Mercury Sulfide Research Articles

HgS NANOPARTICLES FROM CYCLODODECANONETHIOSEMICARBAZONE COMPLEX OF MERCURY AS SINGLE-SOURCE MOLECULAR PRECURSOR

Hg(II) complex of a new ligand cyclododecanonethiosemicarbazone (CDDTSC), was synthesized and characterized by spectral studies and elemental analysis. Synthesis of nano mercuric sulphide was done using the polyol method with glycerol as solvent. UV- Vis spectroscopy, PL, XRD, SEM, EDX, and TEM studies were done for characterization. Though Capping agents or surfactants were not used, highly crystalline, monodispersed HgS nanoparticles were obtained in good yield.

Significance of soil moisture on temperature dependence of Hg emission

Soil moisture is a key factor for mercury (Hg) emission from soil. Despite its significance for Hg emissions, the effect of soil moisture on Hg flux and fractions has not been thoroughly investigated. The objective of this study was to elucidate the influences of soil moisture and temperature on Hg fluxes from soils and Hg fractions. A kinetic study was performed to measure Hg emission fluxes of six soil samples under different temperature (T) (15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) and moisture conditions (0%, 10%, and 20% added water). The results showed that the Hg fluxes increased with increases in T and soil moisture. A linear correlation was found between ln (Hg emission flux) and 1/T for the six soil samples at different moisture contents (R2 = 0.73–0.99). The range of activation energy (Ea) values was 25.31–57.86 kJ/mol. The Hg fractions in soils of different moisture content were determined by a sequential extraction method. The results demonstrated that soil moisture affected the Hg fractions in soils. The Ea values had different relationships with soil moisture in different soils. There were correlations between Ea and the elemental and mercuric sulfide fractions for air-dried soils. However, for moist soils, Ea was negatively correlated with the water-soluble and acid-soluble fractions. Collectively, the combination of the Hg emission kinetics and Hg fraction measurement of different moist soils indicated that Hg emission was affected by both total Hg concentration and Hg fractions.

Mechanisms controlling the transformation of and resistance to mercury(II) for a plant-associated Pseudomonas sp. strain, AN-B15

Bioremediation using mercury (Hg)-volatilizing and immobilizing bacteria is an eco-friendly and cost-effective strategy for Hg-polluted farmland. However, the mechanisms controlling the transformation of and resistance to Hg(II) by these bacteria remain unknown. In this study, a plant-associated Pseudomonas sp. strain, AN-B15 was isolated and determined to effectively remove Hg(II) under both nutrient-poor and nutrient-rich conditions via volatilization by transforming Hg(II) to Hg(0) and immobilization by transforming Hg(II) to mercury sulfide and Hg-sulfhydryl. Genome and transcriptome analyses revealed that the molecular mechanisms involved in Hg(II) resistance in AN-B15 were a collaborative process involving multiple metabolic systems at the transcriptional level. Under Hg(II) stress, AN-B15 upregulated genes involved in the mer operon and producing the reducing power to rapidly volatilize Hg(II), thereby decreasing its toxicity. Hydroponic culture experiments also revealed that inoculation with strain AN-B15 alleviated Hg-induced toxicity and reduced the uptake of Hg(II) in the roots of wheat seedlings, as explained by the volatilization and immobilization of Hg(II) and plant growth-promoting traits of AN-B15. Overall, the results from the in vitro assays provided vital information that are essential for understanding the mechanism of Hg(II) resistance in plant-associated bacteria, which can also be applied for the bioremediation of Hg-contamination in future.

