L-cysteine mediated rapid separation of Hg2+ and MeHg+ by anion-exchange HPLC.

Owing to the on-going emission of Hg into the global environment, new insight into their bioinorganic chemistry in mammals is urgently required to better understand their adverse health effects and analytical methods to quantify Hg2+ and MeHg+ in environmental samples are needed. Analytical separations can help to address both of these needs. While Hg2+ and MeHg+ have been most frequently separated by cation and reversed-phase (RP) HPLC, we here report on using anion-exchange (AEX) HPLC in conjunction with a flame atomic absorption spectrometer (FAAS) to observe the retention behavior of these mercury species in the pH range 5.0-8.0 using mobile phases comprised of 10 mM l-cysteine (Cys) in 100 mM phosphate buffer. The results obtained for pH 5.0 served as a starting point to develop a rapid HPLC separation for these mercurials. The addition of 5-20 % methanol (MeOH) to this mobile phase revealed that MeOH did not appreciably change the retention of Hg2+, but significantly reduced the retention of MeHg+. A 15 % MeOH-containing mobile phase offered the best compromise between achieving a rapid baseline separation in <400 s at affordable costs. To assess the suitability and robustness of the developed AEX-HPLC separation method for the analysis of environmental samples an inductively coupled plasma atomic emission spectrometer (ICP-AES) was employed as the mercury-specific detector. The developed AEX-HPLC-ICP-AES method allowed to achieve detection limits of 1.5 ppm for Hg2+ and 2.9 ppm for MeHg+ and was successfully applied to analyze wastewater that had been spiked with Hg2+ and MeHg+.

Tailoring of spherical nanocellulose via esterification with methionine followed by protonation to generate two different adsorbents for mercuric ions and Congo red.

Herein, we report two different adsorbents from spherical nanocellulose (SNC) in successive steps, for the adsorption of Hg2+ ions and Congo red (CR). Cellulose extracted from pine needles was subsequently converted to SNC through mixed acidic hydrolysis. As-obtained SNC was esterified with methionine at C6 of the anhydroglucose unit to produce SNC-methionine ester (SNC-ME). The amino group of methionine residue in SNC-ME was protonated to SNC-PME with positive surface charge. The SNC-ME and SNC-PME were evaluated as Hg2+ ions and CR adsorbents, respectively. The SNC, SNC-ME, SNC-PME, Hg2+-loaded SNC-ME, and CR-loaded SNC-PME were characterized by FTIR, XRD, XPS, Zeta potential, BET, FESEM, EDS, and surface charge analysis. SNC-ME showed Hg2+ ions removal efficiency of 94.8 ± 1.9 % in 40 min, while SNC-PME showed CR removal efficiency of 96.1 ± 3.8 % in 90 min. The adsorption data of both the adsorbents fitted best into pseudo-second order kinetic and Langmuir isotherm. The maximum adsorption capacity of SNC-ME for Hg2+ ions was 211.5 ± 3.1 mg/g and that of SNC-PME for CR was 281.1 ± 7.1 mg/g. The astounding recyclability of the adsorbents for ten repeat cycles with significant cumulative adsorption capacity of 760.9 ± 12.8 mg/g for Hg2+ ions and 758.8 ± 12.7 mg/g for CR endorses their spectacular potentiality for wastewater treatment.

Development of nanocomposite-selenium filter for water disinfection and bioremediation of wastewater from Hg and AgNPs.

