Quantitative Evaluation of the Concentration of Phosphorus Removed during Thermo-Leaching of Haematite with Potassium Hydroxide Solution

A model was derived for predictive evaluation of the concentration of removed phosphorus during thermo-leaching of haematite. A leaching solution of potassium hydroxide was used and the reaction vessel containing the solution and ore was heated at a temperature of 6000C for 10minutes. The model; P = ? [( N3 – exp(1.4 x 10-5? - 1.2 x 10-6 ?2 )]-1 indicates that the concentration of removed phosphorus is directly dependent on the concentration of iron simultaneously leached-out during the leaching process, since phosphorus is a locked up in the ore as an impurity. It was observed that the validity of the model is rooted in the expression ln ? + ? ? ? ln N3 + ln P + ? ?2 where both sides of the expression are approximately equal to 11. The maximum deviation of the model-predicted concentration of removed phosphorus from the corresponding concentration obtained from the experiment was less than 5%. Comparative evaluation of the concentrations of phosphorus removed per unit mass-input of iron oxide ore as obtained from experiment and derived model gives 0.8917 and 1.0266 mg/kg/g respectively. Similarly, the concentrations of phosphorus removed per unit concentration of iron simultaneously leached-out, as evaluated from experimental and model-predicted results are 8.2740 x10- 4 and 9.5261 x10- 4 mg/kg (mg/kg)-1 respectively. The dissolution coefficient of phosphorus in KOH solution at 6000C was found to be approximately equal to the cube root of the ratio of the concentration of leached-iron to the concentration of removed phosphorus..