Influence of Na2O/Al2O3 and SiO2/Al2O3 ratios on the immobilization of Pb from electric arc furnace into the fly ash based geopolymersR. Zejak, I. Nikolić, D. Đurović, B. P. Mugoša, D. Blečić and V. RadmilovićE3S Web of Conferences, 1 (2013) 31007DOI: https://doi.org/10.1051/e3sconf/20130131007