Different contaminants are released to wastewater with the rapid industrialization of human society, including heavy metal ions, organics, bacteria, viruses, and so on, which are serious harmful to human health. Among all water contaminations, heavy metal ions, such as Pb2+, Cd2+, Zn2+, Ni2+ and Hg2+, have high toxic and nonbiodegradable properties, can cause severe health problems in animals and human beings. It is well-known that chronic cadmium toxicity is the inducement of Japan Itai-Itai disease. The harmful effects of Cd also lead a number of acute and chronic disorders, such as renal damage, emphysema, hypertension, testicular atrophy, and skeletal malformation in fetus [1, 2]. Wastewater from many industries, including chemical manufacturing, battery manufacturing industries, metallurgical, leather tanning, and mining, contain these heavy metal ions [3]. These wastewater with heavy metal ions are discharged into natural water directly, not only threat the aquatic organisms, but may be enriched by precipitation, adsorption, and harmed human health through the food chain. Thus, the removal of such toxic metal ions from wastewater is becoming a crucial issue.

Heavy metal ions could be eliminated by several traditional techniques [4], including chemical precipitation [5], reverse osmosis [6], electrochemical treatment techniques [7], ion exchange [8], membrane filtration [9], coagulation [10], extraction [11], irradiation [12], and adsorption [13]. Due to its low cost-effective, high efficiency, and simple to operate for removing trace levels of heavy metal ions, adsorption technology [14] is regarded as the most promising one to remove heavy metal ions from effluents among these techniques mentioned above. Several types of materials, such as activated carbons [15], clay minerals [16], chelating materials [17], and chitosan/natural zeolites [18] have been researched to adsorb metal ions from aqueous solutions. Although traditional sorbents could remove heavy metal ions from wastewater, the low sorption capacities and efficiencies limit their application deeply.