In situ studies into the formation kinetics of potassium jarosite
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Date
2012-06-01
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Wiley Blackwell
Abstract
This paper reports the results of time-resolved synchrotron powder diffraction and small-angle scattering experiments designed to investigate the kinetics of formation of potassium jarosite by co-precipitation at 353, 368 and 393 K. Only jarosite was produced in these syntheses, and the particles that formed nucleated on the walls of the capillary reaction vessels with a disc-like shape. Relative Rietveld scale factors indicating jarosite abundance have been used as the basis for kinetic modelling of the nucleation and growth stages using a modified form of the Avrami kinetic equation. The results show that jarosite forms by a single nucleation event followed by two distinct stages of growth, each characterized by a different Avrami exponent. The value of this exponent is initially between 1 and 2, and then reduces to around 1. This suggests that jarosite growth after nucleation is controlled by effects at the solution-boundary interface, with the first stage best described by two-dimensional growth which transitions to one-dimensional growth later in the reaction. An activation energy of 89 kJ mol(-1) was estimated for the first stage of growth, in good agreement with previous work. © 2012, Wiley-Blackwell.
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Keywords
Diffraction, X-ray diffraction, Crystallization, Hydrothermal systems, Precipitation, Energy
Citation
Brand, H. E. A., Scarlett, N. V. Y., & Grey, I. E. (2012). In situ studies into the formation kinetics of potassium jarosite. Journal of Applied Crystallography, 45(part 3), 535-545. doi:10.1107/S002188981201607X