Synthesis, Thermodynamic, and Kinetics of Rubidium Jarosite Decomposition in Calcium Hydroxide Solutions

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2012-08, Vol.43 (4), p.773-780
• Main Authors: Perez-Labra, Miguel, Romero-Serrano, Antonio, Salinas-Rodriguez, Eleazar, Avila-Davila, Erika O., Reyes-Perez, Martin
• Format: Article
• Language: English
• Subjects: Applied sciences; Aqueous solutions; Characterization and Evaluation of Materials; Chemical synthesis; Chemistry and Materials Science; Decomposition; Exact sciences and technology; Jarosite; Kinetics; Materials Science; Mathematical models; Metallic Materials; Metallurgy; Metals. Metallurgy; Nanotechnology; Process metallurgy; Production of metals; Rubidium; Slaked lime; Structural Materials; Surfaces and Interfaces; Thermodynamics; Thin Films
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-011-9601-7

Rubidium jarosite was synthesized as a single phase by precipitation from aqueous solution. X-ray diffraction and scanning electron microscopy energy-dispersive spectrometry analysis showed that the synthetic product is a solid rubidium jarosite phase formed in spherical particles with an average particle size of about 35  μ m. The chemical analysis showed an approximate formula of Rb 0.9432 Fe 3 (SO 4 ) 2.1245 (OH) 6 . The decomposition of jarosite in terms of solution pH was thermodynamically modeled using FACTSage by constructing the potential pH diagram at 298 K (25 °C). The E-pH diagram showed that the decomposition of jarosite leads to a goethite compound (FeO·OH) together with Rb + and ions. The experimental Rb-jarosite decomposition was carried out in alkaline solutions with five different Ca(OH) 2 concentrations. The decomposition process showed a so-called “induction period” followed by a progressive conversion period where Rb + and ions formed in the aqueous solutions, whereas calcium was incorporated in the solid residue and iron gave way to goethite. The kinetic analysis showed that this process can be represented by the shrinking core chemically controlled model with a reaction order with respect to Ca(OH) 2 equals 0.4342 and the calculated activation energy is 98.70 kJ mol –1 .