Iron-57 Mossbauer spectroscopy coal minerals

In this paper the application of Mossbauer spectroscopy ( Fe) to determine the iron-bearing minerals will be described, and a critical view of the advantages and disadvantages of the technique will be presented. In this study more than 200 coal samples were investigated and more than 2000 Mossbauer runs were carried out on those samples. Before going into the experimental results, a brief description of the Mossbauer parameters that give the necessary information to determine the compounds seems appropriate. 

The different iron-bearing minerals detected in coal by using Mossbauer spectroscopy are classified below according to their major groups, i.e., sulfides, clays, carbonates, and sulfates. 

Other Minerals. In this work only the minerals mentioned above were detected using Mossbauer spectroscopy. However, in heavily weathered coals and coal refuse the presence of iron oxides (hematite and, to a lesser extent, magnetite) was observed. The Mossbauer parameters for the major iron oxides are given in Table IV. 

The Mossbauer effect has been used as an analytical tool to characterize the diffrent iron-bearing minerals in coal. It has been pointed out that by the use of low-temperature measurements (in the presence of a large external magnetic field) and treatment of the coal samples, all the iron-bearing minerals can be identified correctly. The use of Mossbauer spectroscopy as a quantitative analytical tool presents several experimental difficulties. It is recommended that this spectroscopy be used as a complement to and not as a substitute for the standard techniques. 

The speciation of iron and sulfur in coals has been extensively studied by Mossbauer spectroscopy and is well established. Due to the presence of iron in a large percentage of mineral matter appearing in coal, Mossbauer spectroscopy is a useful, and to a certain degree unique, analytical tool in the identification of iron-bearing minerals [5,6]. 

It is evident that Mossbauer spectroscopy can be a handy tool in differentiating between various coal fields on the basis of the Fe mineral composition of the coal. It should, however, be noted that a detailed analysis of all coal seams needs to be done to determine the run-of-mine coal iron mineral composition. The technique is also suitable for determining the iron components and the presence of sulfur associated with the iron-bearing minerals as part of the impurities found in coal. 

D. Bandyopadhyay, Study of kinetics of iron minerals in coal by Fe Mossbauer and FT-IR spectroscopy during natural burning. Hyperfme Interact. 2005, /63(l-4), 167-176. 

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