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HgBr crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Hg1+ is bonded in a distorted single-bond geometry to one Hg1+ and five equivalent Br1- atoms. The Hg–Hg bond length is 2.63 Å. There are one shorter (2.58 Å) and four longer (3.54 Å) Hg–Br bond lengths. Br1- is bonded in a distorted single-bond geometry to five equivalent Hg1+ atoms.
Mass spectrometry methods are currently under development by the atmospheric mercury (Hg) research community to elucidate the identity of atmospheric oxidized mercury (Hg II ) compounds. Due to high instrument detection limits, materials that can quantitatively preconcentrate atmospheric Hg II without facilitating compound-altering chemical reactions are needed to support these methods. Cation exchange membranes (CEM) and nylon membranes are currently used to preconcentrate ambient Hg II for concentration measurements and Hg II compound estimation, respectively. However, CEM and nylon membranes are poor candidates for observations by mass spectrometry methods due to release of interfering compounds upon heating; glasses do not have this problem. Here, three metal oxide glasses were explored as potential alternatives for Hg II preconcentration for future use with mass spectrometry methods: calcium phosphate (CaP), iron phosphate (FeP), and calcium aluminate (CaAl). The glasses demonstrated quantitative selective capture of HgBr 2 without capture of Hg 0 . Under ambient conditions, the CaP, FeP, and CaAl sorbed 36.4 ± 12.6% of the total HgII as the CEM. However, when Hg concentrations were normalized to surface area, CaP, FeP, and CaAl sorbed more HgBr 2 in the laboratory and ambient HgII compared to CEM. The CEM and CaP retained similar concentrations of HgBr 2 when preloaded samples were deployed in the field. Additionally, a permeation tube-based calibrator was used to load sorbents with HgBr 2 for investigation of HgII retention on CEM and thermal desorption profile changes on nylon membranes during active sampling. Nylon membranes were purchased from three vendors and used to compare HgBr 2 retention; a different HgBr 2 thermal desorption profile was achieved for each vendor’s nylon membrane.
Here we report on the development of a Brewster angle-cavity ringdown spectroscopy (BA-CRDS) system for low temperature plasma diagnostics. The system can measure gas species in solutions, with a detection limit (minimum detectable absorbance) of 9.1 × 10 -5 , which is equivalent to a detection limit of 0.04 parts per billion for measuring OH radicals in water at 308 nm. With higher reflectivity ringdown mirrors and improved design of a Brewster angle cell, the detection limit can potentially be up to 10 -6 or lower. In this exploratory study, the absorption cross sections of HgBr 2 and H 2 O 2 in the aqueous phase at 256 nm are measured to be (1.8 ± 0.1) × 10 -18 cm 2 and (5.2 ± 0.5) × 10 -20 cm 2 , respectively. Furthermore, temporal profiles of absorbance from distilled water, HgBr 2 , and H 2 O 2 solutions when interacting with a helium atmospheric plasma jet are individually characterized at different plasma powers, gas flow rates, and/or solute concentrations. The observed linear temporal profiles of absorbance from the plasma-interacted water suggest formation of H 2 O 2 from plasma-generated OH radicals, while the nonlinear temporal profiles from the plasma-treated HgBr 2 solutions reveal possible removal of HgBr 2 by OH radicals. Our results demonstrate that the new BA-CRDS system is a powerful tool for quantification of reactive plasma species in multiphases or other complex settings.
Anthropogenic mercury emission to the atmosphere adversely affects the environment, wildlife, and human health. Accordingly, the design and implementation of improved mercury-capture technologies have received increased attention. We present a computational chemistry-based screening study to guide the development of mercury-capture materials. We use density functional theory (DFT) to probe the efficacy of metal salts and metal oxides (NaCl, NaBr, KCl, KBr, CaCl 2 , CaBr 2 , NaNO 3 , and MgO) toward mercury capture and their ability to be regenerated for continued use. We focus on three primary sources of mercury emission as elemental gaseous mercury (Hg(0)) or oxidized gaseous mercury species (Hg(II); HgCl 2 or HgBr 2 ): (i) Hg(0) emission from artisanal Au production; (ii) Hg(II)/Hg(0) emission from inlet/outlet streams for flue-gas desulfurization (FGD) operation; and (iii) Hg(0) and Hg(II) emission from cement production. Our results suggest that CaCl 2 and CaBr 2 are good candidates for capturing Hg(0) in artisanal Au production. For FGD operation, KBr, MgO, CaCl 2 , and CaBr 2 are good candidates for capturing HgCl 2 and HgBr 2 , while CaBr 2 is the only studied material that can capture Hg(0) from the outlet FGD stream. For cement production, CaBr 2 is the only material of those studied that can capture Hg(0), HgCl 2 , and HgBr 2 . Furthermore, our DFT results can accelerate the development of cheap and regenerable mercury-capture materials, as well as better prevent the release of mercury to the environment.
