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Purpose: Mineralogical and geochemical features of mining and processing wastes collected in Owen County, part of the Central Kentucky Lead-Zinc district, were investigated. The Gratz mine, abandoned in the 1940’s, is on a dairy farm. Aside from discerning the nature of mining refuse at the site, the investigation was part of the University of Kentucky College of Pharmacy’s mission to explore unusual environments in the search for unique microbiological communities. Materials and methods: Four samples of a soil-plus-spoils mix were collected from spoil piles and two samples, the sluice and coarse samples, were closely associated with the site of the ore processing. Optical petrology (polarized reflected-light, oil- immersion optics at a final magnification of 500x), X-ray diffraction, X-ray fluorescence, Inductively coupled plasma mass spectrometry, Field emission scanning electron microscopy (FE- SEM), and high-resolution transmission electron microscope (HR-TEM) with selected area electron diffraction (SAED) and/or microbeam diffraction (MBD), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectrometer (EDS) analyses were employed to characterize the samples. Results and discussion: Calcite is the main mineral in most samples, followed by near equal amounts of quartz and dolomite. Sphalerite and galena are the principal sulfides and barite is the dominant sulfate. Geochemistry of major elements reflected the mineralogy ; whereas trace elements showed different groupings between the minerals. Scandium, Cu, Ga, Ge, Cd, and Sb were found predominantly associated with Zn and Pb and sulfide minerals ; Bi, Hf, In, Sn, and Zr with heavy mineral fraction ; while the remaining trace elements, including the rare earths, were mostly distributed among other present phases, i.e., oxyhalides, oxides, silicates, and carbonaceous material. The data were used to illustrate the processes and conditions that control the sulfide- mineral oxidation and its potential for the environmental release of associated reaction products. Conclusions: The wastes represent a potential source of environmentally disruptive concentrations of Zn, Pb, and other sulfide- associated elements. The high share of carbonates suggests near-neutral conditions in deposited wastes, restricting sulfide weathering and further limiting the oxidant activity of Fe. The low-Fe content and its predominant presence in highly resistant hematite also constrains sulfide weathering. Consequently, the spoils have a low potential for generation of acidity and release of heavy metal(loid)s in the surrounding environment.

Both the Tiptop and Ruth Mullins coal fires, Kentucky, were reinvestigated in 2009 and 2010. The Tiptop fire was not as active in 2009 and may have been on the path to burning out at the time of the 2009 visit. The Ruth Mullins coal mine fire, Perry County, Kentucky, has been the subject of several field investigations, including November 2009–February 2010 investigations in which we measured gas emissions, collected minerals and tars, and characterized the nature of the fire. Vents exhibiting the greatest gas flux (>100,000 mg/s/m2) are those with the largest amount of condensate minerals and tars. Vents with moderate gas flux (10,000–100,000 mg/s/m2) are less likely to contain condensate minerals, but are collocated with tars, and vents with the lowest flux (

The Kentucky State University heating plant stoker ash, with over 1000 μg/g Rare earth elements + yttrium (REY), was previously shown to be more resistant to acid-extraction than pulverized-coal fly ashes of similar bulk composition. In this study, the petrology and mineralogy of this stoker ash was examined in greater detail as a means to better understand why the REY were relatively inert towards acid extraction. The results showed that this stoker ash is dominated by mullite and quartz/cristobalite with lesser amounts of hematite and magnetite compared to the glass-dominated assemblages of pulverized-coal-combustion fly ashes with similar chemical compositions. On the nanometer to micron scale, La-Ce-Nd-bearing monazite and Ce phosphates (monazite – CePO4 and CeP3O9) are seen to be part of the mineral assemblage. Overall, the results demonstrate that despite the presence of discrete REY-bearing minerals in the sample, their encapsulation within other phases may explain their low extractability.

