Recovery of phosphate from lean resources

Indian phosphate fertilizer industry is facing constraints in attaining self sufficiency in supply due to the paucity of domestic raw materials. Indigenous rock phosphate supplies meet only 5–10% requirement of P₂O₅. The present investigation of recovering phosphate from lean resources is an attempt to utilize our own resources which can reduce import. The paper deals with the recovery of phosphate from (i) a lean grade ore assaying 2.13% P₂O₅, and (ii) from an iron ore tails reject assaying 6.97% P₂O₅. Beneficiation of low grade phosphate ores containing carbonate gangue, by physical separation like flotation process alone is not efficient in achieving the desired grade with reasonable recovery, due to the similarities in physico-chemical properties of phosphate and carbonate. Flotation followed by selective leaching of phosphate-carbonate concentrate with organic acids is a promising route to achieve the desired grade with good recovery. Moreover, this route has the following advantages, viz., (i) avoids the differential flotation stage and hence avoids the usage of phosphoric acid as depressant, (ii) prevents the loss of phosphate during pre-flotation of carbonate, which enables to achieve maximum recovery. The phosphate concentrates thus obtained assaying 18–20% P₂O₅, are found to be suitable for direct application to soil and for pig iron industry.