Aqueous Sulfate Separation by Sequestration of [(SO4)(2)(H2O)(4)](4-) Clusters within Highly Insoluble Imine-Linked Bis-Guanidinium Crystals

作者：Custelcean Radu^*; Williams Neil J; Seipp Charles A; Ivanov Alexander S; Bryantsev Vyacheslav S

来源：Chemistry - A European Journal, 2016, 22(6): 1997-2003.

DOI：10.1002/chem.201504651

• anions
• cluster compounds
• crystallization
• guanidines
• self-assembly

Selective crystallization of sulfate with a simple bis-guanidinium ligand, self-assembled in situ from terephthalaldehyde and aminoguanidinium chloride, was employed as an effective way to separate the highly hydrophilic sulfate anion from aqueous solutions. The resulting bis-iminoguanidinium sulfate salt has exceptionally low aqueous solubility (K-sp=2.4x10(-10)), comparable to that of BaSO4. Single-crystal X-ray diffraction analysis showed the sulfate anions are sequestered as [(SO4)(2)(H2O)(4)](4-) clusters within the crystals. Variable-temperature solubility measurements indicated the sulfate crystallization is slightly endothermic (H-cryst=3.7kJmol(-1)), thus entropy driven. The real-world utility of this crystallization-based approach for sulfate separation was demonstrated by removing up to 99% of sulfate from seawater in a single step.

• 出版日期2016-2-5