The desulphurization of Nevsehir-Dadagi lignite with acidic ferric chloride solution and its kinetics and mechanism were investigated. It was found that the effects of the leaching temperature and particle size on the removal of pyritic sulphur are very significant. For larger particles (+ 250 and + 355 mum), the amount of pyritic sulphur removed was 20 wt%. For particles smaller than 250 mum a pyritic sulphur removal of 40-65 wt% was obtained. The removal of pyritic sulphur increased with increase in temperature. The increase of the FeCl3 concentration and the decrease of the acidity also increased the removal of pyritic sulphur. The desulphurization process was found to be well described by the unreacted core model of unchanging size. The overall controlling step was found to be diffusion from the ash layer. A rate equation including the reaction parameters for the decomposition of pyritic sulphur was also established. The activation energy and Arrhenius constant of the reaction were found to be 30.6 kJ mol-1 and 117.5 s-1, respectively.