Solid Hg Research Articles

Aqueous monomethylmercury degradation using nanoscale zero-valent iron through oxidative demethylation and reductive isolation

This paper proposes a Fenton-like reaction activated by nanoscale zero-valent iron (nZVI) for aqueous monomethylmercury (MMHg) decomposition. Reacting 10 μg L−1 MMHg with 280 mg L−1 nZVI removed 70% of the aqueous MMHg within 1 min, and its main product was aqueous Hg(II). Within 1 − 5 min, the aqueous Hg(II) decreased while the aqueous, solid, and gas-phase Hg(0) increased with 92% MMHg removal. Then, a secondary Hg(II) reduction to solid Hg(0) was prevalent within 30 − 60 min, with 98% MMHg removal. Diverse-shaped magnetite crystals were observed on the surface of nZVI in 2 h, suggesting that Fe(II) oxidation on magnetite can be a source of electrons for secondary Hg(II) reduction. When FeCl2 and H2O2 were added to the MMHg solution without nZVI, 99% of the MMHg changed to Hg(II) within 1 min. The reactive oxygen species (ROS) produced by the Fenton-like reaction accounted for the rapid demethylation but not for the further reduction of Hg(II) to Hg(0). The results suggest a three-step pathway of MMHg decomposition by nZVI: (1) rapid MMHg demethylation by ROS; (2) rapid Hg(II) reduction by Fe(0); and (3) slow Hg(II) reduction by magnetite on the nZVI surface.

Mercury goes Solid at room temperature at nanoscale and a potential Hg waste storage

While room temperature bulk mercury is liquid, it is solid in its nano-configuration (Ønano-Hg ≤ 2.5 nm). Conjugating the nano-scale size effect and the Laplace driven surface excess pressure, Hg nanoparticles of Ønano-Hg ≤ 2.4 nm embedded in a 2-D turbostratic Boron Nitride (BN) host matrix exhibited a net crystallization at room temperature via the experimentally observed (101) and (003) diffraction Bragg peaks of the solid Hg rhombohedral α-phase. The observed crystallization is correlated to a surface atomic ordering of 7 to 8 reticular atomic plans of the rhombohedral α-phase. Such a novelty of size effect on phase transition phenomena in Hg is conjugated to a potential Hg waste storage technology. Considering the vapor pressure of bulk Hg, Room Temperature (RT) Solid nano-Hg confinement could represent a potential green approach of Hg waste storage derived from modern halogen efficient light technology.

Increasing mercury risk of fly ash generated from coal-fired power plants in China

The trend in mercury (Hg) content of fly ash, the primary solid Hg waste from coal-fired power plants (CFPPs), has not been well evaluated in China. This study integrated a national sampling campaign, a literature survey, and model predictions to investigate the trend in Hg content of fly ash and associated output nationwide. The results demonstrated that Hg content of fly ash from both our campaign conducted in 2020 and the literature survey met the Weibull distribution. The best estimate for the distribution of Hg content in our campaign (401.4 µg/kg) was about two-fold higher than that from the literature survey (236.6 µg/kg). The increasing trend was mainly attributed to the increasing installation of advanced air pollution control devices (APCDs) in CFPPs. The total national Hg output by fly ash was estimated to be 217.7 tons (64.1−501.8 tons) currently. Regarding the disposal of fly ash, a total of 16.1 tons and 105.8 tons of Hg were re-emitted into the air and immobilized in materials, respectively. The increasing trend in the Hg content of fly ash suggested the need for more stringent requirements for the disposal of solid Hg waste from CFPPs in China.

Sustainable existence of solid mercury (Hg) nanoparticles at room temperature and their applications.

Although liquid mercury (Hg) has been known since antiquity, the formation of stable solid nano forms of Hg at room temperature has not been reported so far. Here, for the first time, we report a simple sonochemical route to obtain solid mercury nanoparticles, stabilized by reduced graphene oxide at ambient conditions. The as-formed solid Hg nanoparticles were found to exhibit remarkable rhombohedral morphology and crystallinity at room temperature. Extensive characterization using various physicochemical techniques revealed the unique properties of the solid nanoparticles of Hg compared to its bulk liquid metal phase. Furthermore, the solid nature of the Hg nanoparticles was studied electrochemically, revealing distinctive properties. We believe that solid Hg nanoparticles have the potential for important applications in the fields of electroanalytical chemistry and electrocatalysis.

