilm reactor (i.e., an upflow anaerobic reactor). The simulated wastewater contained SeO42− at a typical concentration of 5 mg Se/L, SO42− at a typical concentration of 1000 mg S/L, and NO3− at concentrations that varied from 0 to 10 mg N/L. The impact of sulfate on the BEC reactor was much lower than that on the conventional reactor: The selenium removal, defined as (selenate in influent – dissolved selenium in effluent)/selenate in influent, was 99 % in the BEC reactor versus 69 % in the conventional biofilm reactor. The lower selenium removal in the conventional reactor was mainly due to the >10 times higher reduction of sulfate, which directly caused competition between sulfate and selenate for the common resources such as electrons. The more reduction of sulfate in the conventional reactor further led to 45 times higher production of selenide. Selenide is usually assumed to be minimal and therefore not measured in the literature. This simplification may significantly overestimate selenium removal when the influent sulfate concentration is very high. NO3- in the influent of the BEC reactor promoted selenium removal when it was less than 5.0 mg N/L but inhibited selenate removal when it was more than 7.5 mg N/L. This was supported by the microbial community analysis and intermediate (nitrite) analysis.

Layered Double Hydroxides as Next-Generation Adsorbents for the Removal of Selenium from Water

This research paper provides a comprehensive overview of the use of layered double hydroxides (LDH) in the removal of selenium species from contaminated water sources. Key studies on sorption mechanisms and the impact of competing ions on selenium removal are presented, and the effectiveness of LDH is compared across different structures and compositions. Scholarly sources extensively document the application of conventional LDH for effective selenium removal, with notable advancements achieved through innovative synthesis approaches. Comparative studies between LDH synthesized through various methods reveal the potential of tailored LDH for enhanced selenium adsorption. The paper further explores the influence of competing anions on LDH efficacy, emphasizing the impact of sulfate on selenium removal. Additionally, investigations into calcined LDH and commercially available variants underscore the potential for industrial applications. Beyond conventional LDH, the paper delves into iron-based LDH, LDH with intercalated thiomolybdate anions, and layered rare earth hydroxides, exploring their effectiveness in separating different selenium species. The role of pH in the removal of selenium species and the impact of three-metal cation LDH are also discussed. The study extends to nanocomposites, combining LDH with zero-valent iron, carbon-based materials, and organic compounds, illustrating their potential for selenium species immobilization. The presented findings offer valuable insights for researchers and practitioners in environmental science, addressing the growing demand for efficient selenium remediation strategies.

Effective Removal of Selenium from Aqueous Solution using Iron-modified Dolochar: A Comprehensive Study and Machine Learning Predictive Analysis

Selenium (Se) is an essential micronutrient for human beings, but excess concentration can lead to many health issues and degrade the ecosystem. This study focuses on the removal of selenium from an aqueous solution using iron-doped dolochar. SEM, EDX, BET, XRD, FTIR, and Pzpc were conducted to determine the surface characteristics of iron-doped dolochar (FeD). The characterization of the adsorbent gave an insight into surface morphology, surface area (100 m2/g), average pore diameter (3.9 nm), and surface composition, which contributed to the Se adsorption. The pHzpc of the iron-doped adsorbent surface was found to be 7.02, which provided a broad range for effective Se adsorption. To detect the optimum parameters, the parametric influence on removal efficiency was conducted by varying pH, dosages, contact time, and initial concentration. The experiment achieved maximum selenium removal, ∼98 %, at low concentration, 10 g/L dosage, and low pH (2) within 90 min at room temperature. It fits the Langmuir better than the Freundlich isotherm (R2 = 0.99), indicating monolayer adsorption. It fitted well with pseudo-second-order kinetics. The experiment is a spontaneous, endothermic (ΔH0 = 9.22 kJ/mol) and high randomness (ΔS0 = 45.37 kJ/mol) suggested by thermodynamic study. The adsorption was influenced by competing ions as follows: phosphate > sulfate > nitrate > manganese > aluminum > zinc > iron. A regression learner tool was used to compare different models using the experimental data that showed the best fit with the Gaussian Process Regression with RMSE = 0.246, MSE = 0.061, and R2 = 0.99. Thus, it can be concluded that FeD is preferred as a better adsorbent for selenium removal from aqueous solutions and could produce 35.5% ROI, 21.5% IRR, and 24.59% BEP on FeD production.

