As a low-cost adsorbent, sepiolite has been used for the adsorption of Fe(II) and Fe(III) from aqueous solutions. The proposed method was applied to the determination of iron in tap water, employing standard addition. The results reported with a confidence interval for the 95% confidence level show the applicability of the proposed method to water analysis. Speciation studies are very important for understanding of the toxicity, bio-availability, bio-accumulation, and transport of an element in different environmental media. In this study, Fe(II) and Fe(III) speciation was investigated for optimum concentration and pH in aqueous solutions with MINEQL+ computer program.