In this study removal of mercury(II) cations from aqueous solution was investigated. Effect of different parameters like optimum pH, dose of adsorbent, contact time between adsorbent and Hg(II) solution were examined. Variations of Hg(II) concentration in solution have been studied through measuring the amount of dithizone–Hg(II) complex by a double-beam spectrophotometer. Because of absorbance interference of dithizone–Hg(II) complex with dithizone ligands at  495 nm, which is λ_max of the complex, the absorbance peak was checked at 635 nm, which belongs to dithizone ligands