Confronting two nanofiltration membranes for lithium-calcium selective separation in natural brines

This work reports the main results of an experimental investigation aimed to improve the purity of lithium salts extracted from natural brines using two different nanofiltration (NF) membranes. The idea is to use NF membrane separation to further increase Li to Ca concentrations’ ratios. A synthetic brine, miming the reextraction water of a solvent extraction operation from Chilean Atacama Salar–inspired brines, was treated in a pilot unit. Two different membranes were investigated and compared for the best performances. The filtration results showed that a layer-by-layer (LbL)-modified hollow-fiber membranes, denoted dNF40 with end-of-Life NF90 flat-sheet membranes, referred to as EoL-NF90, operated at transmembrane pressures of 2 bar and 20 bar, respectively, show a 10 times lower energy consumption for dNF40. Also, both tested NF membranes were capable of selectively enriched permeates in Li versus Ca with a better performances observed for dNF40.