Beneficiated fly ash from the combustion of Central Appalachian high volatile bituminous coals was extracted with HNO3 in a pilot-scale processing plant. Several major oxides (notably CaO and SO3, but also including Fe2O3, MgO, K2O, and P2O5) and minor elements (Mn, As, Sr, Ba, and Pb) are depleted in the post-HNO3-extraction spent ash. The total lanthanides, Y, and Sc concentration is reduced by about 20% in the spent ash, with Gd showing the greatest decrease. Along with Gd, Nd and Dy are also well differentiated between the feed and spent ashes, with La and Sm showing minimal partitioning. The Gd decrease is correlated with the depletion of Fe2O3. The heavy rare earth elements (REE heavier than Eu) and Y are disproportionately concentrated in the HNO3-leachate compared to the light REE. For the ashes studied, Sc did not partition between the feed and spent ashes. Pozzolanicity tests show that the compressive strength and strength activity indices of the spent ash + ordinary Portland cement (OPC) mixes are comparable to 100% OPC, indicating that the spent ashes produced in the pilot-scale runs have the potential to be sold as a Class F fly ash. Ultimately, the beneficiated ash chemistry influences the chemistry of the post-HNO3-extraction spent ash and the HNO3-leachate. A 500-ppm-REE fly ash will presumably be a more economically favorable feedstock than an ash with a significantly lesser concentration.

The Lotts Creek coal mine fire is burning in abandoned works of the Pennsylvanian Hazard No. 9 coal, Perry County, Kentucky. Over the few months separating sampling trips, the fire showed a definite migration to the south. Several vents sampled on the first trip were extinct on the second trip. The flux of major gases varies from 1100 to 440,000 mg/s/m2 CO2 and

Fly ash was collected from individual mechanical and electrostatic precipitator (ESP) hoppers at a 130-MW pulverized-coal utility unit burning a southeastern Kentucky moderate- to high-S Pennsylvanian Fire Clay coal. The fly ash particle size is generally similar within each row of the mechanical and ESP hoppers, with the mean particle diameter decreasing from \>36 µm in the mechanical hoppers to 6 µm in the last ESP row. Rare earth element (REE)-bearing phases occur within fine minerals and, possibly, as part of the fly ash glass phase. Transmission electron microscopy was used to identify Y-Ce-Nd-La-bearing regions within a glassy matrix. Y- and U-bearing zircons were also found in the fly ash. Total REE plus yttrium (REY) occupies a narrow range from 719 to 775 ppm, showing an overall lack of partitioning of the REY elements with respect to particle size and temperature in ash collection systems. The heavy REE increase and the light REE/heavy REE ratio decreases from the mechanical hoppers through ESP rows.

Low- to high-iron alite-calcium sulfoaluminate-ferrite clinkers were designed through new compositional parameters and synthesized. Clinker compositions were optimized through different firing regimes and verified through characterization methods, such as free lime determination, X-ray diffraction (XRD)/Rietveld, and scanning electron microscopy/energy-dispersive spectroscopy methods. Clinkers with 5–45% of ferrite (C4AF) were produced at a temperature of 1275–1325 °C for a dwell time of 60 min, with the incorporation of fluxes and mineralizers. The hydration processes and the mechanical properties were studied by calorimetry, XRD, thermogravimetry, and compressive strength analyses. The more ferrite that was present in a clinker, the lower the compressive strength, which was mainly due to the unreacted ferrite still present even after six months. Additions of triisopropanolamine to these compositions caused the ferrite to entirely react within seven days, allowing the incorporation of larger amounts of c...

Certain Central Appalachian coals, most notably the Fire Clay coal with a REY-enriched volcanic ash fall tonstein, are known to be enriched in rare earth elements. The Fire Clay tonstein has a greater contribution to the total coal + parting REY than would be inferred from its thickness, accounting for about 20%–35% of the REY in the coal + parting sequence. Underground mining, in particular, might include roof and floor rock and the within-seam partings in the mined product. Beneficiation, necessary to meet utility specifications, will remove some of the REY from the delivered product. In at least one previously published example, even though the tonstein was not present in the Fire Clay coal, the coal was enriched in REY. In this case, as well as mines that ship run-of-mine products to the utility, the shipped REY content should be virtually the same as for the mined coal. At the power plant, however, the delivered coal will be pulverized, generally accompanied by the elimination of some of the harder rock, before it is fired into the boiler. Overall, there are a wide range of variables between the geologic sample at the mine and the power plant, any or all of which could impact the concentration of REY or other critical materials in the coal combustion products. Published version

