Impurities in Eppawala rock phosphate and removal methods

Abstract

Apatite mined f r om Eppawala (Eppawala Rock Phosphate - ERP) cannot be directly used as a fertilizer for armual crops such as paddy and vegetables because of its low water solubility. It is difficult to manufacture water soluble phosphate fertilizers from ERP due to its stable chemical formation and impurities in ERP. This study focuses on impurities i n ERP and methods of their removal. Removing the impurities in ERP will help to produce water soluble phosphate fertilizers for annual crops. Literature shows high contents of Fe203, AI2O3 and chlorine as impurities i n ERP. This investigation helped us to reduce combined Fe203 and AI2O3 content from 12.36% to 6.42% i n test 1 of this study and to 4.61% i n test 2 by using froth floatation technique. Acceptable level of combined Fe203 and AI2O3 content for the production of water soluble phosphate fertilizer is less than 5%. Therefore, the concentrate of test 2 is suitable for the production process, but high chlorine content in the concentrate w i l l create difficulties in the formation of water soluble phosphate fertilizers.