Selenium and concomitant anions removal in a fixed bed bioreactor to satisfy drinking water regulations and subsequent stability check of selenium-laden biosludge

This is the first successful report on selenium bio-attenuation to satisfy drinking water regulations as per Indian Standards (10 μg/L) in the presence of concomitant nitrate and sulfate from water sources utilizing a fixed bed bioreactor. The bioreactor was immunized with blended microbial culture and worked in downflow mode under anoxic conditions at 30 ± 2 °C for around 190 days under varying influent selenate (100–500 μg/L as selenium), nitrate (50 mg/L), sulfate concentrations (as per selenium removal) and necessary dose of acetic acid (as COD, a carbon source) in synthetic groundwater, operated at an empty bed contact time (EBCT) of 45–120 min. After supplying an adequate dosage of sulfate and alteration of EBCT, selenium was found to comply with drinking water regulations and nitrate was completely removed. X-ray diffraction and transmission electron microscopy analyses depicted nanocrystalline selenium sulfides (SeS and SeS2) formation as the possible mechanisms of selenium removal. Extended toxicity characteristic leaching procedure (TCLP) extractions confirmed a maximum selenium leaching of 52 and 282 μg/L during anoxic and oxic extractions, respectively. Long-term column leaching (>3-month equilibration) under aerobic conditions at pH 7 confirmed the produced precipitate to be essentially stable (∼0.14% Se leaching). This work exhibits the synchronous bioremoval of selenium and its co-anions from contaminated water complying with drinking water standards, and leaving a stable and non-hazardous selenium-laden biosludge.

Enhancement of selenium removal in coal-fired flue gas across wet flue gas desulfurization spray tower by internal components-part 1: Demister and wall ring

Wet flue gas desulfurization (WFGD) device is a key piece of equipment used to control selenium, but its removal efficiency is highly variable (13%–95%). Adding internal components into WFGD can alter the gas-liquid flow pattern and is regarded as a promising technology for selenium removal. In this study, the demister and wall ring were adopted as internal components to investigate their feasibility on selenium removal and inherent mechanisms. Compared with the open tower (without internal components), the outlet selenium concentration was reduced by 52.2%–61.7% by installing a demister. This was because a liquid film was formed on the baffle plates of the demister after intercepting mists, which leaded a secondary absorption process for selenium. The lower plates of the demister made a major contribution to selenium removal, and increasing the plate area of the demister was beneficial to this process. The wall ring reduced the selenium emission by up to 56.5%, because it could force the flue gas and liquid column near/on the walls to flow towards the center, and significantly improve the gas-liquid contact. The enhanced method and mechanisms reported in this study can help to develop a low-cost technology to improve the selenium purification efficiency of existing WFGDs.

Molybdenum-Oxysulfide-Functionalized MgAl-Layered Double Hydroxides─A Sorbent for Selenium Oxoanions.

Effective removal of chemically toxic selenium oxoanions at high-capacity and trace levels from contaminated water remains a challenge in current scientific pursuits. Here, we report the functionalization of the MgAl layered double hydroxide with molybdenum-oxysulfide (MoO2S2) anion, referred to as LDH-MoO2S2, and its potential to sequester SeVIO42- and SeIVO32- from aqueous solution. LDH-MoO2S2 nanosheets were synthesized by an ion exchange method in solution. Synchrotron X-ray pair distribution function (PDF) and extended X-ray absorption fine structure (EXAFS) revealed an unexpected transformation of the MoO2S22- to Mo2O2S62- like species during the intercalation process. LDH-MoO2S2 is remarkably efficient in removing SeO42- and SeO32- ions from the ppm to trace level (≤10 ppb), with distribution constant (Kd) ranging from 104 to 105 mL/g. This material showed exceptionally high sorption capacities of 237 and 358 mg/g for SeO42- and SeO32-, respectively. Furthermore, LDH-MoO2S2 demonstrates substantial affinity and efficiency to remove SeO32-/SeO42- even in the presence of competitive ions from contaminated water. Hence, the removal of selenium (VI/IV) oxoanions collectively occurs through reductive precipitation and ion exchange mechanisms. This work provides significant insights into the chemical structure of the MoO2S2 anion into LDH and emphasizes its exceptional potential for high-capacity selenium removal and positioning it as a premier sorbent for selenium oxoanions.

