Kinetic analysis of the decomposition of the KFe3 (SO4 )2-x (CrO4 )x (OH)6 jarosite solid solution in Ca(OH)2 medium Article uri icon

abstract

  • The decomposition of the solid solution of potassium jarosite with chromium(VI) in Ca(OH)2 media was studied in the present work. According to experimental results, the incorporation of CrO4 2-into the crystal structure of jarosite resulted in a solid solution with the following approximate formula: [K0.86 (H3 O)0.14 ]Fe2.67 [(SO4 )1.23 (CrO4 )0.77 ][(OH)5.01 (H2 O)0.99 ]. The experimental data describe a reaction based on the shrinking core model with chemical control for spherical particles. A reaction order of n = 0.67 and an activation energy (Ea ) of 63.75 kJ mol-1 were obtained in the induction period (tind ). The progressive conversion period is characterized by the diffusion of K , SO4 2-and CrO4 2-ions into the solution. In this stage, n = 1.99 with respect to OH- , and Ea = 51.56 kJ mol-1 . The CrO4 2-diffusion is slower compared to that of sulfate, a slight amount of chromate is adsorbed in the layer of the solid residue consisting on Fe(OH)3 . Finally, the equations that satisfactorily describe the reaction process were established from the data obtained. ©2016 Sociedade Brasileira de Química.
  • The decomposition of the solid solution of potassium jarosite with chromium(VI) in Ca(OH)2 media was studied in the present work. According to experimental results, the incorporation of CrO4 2-into the crystal structure of jarosite resulted in a solid solution with the following approximate formula: [K0.86 (H3 O)0.14 ]Fe2.67 [(SO4 )1.23 (CrO4 )0.77 ][(OH)5.01 (H2 O)0.99 ]. The experimental data describe a reaction based on the shrinking core model with chemical control for spherical particles. A reaction order of n = 0.67 and an activation energy (Ea ) of 63.75 kJ mol-1 were obtained in the induction period (tind ). The progressive conversion period is characterized by the diffusion of K%2b , SO4 2-and CrO4 2-ions into the solution. In this stage, n = 1.99 with respect to OH- , and Ea = 51.56 kJ mol-1 . The CrO4 2-diffusion is slower compared to that of sulfate, a slight amount of chromate is adsorbed in the layer of the solid residue consisting on Fe(OH)3 . Finally, the equations that satisfactorily describe the reaction process were established from the data obtained. ©2016 Sociedade Brasileira de Química.

publication date

  • 2016-01-01