Richard Markuszewski

The infrared spectra and structures of the three solid forms of fluorescein and related compounds.

The three solid forms of fluorescein, yellow, red and (newly isolated) colourless, have been shown to differ distinctly in structure. By spectroscopic methods, principally infrared absorption, the colourless form has been assigned the lactone structure, the red solid the p-quinone structure, and the yellow solid a zwitterion structure with a positive charge distributed over the oxygen-bearing ring.

Morphological and chemical characterization of iron-rich fly ash fractions.

Fly ash samples collected from the electrostatic precipitator of a coal-fire power plant were separated into relatively magnetic and nonmagnetic fractions. The magnetic portions of these samples were examined by scanning electron microscopy, optical microscopy, and X-ray diffraction. The fly ash particles in the magnetic concentrates were predominately spherical and were generally solid in cross section, although vesicular particles were common in the larger sizes (e.g., >50 ..mu..m). The larger particles also exhibited the most diversity with respect to internal morphology. A variety of dendritic growths were among the features observed. X-ray diffraction analyses revealed that the magnetic fly ash fraction was composed primarily of magnitude and less amounts of hematite. Results of this study suggest a potential for increasing ash density and purity by selecting a particle size range that will optimize these parameters. This in turn could make it more suitable for use as a heavy medium in physical coal beneficiation. 22 references, 9 figures.

Studies on fluorescein—VII: The fluorescence of fluorescein as a function of pH

The relative fluorescence of fluorescein over the pH range 3-12 has been measured at 516 nm, with excitation at 489 nm. The relative fluorescence is essentially zero at pH 3, increases slowly between pH 4 and 5, rises rapidly between pH 6 and 7, reaches a maximum at pH 8, and remains constant at above pH 8. The curve of relative fluorescence as a function of pH lies somewhat above the corresponding curve describing the fraction of fluorescein present as the doubly charged anion, Fl(2-), indicating much weaker fluorescence of the singly charged anion, HFl(-), and very much weaker fluorescence by the neutral species, H(2)Fl. The fluorescence data have been used to calculate a value for the third dissociation constant. Because of the complexity of the system, one unknown dissociation constant and three (relative) fluorescence constants, a series of three variable regressions on the data was made. The final values were K(HFl) = 4.36 x 10(-7) (mu = 0.10) for the third dissociation constant and K(H(2)Fl) = 0.8; kappa(HFl) = 5.7; kappa(Fl) = 100.0 for the relative fluorescence constants.

Desulfurization of coal by oxidation in alkaline solutions

Abstract Bituminous coals were desulfurized by leaching in a small, stirred autoclave with hot, dilute solutions of alkali containing dissolved oxygen under pressure. Most of the inorganic sulfur and a significant portion of the organic sulfur were removed. The effect of process conditions such as temperature, pressure, oxygen partial pressure, and alkalinity on the degree of desulfurization was studied. Under alkaline conditions more sulfur was removed than under acidic conditions. Among different alkalis tested, sodium carbonate or bicarbonate were among the most effective and lowest in cost. At a moderate temperature of about 150° C, the total amount of sulfur extracted in a given period of time increased with increasing oxygen partial pressure, while the heating value was not significantly affected. The effect of temperature on sulfur removal was complex. For coal with a high proportion of pyritic sulfur, the total sulfur reduction was maximum at 120–160° C, depending on the oxygen pressure. For coal with a high proportion of organic sulfur, the total sulfur reduction increased continuously with increasing temperature. With increasing temperature, the heating value recovery decreased gradually at low oxygen partial pressures. However, at higher oxygen partial pressures, the heating value recovery decreased rapidly above 150° C.

Studies on fluorescein—II: The solubility and acid dissociation constants of fluorescein in water solution

The solubility of yellow fluorescein and of red fluorescein as a function of pH has been measured in water at ionic strength 0.10. The pH of minimum solubility is the same for both, 3.28. The intrinsic solubility, defined as the solubility of the undissociated species, H(2)Fl, and assumed to be constant and independent of pH, was calculated from the observed solubilities on the low-pH side of the minimum: S(i, yellow) = 3.80 x 10(-4)M: S(i, red) = 1.45 x 10(-4)M. The first dissociation constants were evaluated from the intrinsic solubilities and the observed solubilities on the low-pH side: both fluoresceins yielded the same value, pK(H3Fl) = 2.13. In using the observed solubilities on the high-pH side of the minimum to evaluate the intrinsic solubility and the second dissociation constant it was necessary to modify the existing theoretical approach by taking into account the presence of the fully dissociated anion. Appropriate mathematical treatments were devised to handle the more complex equations. Both fluoresceins yielded the same value for the second dissociation constant, pK(H2Fl) = 4.44. Both fluoresceins give the same yellow colour in saturated solution and the results just reported for the pH of minimum solubility and for the dissociation constants also indicate that for each of the three prototropic forms of fluorescein present in solution, H(3)Fl(+), H(2)Fl, and HFl(-), only one structure exists.

