The impact of lithium impurities on the microstability and turbulent transport characteristics in the core of a typical FTU liquid lithium limiter (LLL) (Mazzitelli et al 2011 Nucl. Fusion 51 073006) discharge during the density ramp-up phase is studied. A non-linear gyrokinetic analysis performed with GKW (Peeters et al 2009 Comput. Phys. Commun. 180 2650) accompanied by a quasi-linear fluid analysis is presented. We show that a centrally peaked, high concentration lithium profile contributes to the electron peaking by reducing the outward electron flux, and that it leads to inward turbulent deuterium transport through ion flux separation.