In this study, formic acid was used to reduce the carbonate content of the ground phosphate rock. Effect of acid concentration, liquid/ solid ratio (v/w),. reaction time and temperature has been studied to get marketable and industrially acceptable phosphate grades. Depending on leaching conditions, it was found that the P2O5% could be raised by 30-35% along with corresponding reduction in CO2% up to 67-72% at a phosphate recovery of more than 70 wt.%. (c) 2006 Elsevier Ltd. All rights reserved.