Mathematical Modelling and Response Surface Methodology Approach of Electrocoagulation Hybrid Activated Sludge Process for an Efficient Removal of Selenium from Mining Wastewater

Mathematical Modelling and Response Surface Methodology Approach of Electrocoagulation Hybrid Activated Sludge Process for an Efficient Removal of Selenium from Mining Wastewater

Potential of biochar and humic substances for phytoremediation of trace metals in oil sands process affected water

Oil sands process affected water (OSPW) is produced during bitumen extraction and typically contains high concentrations of trace metals. Constructed wetlands have emerged as a cost effective and green technology for the treatment of metals in wastewaters. Whether the addition of amendments to constructed wetlands can improve metal removal efficiency is unknown. We investigated the synergistic effects of carbon based amendments and wetland plant species in removal of arsenic, cadmium, cobalt, chromium, copper, nickel, and selenium from OSPW. Three native wetland species (Carex aquatilis, Juncus balticus, Scirpus validus) and two amendments (canola straw biochar, nano humus) were investigated in constructed wetland mesocosms over 60 days. Amendment effect on metal removal efficiency was not significant, while plant species effect was. Phytoremediation resulted in removal efficiencies of 78.61–96.31 % for arsenic, cadmium, and cobalt. Carex aquatilis had the highest removal efficiencies for all metals. Amendments alone performed well in removing some metals and were comparable to phytoremediation for cadmium, cobalt, copper, and nickel. Metals were primarily distributed in roots with negligible translocation to shoots. Our work provides insights into the role of plants and amendments during metal remediation and their complex interactions in constructed treatment wetlands.

Insights into the influence mechanism of SO2 on the selenium capture by Fe/Al-MgO-based adsorbents: Experiment and DFT

The adsorption experiments and density functional theory (DFT) analysis revealed together the adsorption characteristics of composite adsorbents for selenium and the mechanism of SO2 influence. Adsorption experiments indicated that the optimal adsorption capacity for selenium occurred at 500 °C with a molar ratio of Mg/Fe/Al as 20:1:1 (MFA), yielding 9.30 mg/g, surpassing that of single or binary magnesium-based adsorbents. The presence of SO2 diminished the selenium removal capability of the ternary adsorbent, although maintaining a high adsorption capacity of 7.06 mg/g even at a concentration of 2000 ppm SO2. X-ray photoelectron spectroscopy (XPS) results showed selenium primarily existed as Se4+/Se0 species on the MFA surface. Sulfur appeared as MgSO4/MgSO3/MgS, which confirmed that sulfur-containing low-valent products was formed. Characteristic peaks of Se0 on pure MgO surfaces, providing substantial evidence of SO2-induced SeO2 reduction. Furthermore, DFT computations suggested that the doping of Fe/Al activated the adsorption activity of the MgO surface. At 500 °C, SeO2 exhibited enhanced chemisorption on the MFA surface, with an adsorption energy of −547.56 kJ/mol. Reaction rate constants and activation energies corroborated the propensity for redox reactions between SO2 and SeO2 to occur in the heterogeneous phase.

Effect of acetate and methanol on the kinetics of total dissolved selenium removal in a chemostat

AbstractBACKGROUNDCarbon (C) source consumption in industrial bioreactors removing soluble selenium (Se) contributes to the operating cost and can influence the rate of removal. This study used a laboratory chemostat to investigate the dependency of the rate of dissolved Se removal on the concentration of acetate and methanol, two C sources used in treatment of Se containing mine‐influenced water. It was hypothesized that the rate of dissolved Se removal follows a Monod kinetic model with C source as the limiting substrate.RESULTSA chemostat fed with 25 mg‐selenate‐Se L−1 and acetate as C source at different concentrations operated over a range of hydraulic retention times (HRTs) achieved maximal removal of 99.7% dissolved Se at an HRT of 1.5 days [rate 16.7 mg‐Se (L day)−1]. When methanol was fed into the chemostat as the C source instead of acetate, the extent and rate of removal were much less [65% at an HRT of 6 days, rate 2.7 mg‐Se (L day)−1]. Carbon source consumption per mole of dissolved Se removed was not constant and exceeded stoichiometric estimates. Monod kinetic parameters for the Dechloromonas/Ralstonia consortium growing on acetate were estimated as = 3.36 mg‐C L−1 and = 0.70 L day−1. The Methylophilaceae consortium growing on methanol did not exhibit Monod kinetic growth.CONCLUSIONSUsing acetate as a C source achieved greater efficiency of dissolved Se removal than when methanol was used. Total dissolved Se removal rate was dependent on acetate only at low concentrations and when the HRT was close to washout. However, total dissolved Se removal rate was strongly dependent on HRT when methanol was used. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Developing a versatile tool for studying kinetics of Selenate-Se removal from aqueous solution using a chemostat bioreactor

