<p>The growing demand for lithium underscores the need to recover it efficiently from secondary resources such as spent lithium-ion batteries. This study investigates four commercial nanofiltration membranes (XN-45, NF-270, NF-90, and NFW) for lithium recovery from LIB synthetic leachate. These membranes, expected to have high permeability and moderate salt selectivity, were evaluated using single-ion and mixed-ion feed solutions containing Li⁺, Ni²⁺, Co²⁺, Mn²⁺, Al³⁺, and Fe³⁺. Lithium exhibited a low rejection by all membranes due to its monovalent nature, with XN-45 and NF-270 showing the rejection (18.5% and 19%), and the highest permeation indicating their potential for lithium recovery. Multivalent ions showed markedly higher rejections, particularly for the tighter NF-90 and NFW membranes, where multivalent ions exceeded 90% rejection. Mixed-ion conditions further enhanced rejection through competitive electrostatic interactions. The established order of performance based on rejection was NFW &gt; NF-90 &gt; NF-270 &gt; XN-45 for multivalent ions, which displayed a clear basis for membrane selection. The findings demonstrate the applicability of commercial nanofiltration for lithium recovery and highlight its potential as an effective strategy in battery recycling and circular-economy processes and provides a clear framework for membrane selection in integrated lithium recovery and heavy-metal removal processes.</p>