Arsenic (As) is a trace element in the Earth’s crust. However, its presence in elevated concentrations in groundwaters of major aquifers around the world raises concern about its primary source(s). A close look at the global distribution of known As enriched areas reveals an intriguing systematic pattern, where most of the As enriched aquifers are parts of large sedimentary basins adjoining major orogenic belts, suggesting the existence of a large-scale geological process. Many of these sedimentary basins may be tectonically regarded as foreland basins that developed by lithospheric flexure at the time of mountain building processes (orogenesis) along convergent plate boundaries. Arsenic enrichment in the groundwater of these foreland basin aquifers may be ultimately sourced to crustal evolution processes related to plate tectonics, along with transportation of As-enriched magmatic rocks from the depth to surficial deposits, which subsequently release or mobilize the As to groundwater under conducive surficial biogeochemical processes. Circulating As-laden hydrothermal fluids may also be derived from magmas and form part of the discharge in the surficial hot springs in arc environments. These hydrothermal-genic deposits in orogenic belts may also act as the primary provenance for the As-laden sediments that are transported into foreland basins by wind, glacial erosion, and/or streams. Ultimately, the As-laden foreland sediments serve as modern-day aquifers, where the sediments release As into groundwater by water–rock interaction during various biogeochemical processes under conducive hydrogeochemical conditions. The significance of this hypothesis is that it proposes the existence of a common primary source for globally dispersed geogenic As-enriched aquifers, that have been so far mostly studied as individual occurrences. The proposed hypothesis can explain the widespread presence of As in areas as diverse as the Indus–Ganges–Brahmaputra basin (Himalayan orogen), the Chaco-Pampean basin (Andean orogen), Rocky mountain basin (Western Cordilleran orogen), New England and northeastern USA (the Applachian orogen).

Fly ash and bottom ash are fundamentally the products of the chemistry, petrology, and mineralogy of the input fuel, both the coal and any noncoal fuel, and the nature of the combustion or gasification system. In this chapter, the basic properties of ashes from both combustion and gasification are outlined.

The present study assesses the hydration behavior of polymer modified and non-polymer containing calcium sulfoaluminate (CSA) cement pastes containing minor phase tri-calcium aluminate (C3A) when cured at ambient laboratory temperature with 50% relative humidity. The particular CSA cement is unique as it offers two potential paths for ettringite formation. In the presence of sufficient calcium sulfate, these two potential paths stem from either hydration of yeelimite or hydration of tri-calcium aluminate. The study assesses the microstructural behavior of cement pastes utilizing powdered x-ray diffraction (XRD) and thermogravimetric analysis (TGA/SDT). Additionally, the study utilizes direct tensile strength testing according to ASTM C307, Standard Test Method for Tensile Strength of Chemical Resistant Mortar, Grouts and Monolithic Surfacings to quantify relationships between microstructural characteristics and mechanical property performance for representative mortars. The present study is significant as it illustrates differences in microstructural behavior for CSA cement materials with and without polymer cured at constant 50% relative humidity. The present study suggests ettringite decomposition occurs within non-polymer containing CSA cement paste samples cured at constant low humidity. The present study presents polymer modification as an effective means for mitigating ettringite decomposition and subsequent strength loss in materials containing CSA cement cured at constant 50% relative humidity and 23°C.

The Truman Shepherd coal mine fire, Floyd and Knott counties, Kentucky, has been the subject of several field investigations over the last four years. During July and November 2011 and January 2012 field investigations, we measured gas emissions, collected minerals, and characterized the nature of the fire. New vents opened over the course of the study and have continued to open since January 2012, coincident with the eastward advance of the fire. This is the first study of Kentucky coal fires where the original vents were able to be studied in addition to new vents on each subsequent trip. Neoformed minerals associated with the vents are primarily ammonium sulfates and ammonium chlorides with minor zeolites. BTEX emissions, especially benzene, vary considerably, ranging from relatively low to comparable to those from very large fires, such as the Ankney coal fire in Wyoming. Vent emission data collected displays a general trend of decreasing carbon dioxide and carbon monoxide emissions from July through January. The projected annual greenhouse gas and mercury emissions from the fire are 65.69 t of CO 2 , 4.51 t of CO, 5.73 t of CH 4 , and 1.667 kg Hg. The November 2011 CO/CO 2 ratios are indicative of more complete combustion than at any other time during the study, possibly indicative of decreased moisture in the system.

