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.
Fowler
Christopher J
CJ
Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
Haverlock
Tamara J
TJ
Moyer
Bruce A
BA
Shriver
James A
JA
Gross
Dustin E
DE
Marquez
Manuel
M
Sessler
Jonathan L
JL
Hossain
Md Alamgir
MA
Bowman-James
Kristin
K
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