The adsorption ability of a powdered activated carbon (PAC) derived from walnut shell was investigated in an attempt to produce more economic and effective sorbent for the control of Hg(II) ion from industrial liquid streams. Carbonaceous sorbents derived fromIranianwalnut shell(WS)were prepared by chemical activation method using ZnCl2 as an activating reagent. To the best of our knowledge, this adsorbent was not used before for removing mercury from water. Adsorption of Hg(II) from aqueous solutions was carried out under different experimental conditions by varying treatment time, metal ion concentration, adsorbent amount, pH and solution temperature. It was determined that Hg(II) adsorption follows both Langmuir and Freundlich isotherms aswell as pseudo-second-order kinetics. Itwas also shownthat Hg(II) uptake decreases with increasing pH of the solution. The proper choice of preparation conditions resulted in a microporous activated carbon with 0.45 g/cm3 density, 737 mg/g iodine number and 780m2/g BET surface area. The monolayer sorption capacity of this optimum adsorbent was obtained as 151.5 mg/g.

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