Study of electric field-enhanced mass transfer and Li/Mg separation of N,N-bis (1-methylheptyl) acetamide/TBP-NaFeCl4 composite membrane

Using N,N-bis(1-methylheptyl)acetamide (N503) synergized with TBP-NaFeCl4 (T-Fe), a ternary composite extraction membrane known as TFeN-PIM was created. Under optimum membrane phase conditions, the mass transfer properties of TFeN-PIM-Li(I) and its Li/Mg selective separation performance by electric field augmentation were examined, and confirmed the mechanism of TFeN-PIM-Li(I) electric field enhanced mass transfer. The findings demonstrate a homogeneous distribution of [FeCl4-] in the TFeN-PIM membrane phase and a decrease in the water contact angle as the T-Fe content increases. In the TFeN-PIM membrane, the cation binding order of the composite carrier was H+>Li+>Na+>Mg2+, and the mass transfer was carried out at the interface of the two phases of the membrane through the mechanism of "cation exchange-neutralization", in which Li(I) was bonded with the carrier in the form of 2N503-LiFeCl4-2TBP, and showed a fixed-site "hopping" mass transfer characteristics under the reinforcement of electric field. The mass transfer process of the TFeN-PIM- Li(I) system under electric field enhancement conforms to the first-order kinetic rate equation, and the voltage (5-45 V) is positively correlated with the permeability coefficient P-Li(I) but decreases the Li/Mg selectivity of TFeN-PIM. The S-Li(I)/Mg(II) of TFeN-PIM was 9.18 at 3 V. After three cycles of 72 h cycling at 40 V, the decrease rate of P-Li(I) was <7.42 %, which showed good stability.