Selenium nanoparticles (SeNPs) are used in several sectors as antitumor, antimicrobial, and environmental adsorbents. Thus, the present research objective was the production of bacterial-SeNPs as an active and environmentally-friendly antibacterial and adsorbent agents and application into novel nanocomposite filter. From a total of 25 samples (soil, wastewater, and water) obtained from different locations in Egypt, 60 selenium-resistant bacterial isolates were obtained (on a mineral salt medium supplemented with selenium ions). After screening (based on the conversion of selenium from ionic form to nanoform), a superior bacterial isolate for SeNPs formation was obtained and molecular identified as Bacillus pumilus isolate OR431753. The high yield of SeNPs was noted after optimization (glucose as carbon source, pH 9 at 30 °C). The produced SeNPs were characterized as approximately 15 nm-diameter spherical nanoparticles, in addition to the presence of organic substances around these particles like polysaccharides and aromatic amines (protein residues). Also, they have antibacterial activity increased after formation of nanocomposite with nano-chitosan (SeNPs/NCh) against several pathogens. The antibacterial activity (expressed as a diameter of the inhibitory zone) averaged between 2.1 and 4.3, 2.7 and 4.8 cm for SeNPs and SeNPs/NCh, respectively compared with 1.1 to 1.8 cm for Amoxicillin. The produced nanoselenium/chitosan was used as a biofilter to remove mercury (Hg) and AgNPs as model chemicals with serious toxicity and potential pollutant for water bodies in many industries. The new SeNPs/NCh biofilter has proven highly effective in individually removing mercury and AgNPs from their synthetic wastewaters, with an efficiency of up to 99%. Moreover, the removal efficiency of AgNPs stabilized at 99% after treating them with the syringe filter-Se nanocomposite for 4 cycles of treatment (5 min each).

Preparation of porous lignocellulose biochar adsorbent by cold isostatic pressing pretreatment and study on Hg (II) adsorption properties of C and N dual activity sites.

Utilizing corn straw (CS) mainly composed of lignocellulose to prepare physically modified biochar (PCSB) via cold isostatic pressing (CIP) in order to increase the biochar' s Hg (II) adsorption capacity. The results of the characterization indicated that CIP pretreatment renders PCSB-400' s structure more porous and higher N content of 16.65 %, leading to more N-containing functional groups partaking in the adsorption process. PCSB-400 adsorbed Hg (II) primarily via C/N synergistic complexation and electrostatic attraction between pores, in addition to the presence of redox reactions of surface functional groups on PCSB-400. The adsorption experiment reveals that PCSB-400 has a high selectivity for the adsorption of Hg (II). The adsorption process of Hg (II) by PCSB-400 more closely resembles the Langmuir model and pseudo-first-order adsorption kinetics equation. The adsorption quantity at saturation is 282.52 mg/g at 25 °C. This paper provided an effective idea to selectively remove Hg (II) in wastewater.

Cellulose-based adsorbent using in mercury detection and removal from water via an efficient grafting strategy of fluorometric sensors by click reaction.

Mercury pollution in waters attracts lots of attention due to its serious toxicity and high bioenrichment and many efforts have been devoted in the development of adsorbents for mercury detection and removal. Herein, a cellulose-based adsorbent Cell-TriA-HQ is functionalized with quinoline fluorophore by covalent immobilization through "Click reaction" with high yield. In addition to the admirable adsorptive performance, the prepared adsorbent exhibits excellent selectivity and sensitivity towards Hg (II) in water that the detection limit for Hg (II) is determined to be as low as 1.92 × 10-7 M. The sensitive fluorescence enhancement response is considered to be resulted from the inhibition of photo-induced electron transfer between triazole and quinoline groups and the reinforcement of structural rigidity. The easy manipulation along with excellent performance of adsorption capacity, detective ability and reusability for the multifunctional adsorbent makes it potential in mercury monitoring and removal from aqueous solutions in the field of water treatment.

MOF derivatization of multifunctional nanozyme: Peroxidase-like catalytic activity combined with magnetic solid phase extraction for colorimetric detection of Hg2.

Nanozyme-based colorimetric sensing has drawn immense attention due to the rapid development of nanozyme in recent years. However, the selectivity of nanozyme-based colorimetric sensing greatly limits its subsequent practical application. It is well known that sample pretreatment can not only improve selectivity by eliminating the sample matrix interference, but also improve sensitivity by enriching trace targets. Based on the easy facile surface modification properties of nanozyme, we rationally designed nanozyme combined with sample pretreatment for colorimetric biosensing, through separation and enrichment, thereby improving the selectivity and sensitivity of the nanozyme colorimetric biosensing. As a proof of concept, the detection of Hg2+ by nanozyme-based colorimetric sensing was used as an example. Magnetic peroxidase-like nanozyme Fe3S4 was designed and synthesized. The selectivity is improved by the specific adsorption of S-Hg bond and the interference elimination after magnetic separation. In addition, the sensitivity is improved by magnetic solid-phase extraction enrichment. Our established colorimetric sensing based on Fe3S4 nanozyme integrated sample pretreatment with an enrichment factor of 100 and the limit of detection (LOD) is 26 nM. In addition, this strategy was successfully applied to detect Hg2+ in environmental water samples. Overall, the strategy showed good selectivity and sensitivity, providing a new practical method for the application of nanozyme-based biosensing in sample pretreatment.

