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2018-02-13

Researchers discover new efficient lithium collection method using MOF membranes; Li from produced water




(A to C) A redox-active MOF Cu(2,7-anthraquinonedicarboxylate) [Cu(2,7-AQDC)] for lithium batteries: (A) structural schematic, (B) charge-discharge profiles, and (C) cycling performance [(A) to (C), adapted with permission from Zhang et al. ]. (D) Schematic of electrochemical Na storage in Prussian blue crystal [(D), adapted with permission from You et al. ]. (E and F) Electrochemical capacitors fabricated with nanocrystals of MOFs (nMOFs): (E) structure of nMOF electrochemical capacitor and (F) comparison of energy and power densities for electrochemical capacitors made from nMOF-867 and activated carbon [(E) and (F), adapted with permission from Choi et al. ]. (G to I) Electronic conductive MOF for electrochemical capacitors: structural schematics of (G) conductive MOF Ni3-hexaiminotriphenylene)2 [Ni3(HITP)2] and (H) electrolyte components in Ni3(HITP)2; (I) cyclic voltammetry at a scan rate of 10 mV s-1 at different cell voltages [(G) to (I), adapted with permission from Sheberla et al.]. (J to L) MOFs as sulfur host for lithium-sulfur (Li-S) batteries: (J) schematic showing the interaction between polysulfides and MOF scaffold, (K) comparison of binding energy of lithium polysulfides to Ni-MOF or Co-MOF, and (L) charge-discharge profiles of MOF/S composite cathodes

Researchers at the University of Texas at Austin, Monash University (Australia) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia have recently discovered a new, efficient way to extract lithium and other metals and minerals from water. They published their findings in an open-access paper in Science Advances.
The team’s technique uses metal-organic-framework (MOF) membranes that mimic the filtering function, or “ion selectivity,” of biological cell membranes. The membrane process easily and efficiently separates metal ions, opening the door to new advanced technologies in the water and mining industries and potential economic growth opportunities in Texas.
We report metal organic framework (MOF) membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions. The angstrom-sized windows acted as ion selectivity filters for selection of alkali metal ions, whereas the nanometer-sized cavities functioned as ion conductive pores for ultrafast ion transport. The ZIF-8 and UiO-66 membranes showed a LiCl/RbCl selectivity of ~4.6 and ~1.8, respectively, which are much greater than the LiCl/RbCl selectivity of 0.6 to 0.8 measured in traditional porous membranes. (Zhang et al.)
The Barnett and Eagle Ford shale formations in Texas contain high amounts lithium, and the produced wastewater generated by hydraulic fracturing in those areas has high concentrations of lithium. Instead of discarding the produced water, the team’s membrane filter could extract the resulting lithium and put it to use in other industries.
Produced water from shale gas fields in Texas is rich in lithium. Advanced separation materials concepts such as ours could potentially turn this waste stream into a resource recovery opportunity. (Benny Freeman, UT Austin)
Each well in the Barnett and Eagle Ford can generate up to 300,000 gallons of produced water per week. Using their new process, Freeman and his team conservatively estimate that from just one week’s worth of produced water, enough lithium can be recovered to power 200 electric cars or 1.6 million smartphones.
In addition, the team’s process could help with water desalination. Unlike the existing reverse-osmosis membranes responsible for more than half of the world’s current water desalination capacity, the new membrane process dehydrates ions as they pass through the membrane channels and removes only select ions, rather than indiscriminately removing all ions. The result is a process that costs less and consumes less energy than conventional methods.
The team’s material operates on principles inspired by highly effective biological cell membranes, whose mechanism of operation was discovered by Roderick MacKinnon and Peter Agre and was the subject of the 2003 Nobel Prize in chemistry.