Heavy metals are a class of pollutants that require extensive treatment before discharge in water system. These metals are harmful to human, animals and living creatures. Lead, for example, is the second top priority hazardous substance according to the Agency of Toxic Substances & Disease Registry (ATSDR) in year 2007 [1]. It is a very toxic element, causing brain damage, kidney damage, and gastrointestinal distress to human at short term exposure. Chronic exposure to lead can affect the central nervous center, urinal system, and leads to kidney damage and death. The potential sources of lead come from manufacturing of batteries, metal products, paints, and ceramic glazes.
Several technological methods may be employed to treat lead from aqueous solutions such as ion exchange, chemical precipitation, oxidation, reduction, and reverse osmosis [2]. These methods are either costly, difficult to implement or produce by-products that require further treatment. Adsorption process, on the other hand, is cost-effective and efficient even at trace quantity of lead. The major drawback of this method is the high price of adsorbents which increases the cost of treatment method. To overcome this disadvantage, several research efforts have been performed in order to develop new cost-effective adsorbents or utilize naturally occurring materials.
Rashid [3] used talc, chalcopyrite and barite as adsorbents for the removal of lead ions from liquid wastes. The results indicated that chalcopyrite is preferred among the studied adsorbents with an adsorption capacity of 99 mg/kg. Peric et al. [4] utilized natural zeolitic tuff to remove zinc, copper, and lead from aqueous solutions. They found that the removal efficiency was higher for Pb and Cu than for Zn ions. Issabayeva et al. [5] showed that palm shell activated carbon has high adsorption capacity for lead ions, especially at pH 5 with an ultimate uptake of 95.2 mg/g. Shawabkeh et al. [6] converted oil shale ash into zeolite using hydrothermal activation; the produced zeolite was utilized for cadmium and lead removal from aqueous solutions. The maximum sorption capacity was found to be 70.58 and 95.6 mg/g zeolite, respectively.
Other researchers have modified the surface of several adsorbents in order to enhance the removal capacity of heavy metals. Pe Β΄rez-Quintanilla et al. [7] have modified a mesoporous silica (MCM-41) with 5-mercapto-1-methyltetrazole. The produced material was then employed as a Zn(II) adsorbent from aqueous solutions with a maximum adsorption value of 103.95 mg/g. Caballero et al. [8] were synthesized X-type zeolite from kaolinite by reacting it with sulfuric acid at high temperature to increase SiO 2 /Al 2 O 3 ratio. Bosch et al. [9] also produced A, X and