Continuous and selective extraction of Cs+ using a t-BAMBP/P204/MWCNTs supported liquid membrane

A novel 4-tert-butyl-2-(α-methylbenzyl) phenol/bis(2-ethylhexyl) phosphate/ Multi-Walled Carbon Nanotubes (t-BAMBP/P204/MWCNTs) supported liquid membrane (SLM) was prepared via an in-situ impregnation method. The MWCNTs network effectively anchored the t-BAMBP/P204 synergistic extractants, enhancing membrane stability. Through proton exchange and coordination interactions, this membrane efficiently extracts Cs + in weakly alkaline environments. A systematic investigation was conducted into the effects of MWCNTs, t-BAMBP and P204 ratios, diluent ratio (kerosene: cyclohexane), pH value, and temperature on Cs + extraction performance. In this system, at equal concentrations (C Cs+, Rb+  = 200 ppm), the Cs + permeation flux reached 25.2 mmol/m 2 /h, and the Cs + /Rb + separation coefficient was 8.90. In selective permeation experiments conducted in a mixed solution containing equal concentrations of Cs + , Rb + , K + , Na + , and Li + , the separation factors for Cs + /Li + , Cs + /Na + , Cs + /K + , and Cs + /Rb + were 144.6, 45.75, 18.09, and 8.93, respectively. Furthermore, the t-BAMBP/P204/MWCNs SLM was applied to the extraction and separation of cesium from simulated lithium mica lithium-extraction tail liquor, and the system demonstrated excellent selectivity. The separation factors for Cs + /Li + , Cs + /Na + , Cs + /K + , Cs + /Rb + , Cs + /Mg 2+ , and Cs + /Ca 2+ reached 380.67, 571, 76.13, 16.79, 17.57, and 3.525, respectively. Following ten permeation experiments, both the Cs + permeation flux and the separation factors of Cs + /Rb + maintained high cycle stability. Through slope analysis and electrospray ionization mass spectrometry, it was confirmed that Cs + coordinates with t-BAMBP and P204 to form compounds with the chemical formulae [(ROCs)·(ROH)], [(ACs)·(HA)], and [CsOR·ROH(HA)]. Additionally, Cs + was found to form complexes with the two extractants individually. DFT calculations indicated that the reaction process was predominantly governed by the formation of complexes between t-BAMBP dimers and Cs + . This study presents a promising new method for Cs + recovery based on membrane separation processes.