Improved Strapped Calix[4]pyrroles as Selective Extractants for Lithium Chloride

Physical Sciences : Chemical

Available for licensing


  • Jonathan Sessler, Ph.D. , Chemistry and Biochemistry
  • Qing He, Ph.D. , Chemistry
  • Sung Kuk Kim , University of Texas at Austin

Background/unmet need

Over the past two decades, the worldwide demand for lithium has increased substantially. This rise is consumption-driven by the critical role of lithium in areas as diverse as modern materials, pharmaceuticals, and lithium-ion batteries (LIBs). However, the global lithium reserve is finite. Some estimates show supply from readily accessible lithium resources not being able to meet demand by 2023. Compounding the problem is that the global rate of lithium recycling is <1%.This provides an incentive to develop new strategies that might allow lithium salts to be isolated from non-traditional supply sources, such as brackish brines, where LiCl is expected to define the dominant lithium form.

Invention Description

The present invention comprises an approach to separating lithium chloride directly from mixtures that are rich in often-competitive sodium salts and potassium chloride anion salts. Due to the nature of the ion pair receptors of this invention, it is possible to capture both the chloride anion and the lithium cation concurrently. The synthetic calix[n]pyrrole-based ion pair receptors of this invention have proved effective and efficient and have allowed the selective removal of lithium salts from complex mixtures of salts. This is expected to provide economically and technologically viable alternatives to more conventional methods, which typically involve long and tedious purification processes.


  • The proposed extractants are applicable to both the initial mining and subsequent post-consumer recycling of lithium resources.
  • Cost saving technology


  •  The invention consists of two ditopic ion pair receptors, a new hemispherand-strapped calix[4]pyrrole and a phenanthroline-strapped calix[4]pyrrole. The hemispherand-strapped calix[4]pyrrole was found capable of binding alkali salts in the order of LiCl > NaCl > KCl > CsCl, while the phenanthroline-strapped calix[4]pyrrole proved capable of binding LiCl selectively.
  • Under conditions of solid-liquid extraction the hemispherand-strapped calix[4]pyrrole was found effective as an extractant for LiCl. Indeed, LiCl could be separated from a NaCl-KCl salt mixture containing as little as 1% LiCl. The phenanthroline-strapped calix[4]pyrrole achieved similar separations when the LiCl level was as low as 200 ppm.
  • Under liquid-liquid extraction conditions using chloroform as the non-aqueous phase, the phenanthroline-strapped calix[4]pyrrole displays high selectivity towards LiCl over NaCl and KCl, with no appreciable extraction being observed in the case of the latter two salts.

Market potential/applications

Lithium mining/recycling industry. 

Development Stage

Lab/bench prototype

IP Status

  • 1 U.S. patent application filed