Fabrication of a novel polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 nanocomposite for efficient adsorption of Pb(II) and Hg(II) ions from aqueous solution.

A novel magnetic polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 (PVP/CS-SB/Fe2O3) adsorbent was prepared by one-pot facile co-precipitation route for adsorption of Pb(II) and Hg(II) ions from aqueous solution. Fourier transform infrared-spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) were used to characterize the synthesized PVP/CS-SB/Fe2O3. The results predicted that the successfully synthesis of magnetic CSSB-PVP@Fe2O3. The effects of important factors such as pH solution, contact time, concentration of metal ions, adsorbent dose and co-existing ions on Pb(II) and Hg(II) adsorption were investigated. The maximum adsorption capacities of Pb(II) and Hg(II) ions at optimal conditions were 120 mg/g and 102.5 mg/g, respectively. The kinetic studies predicted that the adsorption followed the pseudo-second-order (PSO) model as chemisorption using the coordination of active sites of PVP/CS-SB/Fe2O3 with the metal ions and also n-π interactions. Reproducibility results predicted that the excellent regeneration ability after 6 adsorption cycles. According to the results of this work, the PVP/CS-SB/Fe2O3 nanocomposite is promising for Pb(II) and Hg(II) ions adsorption and can be potential as a simple, low-cost, high-efficient adsorbent for decontamination of other heavy metal ions from aqueous solution.

Electrochemical sensor applying ZrO2/nitrogen-doped three-dimensional porous carbon nanocomposite for efficient detection of ultra-trace Hg2+ ions.

In this study, a ZrO2/nitrogen-doped three-dimensional porous carbon (ZrO2/N-3DPC) nanocomposite was manufactured to fabricate an effective electrochemical sensor for the detection of ultra-trace mercury ion (Hg2+). The synthesized N-3DPC had an open pore structure, large specific surface area and enough continuous mass transfer channels, which can facilitate the diffusion and transmission of electrons and ions at the sensing interface, providing an effective adhesion platform for electrochemical deposition of ZrO2 nanoparticles. Benefiting from the synergistic effect of ZrO2 and N-3DPC, the developed electrochemical sensor had good adsorption and catalytic performance for Hg2+ with a wider linear range of 0.1-220 µg L-1 and a lower detection limit of 0.062 µg L-1. Meanwhile, the sensor exhibited remarkable repeatability, reproducibility, stability and anti-interference, and was further applied to detect Hg2+ in seafood and tap water with satisfactory recoveries (97.1-103.1%) and lower relative standard deviation (≤4.3%). The proposed strategy of electrochemical sensing detection of Hg2+ provides a new idea and direction for the research of ZrO2/N-3DPC nanocomposite in the field of analysis and detection, which is also of great significance to ensure foods, environmental safety and human health.

Magnetic solid-phase extraction based on sulfur-functionalized magnetic metal-organic frameworks for the determination of methylmercury and inorganic mercury in water and fish samples.