Synthesis of some metal nanoparticles using the effective media of choline chloride based deep eutectic solvents

Nanoparticles are potential candidates for numerous biological as well as chemical applications due to their exotic properties 1 - 3. Low lattice energy ions are found in deep eutectic solvents (DES). A quaternary ammonium salt is frequently complexed with a metal salt or hydrogen bond donor to produce these compounds (HBD) 4 - 6. The green synthesis of nanoparticles using DESs is always eco-friendly and attractive. The current study focuses on the synthesis of mercuric sulphide, Zirconium oxide, Manganese oxide and Copper oxide nanoparticles using the Choline Chloride - Ethylene Glycol DES as the solvent in presence of a reducing agent, hydrazine hydrate. The UV-Visible, FTIR spectra, XRD, SEM and EDAX analysis were carried out on these metal nanoparticles. The average sizes of these metal nanoparticles were found to be 50 to 150 nm. Hence the green synthesis of metal nanoparticles using Ch. Cl – EG can be considered as an alternative route in chemical synthesis of metal nanoparticles.

The chemical state of Hg in synthetic crystals of zinc and mercury sulfides studied by XAFS spectroscopy

In this study, a series of synthetic mercury-bearing sphalerite and zinc-bearing metacinnabar crystals was grown using the salt flux method at 605-650 ​°C at the hot and cold ends of the ampoule, respectively, in a composition range from 2 to 82 ​mol.% of the HgS component. According to the XAFS (X-ray Absorption Fine Structure) measurements, mercury in the sphalerite-metacinnabar crystals exists in the form of a solid solution. The EXAFS (Extended X-ray Absorption Fine Structure) spectra confirm the increase in the ionic radius of all coordination shells in the crystal structure of the Hg-sphalerite and Zn-metacinnabar on 0.14–0.28 ​Å, depending on the calculated model compared to the distances in pure sphalerite. However, the crystal structure does not change. The established nominal oxidation state of mercury in the (Zn, Hg)S is 2+.

The underappreciated role of natural organic matter bond Hg(II) and nanoparticulate HgS as substrates for methylation in paddy soils across a Hg concentration gradient

Rice consumption is the major pathway for human methylmercury (MeHg) exposure in inland China, especially in mercury (Hg) contaminated regions. MeHg production, a microbially driven process, depends on both the chemical speciation of inorganic divalent mercury, Hg(II), that determines Hg bioavailability for methylation. Studies have shown that Hg(II) speciation in contaminated paddy soils is mostly controlled by natural organic matter and sulfide levels, which are typically thought to limit Hg mobility and bioavailability. Yet, high levels of MeHg are found in rice, calling for reconsideration of the nature of Hg species bioavailable to methylators in paddy soils. Here, we conducted incubation experiments using a multi-isotope tracer technique including 198Hg(NO3)2, natural organic matter bond Hg(II) (NOM-199Hg(II)), ferrous sulfide sorbed Hg(II) (≡FeS-200Hg(II)), and nanoparticulate mercuric sulfide (nano-202HgS), to investigate the relative importance of geochemically diverse yet relevant Hg(II) species on Hg methylation in paddy soils across a Hg concentration gradient. We show that methylation rates for all Hg(II) species tested decreased with increasing Hg concentrations, and that methylation rates using NOM-199Hg(II) and nano-202HgS as substrates were similar or greater than rates obtained using the labile 198Hg(NO3)2 substrate. ≡FeS-200Hg(II) yielded the lowest methylation rate in all sites, and thus the formation of FeS is likely a sink for labile 198Hg(NO3)2 in sulfide-rich paddy soils. Moreover, the variability in the methylation data for a given site (1 to 5-fold variation depending on the Hg species) was smaller than what was observed across the Hg concentration gradient (103–104 fold variation between sites). These findings emphasize that at broad spatial scales, site-specific characteristics, such as microbial community structure, need to be taken into consideration, alongside the nature of the Hg substrate available for methylation, to determine net MeHg production. This study highlights the importance of developing site-specific strategies for remediating Hg pollution.

