Petrological Considerations for the Demineralization of Rajmahal Coals with Pseudomonas mendocina B6-1

Abstract

ABSTRACT The present study entails the results of the petrological coniderations for demineralization of Rajmahal Gondwana coals with Psudomonas mendocina B6-1. Inertinite group macerals are the dominant constituents of these coals, followed by vitrinite group, while liptinite occurs in low concentration. The amount of Mineral matter is moderately high. The concentration of major, minor and trace elements is high when compared with Clarke values. After the treatment of these coals with Pseudomonas mendocina strain B6-1, a significant reduction in the elemental content of oxygen, hydrogen and sulphur was observed. A gradual reduction of pyrite phase due to bioleaching was identified and its signatures were reflected in the XRD spectra and FTIR absorption bands. Over 5 % reduction in the ash content and decrease of major, minor and trace element to variable degrees were also noticed. Fe, As, and Ca positively correlate with the ash removal percentage indicating that the samples with high concentration of these elements were prone to demineralization with Pseudomonas mendocina strain B6-1 whereas Ni, Zn, Cr and Cu, negatively correlate with the ash removal percentage and shows that their enrichment impeded the process of demineralization. With increasing concentration of vitrinite the removal of major/minor/trace elements also increased which is attributed to the possible association of these elements with the mineral matter occurring as superficial mounting and superficial blanketing over the vitrinite macerals. This could facilitate the bacterial access to the elements to act upon and remove it to the variable extent. Some minerals occur intergrown with inertinites causing restricted bacterial action owing to the non-exposure of the mineral particles and less surface area available to the bacteria for bioleaching. Sulfur removal strongly relates with increase in inertinite content and decrease in liptinite content. This appears that sulfur associated with liptinites have shown difficult removal condition. The maximum removal of the trace elements like Cd, Cu, Co, Zn and Pb was observed from the ‘banded dull coal’ samples of the Rajmahal basin while maximum removal of major/minor elements like Fe, Ca and Mg was noticed from the ‘banded bright coal’ samples. However, maximum removal of Mn and As was also observed in the samples of ‘banded coal’.