A novel magnetic metal-organic frameworks (Fe3O4@UiO-66-SH) was successfully prepared by coating Fe3O4 nanospheres with sulfur-functionalized UiO-66. The Fe3O4@UiO-66-SH possesses both the magnetic properties of Fe3O4 and the diverse properties of metal-organic framework (MOF) in one material, which has the superiority of high surface area, easy-operation and strong adsorb ability with mercury, is used for the magnetic solid-phase extraction of methylmercury (MeHg+) and inorganic mercury (Hg2+) in water and fish samples. The analyzes were conducted by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The different pretreatment conditions influencing the extraction recoveries of Hg2+ and MeHg+, including adsorbent amount, pH, extraction time, elution solvent, elution volume, desorption time, co-existing ions and dissolved organic materials were investigated. Under the optimized conditions, the limits of detection (LODs) of Hg2+ and MeHg+ for water samples were 1.4 and 2.6 ng L-1, and the limits of quantification (LOQs) of Hg2+ and MeHg+ for water samples were 4.7 and 8.7 ng L-1. The enrichment factors (EFs) were 45.7 and 47.6 fold for Hg2+ and MeHg+, respectively. The accuracy of the proposed method was demonstrated by analyzing the certified reference material of fish tissue (GBW10029) and by determining the analyte content in spiked water and fish samples. The determined values were in good agreement with the certified values and the recoveries for the spiked samples were in the range of 84.5-96.8%.

Identification of metal binding motifs in protein frameworks to develop novel remediation strategies for Hg2+ and Cr(VI).

Amino acid sequences in metal-binding proteins with chelating properties offer exciting applications in biotechnology and medical research. To enhance their application in bioremediation studies, we explicitly aimed to identify specific metal-binding chelating motifs in protein structures for two significant pollutants, such as mercury (Hg2+) and chromium Cr(V1). For this purpose, we have performed an extensive coordination chemistry approach by retrieving Hg2+ and Cr(V1) binding protein structures from the protein database and validated using the B-factor, a term defining uncertainty of the atoms and with occupancy to obtain the best binding motifs. Our analysis revealed that acidic amino acids like aspartic acid, glutamic acid, and basic amino acids such as cysteine and histidine are predominant in coordinating with these metals. The order of preference in Hg2+-bound structures is predicted to be Cys > His > Asp > Glu, and for Cr(V1) is His > Asp > Glu. Examination of the atomic coordinates and their distance from each metal revealed that the sulfur atoms of cysteine showing more preference towards Hg2+coordination with an atomic distance ranging from 1.5 to 2.9 Å. Likewise, oxygen atoms of aspartic acid, glutamic acid and nitrogen atoms of histidine are within 2 Å of Cr(V1) coordination. Based on these observations, we obtained C-C-C, C-X(2)-C-C-(X)2-C, H-C-H motifs for Hg2+, and D-X(1)-D, H-X(3)-E motif for Cr(V1) to be shared within the coordination space of 3 Å. As a future scope, we propose that the identified metal-binding chelating motifs are oligopeptides and can display on the surface of microorganisms such as Escherichia coli and Saccharomyces cerevisiae for effective removal of natural Hg2+ and Cr(V1) through biosorption. Hence, our results will provide the basis for futuristic bioremediation.

Chitosan crosslinked with polyamine-co-melamine for adsorption of Hg2+: Application in purification of polluted water.

A batch experiment was carried out in order to remove Hg2+ from the aqueous solution as well as the polluted water using modified chitosan (CS) with polyamine compounds (triethylenetetramine (TETA), tetraethylenepentamine (TEPA)), and melamine. The obtained polyamine-co-melamine crosslinked CS derivatives (MCS-4N and MCS-5N) were characterized and used as adsorbents. In comparison to the raw CS, the modification significantly promoted the adsorption of Hg2+ ions. The results of the pseudo-second-order kinetic model revealed that pH-dependent derivatives adsorbents achieved the equilibrium state within 12 h. The Langmuir model was best fitted with the Hg2+ adsorption isotherm and showed the highest adsorption capacities of 140.3 and 109.7 mg/g for MCS-4N and MCS-5N, respectively. A slight decrease in the adsorption efficiency of Hg2+ was noticed with the increment of the ionic strength of the solution. However, the studied adsorbents were easily regenerated and presented adequate reusability. The Hg2+ adsorption was regulated by the combined process of coordination reaction and electrostatic attraction as well. The as-prepared polyamine-co-melamine crosslinked CS derivatives were found potential adsorbents for the adsorptive capture of Hg2+ ions from aqueous solutions and polluted waters.

Fabrication of thiophene-chitosan hydrogel-trap for efficient immobilization of mercury (II) from aqueous environs.