The purpose of this study was to assess the mechanical property performance behavior of calcium sulfoaluminate (CSA) cement mortar when cured at ambient laboratory temperature of ~23°C (73°F) and constant 50% relative humidity for an extended period of time. Four CSA cement mortars were tested. Three CSA cement mortars contained equivalent mass amounts of calcium sulfate; whereas, the fourth mortar contained double the amount of calcium sulfate. The three CSA cement mortars containing constant mass amounts of calcium sulfate differed as the specific type of calcium sulfate varied across the three formulations—one mortar containing solely anhydrite, one mortar contained half anhydrite and half gypsum while the other mortar solely contained gypsum. The fourth mortar contained double the amount of calcium sulfate when compared with the others while having a 1/1 blend of anhydrite and gypsum. Specific mortars were either tested for direct tensile strength according to ASTM C307 or for compressive strength according to ASTM C109. All tested mortars displayed statistically significant strength loss trends versus time when cured at constant 50% relative humidity. Cement paste samples were analyzed with TGA/SDT and XRD in an effort to identify microstructure changes corresponding to observed strength loss. Cement paste analysis suggests strength loss within the tested CSA cement mortars occurred as a result of ettringite decomposition.

Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals. Diffuse (carbon dioxide (CO(2)) only) and vent (CO(2), carbon monoxide (CO), methane, hydrogen sulfide (H(2)S), and elemental mercury) emission estimates were made for each of the fires. Additionally, gas samples were collected for volatile organic compound (VOC) analysis and showed a large range in variation between vents. The fires produce locally dangerous levels of CO, CO(2), H(2)S, and benzene, among other gases. At one fire in an abandoned coal mine, trends in gas and tar composition followed a change in topography. Total CO(2) fluxes for the fires from airborne, ground-based, and rate of fire advancement estimates ranged from 0.9 to 780mg/s/m(2) and are comparable to other coal fires worldwide. Samples of tar and coal-fire minerals collected from the mouth of vents provided insight into the behavior and formation of the coal fires.

Coal fires in natural outcrops, in abandoned and active coal mines, and in coal and coal-refuse piles are responsible for the uncontrolled emissions of gases, including CO, CO 2 , H 2 S, hydrocarbons, and volatile aromatics. Typically, measurements of gases at a mine vent are made over a short time interval, perhaps no more than 10 min, including the time for replicate measurements. Such timing provides little information on longer-term variations in emissions, although comparisons of seasonal measurements suggest such changes do occur. To address this problem, we placed temperature and CO data loggers in coal fire vents to collect time series measurements for a period of up to three weeks. For one experiment, 11 days of data at one-minute intervals indicated that the CO emissions were generally in the 400–550 ppmv range. However near daily depressions in CO concentrations occurred and in some cases fell below 50 ppmv; followed by an increase to ~ 700–800 ppmv; in turn followed by a return to the ambient conditions. Data for a separate 21-day collection period in a different vent of the same fire exhibited similar trends, albeit at a higher CO concentration. The drop in CO concentration may be associated with a meteorologically-driven inhalation cycle of the fire, whereby air diluted the combustion generated CO. We propose this was followed by an increase in the intensity of the fire due to increased O 2 from the inhaled air, producing increased CO concentrations, before settling back to the ambient conditions.

Coal fires occur in all coal-bearing regions of the world and number, conservatively, in the thousands. These fires emit a variety of compounds including greenhouse gases. However, the magnitude of the contribution of combustion gases from coal fires to the environment is highly uncertain, because adequate data and methods for assessing emissions are lacking. This study demonstrates the ability to estimate CO 2 and CH 4 emissions for the Welch Ranch coal fire, Powder River Basin, Wyoming, USA, using two independent methods: (a) heat flux calculated from aerial thermal infrared imaging (3.7–4.4 t d −1 of CO 2 equivalent emissions) and (b) direct, ground-based measurements (7.3–9.5 t d −1 of CO 2 equivalent emissions). Both approaches offer the potential for conducting inventories of coal fires to assess their gas emissions and to evaluate and prioritize fires for mitigation.