Bioavailability and methylation of bulk mercury sulfide in paddy soils: New insights into mercury risks in rice paddies

Mercury sulfide (HgS) constitutes the largest Hg reservoir in the lithosphere but has long been considered to be not bioavailable and a minor participant in Hg biogeochemical cycling. Herein, we report that bulk α-HgS can be dissolved and methylated in paddy soils, especially with rice culture. Bulk α-HgS exposure did not affect rice growth compared to the control group but significantly increased methylmercury (MeHg) contents in the rhizospheric soils (e.g., 80.15% and 108.71% higher for bulk α-HgS treatment vs. control at the seedling and maturation stages, respectively). Moreover, bulk α-HgS exposure induced an apparent accumulation of MeHg (50% higher for bulk α-HgS treatment vs. control) and markedly elevated total Hg (THg) in rice grains. The presence of DOM and reduced sulfide in paddy soils was further evidenced to drive the mobilization and dissolution of bulk α-HgS, thereby resulting in THg and MeHg accumulation in rice grains. These findings highlight the bioavailability of HgS in rice paddies and suggest that bulk HgS should be considered when assessing Hg health risks and developing efficient remediation approaches in Hg-contaminated croplands.

The fate of methylmercury through the formation of bismethylmercury sulfide as an intermediate in mice

A previous study by our group indicated that methylmercury (MeHg) is biotransformed to bismethylmercury sulfide [(MeHg)2S)] by interaction with reactive sulfur species (RSS) produced in the body. In the present study, we explored the transformation of MeHg to (MeHg)2S in the gut and the subsequent fate of (MeHg)2S in vitro and in vivo. An ex vivo experiment suggested the possibility of the extracellular transformation of MeHg to (MeHg)2S in the distal colon, and accordingly, the MeHg sulfur adduct was detected in the intestinal contents and feces of mice administered MeHg, suggesting that (MeHg)2S is formed through reactions between MeHg and RSS in the gut. In a cell-free system, we found that (MeHg)2S undergoes degradation in a time-dependent manner, resulting in the formation of mercury sulfide and dimethylmercury (DMeHg), as determined by X-ray diffraction and gas chromatography/mass spectrometry, respectively. We also identified DMeHg in the expiration after the intraperitoneal administration of (MeHg)2S to mice. Thus, our present study identified a new fate of MeHg through (MeHg)2S as an intermediate, which leads to conversion of volatile DMeHg in the body.

X-RAY DIFFRACTION ANALYSIS OF MRITYUNJAYA RASA

Introduction: Mrityunjaya Rasa is a Herbo-Mineral formulation, mentioned in Jwara Chikitsa along with various Anupana like Madhu, Aardraka Swarasa, and Jeeraka Kashaya with Guda. Ingredients like Shudha Hingula, Shudha Gandhaka, Shudha Vatsanabha, Shudha Tankana, Pippali and Maricha with properties of Tikta, Katu Rasa Teekshna Guna and Deepana-Pachana, Swedajanana, Yogavahi and Jwaraghna action show the significant result on various types of fever. To attain desired qualities in the finished product, it is much needed to check efficacy on modern parameters for standardization purposes. Thus, Mrityunjaya Rasa was subjected to X- ray diffraction spectroscopy to ensure SOPs followed for preparation. Aim: The study aimed to analyse the results of X-ray diffraction spectroscopy of Mrityunjaya Rasa. Materials and Methods: X-ray diffraction spectroscopy of Mrityunjaya Rasa was carried out at MIT–central instrumentation facility – innovation centre, Manipal, Udupi. Results: XRD study indicates that Mrityunjaya Rasa contains HgS (cinnabar), mercury sulphide in major phase and borax and elements Na, Ca, Mn, Mg, K, P, Zn, C, Cl2, Fe and B in minor phase. Conclusions: Mrityunjaya Rasa contains HgS (cinnabar), mercury sulphide in major phase and borax and other elements like Na, Ca, Mn, Mg, K, P, Zn, C, Cl2, Fe, and B are also present. Compounds and elements are present due to ingredients and Shodhana media which were used. This study can be a path for establishing the thumbprint of SOP for Mrityunjaya Rasa, a herbomineral compound formulation. Keywords: Mrityunjaya Rasa, XRD, HgS, S, Borax, Na, Ca, Mn etc.