Understanding the impact of various parameters on the kinetics of dissolved selenium (Se) removal in bioreactors can be a challenging task, primarily due to the mass transfer limitations inherent in bioreactors employing attached growth configurations. This study successfully established a proof-of-concept for the efficient removal of Se from aqueous solutions using a chemostat bioreactor that relies solely on suspended growth. The research investigated the effect of selenate-Se feed concentrations under two distinct Se concentration conditions. One experiment was conducted at a considerably elevated concentration of 25 mg/L to impose stress on the system and evaluate its response. Another experiment replicated an environmentally relevant concentration of 1 mg/L, mirroring the typical Se concentrations in mine water. The bioreactor, featuring a working volume of 0.35 L, was operated as an anaerobic, fully mixed chemostat with hydraulic retention times (HRTs) ranging from 5 to 0.25 days. The outcomes revealed the chemostat's capacity to remove up to 25 mg/L of dissolved Se from water for all HRTs exceeding 1 day, under otherwise optimal conditions encompassing temperature, pH, and salinity. The research's significance lies in the development of a versatile tool designed to examine Se removal kinetics within a system devoid of mass transfer limitations. Furthermore, this study verified the ability of the bacterial consortium, obtained from a mine-influenced environment and enriched in the laboratory, to grow and sustain Se removal activities within a chemostat operating with HRTs as short as 1 day.

Native selenium in the apical rocks of the Gaisky copper-pyrite deposit

Research subject. Selenium mineralization in altered rocks of the Gaisky deposit. Aim. Determination of formation conditions of native selenium in altered rocks. Results. Selenium mineralization is established in three zones of altered rocks in the sides of the 3rd quarry and is confined to the upper part of the sulfur-quartz rocks. Layers with a high content of native selenium and tiemannite are distinguished by a carbon-black color against the general background of yellow-green sulfur-quartz rocks, forming subvertical trickle textures. The maximum propagation of selenium mineralization was found in the southwestern zone of the quarry. Here, selenium-containing rocks are traced vertically by 6 m, forming a lens with a diameter of up to 70 cm. The accumulation of selenium occurs due to its physical properties. Selenium is similar to sulfur in volatility, although it undergoes more intense condensation under decreased temperatures. The accumulation of selenium condensate is facilitated by a silicic acid gel, which prevents the removal of selenium by a hydrothermal flow. Conclusion. The native selenium of the Gaisky deposit is characterized by a hydrothermal genesis, which, along with the presence of monoclinic native sulfur in the rocks, indicates the hydrothermal formation of the entire complex of altered rocks.

Insights into selenium capture by Fe-modified MgO: Experimental and density functional theory study

Fe-doped MgO sorbents were developed for gaseous selenium removal in the flue gas. Combined with the density functional theory (DFT), the molecular interaction was described. The experimental results showed that the synthesis of MgFe2O4 increased the number of lattice oxygen in the adsorbent. Moreover, the oxygen vacancy played as a pit in the filling of O atoms in SeO2. There were two desorption peaks of SeO2 on the surface of Fe-loaded MgO, 420 °C and 540 °C, respectively. Fe0.02MgO and Fe0.05MgO exhibited the best selenium capture capacity at 500 °C, which depended on the SeO2 desorption temperature of 540 °C. Fe0.1MgO had advantages in capturing selenium at 400 and 700 °C. DFT results indicated that the exposed Fe atoms on the surface of MgFe2O4 provided abundant adsorption sites for selenium. The adsorption energy of SeO2 on MgFe2O4 was 2.4 times that of pure MgO. SeO2 decomposed on MgFe2O4 surface to form Se0 with a conversion energy barrier of 52.4 kJ/mol. Thermodynamic calculations showed that the selenium capture capacity of MgFe2O4 gradually decreased with the increase of temperature, while the conversion of selenium on the MgFe2O4 surface was promoted.

Coupling protein recovery to methane and lactic acid production to valorize duckweed used in selenate remediation

Duckweed (DW) can be used for metal bioremediation, but can also serve as a renewable feedstock for various processes such as protein production, acidogenesis and methanogenesis. In this study, a selenate (3 mg L−1) supplemented modified Steinberg medium was used as a feed for DW cultivation, which gave a selenate removal efficiency of 55%. Thereafter, an optimized protein extraction protocol was developed yielding a∼20% protein extraction efficiency from both the control and selenate-enriched DW. The solid fraction obtained during protein extraction was utilised for lactic acid (LA) production (upto 5 g L-1), whereas the liquid fraction (after protein extraction) was used as the substrate for methane production (∼150 mL gCOD−1). Selenate enriched DW achieved faster LA production and showed better methane production kinetics when compared to the control DW. This study shows that bioenergy and biocommodity production can be efficiently coupled to selenium removal from polluted wastewaters using DW.