Lattice parameters and equation of state of Cd and Hg at high pressure: A first-principles investigation

First principles calculations have been performed to study high pressure behavior of Cd and Hg. Calculated results are consistent with the published experimental results. Anomaly has been found in the pressure dependence of the axial ratio c/a of hexagonal Cd, in the same pressure range in which it has been reported experimentally. BCT–monoclinic and monoclinic–HCP structural phase transitions have been found in the solid Hg at 11.4 and 35GPa respectively. The transition pressures are in good agreement with the published experimental results. Calculated high pressure lattice constants and equation of state of both elements agree with the experimental results. Elastic constants of BCT and HCP phases of Hg have also been calculated to test the mechanical stability of these phases at various pressures, using Born stability criteria. FPLAPW total energy method has been used for these calculations.

Direct Detection of Solid Inorganic Mercury Salts at Ambient Pressure by Electron-Capture and Reaction-Assisted HePI Mass Spectrometry

Solid HgCl2 is readily detected at ambient conditions by electron capture in a HePI-MS source. The captured electron occupies the empty 6 s orbital of the Hg atom. The resulting radical-anion HgCl2 (-•) can exist as three "flexomers" of different Cl-Hg-Cl angle. The facile in-source formation of HgCl2 (-•) and the adduct [HgCl3](--) is exploited to detect other solid Hg compounds by exposing them to an external chloride source, such as HCl, NaCl, or vapors emanating from solid TiCl3. In situ oxidation of Hg2Cl2 with H2O2 generated signals for HgCl2 (-•) and [HgCl3] (-), suggesting that oxidation makes Hg 6 s orbital available for electron capture.

A straightforward wet-chemistry method for the determination of solid and gaseous mercury fractions in Backlight Cold Cathode Fluorescence Lamps

Backlight Cold Cathode Fluorescence Lamps (B-CCFLs) are already applied in many electronic consumer products such as LCD screens, flat screen TVs, and laptop monitors. In consequence, an increase of such products entering the waste streams can be expected in the near future. As a result of the mercury (Hg) employed in such lamps, the development of recycling techniques to create a best practical environmental option for appropriate end-of-life strategies are necessary. For this purpose the knowledge about speciation in terms of solid and gaseous state of Hg in such lamps is inevitable. However, analytical techniques to discriminate solid and gaseous Hg require a special setup, not available in most routine laboratories. Thus a straightforward and cost efficient analytical technique is of need.In this work we describe sample preparation procedures and analysis techniques, which only require equipment already available in most routine laboratories. The volatile fraction is extracted with a KMnO4 solution utilizing a novel approach, taking the advantage that the B-CCFL glass tubes have a negative pressure. Thus the extraction solution is directly sucked into the tube where the volatile Hg-fraction is immediately extracted. Subsequently, the solid fraction is dissolved via microwave assisted pressure acid digestion after cryo-milling. Analysis for both fractions took place employing a cold vapor atomic absorption system.To prove the new method is fit for purpose, spiking experiments and analysis of reference materials (when available) was performed with recoveries being between 90% and 110%. First results obtained for a stack of lamps from an used LCD-TV display reveal that solid Hg fractions in all lamps show a variation of 20% between samples whereas the gaseous Hg content can vary up to 600%.

Using the INCA-Hg model of mercury cycling to simulate total and methyl mercury concentrations in forest streams and catchments

We present a new, catchment-scale, process-based dynamic model for simulating mercury (Hg) in soils and surface waters. The Integrated Catchments Model for Mercury (INCA-Hg) simulates transport of gaseous, dissolved and solid Hg and transformations between elemental (Hg0), ionic (Hg(II)) and methyl (MeHg) Hg in natural and semi-natural landscapes. The mathematical description represents the model as a series of linked, first-order differential equations describing chemical and hydrological processes in catchment soils and waters which we believe control surface water Hg dynamics. The model simulates daily time series between one and 100years long and can be applied to catchments ranging in size from <1 to ~10,000km2. Here we present applications of the model to two boreal forest headwater catchments in central Canada where we were able to reproduce observed patterns of stream water total mercury (THg) and MeHg fluxes and concentrations. Model performance was assessed using Monte Carlo techniques. Simulated in-stream THg and MeHg concentrations were sensitive to hydrologic controls and terrestrial and aquatic process rates.