Nanosized Cu-In spinel-type sulfides as efficient sorbents for elemental mercury removal from flue gas

Mercury emitted from human activities has received increasing attention because of its extreme toxicity, persistence and bioaccumulation. The development of highly-efficient sorbent with abundant active sites that exhibit high affinity toward Hg0 is the key challenge for elemental mercury capture at low temperature. Herein, Cu-In spinel-type sulfides were synthesized through a hydrothermal synthesis. The Hg0 removal performance of CuxIn2-xS2 sorbents was evaluated in the temperature range of 75 °C to 175 °C. The synthesized CuxIn2-xS2 sorbents showed excellent performance for Hg0 removal at low temperatures, which perfectly matches the optimal temperature of flue gas at the downstream of desulfurization system. Hg0 removal efficiency of CuxIn2-xS2 sorbents significantly improved as the Cu proportion increased. CuInS2 sorbent showed superior mercury removal performance, the mercury removal efficiency reached 99.6% at 125 °C. O2 and NO showed a slight inhibition on Hg0 capture. The coexistence of SO2 and H2O showed no obvious negative effects on Hg0 removal. The CuInS2 sorbent displayed a superior tolerance to SO2 and H2O. TPD and XPS analyses demonstrated that the adsorbed mercury mainly existed in the form of mercuric sulfides (HgS). Hg0 adsorption over CuInS2 sorbent occurred via the Mars-Maessen mechanism. In this mechanism, Hg0 vapor was physically adsorbed on CuInS2 sorbent and then converted to HgS. This study provides future potential for applying CuxIn2-xS2 sorbents to capture gaseous mercury at low temperature.

Spontaneous chiral self-assembly of CdSe@CdS nanorods

Spontaneous chiral self-assembly of CdSe@CdS nanorods

Mercury Speciation in Natural and Mining-Related Systems

Mercury speciation and the composition of mercury phases in natural and mining-related environments is studied by the thermal release analysis combined with electrothermal atomic absorption spectroscopy (TA-ET-AAS), as well as scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDS). The analyses are applied to laboratory-made samples bearing mercury selenide and to field samples from sites known for relatively high natural or industrially induced Hg background. They are, namely, material from the dispersion train of the Ursk sulfide tailings (Ursk Village, Kemerovo region) and debris precipitated from snow sampled in the Kurai mercury zone (Aktash Village, Gorny Altai). The TA-ET-AAS method works well in discrimination and identification of Hg sulfide and Hg selenide provided that the samples contain sufficient amounts of both compounds, but the sum HgS + HgSe can be determined at any contents of the two compounds. The presence of both mercury sulfide and mercury selenide in the samples has been confirmed by SEM-EDS microanalysis. The temperature ranges for the mercury species (Hg2+; HgS+HgSe mixture; mercury bound with organic matter (Hg-OM), including CH3Hg+) are identical in the laboratory and field samples. Therefore, the suggested approach can ensure fast and reliable detection of Hg phases in rocks exposed to supergene alteration

Terahertz Spectroscopic Analysis of the Vermilion Pigment in Free-Standing and Polyethylene-Mixed Forms.

Terahertz spectroscopy can be utilized as an effective nondestructive identification tool for the study of artist’s pigments. Consequently, extensive measurements have been conducted on representative pigment species, and a few terahertz spectral databases have been constructed. However, the reported spectra were often acquired from pigment samples mixed with polyethylene at room temperature with low resolution, which often led to low-quality spectra with unresolved overlapping lines further broadened due to thermal effects. Here, we present our study of vermilion (HgS, mercury sulfide) as an illustration of how we can overcome such difficulties by studying free-standing oil-paint samples at room temperature and then by performing low-temperature measurements on polyethylene-mixed samples to minimize line broadening due to thermal effects. Our results identify clearly resolved absorption peaks due to lattice vibrations of vermilion at 40.4, 44.5, and 89.9 cm–1 at 2 K. The temperature dependence of the peak shift and line broadening reveals anharmonic characteristics of these lattice vibrational modes. Our approach will definitely suggest new ways to improve and enhance existing terahertz spectral databases of ancient and modern pigments toward actual analysis, diagnosis, and conservation of heritage artworks.

