Selective leaching of calcareous phosphate rock in formic acid: Optimisation of operating conditions

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 70wt.%.