The fabrication of thiophene-chitosan (TCS) hydrogel has been carried out to show the excellent binding performance of Hg(II) from an aqueous solution of heavy metal ions in presence of thiophene moiety within the hydrogel network. Thiophene moiety has been implanted within chitosan, a wild bio-resources, through a facile Schiff base condensation strategy with 2-thiophenecarboxaldehyde to develop a three-dimensional network of TCS hydrogel. The parameters influencing adsorption capacity such as pH, volume of functional agent, contact time, amount of the hydrogel are included to broaden the in-depth study for the adsorption window of Hg(II) followed by the desorption and reusability performance of TCS. The results indicate that the TCS hydrogel for Hg(II) followed pseudo-second-order kinetics. Ethylenediaminetetraacetic acid (EDTA), acts as a better eluent compared to HCl to desorb Hg(II) and even after recurring adsorption/desorption cycles, removal efficacy of TCS hydrogel could be retained.

Magnetic solid-phase extraction for speciation of mercury based on thiol and thioether-functionalized magnetic covalent organic frameworks nanocomposite synthesized at room temperature.

A simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method for extraction and determination of trace mercury species, including inorganic mercury (IHg), monomethylmercury (MeHg) and ethylmercury (EtHg), was developed. The MSPE adsorbent, urchin-like thiol and thioether-functionalized magnetic covalent organic frameworks (Fe3O4@COF-S-SH), was synthesized by coating covalent organic frameworks (COFs) on the surface of Fe3O4 nanoparticles at room temperature and then easily grafting 1,2-Ethanedithiol on the COFs. The as-prepared Fe3O4@COF-S-SH has strong adsorption capacity for IHg, MeHg and EtHg, with excellent static adsorption capacity: 571, 559 and 564 mg g-1, respectively. The parameters influencing the extraction and enrichment had been optimized, including pH, adsorption and desorption time, composition and amount of the eluent, co-existing ions and dissolved organic materials etc. Under the optimized condition, the limit of detection (3δ) of the proposed method were 0.96, 0.17 and 0.47 ng L-1 for IHg, MeHg and EtHg, and the developed method has high actual enrichment factors of 370, 395, 365-fold for IHg, MeHg and EtHg based on 200 mL samples, respectively. The high accuracy and reproducibility has been proved by the spiked recoveries (96.0‒108 %) in real water samples and determination of the certified reference material. Both the adsorption and desorption process can be completed within 5 min. The proposed method with simple operation, short pre-concentration time and high sensitivity has been successfully applied to mercury speciation at trace levels in the samples with complicated matrices, including underground water, surface water, sea water and fish samples.

Metallomics Analysis for Assessment of Toxic Metal Burdens in Infants/Children and Their Mothers: Early Assessment and Intervention Are Essential.

Accumulation of toxic metals in infants/children is of serious concern worldwide, from the viewpoint of their harmful effects on the normal growth and development. This metallomics study investigates the extent of toxic metal burdens in infants/children and the relationship to those in their mothers for 77 child/mother pair subjects. For mercury, its geometric mean concentration in infants/children was of similar level to that in their mothers, and a high-significant close correlation was observed between infants/children and their mothers (ß = 0.758, r = 0.539, p < 0.0001). A significant but less intimate mother/child relationship was observed for arsenic (ß = 0.301, r = 0.433), lead (ß = 0.444, r = 0.471) and aluminum (ß = 0.379, r = 0.451). Remarkably, the burden levels of lead, cadmium and aluminum in infants/children were approximately three times higher than those in their mothers (p < 0.0001), and the burden levels in some individuals were several tens of times higher than in the mothers. In contrast, some essential metal levels such as zinc, magnesium and calcium in infants/children were significantly lower than those in their mothers, and 29 individuals (37.7%) in the child subjects were estimated to be zinc-deficient. In addition, significant inverse correlations were observed between zinc and lead (r = -0.267, p = 0.019), and magnesium and arsenic (r = -0.514, p < 0.0001). These findings suggest that these toxic metal burdens and essential metal deficiencies in infants/children are of serious concern for their neurodevelopment, indicating that the early assessment and intervention are crucial. It is expected that larger epidemiological and intervention studies will provide a reasonable and essential pathway for intervention of neurodevelopment disorders.

