This work investigates the ability of 1-ethyl-3-methylimidazolium methanesulphate ([EMIM][MeSO3]) as a green and tuneable solvent for denitrification and desulphurisation studies. Experimental density, surface tension and refractive index data have been measured for the following systems: [EMIM][MeSO3] (1)?+?pyridine (2), [EMIM][MeSO3] (1)?+?pyrrole (2), [EMIM][MeSO3] (1)?+?quinoline (2), [EMIM][MeSO3] (1)?+?indoline (2), [EMIM][MeSO3] (1)?+?thiophene (2) and [EMIM][MeSO3] (1)?+?water (2) over the entire mole fraction of [EMIM][MeSO3] at T?=?298.15323.15?K and P?=?1?bar. Further from experimental density, surface tension and refractive index, coefficient of thermal expansivity, excess molar volume, deviation of surface tension and refractive index deviation were also calculated. It was found that the heteroaromatic nitrogen/sulphur compounds are completely miscible in [EMIM][MeSO3]. The surface tension values were found to increase while the refractive index decreases with increasing mole fraction of [EMIM][MeSO3]. The experimental values for surface tension increased in the order: pyridine?>?thiophene?>?pyrrole?>?indoline?>?quinoline?>?water and for refractive index: pyridine?>?pyrrole?>?indoline?>?quinoline?>?thiophene?>?water. It was found that the composition of [EMIM][MeSO3] has a greater influence than temperature in deciding the surface, optical and thermodynamic properties for similar molecular interaction such as ILthiophene and ILpyrrole than dissimilar molecules such as ILwater. Further quantum chemical-based COSMO-RS tool was used to estimate the activity coefficient at different composition. (c) 2012 Canadian Society for Chemical Engineering