Electron-phonon interaction and nonlinear transport phenomena in solid Hg point-contacts

At cryogenic temperatures the conductivity of Hg point-contacts was studied in both the superconducting and normal state. An original method of fabricating the Hg-based point-contacts directly in liquid 4He was proposed, which guaranteed creation of small-size high-purity ballistic contacts. The resistance of the contacts as well as the current-voltage characteristics along with the voltage dependence of their first and second derivatives were experimentally investigated at 1.5 K. We analyze such characteristics of the contacts as Josephson critical current, excess current, energy gap and the nonlinear part of conductivity caused by electron-phonon interaction (EPI). The point-contact EPI function gpc(ω) for Hg was reconstructed and integral parameters of EPI were calculated. The gpc(ω) was then used as an approximation to the phonon density of states for estimations of the thermodynamic characteristics in Hg. Finally we discuss the results of our calculations of non-linear conductivity caused by manifestation of the frequency dependence of the energy gap function in the elastic current component through the contact.

The competitive role of organic carbon and dissolved sulfide in controlling the distribution of mercury in freshwater lake sediments

The detailed distribution of mercury was studied in sediments and porewaters of two freshwater lakes, which were selected because of the contrasting conditions they present at their respective sediment–water interface (SWI). One lake is characterized by a SWI that remains oxic all year long whereas the other one shows a clear seasonal variation with the evolution of strongly anoxic conditions through the summer season. The results of the study clearly identify the importance of redox conditions on the geochemical behaviour of Hg at the SWI of both lakes but a very limited influence of an oxidized layer enriched in Fe and Mn oxyhydroxides at the top of the sediment of the oxic lake. In both lakes, a competitive effect on the cycling and mobility of the element was observed between natural organic matter and amorphous or organo-sulfide compounds. The proportion of Hg associated to natural organic matter in sediments showed a general increase with sediment depth. A fraction containing elemental Hg and Hg suspected to be bound to iron sulfides and organo-sulfides constituted the other major fraction of solid Hg in the sediments of both lakes. This second pool of Hg was generally larger at the top of the sediment where the production of dissolved sulfides is usually more detectable and it decreases with depth, suggesting that the metal is partially transferred from one pool being the sulfides including amorphous FeS and organo-sulfides to the organic matter pool. Methyl Hg represented less than 1% of the total Hg in sediments of both lakes. Our results obtained at different times of the summer season from two lakes contrasted by their SWI emphasize the competitive or alternating role played by dissolved and solid natural organic matter and sulfides on the fate of Hg in freshwater systems.

Preparation and Characterization of a Surface Renewable Solid State Hg/HgO Reference Electrode Utilizing Gold Amalgam

A solid state Hg(Au)/HgO reference electrode was prepared utilizing gold amalgam solid particles. Solid fine powder of the gold amalgam was prepared by chemical reduction of Au(III) with NaBH4 followed by reduction of Hg(II) in the presence of gold fine particles. The solid content in the suspension of the gold amalgam particles and fine mercury oxide particles in DMF containing PVC was precipitated by the addition of a large amount of water to give solid Hg(Au)/HgO/PVC mixture. After drying, the mixture was pressure-molded to a physically stable Hg(Au)/HgO composite reference electrode material. The electrochemical characteristics of the electrode as a reference electrode were very similar to an ordinary Hg/HgO reference electrode. The electrode material can be molded and fabricated in any desired shape and size. The surface can be renewed by a simple polishing process whenever contaminated or deactivated. The applicability of the electrode in the electrochemical detection of carbohydrates after anion exchange separation was evaluated.

Infrared Spectrum of Hg(OH)2 in Solid Neon and Argon.

Mercury(II) hydroxide molecules have been prepared upon mercury arc lamp irradiation of Hg, H2, and O2 mixtures in solid neon and argon. The strongest three infrared absorptions are identified through isotopic substitution (D2, HD, 18O2, 16O18O) and comparison to frequencies from DFT calculations. The isolated Hg(OH)2 molecule is stable and has a linear O−Hg−O linkage in a C2 structure with an 86° dihedral angle. However, in aqueous solution Hg2+ and 2OH- may form an Hg(OH)2 intermediate, which eliminates water and precipitates solid HgO: The solid Hg(OH)2 compound is not known.

