The present paper entails the results of the demineralization of the Rajmahal Gondwana coals of India with Pseudomonas mendocina strain B6-1 and its signatures revealed in the X-ray Diffraction (XRD) and Fourier transform infrared (FTIR) spectra. The XRD study reveals the reduction of pyrite phase in the coal samples after bacterial treatment due to bio-oxidation of pyrite and the appearance of few new phases of jarosite. Moreover, the intensity of jarosite peaks has been noticed to increase after the bacterial treatment. The FTIR spectra of the bacterial treated Rajmahal coal samples indicate shifting of the absorption peaks as compared to the control samples. The oxidation of pyrite due to the bacterial action and its conversion into jarosite is indicated by the stretching of OH bond at 630 cm⁻¹peak. While the bacterial action on clay minerals in all the samples is indicated by the stretching of bonds at 1114 cm⁻¹to 430 cm⁻¹peaks.

We present the results of the investigations carried out on the demineralization of coal of the Rajmahal Gondwana basin of India using Pseudomonas mendocina strain B6–1. Petrographically these coals are characterized by high concentration of inertinite macerals with subordinate amount of vitrinite and liptinite macerals. The mineral matter content occurs in high concentration which gives a high ash yield. This coal contains relatively high content of major, minor and trace elements when compared with the Clarke values in coal.After the bacterial treatment a considerable reduction in the elemental content of oxygen, hydrogen and sulphur was seen. Reduction in the ash content (>5%) was achieved and variable degrees of removal of the various major, minor and trace element concentration was also noticed. Nearly 59% removal of Mn, 53% of Na, 13% of Fe was achieved among the major/minor elements while nearly 54% of As, 41% of Cd, 39% of Cu, 34% of Ni, 32% of Zn, 13% of Cr, 43% of Co and 66% of Pb could be removed. Arsenic, Fe and Ca have a strong positive correlation with the ash removal percentage indicating that the samples having increased concentration of these elements are prone to demineralization with Pseudomonas mendocina strain B6–1. Whereas the elements like Ni, Zn, Cr and Cu maintain a strong negative correlation with the ash removal percentage indicating that their enrichment could have hampered the process of demineralization.

The present paper entails the investigations on the removal of total sulfur (S _t) from the coal samples of four coal and lignite fields of India and Indonesia by Ralstonia sp and Pseudoxanthomonas sp. Minimum desulfurization (in relative%) was observed in Nagaland coals (India) which contain maximum quantity of S _t (6.86%) among the samples of the studied area while higher removal (in relative%) was observed in coals containing relatively low quantity of S _t. Nevertheless, a positive correlation exists between S _t and removal percentage in samples of all coalfields indicating an increase in removal% with increasing concentration of S _t. The removal percent (with respect to its initial S _t) by Pseudoxanthomonas sp in the investigated area is in order of: Vastan (mean 41.84%) > Indonesian (mean 34.16%) > Nagaland (mean 18.26) coals. In case of removal by Ralstonia sp the order of removal % can be put as: Vastan (mean 45.50%) > Rajpardi (mean 42.93%) > Indonesian (mean 20.22%) > Nagaland (mean 11.83%) coals.