Dephosphorisation of Western Australian iron ore by hydrometallurgical process

More than 80% of Western Australian iron ore contains an average of 0.15% phosphorus, and attracts a penalty due to its high level of phosphorus when it is exported. At the current rate of mining, identified premium grade iron ore with low phosphorus content (<005%) will be depleted in 30 years. The development of an economical dephosphorisation process is critical for the future success of the Western Australian iron ore industry. In the current work, effective dephosphorisation of Western Australian iron has been demonstrated. Sulphuric acid was chosen as the leachant on the basis of its availability and low cost. The iron ore sample used in this study typically contained 0.126% phosphorus, was from the Pilbara region of Western Australia. After roasting at 1250 degrees C, lump ore (P-80 5.6 mm), pellet 1 (grinding to 100% -1.5 mm before pelletisation) and pellet 2 (grinding to 100% -0.15 mm before pelletisation) were leached in solutions with different sulphuric acid concentrations. After leaching for 5 hours at 60 degrees C in 0.1 M sulphuric acid solution, 67.2%, 69.0% and 68.7% of the phosphorus was leached from the above three samples, respectively. The phosphorus content was reduced from 0.126% to 0.044%, 0.055% and 0.042% respectively. The dissolution of iron during leaching was negligible. The optimum sulphuric acid concentration was 0.1 M in terms of acid cost and iron loss. The acid consumption cost is as low as $A 0.47/tonne. (C) 1999 Elsevier Science Ltd. All rights reserved.