Promising transport and high-selective separation of Li(I) from Na(I) and K(I) by a functional polymer inclusion membrane (PIM) system

This paper first reports on the high-selective separation and recovery of Li(I) from Na(I) and K(I) using the polymer inclusion membrane (PIM) system containing both thenoyltrifluoroacetone (TTA) and trioctylphosphine oxide (TOPO) as the carrier molecules, and cellulose triacetate (CTA) as the base polymer. To characterize the PIM, we used Fourier Transform infrared (FT-IR) spectroscopy, scanning election microscopy (SEM) and thermogravimetric analysis (TGA). The optimized results of this work showed that initial flux ( J 0 ) $J_0)$ of Li(I) that was as high as 1.04  × $\times$  10 −2  mol m −2  h −1 , corresponding to permeability ( P $P$ ) of 3.62  × $\times$  10 −3  m h −1 , were recorded using the PIM composed of 50 wt% CTA and 26.74 wt% TTA + 23.26 wt% TOPO from a feed phase containing Li(I), Na(I) and K(I) in an alkaline chloride solution into an acceptor phase containing 0.1 M HCl. Li(I) was transported successfully to the acceptor phase but Na(I) and K(I) barely passed in the first 20 h. The separation factor ( S F $SF$ ) of Li(I) over the Na(I) and K(I) respectively ( S F L i ( I ) / N a ( I ) ≒ $S{F}_{Li\left(I\right)/Na\left(I\right)}\fallingdotseq$ 54.25, S F L i ( I ) / k ( I ) ≒ $S{F}_{Li\left(I\right)/k\left(I\right)}\fallingdotseq$ 50.60) demonstrated that Li(I) can be high-selectively separated. It is expected that this membrane can be applied for selective recovery of Li(I) from salt lakes or sea water that contains significant concentrations of Na(I) and K(I).