Potential leaching of mercury from stable mercury sulphide

Potential leaching of mercury from stable mercury sulphide

Acceleration of the reaction of H2S and SO2 by non-thermal plasma to improve the mercury adsorption performance of activated carbon

Activated carbon (AC) loading sulfur can improve mercury adsorption performance. Fine sulfur clusters can be generated by the H2S and SO2 reaction, but the reaction is extremely slow at ambient temperatures. This study proposes a cost-effective and efficient method for non-thermal plasma (NTP) to accelerate the reactions between H2S and SO2 on AC to improve elemental mercury (Hg0) removal performance. The NTP treatment experiment was carried out on a laboratory-scale dielectric barrier discharge system. The Hg0 adsorption experiment was conducted via the Tekran Hg CEMS online monitoring device. The results showed that NTP treatment accelerated the reaction of H2S and SO2. The specific surface area and surface morphology of the AC had no significant changes after NTP treatment. However, the surface of AC was enriched with more sulfur in a very short time. H2S and SO2 presented an optimum mixing ratio of 2:1. NTP exhibited an optimum treatment time and voltage of 1 min and 3 kV, respectively. The Hg0 removal efficiency was increased by approximately 70% as compared to AC. In addition, the effects of the adsorption temperature and individual flue gas composition were explored. Further X-ray photoelectron spectroscopy analysis and temperature programmed desorption were also performed. Hg0 adsorption was mainly controlled by chemisorption, wherein the elemental sulfur loaded on AC was the main active site for Hg0 conversion to mercuric sulfide (HgS).

Microbial methylation potential of mercury sulfide particles dictated by surface structure

Environmental contamination by mercury in its organometallic form, methylmercury, remains a major global concern due to its neurotoxicity, environmental persistence and biomagnification through the food chain. Accurate prediction of mercury methylation cannot be achieved based on aqueous speciation alone, and there remains limited mechanistic understanding of microbial methylation of particulate-phase mercury. Here we assess the time-dependent changes in structural properties and methylation potential of nanoparticulate mercury using microscopic and spectroscopic analyses, microcosm bioassays and theoretical calculations. We show that the methylation potential of a mercury sulfide mineral ubiquitous in contaminated soils and sediments (nanoparticulate metacinnabar) is determined by its crystal structure. Methylmercury production increases when more of nano-metacinnabar’s exposed surfaces occur as the (111) facet, due to its large binding affinity to methylating bacteria, likely via the protein transporter responsible for mercury cellular uptake prior to methylation. During nanocrystal growth, the (111) facet diminishes, lessening methylation of nano-metacinnabar. However, natural ligands alleviate this process by preferentially adsorbing to the (111) facet, and consequently hinder natural attenuation of mercury methylation. We show that the methylation potential of nanoparticulate mercury is independent of surface area. Instead, the nano-scale surface structure of nanoparticulate mercury is crucial for understanding the environmental behaviour of mercury and other nutrient or toxic soft elements. The environmental behaviour of mercury and other toxic soft elements is in part dictated by the surface structure of nanoparticulates, according to a combination of microcosm bioassays and theoretical calculations.

Speciation of Inorganic Mercury Compounds in Solid Samples via Thermo‐desorption Experiments

AbstractTo establish a standardized method for specifying mercury in solid samples, a database of relevant mercury species is created via thermo‐desorption. By measuring Hg(t) and Hg(0), different evaporation characteristics of mercury halides, sulfide, oxides, nitrates, and sulfates were recorded. It was possible to create a baseline for analyzing solid samples with unknown mercury content. All mercury species without a halide compound evaporate over 200 °C and as elemental mercury. All mercury halides evaporate mainly as oxidized species. From this fact it can be concluded that mercury halides desublimate when heated and have a vapor pressure as a solid. This unique characteristic was only seen by mercury halides. All other species seem to decompose into their single components when heated.