A potent insight into the microalgal and surface-modified magnetic microalgal biomass synthesis and treatment strategies in the removal of selenium and chromium metal ions

A potent insight into the microalgal and surface-modified magnetic microalgal biomass synthesis and treatment strategies in the removal of selenium and chromium metal ions

Novel CTAB functionalized graphene oxide for selenium removal: adsorption results and ANN & RSM modeling

Novel CTAB functionalized graphene oxide for selenium removal: adsorption results and ANN & RSM modeling

Differences Between Heterotrophic and Nitrate-dependent Iron-oxidizing Microbial Communities in Bioreactor Sediment Treating Mine Wastewater

Nitrate-dependent iron oxidation (NDFO) is a novel mechanism for microbial bioremediation of metal and metalloid contaminants. During NDFO, microbes catalyze a redox reaction wherein nitrate is reduced to nitrite and nitrogen gas while Fe(II) is oxidized to solid Fe(III) hydroxide minerals. Metalloid contaminants such as selenium and arsenic have a propensity for adsorption to iron minerals produced during NDFO; some contaminants may also be concurrently bioreduced. A number of bacterial isolates have been shown to be capable of NDFO (e.g., Kappler et al. (2005), Kiskira et al. (2017)), but little work has been done to date characterizing mixed microbial communities performing NDFO. Some autotrophic communities have been characterized, with high relative abundances for strains of Gallionellaceae in both a freshwater sediment enrichment culture and an activated sludge culture (Blöthe and Roden 2009, Tian et al. 2020). In mixotrophic activated sludge cultures, the concentration of Fe(II) amendment was found to significantly impact microbial community composition; these cultures were fed with methanol in addition to Fe(II), and the dominant community members were Methyloversatilis and other methylotrophic strains (Liu et al. 2018). The work presented here examines microbial communities performing NDFO in the context of remediation, and in particular how differences between NDFO and heterotrophic communities may influence remediation effectiveness. This research characterizes and compares microbial communities performing NDFO versus heterotrophic denitrification during removal of selenium and nickel from mining wastewater. Sediment and influent water from a subsurface bioreactor treating mining wastewater were used to construct batch bioreactors, which were amended with selenium and nickel as well as either Fe(II) or methanol to investigate contaminant removal and microbial community composition in NDFO versus heterotrophic microbial communities. Both Fe(II) and methanol reactors removed total aqueous selenium to below the quantification limit, but Fe(II) reactors removed it more rapidly, likely due to adsorption of selenite. For nickel, removal to below the detection limit was achieved with methanol amendment, while Fe(II) amendment resulted in 42-95% removal. This was likely due to precipitation of nickel sulfide during sulfate reduction in methanol-amended reactors. DNA from the batch bioreactors will be sequenced and the results analyzed for differences among communities. Permutational multivariate analysis of variance and non-metric multidimensional scaling will be used to determine significant correlations of community composition with experimental variables, selenium and nickel removal, and NDFO (Roberts 2023, Kruskal 1964). Indicator species analyses (De Cáceres et al. 2010) will be applied to identify taxa found significantly more often (i.e., at a higher relative abundance) in one group of microbial communities than in any other group. The indicator species analysis may reveal whether there are groups of denitrifiers that predominate in NDFO conditions vs. groups that predominate during heterotrophic denitrification. The results of these microbial community analyses, in combination with the geochemical analyses, will improve our understanding of microbial communities performing NDFO in remediation environments.

Simultaneous removal of selenium and microbial contamination from drinking water using modified ferrihydrite-based adsorbent

The ferrihydrite and modified ferrihydrite-based adsorbents were explored in the present study to remove selenate and bacterial contamination from drinking water. All the zinc-modified absorbents show >80 % bacterial count reduction, contrary to the unmodified adsorbents (30–40 % reduction). Ferrihydrite-based adsorbent modified with zinc (FH2–10) was the most efficient for selenate adsorption and exhibited the highest bactericidal activity. Sorption experiments showed that for Se (VI) concentration of 400 μg L−1, a sorbent dose of 0.5 g L−1 was sufficient to meet drinking water guidelines within the first 10 min. The maximum adsorption capacity of 40.984 mg/ g was obtained for FH2–10. The regeneration and reuse studies show that the selenium removal efficiency retained was >85 % even after three consecutive adsorption-desorption cycles. Column adsorption studies were performed to assess the adsorbent's field applicability, which inferred the adsorption capacity of 1.3 mg/ g. The FH2–10 adsorbent also showed >95 % bacterial growth reduction against E. coli. Hence the present detailed studies infer that FH2–10 is an efficient material for the simultaneous removal of selenium and bacterial contamination from drinking water, with potential for field application if the sulfate co-ions are not present in higher concentrations.