A carbonaceous sorbent derived from an Iranian walnut shell (WS) were prepared by chemical activation method using ZnCl2 as an activating reagent. WS may be used in water treatment to remove mercury (Hg++) from water. The adsorption of mercury ion (Hg++) were performed from aqueous solutions at 302 K. Adsorption studies of Hg (II) were carried out by varying several conditions such as: treatment time, metal ion concentration, adsorbent amount, pH and solution temperature. It was also determined that Hg (II) adsorption follows both Langmuir and Freundlich isotherms. It was shown that Hg (II) uptake decreases with increasing pH of the solution. The monolayer sorption capacity was obtained as 151.5 mg/g.

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