Vent emissions of the Old Smokey coal fire, Floyd County, Kentucky, were studied in May and July, 2010. Vent emissions were generally lower in July, perhaps due to a shift in the fire front, change in vent structure, or another unidentified factor. Volatile organics in the vent gasses contain dangerous levels of toxic, carcinogenic, and other hazardous compounds. Benzene ranges to nearly 400 parts per billion (volume) at one vent. Toluene exceeds 104 parts per billion (volume) at the same vent. Flux rates for CO 2 and CO range to 85,000 mg/s/m 2 and 89 mg/s/m 2 , respectively, for various vents for the two measuring times. Estimates of total CO 2 emissions, possibly less than 1000 t/year, are within the range of other eastern Kentucky coal fires.

Mineral sublimates from the Ruth Mullins fire in abandoned underground and surface mines in the high volatile A bituminous Middle Pennsylvanian Hazard No. 7 coalbed, Perry County, Kentucky, were examined by optical mineralogy, X-ray diffraction (XRD), and high-resolution–transmission electron microscopy (HR-TEM). Optical examination revealed the presence of salammoniac and a fine, unidentified fibrous mineral. XRD also showed the presence of salammoniac, along with trace amounts of quartz, kaolinite, and, possibly, phengite. Both cubic and dendritic salammoniac forms were observed with HR-TEM. Gypsum, jarosite, with cubic pseudomorphs after pyrite, and Fe-minerals, including Cr-bearing hematite in association with jarosite, were observed with HR-TEM. Dehydration of jarosite can lead to the formation of less hydrous Fe-sulfates and hematite.

Carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400 t CO2/yr and 16 kg Hg/yr resulting from a coal combustion rate of 450–550 t/yr. The sum of CO2 emissions from seven vents at the Ruth Mullins fire is 726 ± 72 t/yr, suggesting that the fire is consuming about 250–280 t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21 ± 1.8 t/yr and > 840 ± 170 g/yr, respectively. The CO2 emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9 × 106 t CO2/yr for a 514-MW boiler in Kentucky. Using simple calculations, CO2 and Hg emissions from coal-fires in the U.S. are estimated at 1.4 × 107–2.9 × 108 t/yr and 0.58–11.5 t/yr, respectively. This initial work indicates that coal fires may be an important source of CO2, CO, Hg and other atmospheric constituents.

The Tiptop underground coal-mine fire in the Skyline coalbed of the Middle Pennsylvanian Breathitt Formation was investigated in rural northern Breathitt County, Kentucky, in May 2008 and January 2009, for the purpose of determining the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) in the vent and for measuring gas-vent temperatures. At the time of our visits, concentrations of CO2 peaked at 2.0% and > 6.0% (v/v) and CO at 600 ppm and > 700 ppm during field analysis in May 2008 and January 2009, respectively. For comparison, these concentrations exceed the U.S. Occupational Safety & Health Administration (OSHA) eight-hour safe exposure limits (0.5% CO2 and 50 ppm CO), although the site is not currently mined. Mercury, as Hg0, in excess of 500 and 2100 μg/m3, in May and January, respectively, in the field, also exceeded the OSHA eight-hour exposure limit (50 μg/m3). Carbonyl sulfide, dimethyl sulfide, carbon disulfide, and a suite of organic compounds were determined at two vents for the first sampling event. All gases are diluted by air as they exit and migrate away from a gas vent, but temperature inversions and other meteorological conditions could lead to unhealthy concentrations in the nearby towns. Variation in gas temperatures, nearly 300 °C during the January visit to the fire versus

Mercury capture by coal-combustion fly ash is a function of the amount of Hg in the feed coal, the amount of carbon in the fly ash, the type of carbon in the fly ash (including variables introduced by the rank of the feed coal), and the flue gas temperature at the point of ash collection. In their discussion of fly ash and Hg adsorption, Lu et al. [Energy Fuels 2007, 21, 2112−2120] had some fundamental flaws in their techniques, which, in turn, impact the validity of analyzed parameters. First, they used mechanical sieving to segregate fly ash size fractions. Mechanical sieving does not produce representative size fractions, particularly for the finest sizes. If the study samples were not obtained correctly, the subsequent analyses of fly ash carbon and Hg cannot accurately represent the size fractions. In the analysis of carbon forms, it is not possible to accurately determine the forms with scanning electron microscopy. The complexity of the whole particles is overlooked when just examining the outer pa...

