Investigation into the applicability of Moessbauer spectrometry for a quantitative determination of pyrite in coal and as a control possibility in coal cleaning processes

The possibilities and shortcomings for a quantitative determination of pyrite in coal by means of 57Fe-Moessbauer spectrometry are discussed. As coal is nearly transparant for the 14.4 keV #betta#-radiation of the isotope 57Fe, iron-bearing minerals of concentrations down to 0.1 weight% can be indicated. However a quantitative determination of these concentrations is hindered by the particle size effects on the measured total resonant absorption area of the Moessbauer spectrum. This effect is shown in the report for FeS2. Another difficulty is that the resonant absorption spectrum of pyrite and that of the clay-mineral illite may coincide. In this report Moessbauer spectrometry has been applied to ten N.O.K. standard coals and the results are given. Besides these standard samples, coal samples which have been submitted to one of the three different Coal Cleaning Processes under research in the Netherlands have been measured. As yet there is no reason that Moessbauer spectrometry should substitute the ASTM-method for the quantitative determination of pyrite. However, it will be an excellent technique for application to coal cleaning processes, since a quantitative determination is not necessary. It will be rather straightforward to compare the results of the different coal cleaning processes, and it will be most helpful to develop and control these processes. (Auth.)