Effect of Pre-reaction Ball Milling on Kinetics of Lanthanum Phosphate Roasting with Sodium Carbonate

To design economic roasting processes for the recovery of rare earth phosphates from coal-derived feedstocks, it is convenient to study model systems of rare earth phosphate plus a reactant. In this work, the kinetics of the high-temperature roasting of lanthanum phosphate with sodium carbonate were studied. It is typically necessary to heat the reaction mixture above the melting point of Na2CO3 (851 degrees C) to observe appreciable reaction to form La2O3. However, grinding the reactants reduces the necessary temperature to as low as 625 degrees C. It is believed that this increase in reactivity occurs because the ball milling process reduces the reactant particle size in addition to ensuring that the reaction mixture is thoroughly mixed. XRD hot stage results suggest a two-reaction mechanism is the route by which La2O3 is produced from the ball milled sample upon reaction. Apparent activation energy and Arrhenius prefactor for each reaction were determined from TGA experiments.