Enhanced anion exchange for selective sulfate extraction: overcoming the Hofmeister bias.
In this communication, a new approach to enhancing the efficacy of liquid-liquid anion exchange is demonstrated. It involves the concurrent use of appropriately chosen hydrogen-bond-donating (HBD) anion receptors in combination with a traditional quaternary ammonium extractant. The fluorinated calixpyrroles 1 and 2 and the tetraamide macrocycle 4 were found to be particularly effective receptors. Specifically, their use allowed the extraction of sulfate by tricaprylmethylammonium nitrate to be effected in the presence of excess nitrate. As such, the present work provides a rare demonstration of overcoming the Hofmeister bias in a competitive environment and the first to the authors' knowledge wherein this difficult-to-achieve objective is attained using a neutral HBD-based anion binding agent under conditions of solvent extraction.
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
Christopher J
CJ
Fowler
Tamara J
TJ
Haverlock
Bruce A
BA
Moyer
James A
JA
Shriver
Dustin E
DE
Gross
Manuel
M
Marquez
Jonathan L
JL
Sessler
Md Alamgir
MA
Hossain
Kristin
K
Bowman-James
D000577:Amides / Q000737:chemistry; D047250:Calixarenes / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000379:methods; D007474:Ion Exchange; D047029:Lactams, Macrocyclic / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry / Q000302:isolation & purification*
D000577:Amides; D047029:Lactams, Macrocyclic; D011166:Porphyrins; D013431:Sulfates; D047250:Calixarenes