Infrared Spectrum of Hg(OH)2 in Solid Neon and Argon

Mercury(II) hydroxide molecules have been prepared upon mercury arc lamp irradiation of Hg, H(2), and O(2) mixtures in solid neon and argon. The strongest three infrared absorptions are identified through isotopic substitution (D(2), HD, (18)O(2), (16)O(18)O) and comparison to frequencies from DFT calculations. The isolated Hg(OH)(2) molecule is stable and has a linear O-Hg-O linkage in a C(2) structure with an 86 degrees dihedral angle. However, in aqueous solution Hg(2+) and 2OH(-) may form an Hg(OH)(2) intermediate, which eliminates water and precipitates solid HgO: The solid Hg(OH)(2) compound is not known.

Spectroscopic quadrupole moments of high-spin isomers in 193 Pb

The quadrupole interaction of high-spin isomers in 193Pb implanted into solid Hg cooled at a temperature T = 170 K has been investigated by the time-differential perturbed $\gamma$ -ray angular-distribution method. Spectroscopic quadrupole moment values of $\vert Q_{\rm s} \vert = 0.22(2)$ eb and 0.45(4) eb have been deduced for the 21/2- and 33/2 + three-neutron states, respectively. A much higher value $\vert Q_{\rm s} \vert = 2.84(26)$ eb has been determined for the 29/2- isomer, the band head of a magnetic rotational band.

The Hg—Rh (Mercury‐Rhodium) System

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Hg-Rh (Mercury-Rhodium) system

Rh interacts with Hg to form stable intermediate phases. By combining data from several investigations, [1967Jan] constructed a phase diagram for pressures sufficiently high to retain Hg in condensed form. This diagram, with slight modification by the present author, is depicted in Fig. 1. The diagram in Fig. 2 is based on the same data and shows equilibria that would be expected at a pressure of 0.1013 MPa (1 atm). The invariant temperatures of both the higher pressure version and the ambient pressure version of Hg-Rh phase relationships are listed in Tables 1 and 2, respectively. These temperatures were estimated from the vapor pressure equations reported in [1967Jan] (for the equations, see Thermodynamics Section, Table 5); however, because of uncertainties in the logarithms of the vapor pressure data, the resultant invariant temperature values are unlikely to have precisions of better than 10%. Thus, the apparent inversions of the order between the decomposition temperatures of Hg5Rh and Hg4.63Rh in Fig. 1 and 2 may or may not be significant. Likewise, no difference between the melting points of pure Hg and Hg saturated with Rh is experimentally detectable; so whether the invariant equilibria between Hg and Hg5Rh is characterized by a peritectic or eutectic reaction is a meaningless discussion. An initial determination of Rh solubility in liquid Hg was made by [1956Str] by chemical analysis of the saturated filtrate. A value of 0.31 at.% Rh at room temperature was obtained. A later determination by [1973Jan1] reported a value of 1 × 10 at.% Rh at 500 °C. The determination again was made by analysis of the saturated filtrate, but the analysis was done spectroscopically after the Sn was added and then the Hg was evaporated. This latter analysis is believed to be more reliable than the former. [1971Ale] used residual resistivity measurements to estimate a value of <2 × 10 at.% Rh dissolved in solid Hg at −40 °C. In addition, estimates of the Rh solubility in liquid Hg are quite low, with [1964Koz] estimating a value of ∼10 at.% Rh at 25 °C from a semiempirical Schroeder-like formula and [1989Gum] estimating a value of 1.5 × 10 at.% Rh at 25 °C from the Miedema cellular model [1983Nie]. The lack of a meaningful shift in the melting temperature of Hg as well as its vapor pressure at 400 °C [1967Jan] upon Rh saturation also indicates a low Rh content of the Hg-rich solvus. From the presently available evidence, solvus compositions of the order of 10 at.% Rh or less as found by [1973Jan1] and [1971Ale] seem reasonable for either solid or liquid Hg. X-ray powder diffraction (XRD) studies have been performed on alloys in the Hg-Rh system [1967Ett, 1967Now, 1967Jan, 1976Gri, 1980Gri]. [1967Ett, 1967Now] reported