Recent studies indicate that the sodium salt of 1,3-benzenediamidoethanethiol (BDET) is both economical and effective in precipitating mercury and other heavy metals from water. Because wastewaters and contaminated natural waters may contain a variety of heavy metals, it is important to determine how different heavy metals may interact with BDET, and whether free metals may displace those that are bound. To explore this possibility, Cd-, Cu-, Pb-, Mn-, Hg- and Zn-BDET were leached separately under a nitrogen purge for up to 240 h in pH 3 aqueous solutions containing 0.100 mmol of all five heavy metals. The leaching studies indicate that dissolved Hg has a strong tendency to displace Cd, Cu, Mn, Pb, and Zn from the BDET structure.

Toxic heavy metals in air, soil, and water are global problems that are a growing threat to the environment. To meet the federal and state guidelines for heavy metal discharge, companies often use chemical precipitation or chelating agents. In order to be competitive economically, many of these chelating ligands are simple, easy to obtain, and, generally offer weak bonding for heavy metals. Laboratory testing of three commercial reagents, trimercaptotriazine (TMT), Thio-Red potassium/sodium thiocarbonate (STC), and HMP-2000 sodium dimethyldithiocarbamate (SDTC) has shown that the compounds were unable to reduce independent solutions containing 50.00 ppm of divalent cadmium, copper, iron, lead, or mercury to meet EPA standards. Additionally, the compounds displayed high leaching rates and in some cases decomposed to produce toxic substances. In contrast, the studies demonstrate that a recently reported sulfur-containing multidentate ligand is both safe and effective for the removal of these metals.

2,4,6-Trimercaptotriazine, trisodium salt nonahydrate (TMT-55) is a commercial product that is widely used to chemically precipitate cadmium, lead, zinc and other heavy metals from wastewaters and contaminated natural waters. When mixed with aqueous solutions of TMT-55, aqueous solutions of either reagent-grade zinc, cadmium, or lead salts precipitate crystalline "Zn-TMT", amorphous or crystalline "Cd-TMT" or amorphous "Pb-TMT" (M3[S3C3N3]2.nH2O, where M=Cd2+, Pb2+, and Zn2+ and n> or = 0) that may eventually crystallize if stored in air. Laboratory aqueous leaching studies over 78-106 days using pH 3 HCl, distilled water (pH 6) and pH 9-10 NaOH evaluated the stability of the Cd-, Pb-, and Zn-TMT precipitates. Under pH 3 conditions, the amorphous Cd- and Pb-TMT compounds converted to their crystalline forms and amorphous Cd-TMT also crystallized in distilled water. Otherwise, no decomposition products were detected in the leached solid residues. When compared with the aqueous solubilities of corresponding sulfides and most hydroxides, the TMT compounds were significantly more soluble in distilled water and pH 3 HCl.

The acid dissociation constants of 2,4,6-trimercaptotriazine (H(3)TMT, 1) were determined and now can be employed in the preparation of complexes having specific M-TMT (M = divalent metal; TMT = 2,4,6-trimercapto-1,3,5-triazinide, C(3)N(3)S(3)(3-)) ratios. For example, the combination of H(3)TMT (1) with Mg(OH)(2) at pH 7.1 leads to the crystallization of Mg(H(2)TMT)(2).6H(2)O (4). With the appropriate pH adjustment, the contiguous series of compounds Ba(3)(TMT)(2).8H(2)O (3), Ba(H(2)TMT)(2).7H(2)O (5), and BaHTMT.3H(2)O (6) can be isolated. The compounds were characterized by mp, IR, TGA, elemental analysis, and, in the cases of 4, 5, and 6, crystallography. The comparison of 4 with 5 and 6 offers an interesting view of the difference in hard and soft bonding with TMT. In the saltlike Mg structure of 4, there is extensive hydrogen bonding, but in the Ba structures, 5 and 6, covalent Ba-S bonding dominates.