Behavior of Oxidized Coal During Oil Agglomeration

Abstract The surface of Upper Freeport coal was oxidized by air at 150°C for up to 144 h, and the behavior of this coal during oil agglomeration was studied at various pH values. With increased oxidation time the surface concentration of both carboxyl and hydroxyl groups was increased, and the recovery of coal with a given amount of oil was decreased. Spherical agglomeration was possible only with the unoxidized or mildly oxidized coal. The effect of oxidation on the zeta potential and three-phase contact angle was studied as well as the relation between these parameters and the agglomeration behavior. The recovery of coal was also measured as a function of pH, oil dosage, and addition of the surface-active agents sodium oleate and cetyl trimethyl ammonium bromide. The results indicate that the relative oleophilic/hydrophilic nature of the coal surface is more important to the oil agglomeration process than the electrokinetic properties of the system.

Chemical cleaning of coal by molten caustic leaching after pretreatment by low-temperature devolatilization

Pretreatment of coal by devolatization at temperatures ranging from about 420° C. to about 450° C. for from about 10 minutes to about 30 minutes before leaching with molten caustic leads to a significant reduction in carbonate formation, greatly reducing the cost of cleaning coal on a per ton basis.

Direct determination of sulphate, sulphide, pyritic and organic sulphur in a single sample of coal by selective, step-wise oxidation with perchloric acid

Abstract A procedure was developed for the direct determination of each of the sulphur forms in coal by using various strengths of perchloric acid as the selective oxidizing agent. Sulphate, sulphide, pyritic and organic sulphur were each determined sequentially on a single sample of coal. The oxidizing ability of perchloric acid was varied by changing the boiling point and thus the concentration of perchloric acid. Sulphate sulphur was extracted by boiling perchloric acid at 120 °C. Sulphide sulphur was simultaneously evolved as hydrogen sulphide, trapped in hydrogen peroxide, and converted to sulphate. Perchloric acid boiling at 155 °C was used to oxidize pyritic sulphur to sulphate and a sulphur-containing gas, which was also trapped in hydrogen peroxide. Organic sulphur was oxidized to sulphate and a sulphur-containing gas by boiling at 205 °C in a 9:1 solution of concentrated perchloric and concentrated phosphoric acids. The sulphur produced in each of the step-wise fractions was measured as sulphate. Total sulphur was determined by using boiling concentrated perchloric acid. The results were comparable with those obtained by the ASTM procedure. The relative standard deviations for sulphate, pyritic, organic and total recovered sulphur were 2.7, 3.4, 2.4 and 2.4%, respectively.

Trace Element Removal During Physical and Chemical Coal Cleaning

Abstract Trace elements in coal are detrimental from both an environmental and a technological perspective. Since most trace elements in coal are associated primarily with the mineral phases, they are often amenable to removal by conventional physical coal beneficiation methods. However, these methods generally are not adequate for removing those trace elements which are associated with the organic matrix or which are very finely disseminated. Thus, chemical treatments may be necessary for removal of these trace components. Data from a variety of studies indicate that cleaning by concentrating tables, jigs, heavy-media cyclones, hydrocyclones, froth flotation, and oil agglomeration could effectively remove many trace elements from some coals. However, trace element removal efficiencies varied widely between coals. Because cleaning efficiencies are strongly coal-dependent, conclusions regarding the relative effectiveness of various cleaning techniques are difficult to draw since different coals were used a...

Mineralogical characterization of lower rank coals by SEM-based automated image analysis and energy-dispersive X-ray spectrometry

Automated image analysis (AIA) based on scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry was used to characterize the mineral matter in two western subbituminous coals from the Adaville No. 11 seam (Kemmerer, WY) and the Dietz No. 1 and 2 seams (Decker, MT). The samples were ground to — 200 mesh and cleaned by float-sink separation at 1.40 and 1.38 specific gravity, respectively. The samples were characterized before and after cleaning for mineral phase and size distributions. The Adaville sample contained primarily quartz and an iron-rich mineral, along with traces of apatite, while the Dietz coal contained primarily quartz and kaolinite. The mineral particles in the Adaville coal were notably coarser. The total mineral matter content determined by AIA agreed reasonably well with that calculated from the ASTM ash content. Studies on the association of the mineral particles with the coal matrix were performed by SEMAIA to classify the composite mineral-coal particles into 10 particle types or classes of increasing density. The AIA density distributions were consistent with distributions expected from the float-sink cleaning. They also indicated significant differences in the association of minerals with coal between the raw coals. Specifically, the Dietz coal contained relatively more liberated mineral matter and less material between 1.4 and 1.8g cm−3 than did the Adaville coal.