A new route for the beneficiation of low grade calcareous phosphate rocks

The bulk of the world's phosphate reserves is located in sedimentary horizons that contain appreciable amounts of carbonate. During beneficiation of phosphate rocks, huge amounts of oversize phosphate rocks are rejected from crushers. This reject also mostly contains low tricalcium phosphate content and high carbonate content. In this work, various experiments have been carried out to reduce the carbonate content by leaching the ground phosphate rock with dilute formic acid solution in order to get marketable and industrially acceptable phosphate grades. By using this technique, the effect of formic acid concentration, reaction time, process temperature and liquid/solid ratio (vol./wt. basis) have been studied. It was found that upon treatment of the ground rock with formic acid, the P₂O₅ percent can be raised by up to 29% corresponding to a reduction of about 69% in the calcium carbonate content of the samples, depending on the reaction conditions as well as nature and size of the raw phosphate particles used for analysis.