Distribution and bioavailability of mercury in the surface sediments of the Baltic Sea

The study aimed to determine the level of mercury (Hg) and its labile and stable forms in the surface sediments of the Baltic Sea. The work considers the impact of current and historical sources of Hg on sediment pollution, together with the influence of different environmental parameters, including water inflows from the North Sea. Surface sediments (top 5 cm) were collected in 2016–2017 at 91 stations located in different areas of the Baltic Sea, including Belt Sea, Arkona Basin, Bornholm Basin, Gdańsk Basin, West Gotland Basin, East Gotland Basin, and the Bothnian Sea. Besides, the particulate matter suspended in the surface and near-bottom water was also collected. The analysis of total Hg concentration and individual Hg forms in collected samples was carried out using a 5-step thermodesorption method. This method allows for the identification of three labile and thus biologically available, fractions of Hg, which are mercury halides, organic Hg, mercury oxide and sulphate. Two stable fractions, mercury sulphide and residual Hg, were also determined. The highest Hg concentrations, reaching 341 ng g−1, were measured in the highly industrialised Kiel Bay, which was additionally a munition dumping site during and after World War II. High Hg level, ranging from 228 to 255 ng g−1, was also recorded in the surface sediments of the Arkona Basin, which was a result of the cumulative effect of several factors, such as deposition of Hg-rich riverine matter, favourable hydrodynamic conditions and military activities in the past. The relatively elevated Hg concentrations, varying from 60 to 264 ng g−1, were found in the Gdańsk Basin, a region under strong anthropopressure and dominated by soft sediments. The sum of labile Hg in sediments was high and averaged 67% (with the domination of organic Hg compounds), which means that a large part of Hg can be released to the water column. It was found that the water inflows from the North Sea intensify the remobilisation of Hg and its transformation into bioavailable labile forms. As a consequence, the load of Hg introduced into the trophic chain can increase. Despite the significant reduction of Hg emission into the Baltic in the last decades, surface sediments can be an important secondary Hg source in the marine ecosystem. This is especially dangerous in the case of the western Baltic Sea.

Optical, electrical and morphological studies of βHgS thin film prepared by improved chemical bath deposition technique

Polycrystalline mercury sulphide (HgS) thin film at room temperature and in acidic condition was deposited on amorphous glass substrate by using improved chemical bath deposition technique. The structural and morphological analysis of as-deposited and annealed films was carried out by X-ray diffraction and scanning electronic microscopic technique. Ultraviolet and d.c. electrical resistivity measurement were made to study electrical and optical properties of the thin films. The outcome indicates formation of well-crystallized pure βHgS thin films having good electrical and optical properties. For this reason, HgS thin film in acidic medium was deposited properly by using chemical bath deposition technique.

Long-term leaching and volatilization behavior of stabilized and solidified mercury metal waste

With the signing of the Minamata Convention, widespread disposal of mercury metal waste is anticipated in the near future. Due to its environmental effects, mercury metal waste must be stabilized prior to disposal as its mercuric sulfide form and/or solidified with a polymer or cement to reduce leaching and volatilization. This study investigates the long-term leaching and volatilization behaviors from processed mercury waste. Mercury metal waste specimens are stabilized with sulfide and subsequently solidified with either a sulfur polymer or one of three types of low-alkaline cement. The long-term leaching rates from the solidified mercury metal waste specimens as well as the effects of pH and temperature on leaching behavior are evaluated. The long-term volatilization rates of gaseous mercury are also calculated at different temperatures. Mathematical models for mercury leaching, volatilization rates, and their parameters are established to predict the long-term behavior of stabilized, solidified waste mercury in landfill sites.