Selective lithium recovery from dilute brines remains challenging because Li⁺ must be separated from competing ions, particularly Mg²⁺. In this work, a commercial NF90 nanofiltration membrane was used as a non-dispersive interface between a simulated brine and the hydrophobic ionic liquid [P_6,6,6,14][PHOS]. Individual-salt experiments yielded apparent overall mass transfer coefficients of 638 ± 273, 100.5 ± 19.8, and 10.1 ± 0.7 L m⁻² h⁻¹ for Na⁺, Li⁺, and Mg²⁺, respectively. Replacing water with 10% (v/v) [P_6,6,6,14][PHOS] in hexane as the receiving phase increased Li extraction from 18.6 ± 3.0% to 40.9 ± 2.0%. Under direct Li⁺/Mg²⁺ competition, selectivities of 2.19 ± 1.10 and 3.83 ± 0.56 were obtained with the diluted and neat ionic liquid receiving phases, respectively. With neat [P_6,6,6,14][PHOS], Li extraction reached 40.3%, and 6.0% of the extracted Li was subsequently recovered in pure water under non-optimized conditions. CHNS analysis showed no detectable transfer of organic material derived from the ionic liquid to the aqueous feed. Overall, NF90 was the main source of Li⁺/Mg²⁺ transport discrimination, whereas [P_6,6,6,14][PHOS] mainly increased Li uptake.