Behavior of Major Cations in Optimization of Polymer Inclusion Membrane for the Transport of Lithium From Seawater

ABSTRACT Recovery of lithium from seawater remains a problem because of its low concentration. In this study, the extraction of lithium and other metals was carried out in both spiked and real seawater samples. Polymer inclusion membrane (PIM) was synthesized using cellulose triacetate as a base polymer, dibenzylmethane, and trioctylphosphine oxide as carriers as well as 2‐nitrophenyloctyl ether as a plasticizer. The composition of the membrane, effect of the pH and the concentration of the receiver solution were optimized. Six different membrane compositions were tested during the optimization process. The pH of the feed source was adjusted from 8.5 to 12. The concentration of the receiver solution varied between 0.05 M HCl, 0.1 M HCl, and 1 M HCl. The findings demonstrated that in spiked water samples, lithium uptake was much higher than that of the other metals when the pH was increased to pH 12. The combination of 60 wt% DBM: TOPO: 30 wt% CTA: 10 wt% 2‐NPOE in a (1:1) and (2:1) ratio of carriers performed well toward lithium. The order of extraction was Li + > Na + > Ca 2+ > Mg 2+ using 0.05 M HCl and with carriers' composition at a 1:1 ratio. With a 2:1 ratio of carriers, the order of extraction was Li + > Ca 2+ > Na + > Mg 2+ . In real seawater samples, the two PIMs further demonstrated the exclusion of major cations found in seawater with enrichment factors of 0.2 or less with 0.05 M HCl as the acceptor solution.