The aim of this work is to examine the stabilization or immobilization of heavy metals such as Pb (NO₃)₂ in a various paste of slag and slag-FA based and on geopolymer pastes. Geopolymer prepared by 100% slag and partially substitution of slag by 15% Fly ash (FA) [85% slag+15%FA]. The alkaline activator is (1:1) liquid sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH) solution (the concentration of sodium hydroxide is 5 Molar). Different percentages of Pb (NO₃)₂ were added to the alkali activation mixture, 0.5%, and 1% by mass% of the solid binder. The obtained geopolymer specimens are cured in water for 90 days. The compressive strength test, combined water content, X-ray diffraction (XRD), Atomic absorption, and Transform infrared spectrometry (FTIR) are examined. The results showed that the used lead nitrate caused a retarding effect for the hydration of the investigated geopolymer mixes.The best mix for immobilization were 99.98% in mix SF1[85%slag+15%Fly ash +0.5%Pb⁺²].