August 2012 • Vol. 29 No. 3 MINERALS & METALLURGICAL PROCESSING 156 Kinetics of dissolution in H 2 SO 4 of sulfated phosphate rock M. Sınırkaya, A.K. Özer and M.S. Gulaboglu PhD and professors, respectively, Department of Chemical Engineering, Atatürk University, Erzurum, Turkey Abstract In this study, the effects of temperature and acid concentration on the dissolution of the sulfated phosphate samples obtained after flue gas desulfurization in sulfuric acid solution were investigated and compared with the dissolu- tion of raw phosphate rock. The dissolution rate increased as the acid concentration and temperature increased during the dissolution of raw and sulfated samples. The dissolution reaction can be divided into two regions, with different rates of the controlling step. The controlling step was found to be a pseudo-first order reaction before the inflection points, whereas the diffusion through a product layer was found to be the rate-controlling step after the inflection points. The apparent activation energies at the pseudo-first order reaction of the raw and sulfated sample were found to be 38.2 and 25 kJ . mol -1 , respectively, for the temperature range 298-363 K. The apparent activation energies for the ash diffusion model for the raw sample in the temperature range of 298-328 K and sulfated sample in the temperature range of 298-363 K were found to be 32.6 and 36.7 kJ . mol -1 , respectively. Paper number MMP-11-063. Original manuscript submitted December 2011. Revised manuscript accepted for publication March 2012. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to February 28, 2013. Copyright 2012, Society for Mining, Metallurgy, and Exploration, Inc. Introduction Experimental Key words: Sulfated phosphate rock, Flue gas desulfurization, Dissolution kinetics Minerals & Metallurgical Processing, 2012, Vol. 29, No. 3, pp. 156-158. An official publication of the Society for Mining, Metallurgy, and Exploration, Inc.