HgBrHg7(O2Br)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two HgBr ribbons oriented in the (0, 1, 0) direction and two Hg7(O2Br)2 sheets oriented in the (0, 0, 1) direction. In each HgBr ribbon, Hg+1.38+ is bonded in a 2-coordinate geometry to one Hg+1.38+ and two equivalent Br1- atoms. The Hg–Hg bond length is 2.64 Å. There are one shorter (2.58 Å) and one longer (3.01 Å) Hg–Br bond lengths. Br1- is bonded in an L-shaped geometry to two equivalent Hg+1.38+ atoms. In each Hg7(O2Br)2 sheet, there are seven inequivalent Hg+1.38+ sites. In the first Hg+1.38+ site, Hg+1.38+ is bonded in a distorted see-saw-like geometry to two O2- and two Br1- atoms. There are one shorter (2.18 Å) and one longer (2.39 Å) Hg–O bond lengths. There are one shorter (2.66 Å) and one longer (2.90 Å) Hg–Br bond lengths. In the second Hg+1.38+ site, Hg+1.38+ is bonded in a 4-coordinate geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.18–2.52 Å. The Hg–Br bond length is 2.88 Å. In the third Hg+1.38+ site, Hg+1.38+ is bonded in an L-shaped geometry to two O2- atoms. There are one shorter (2.39 Å) and one longer (2.41 Å) Hg–O bond lengths. In the fourth Hg+1.38+ site, Hg+1.38+ is bonded in a 1-coordinate geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.54–2.92 Å. The Hg–Br bond length is 3.48 Å. In the fifth Hg+1.38+ site, Hg+1.38+ is bonded in a distorted linear geometry to two O2- and one Br1- atom. There are one shorter (2.03 Å) and one longer (2.08 Å) Hg–O bond lengths. The Hg–Br bond length is 3.13 Å. In the sixth Hg+1.38+ site, Hg+1.38+ is bonded in a distorted single-bond geometry to one O2- and three Br1- atoms. The Hg–O bond length is 2.20 Å. There are a spread of Hg–Br bond distances ranging from 3.25–3.33 Å. In the seventh Hg+1.38+ site, Hg+1.38+ is bonded in a trigonal planar geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.22–2.29 Å. The Hg–Br bond length is 3.30 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to four Hg+1.38+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to four Hg+1.38+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Hg+1.38+ atoms. In the fourth O2- site, O2- is bonded to four Hg+1.38+ atoms to form distorted corner-sharing OHg4 tetrahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 1-coordinate geometry to four Hg+1.38+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to five Hg+1.38+ atoms.
HgHgBrHg4O3BrHg2OBr crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four mercury molecules; four Hg2OBr clusters; two HgBr ribbons oriented in the (0, 1, 0) direction; and two Hg4O3Br sheets oriented in the (0, 0, 1) direction. In each Hg2OBr cluster, there are two inequivalent Hg+1.38+ sites. In the first Hg+1.38+ site, Hg+1.38+ is bonded in a 1-coordinate geometry to one Br1- atom. The Hg–Br bond length is 3.10 Å. In the second Hg+1.38+ site, Hg+1.38+ is bonded in a single-bond geometry to one O2- atom. The Hg–O bond length is 2.29 Å. O2- is bonded in a bent 120 degrees geometry to one Hg+1.38+ and one Br1- atom. The O–Br bond length is 1.79 Å. Br1- is bonded in a distorted L-shaped geometry to one Hg+1.38+ and one O2- atom. In each HgBr ribbon, Hg+1.38+ is bonded in a 2-coordinate geometry to one Hg+1.38+ and two equivalent Br1- atoms. The Hg–Hg bond length is 2.63 Å. There are one shorter (2.55 Å) and one longer (3.14 Å) Hg–Br bond lengths. Br1- is bonded in an L-shaped geometry to two equivalent Hg+1.38+ atoms. In each Hg4O3Br sheet, there are four inequivalent Hg+1.38+ sites. In the first Hg+1.38+ site, Hg+1.38+ is bonded in a distorted linear geometry to two O2- and three equivalent Br1- atoms. Both Hg–O bond lengths are 2.11 Å. There are a spread of Hg–Br bond distances ranging from 3.21–3.27 Å. In the second Hg+1.38+ site, Hg+1.38+ is bonded in a 2-coordinate geometry to two O2- and one Br1- atom. Both Hg–O bond lengths are 2.47 Å. The Hg–Br bond length is 3.02 Å. In the third Hg+1.38+ site, Hg+1.38+ is bonded in a distorted single-bond geometry to one O2- atom. The Hg–O bond length is 2.90 Å. In the fourth Hg+1.38+ site, Hg+1.38+ is bonded to three O2- and one Br1- atom to form distorted corner-sharing HgBrO3 trigonal pyramids. There are a spread of Hg–O bond distances ranging from 2.29–2.34 Å. The Hg–Br bond length is 2.92 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four Hg+1.38+ atoms to form corner-sharing OHg4 tetrahedra. In the second O2- site, O2- is bonded in a distorted water-like geometry to one Hg+1.38+ and one O2- atom. The O–O bond length is 1.40 Å. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Hg+1.38+ and one O2- atom. Br1- is bonded in a 5-coordinate geometry to five Hg+1.38+ atoms.