Local structure in liquid Hg–Rb alloys studied by EXAFS

The local structures around Hg and Rb atoms in liquid Hg–Rb alloys have been studied by extended X-ray absorption fine structure (EXAFS) measurements. The EXAFS spectra were obtained for Rb K-, Hg L I- and Hg L III-edges as a function of composition. The average distances for Rb–Hg and Hg–Hg obtained by simple model fitting are comparable to the values found in the solid Hg 19Rb 5 crystalline compound, which form Hg n ( n=4 or 5) units around a Rb atom. Based on these results, the anomalous behavior on the electronic properties of liquid Hg-alkali alloys, such as the maximum of the electrical resistivity at 60 at.% alkali, is discussed.

Pyrolysis coupled with atomic absorption spectrometry for the determination of mercury in Chinese medicinal materials

A pyrolysis unit was coupled to an atomic absorption spectrometer for the determination of mercury in solid samples of Chinese medicinal materials (CMMs). This highly sensitive analytical technique provides a simple and rapid method for the screening of Hg in CMM samples including raw herbs, mineral drugs and their derived formulated products. Only 20mg samples were needed and the sensitivity is down to 66pg. The precisions of analyzing solid Hg standard samples and real CM samples were 1.9 and 3–7%, respectively. The recovery of the method was between 97.6 and 102.7% using Hg standard spiked certified reference material of Apple Leaves. No sample pre-treatment was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination. Several CM samples were analyzed and the results obtained agreed well with the certified values. The performance of the method was compared with the widely used cold vapor and inductively coupled plasma–mass spectrometry (ICP–MS) methods. Excellent agreements were observed among these methods for Hg levels in the ng region. With the temperature programming capability of the pyrolysis chamber the instrument can potentially be used for the speciation analysis of Hg.

(Hg, Sb)Ba2Ca2Cu3O8+ thick films on YSZ substrates

Superconducting thick films of (Hg, Sb)Ba2Ca2Cu3O8+ have been fabricated on polycrystalline yttria-stabilized-zirconia substrates utilizing an Hg-free precursor film reacted with Hg vapour, released from a solid Hg source, in a sealed quartz tube. The resulting films have been studied by x-ray diffraction, scanning electron microscopy, ac susceptibility and resistance measurement techniques. A high quality Hg(Sb)-1223 superconducting thick film on YSZ can be fabricated by using a pre-melted Hg-free precursor film. The zero resistance superconducting transition temperature in the post-growth oxygenated thick film is in excess of 130 K and the transport critical current density for the film is 510 A cm-2 at 77 K.

Mercury adsorption to elemental carbon (soot) particles and atmospheric particulate matter

An assessment of the adsorption/desorption of mercury onto/from particulate matter is presented. This assessment addresses both elemental carbon (soot) particles using published data and atmospheric particulate matter using new experimental data. Available experimental data on the adsorption of mercury onto elemental carbon particles have been reexamined in terms of their adsorption isotherms. The experimental data sets analyzed include experiments concerning mercury adsorption on activated carbon in water as well as in the gas phase. Our analysis using partition coefficients derived from published experimental data and typical atmospheric concentrations of elemental carbon particles shows that the amounts of Hg adsorbed to soot in the air or in atmospheric droplets is insignificant. However, if the particle surface/mass ratio is scaled from the experimental data to typical atmospheric conditions, an upper limit of about half the amount of Hg (primarily Hg(II)) could adsorb to elemental carbon particles, for the conditions considered here. Adsorption of Hg(0) appears to be negligible. Experiments were also conducted to investigate the partitioning of mercury between the dissolved (solution) and suspended particulate phases in rain water. The rain-water data are compared with laboratory experimental studies of Hg desorption and adsorption onto atmospheric particulate matter (APM). The results of these experiments suggest that a significant fraction of Hg(II) can be present in atmospheric particulate matter. Our analysis suggests that between 2 and 35% of the dissolved Hg species (e.g. HgCl 2 and Hg(OH) 2) could be adsorbed to APM, for the conditions considered here. The remainder of particulate Hg(II) consists of solid Hg species such as HgO and HgS. An analysis of the adsorption experiments as a function of time suggests that the kinetics of adsorption may need to be taken into account in atmospheric applications.