Nanomaterials as Sorbents to Remove Heavy Metal Ions in Wastewater Treatment

Abstract

Wastewater containing heavy metal ions is considered as the serious environmental problem in human society. Adsorption as the widely used method plays an important role in wastewater treatment, which is based on the physical interaction between metal ions and sorbents. With the development of nanotechnology, nanomaterials are used as the sorbents in wastewater treatment; several researches have proved that nanomaterials are the effective sorbents for the removal of heavy metal ions from wastewater due to their unique structure properties. Three kinds of nanomaterials are presented in this paper, including nanocarbon materials, nanometal particles, and polymer-supported nanoparticles. For heavy metal ions, all these nanomaterials show high selectivities and adsorption capacities. Besides, the adsorption isotherm model and adsorption kinetics are introduced briefly to understand the adsorption procedure. Keywords: Nanomaterials; Adsorption; Heavy metal ions; Wastewater treatment Introduction 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 non- biodegradable 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. Te 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]. Tese 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. Tus, 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. To solve these defects of traditional sorbents, nanomaterials are used as the novel ones to remove heavy metal ions in wastewater. Materials with the particle size between 1 nm to 100 nm are defined as nanomaterials. With novel size- and shape-dependent properties, J Environ Anal Toxicol ISSN:2161-0525 JEAT an open access journal nanomaterials have been extensively