A New Molecular Probe for Colorimetric and Fluorometric Detection and Removal of Hg2+ and its Application as Agarose Film-Based Sensor for On-Site Monitoring.

A new molecule incorporating two units of 7-nitro-benzoxadiazole (NBD), bridged by m-xylylenediamine, was synthesized and characterized on the basis of analytical and spectroscopic techniques. The metal ion sensing property of this molecule was studied spectroscopically with a large number of metal ions. This study revealed that it can perform as a dual-channel probe for colorimetric as well as fluorometric detection of Hg2+. In presence of Hg2+, a substantial change in UV-Vis spectrum with the appearance of a new band at 545 nm and a distinct colour change from yellow to red was observed. In the fluorescence spectrum, the intensity of the emission band was substantially quenched only upon addition of Hg2+. No significant interference from any other metal ion used in this study was noted, the limit of detection (LOD) for Hg2+ was found to be 60 and 10 nM for colorimetric and fluorometric detection method, respectively. This new chemosensor was used for removal of Hg2+ from aqueous solution with 92% efficiency. For on-site monitoring and field application, this molecule was immobilized into the agarose based hydrogel film, which was used successfully for detection of Hg2+ in water. The study on reversible behaviour of this chemosensor revealed that it can be recycled in solution as well as in solid phase by treatment with Na2S.

Removal of Mercury Ions from Aqueous Solutions by Crosslinked Chitosan-based Adsorbents: A Mini Review.

Abatement of mercury emissions in air and waters has become a global challenge due to the toxicity of mercury species for life, yet actual remediation techniques are limited. In particular, adsorption of mercury ions onto solids is widely used but most adsorption techniques are not specific, and in turn, removal efficiency is lower. Adsorbents developed so far include activated carbon, clay, bentonite, cellulose and chitosan. Chitosan derivatives have recently attracted research attention for water purification because their molecular frames contain a large amount of -NH2 and -OH groups that can chelate with metal ions specifically. This manuscript reviews recent advances in chitosan-based adsorbents designed to remove mercury ions from wastewater. Focus is placed on their design, synthesis, characterization, adsorption properties, adsorption mechanisms and applications.

Aggregation-free optical and colorimetric detection of Hg(II) with M13 bacteriophage-templated Au nanowires.

An optical and colorimetric biosensor comprising gold nanowires (Au NWs) templated with genetically engineered M13 bacteriophages expressing a specific Au binding peptides tyrosine-glutamic acid-glutamic acid-glutamic acid (Y3E) is fabricated by silver nitrate and surfactant-mediated biomineralization process. The diameter of the Y3E-Au NWs is around 10 nm and an oriented growth mechanism is identified for the continuous growth of the NWs by interconnecting M13 bacteriophages. The flexible Au NWs have formed an enriched Hg(II) binding sites on its surface and the surface-coated silver nanophase functions as a receptor for more efficient Hg(II) binding. Amalgamation-based colorimetric and optical Hg(II) biosensing of Au NWs are scrutinized in the presence of wild-type M13 bacteriophage-templated Au NWs and spherical Au nanoparticles. It is demonstrated that in comparison with the spherical Au nanoparticles, Y3E-Au NWs exhibits an aggregation-free optical and colorimetric sensor for Hg(II). Mechanistic investigation for the aggregation-free sensor and the Au-Hg amalgam crystals are carried out using TEM, STEM-EDX and XPS analyses.

Dual nanofibrillar-based bio-sorbent films composed of nanocellulose and lysozyme nanofibrils for mercury removal from spring waters.