There are immediate concerns with current commercial ligands that are used for heavy metal precipitation, especially the limited arrays of bonding sites. Previous research has indicated that not only do commercial reagents lack sufficient bonding criteria, but they also fail to provide long-term stability as ligand–metal complexes. For this reason, we have developed a pyridine-based thiol ligand (DTPY) which not only offers multiple bonding sites for heavy metals but also should form stable metal–ligand precipitates. In this study, we used the divalent metals cadmium and copper to model the reactivity and pH stability of divalent metal complexes with the DTPY ligand. Using inductively-coupled plasma spectrometry (ICP), results indicate that a 50.00 ppm (parts per million) copper solution, pH of 4.5, can be reduced to below the ICP detection limits of 0.00093 ppm (>99.99% removal), and a 50.00 ppm cadmium solution, pH of 6.0, can be reduced to 0.06 ppm (99.88%).

Although known for over 100 years, complexes of the TMT ligand with transition metals have not, until now, been prepared in a predictable and controlled manner. In the present work, high yield, intentional syntheses of a series of transition metal–TMT combinations are reported. These are of the form M3(TMT)2·nH2O (M=Co (1), Cu (2), Cd(3)), M(HTMT)·nH2O (M=Co (4), Cu (5)) and M(H2TMT)2·nH2O (M=Co (6), Cu (7)). They are prepared by carefully controlling the pH of aqueous TMT solutions and metal to ligand stoichiometry. Serving to demonstrate that these transition metal–TMT complexes may be useful as materials precursors, nanoparticulate Greenockite (CdS) was formed by increasing the pH of a solution of 3.

2,4,6-trimercaptotriazine, trisodium salt, nonahydrate (TMT-55) is a planar C3 symmetric compound that is used commercially to precipitate mercury and other heavy metals from waste waters and contaminated natural waters. A series of laboratory experiments and analyses were performed to evaluate the chemistry and stability of mercury trimercaptotriazine “Hg-TMT” precipitates that result from the addition of aqueous solutions of TMT-55 to aqueous solutions of mercury(II) chloride (HgCl2). Several Hg-TMT species exist, most of which were previously unrecognized. The leaching properties, chemistry and long-term stability of the solids are very diverse. As examples, the white and yellow varieties of Hg-TMT are often unstable in both water and air, and may release more than 6000 μg/l of mercury into distilled and deionized water leachates. Although waste waters and contaminated ground waters are likely to contain less mercury than the HgCl2 solutions used in this study, individuals should recognize that any Hg-TMT compounds are likely to be chemically complex and perhaps unstable under aqueous or atmospheric conditions.

Thio-Red{reg_sign} is a commercial product that is widely used to precipitate divalent heavy metal contaminants from water. To gain a better understanding of how Thio-Red{reg_sign} reacts with dissolved divalent metals, the product was added to laboratory aqueous solutions, each of which contained one of several dissolved copper, lead, mercury, and zinc compounds. In all of the solutions, precipitates rapidly formed after adding Thio-Red{reg_sign}. X-ray diffraction analyses of the precipitates detected ordinary metal sulfides rather than metal thiocarbonates. Further investigations identified reactions that may be responsible for the formation of the precipitates.

The 2,4,6-trimercaptotriazine (TMT) ligand system is currently being used as a complexing agent for divalent metals although little is known about its chemistry. This report entails a description of the syntheses and structures of TMT complexes having the formula M(TMTH2)2·nH2O (M = Ca (1), Sr (2), and Ba (3), where n = 11, 11, and 4.5, respectively). In 1 and 2, the structures consist of alternating layers of hydrated metal cations and π-stacked TMT groups. A wide range of hydrogen-bonding interactions connect these layers. Compound 3 forms as a polymeric molecule with covalent bonds between the Ba atoms and TMT ligands. Each of the compounds was structurally characterized. X-ray data: 1, C24H104Ca4N24O44S24, triclinic, P1, a = 12.9622(7) A, b = 15.9874(9) A, c = 24.516(1) A, α = 81.191(1)°, β = 89.560(1)°, γ = 72.433(1)°, Z = 2; 2, C6H26N6O11S6Sr, triclinic P1, a = 8.7454(5) A, b = 11.7545(6) A, c = 13.7292(7) A, α = 66.529(1)°, β = 73.201(1)°, γ = 77.034(1)°, Z = 2; 3, C12H18Ba2N12O9S12, monoclinic,...