ABSTRACT The surface of Thar coal has been characterized by spectroscopic, microscopic and chemical methods using atomic absorption spectroscopy, fourier transform infrared analysis, X-ray diffraction, scanned electron microscopy and pH titration. The samples contained high moisture, low volatile and low to moderate sulfur content and ranked as lignite (heating value 2541 - 4289 btu/lb on moist, mineral-matter-free basis). Scanned electron micrographs show porous matrix with calcium, potassium or sodium minerals. Fourier transform infrared analysis confirmed the presence of aluminum, silica and hydrate mineral constituents also. The spectra showed C=C aromatic groups at 1604 - 1609 cm-1. Phenolic ester and carboxylic acid are identified by C=O stretching vibration peaks at 1702 cm-1. The peaks of quartz and kaolinite were observed at 900 - 1100 cm-1. Point of zero charge of Thar coal has been estimated as 6.00 to 6.27 through adsorption of H+ and OH- ions by suspending coal particles in aqueous electrolyte solution. Oxygen containing functional groups, mineral matter, and metal oxides are found to have a remarkable impact on point of zero charge. The surface characterization study will be helpful in the separation of hydrophilic impurities during coal preparation processes considering pzc as the controlling factor
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