The present study explores the preparation of dual nanofibrillar-based bio-sorbent films composed of cellulose nanofibrils (CNFs) and lysozyme nanofibrils (LNFs) for application in the removal of Hg(II) from aqueous solutions. The free-standing films were fabricated via simple vacuum filtration of water suspensions of CNFs and LNFs and disclose good mechanical and thermal properties. The Hg(II) removal efficiency was evaluated by atomic fluorescence spectroscopy in ultra-pure and natural spring waters contaminated with environmental realistic levels of mercury (50 µg L-1). The removal efficiency is pH-dependent reaching a maximum of 99 % after 24 h at a pH value close to the isoelectric point of the protein. Under the experimental conditions, the sorption kinetics are well described by the pseudo-second-order and Elovich models, suggesting a chemisorption mechanism. These results demonstrate the ability of the dual nanofibrillar-based films to remove Hg(II) from water samples reaching a residual concentration lower than the guideline value for water intended for human consumption (1 µg L-1). Therefore, the CNFs/LNFs bio-sorbents might be a solution to treat low-concentrated mercury-contaminated waters.

Oxidative stress, metabolic and histopathological alterations in mussels exposed to remediated seawater by GO-PEI after contamination with mercury.

The modern technology brought new engineering materials (e.g. nanostructured materials) with advantageous characteristics such as a high capacity to decontaminate water from pollutants (for example metal(loid)s). Among those innovative materials the synthesis of nanostructured materials (NSMs) based on graphene as graphene oxide (GO) functionalized with polyethyleneimine (GO-PEI) had a great success due to their metal removal capacity from water. However, research dedicated to environmental risks related to the application of these materials is still non-existent. To evaluate the impacts of such potential stressors, benthic species can be a good model as they are affected by several environmental constraints. Particularly, the mussel Mytilus galloprovincialis has been identified by several authors as a bioindicator that responds quickly to environmental disturbances, with a wide spatial distribution and economic relevance. Thus, the present study aimed to evaluate the impacts caused in M. galloprovincialis by seawater previously contaminated by Hg and decontaminated using GO-PEI. For this, histopathological and biochemical alterations were examined. This study demonstrated that mussels exposed to the contaminant (Hg), the decontaminant (GO-PEI) and the combination of both (Hg + GO-PEI) presented an increment of histopathological, oxidative stress and metabolic alterations if compared to organisms under remediated seawater and control conditions The present findings highlight the possibility to remediate seawater with nanoparticles for environmental safety purposes.

Use of hardwood and sulfurized-hardwood biochars as amendments to floodplain soil from South River, VA, USA: Impacts of drying-rewetting on Hg removal.

Periodic flooding and drying conditions in floodplains affect the mobility and bioavailability of Hg in aquatic sediments and surrounding soils. Sulfurized materials have been recently proposed as Hg sorbents due to their high affinity to bind Hg, while sulfurizing organic matter may enhance methylmercury (MeHg) production, offsetting the beneficial aspects of these materials. This study evaluated hardwood biochar (OAK) and sulfurized-hardwood biochar (MOAK) as soil amendments for controlling Hg release in a contaminated floodplain soil under conditions representative of periodic flooding and drying in microcosm experiments in three stages: (1) wet biochar amended-systems with river water in an anoxic environment up to 200 d; (2) dry selected reaction vessels in an oxic environment for 90 d; (3) rewet such vessels with river water in an anoxic environment for 90 d. In Stage 1, greater Hg removal (17-98% for unfiltered total Hg (THg) and 47-99% for 0.45-µm THg) and lower MeHg concentrations (<20 ng L-1) were observed in MOAK-amended systems (10%MOAKs). In Stage 3, release of Hg in 10%MOAKs was eight-fold lower than in soil controls (SedCTRs), while increases in aqueous (up to 21 ng L-1) and solid (up to 88 ng g-1) MeHg concentrations were observed. The increases in MeHg corresponded to elevated aqueous concentrations of Mn, Fe, SO42-, and HS- in Stage 3. Results of S K-edge X-ray absorption near edge structure (XANES) analysis suggest oxidation of S in Stage 2 and formation of polysulfur in Stage 3. Results of pyrosequencing analysis indicate sulfate-reducing bacteria (SRB) became abundant in Stage 3 in 10%MOAKs. The shifts in biogeochemical conditions in 10%MOAKs in Stage 3 may increase the bioavailability of Hg to methylating bacteria. The results suggest limited impacts on Hg removal during drying and rewetting, while changes in biogeochemical conditions may affect MeHg production in sulfurized biochar-amended systems.