The instrumentation and methodology for real-time computer controlled scanning potential coulometry for multi-component trace analysis is described. The sensitivity limit was determined to be 10^-8 F for electrochemically reversible constituents. The sensitivity limit could be extended if measures were taken to compensate for the periodic signal found on the electrolysis current. Non-linear least squares curve fitting methods accurately resolved iron-platinum and silver-iron interferences to give accurate determinations for iron and silver. The resolving capability of this method was tested using theoretically generated scanning potential coulograms. The computer resolved sample constituents with a 1 to 100 concentration ratio and a formal potential separation of 10 millovolts. It also accurately resolved sample constituents with a 1 to 1000 concentration ratio, one with 1 equivalent per and the other with 2 equivalents per mole, but with no formal potential separation.

The distribution and speciation of trace metals in natural waters is only slightly, at best, understood. Interactions with organic substances can effectively distribute the metals throughout many ill-defined physical and chemical. To better comprehend the complexity of metal-organic interactions this work focused on the delineation of trace iron species present in a natural system. The separation of Fe(II) and Fe(III) was successfully accomplished using a variation of an ion exchange method involving resin-loaded filter paper. The quantitation of the various iron species was determined using linear scan voltammetry and atomic absorption. The total iron concentration, determined as the sum of the various separate species, compares favorably with the total iron concentration as determined directly using atomic absorption methods.

The 1990 Clean Air Act Amendment (CAAA) contains provisions that will establish new emission standards for 190 potentially hazardous air pollutant precursors (HAPPs). Studies have suggested that many of these HAPPs have the potential to be removed prior to combustion. This thesis details the findings of a bench-scale test program that was implemented to evaluate the capabilities of physical coal cleaning technologies on the removal of trace elements from coal. Test work was completed on Pittsburgh No. 8 seam coal that was processed using physical cleaning techniques (i.e., crushing, dense media separation, froth flotation, and enhanced gravity separation). The bench-scale test circuit incorporated crushing and rewashing a coarse, mid-density product with hopes that trace element rejections would improve due to greater liberation of HAPPs. The results of this investigation showed that trace elements were predominately rejected in the coarse coal portions of the processing circuit (i.e., dense media separation), and only slight improvements in rejections could be realized from crushing any portion of the coal. It was also shown that trace element rejection could be incrementally increased with minimal loss of total yield or combustible recovery when froth flotation is put in series with enhanced gravity separation. The results of the bench-scale test work, along with trace element float-sink and release analysis data, were used to develop a simulator that can predict trace element rejections from any coal processing circuit. This was achieved by applying general partition functions to trace element washability and bench-scale processing data. Simulation studies included comparing three physical coal cleaning techniques. The results of these analyses showed that although no net improvement in trace element rejection can be gained through crushing the circuit feed, there is a slight increase in product yield. Crushing a mid-density coarse coal product also showed little or no improvement in trace element rejection. / Master of Science

No description available.

Coal preparation is widely regarded as a cost effective method for reducing the amounts of potentially hazardous air pollutant precursors (HAPPs) that occur as trace elements in the run-of-mine coals. Unfortunately, many existing coal preparation plants are inefficient in removing trace elements because of poor circuit design and inadequate liberation of coal and mineral matter. These problems are often difficult to correct in the absence of characterization data regarding the mineralogical association and washability of trace elements in run-of-mine coals. Therefore, the first step in removing the trace elements through coal preparation is to characterize the modes of association for trace elements in a coal seam. The purpose of this project was to link the occurrence of specific trace elements to the mineralogy and washability characteristics of different eastern U.S. coal seams. Detailed characterization studies were carried out using scanning electron microscopy (SEM) coupled with automated image analysis (AIA) to establish the association between different trace elements and the various components contained in coal. The first step in this analysis required the preparation of 11 different density fractions from a run-of-mine sample of 65 x 100 mesh Pittsburgh No. 8 coal. The samples were then examined using the scanning electron microscope (SEM) to establish the individual mineral constituents contained within each gravity fraction. For comparison, each gravity fraction was also carefully analyzed for trace element content by atomic adsorption spectroscopy (AA). The contribution of various mineral components to the trace element concentrations was determined in the present work using statistical procedures, i.e., individual linear regression and multiple linear regression. After completing the SEM analyses, washability (float-sink) tests were performed on three different coal seams. In this work, several size fractions from each of three different run-of-mine coals were subjected to float-sink testing and release analysis. Because of the overwhelming amount of data, statistical analyses were conducted to show the key relationships identified by this work. The data collected from this study show that trace elements are primarily associated with the mineral matter present in run-of-mine coal. The washability work also shows that the trace elements are concentrated in the heavier specific gravity classes. The characterization work shows that majority of the trace elements are associated with the ash-forming mineral matter and pyrite. The only element found to have a strong association with organic matter was beryllium. The information obtained from this work suggests that a properly designed coal preparation plant can remove substantial amounts of trace elements prior to coal combustion. / Master of Science

Thesis (Ph. D.)--McMaster University (Canada), 1989. / Source: Dissertation Abstracts International, Volume: 62-13, Section: A, page: 0000.

A study has been made of three organic complexing reagents , namely dithizone, oxine and cupferron with a view to developing suitable methods for the separation and concentration of Zn, Co, Ni, Pb, Cu, Mn, Ti , V and Mo prior to the spectrometric determination of their concentrations. In particular the influence of pH on the chloroform extraction of ditihizonates, oxinates and cupferrates from aqueous tartrate and citrate solutions and the separation of iron by oxine extraction has been investigated. The development of a method for the chemical concentration and spectrcgraphic determination of Zn, Co, Ni, Pb, Ti, V and Mo is described and the possibility of determining Nn and Cu flame photometrically as part of the analysis scheme is demonstrated. A specially designed slide rule for the calculation of spectrographic results is described. A direct reading spectrometric method for the determination of Zn, Pb and Cu in plant material is presented. The analysis of plant ash for zinc using the 2138 . 6A spectrum line has been studied and a simple, rapid analysis method is described.

Urban soils are often contaminated with trace metals and the toxicity of the metals depends, in part, on their speciation in soil solutions. The objectives of this project were to estimate the metal speciation in urban soils and to evaluate the predictability of soil metal pools on plant uptake. The chemical speciation of Cd, Cu, Ni, Pb and Zn was estimated by using the Windermere Humic Aqueous Model (WHAM). In soil solutions, Cd, Ni and Zn were present mainly as free ions when the solutions were acidic and their organic complexes were dominant as the pH was over 7.5. The other two metals mostly formed complexes with organic ligands. The activities of Cd2+, Cu2+, Ni2+, Pb2+ and Zn 2+ were affected by soil pH and total soil metal burdens. All five metals were under-saturated with respect to the minerals which could potentially control the metal solubility. / Metal uptake by plants in the contaminated railway yards was generally not correlated with free, dissolved and total soil metal pools. A pot experiment demonstrated better correlations between the metal pools and the metal content in wild chicory. Multiple regression analysis showed that the metals in the leaves and roots of wild chicory could be adequately predicted by the soil total metals and soil properties such as pH and exchangeable Ca.

No description available.

No description available.