Diatomite was used as a Pozzolan to augment lime reactivity. This was confirmed through laboratory wet and dry flue gas desulfurization (FGD) experiments using pH-stat apparatus (representing wet FGD) and fixed bed reactors (representing dry FGD). BET surface area analysis and SEM imaging were used in characterization and to aid in understanding the behavior of the sorbent. After affirming that diatomite improves lime's reactivity, optimization tests were conducted to maximize the reactivity output. The effect of various variables namely; temperature, lime to diatomite ratio, solid to liquid ratio and stirring speed, were maximized linearly, quadratically and interactively. The design of optimization experiments was done through design expert software. Central cubic design was used for regression analysis. As expected, temperature had the highest effect towards reactivity. Some effect showed a mini-max behavior while others had a sinusoidal trend. (C) 2011 Elsevier B.V. All rights reserved.