Acta Metallurgica Sinica · 1987 · 12 citations · 0 references
Natural SciencesChemistryEarth SciencesChemical KineticsMineral ProcessingSurface ScienceChemical Kinetics ModelingChemical Reaction KineticsGeochemical KineticsKinetic ModelingMineral ChemistryMineral Surface ChemistryActivation EnergyActivation Energy DeterminationApparent Activation EnergyChemical Reaction MechanismsDigestionMass Transfer EffectsMineral Reaction KineticsSurface Area
On the basis of steady state principle of kinetics and experimental results, a rate equation was derived: V=kS[(C_N—C_A)/K_E], where V=digestion rate; k=rate constant; S=surface area of diaspore in bauxite; C_N, C_A=concentrations of hydroxide and aluminate ions, mol/L; K_E=equilibrium constant of digestion reaction. An equal-digestion-efficiency method was developed and used to process the digestion kinetics data of Pingguo bauxite. The results show that the chemical reactions on the diaspore surface are of first order to the hydroxide and aluminate ions. At 224—242℃ the apparent activation energy was calculated as 89.5 kJ/mol. It is obvious that in this temperature range the digestion process of Pingguo bauxite is controled by chemical reaction on diaspore surface. At 242—268℃ the Arrhenius plot slope changes rapidly and the apparent activation energy was found to be 44.4 kJ/mol. It is believed that the effect of mass-transfer step on digestion rate should be taken into consideration at 242—268℃.