A New Class of Single-Ion Selective Membranes for Harvesting High-Value Materials From Brine

The Challenge The US economy is dependent on foreign supplies of critical minerals Lithium: pharmaceuticals, glass, grease, batteries, batteries, batteries… Phosphorous: fertilizer Domestic supplies of these minerals are available Wastewater, acid mine drainage, produced water These domestic streams are not necessarily amenable to conventional recovery processes Economic considerations Environmental concerns Facilitated Transport Membranes Facilitated transport: Transport across a membrane – combination of solution-diffusion and a complexation reaction “Extractants” added to a membrane matrix as selective entities Selectively binding with target molecules at the interface and transporting them across the membrane The complexation is similar to adsorption of solute on feed side of the membrane and desorption on the permeate side. Phosphate-Selective Mixed-Matrix CEM Our approach towards ionCEM+NPs selective membranes: mixed – matrix ion exchange membranes Na+ Na+ Phosphate as a proof-of-concept Manganese oxide (HMO) NPs as fixed-site carriers MnO form outer-sphere complexes with phosphate H PO 2 3 Helps phosphate desorb into permeate – – H PO 2 3 Other anions are prevented from passing Cl Selectivity achieved Counter ions (e.g., Na+) rapidly diffuse across membrane (to balance charge) Iddya et al., A reverse-selective ion exchange membrane for the selective transport of phosphates via an outer-sphere complexation–diffusion pathway, Nature Notechnology, 2022 Phosphate Recovery Problem: Phosphate flux through modified membrane ~100X smaller than anion from through standard AEM Challenging for scale-up Performed transport modeling to determine required HMO loading to increase flux Experimental data – 6.7% and 11.7% loading (w/w) Model able to predict experimental flux Model predicted that at 35% loading, phosphate flux will increase to almost reach flux through AEM Working on this… 19 Lithium Recovery ED test results confirm membrane performance Membranes challenged with high salinity brine [Na] = M, [Li] = 0. M, [Mg] = 0. M, [Ca] = 0. M Low limiting current – consistent with high selectivity and limited transport of competing cations – low voltage needed in stack Excellent selectivity towards divalent cations Good selectivity towards Na Good Li flux 22 Lithium selective membrane Fabrication Aminated PPO solution PPO added followed by the ultrasonication of the whole solution LMO Particles dispersed in DMF Aminated PPO solution followed by ultrasonication stabilized LMO particles Thermal Crosslinking Drying in at oven at different temperatures (90 – 130 o C) Poured the whole composite Crosslinked flexible LMO particle composite solution onto the glass plate mixed matrix membrane Schematic Illustrations for Aminated-PPO polymer based composite anion exchange membrane.