Lime and iron waste were blended in various ratios and the resulting sorbents tested in two equipments namely; pH-stat apparatus simulating wet flue gas desulfurization (FGD) and fixed bed reactor for dry FGD, to investigate the effect of the blends in the FGD process. The best blend was found at a ratio of 1:2 (lime to iron waste) by mass. Brunauer, Emmett and Teller (BET) surface area analysis and Scanning Electron Microscopy (SEM) were used to assist in characterizing the resulting sorbents. Temperature, solid to liquid ratio and stirring speed were varied in addition to lime to iron waste ratio in optimization tests that followed. Design expert's central cubic design was used in the design of experiments to aid with regression analysis. Temperature had the highest effect, followed by lime to iron waste ratio. Solid to liquid ratio had the least effect on the overall reactivity of the sorbents. The effects were more pronounced at higher levels of these variables. (C) 2012 Elsevier Ltd. All rights reserved.