A Study of the Process Kinetics of Acidic Decomposition of Eudialyte

Abstract—The raw-material base and the manufacture of zirconium, niobium, and rare-earth products in Russia are briefly reviewed. The prospects for their manufacture on the basis of the integrated processing of eudialyte are shown. The main methods of the acidic processing of this mineral are considered. The results of studying the kinetics of decomposition of eudialyte with hydrochloric and sulfuric acids are given. It is established that the process of acidic decomposition of eudialyte can be described with a high degree of accuracy by the formal equation d(1 – α)/dτ = –k(1 – α)² for the conversion rate, from which the activation energies of the processes are determined (79.69 and 48.90 kJ/mol for HCl and H₂SO₄, respectively). Based on the topochemical kinetic equations describing various types, mechanisms, and geometric models of solid-phase reactions, the experimental data are mathematically processed. It is established that the mechanism of acidic decomposition of eudialyte is most accurately described by the equation (1 – 2α/3 – 1 –α)^2/3 = k_GBτ) for the Ginstling–Brounschtein diffusion-controlled process.