Crystal structure and separation factor in DME-driven fractional crystallization

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Lattice parameters and ionic radii for Fe2(SO4)3•7H2O, CoSO4•7H2O, and FeSO4•7H2O. Ferrous iron sulfate and cobalt sulfate are nearly identical; the structure of ferric iron sulfate differs substantially.
Lattice parameters and ionic radii for Fe2(SO4)3•7H2O, CoSO4•7H2O, and FeSO4•7H2O. Ferrous iron sulfate and cobalt sulfate are nearly identical; the structure of ferric iron sulfate differs substantially.

CMI researchers at Idaho National Laboratory conducted the activity for this highlight

Innovation 
Crystal structure is a key factor for separations in Co and Fe sulfate solutions with dimethyl ether (DME) fractional crystallization.

Achievement

  • High separation factors (αCo:Fe>20) are obtained via DME-FC of metal salts with dissimilar crystal lattices and ionic radii, i.e., CoSO4 and Fe2(SO4)3.
  • Adjacent elements with interchangeable lattices and ionic radii, e.g., CoSO4 and FeSO4, show lower separation factors (αCo:Fe≈0.9-1.1).

Significance and Impact
Improved capability to design selective capture of high value critical materials in crystal matrices.

Hub Target Addressed 
Advancing next-generation atom- and energy-efficient separations.

Separation factor αCo:Fe vs. initial solution xCo as obtained with DME-FC. 
Separation factor αCo:Fe vs. initial solution xCo as obtained with DME-FC.