| Title |
Adsorption of Heavy Metal Iosn From Wastewater used Zeolites |
| Abstract |
Zeolites are crystalline aluminosilicate minerals that contain alkali and alkaline-earth metals, such as sodium, potassium, and calcium, as well as water, in their structural framework. The framework is porous, enclosing interconnected cavities in which the metal cations and water molecules are contained. The zeolites have reversible hydration properties in addition to their ration exchange properties. The adsorption effect of heavy meal ions - Cu(Ⅱ), Cd(Ⅱ), Ni(Ⅱ), Pb(Ⅱ), and Zn(Ⅱ) - in wastewater on zeolites by batch adsorption process is investigated. Besides the influence of NH₄^+ ion or CN^- ion coexisted with the heavy metal ions in the wastewater was discussed. The amount of adsorbed ions was variable by initial pH and ionic concentration, especially initial pH value of solution had an important effect on the adsorption. In case of low pH solution, e.g. below 3.0, clinoptilolite adsorbed Pb(Ⅱ), Cd(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) ions but mordenite almost did not adsorb except Pb(Ⅱ) ion. Under the same adsorption conditions, these ions were more adsorbed on clinoptilolite than on mordenite. Adsorptive rate of heavy metal ions creased equally in order of Pb(Ⅱ)>Cd(Ⅱ)>Cu(Ⅱ)>Zn(Ⅱ)>Ni(Ⅱ) ion on mordenite and clinoptilolite. This tendency was interpreted by the fact that the smaller the radius of hydrated metal ion is, the more is the heavy metal ion adsorbed on zeolites. The adsorption rate of heavy metal ions except Pb(Ⅱ) ion decreased in the presence of NH₄^+ ion in the solution. Especially, the absorptivity of Cu(Ⅱ) ion decreased with increasing CN^- ionic concentration due to the formation of complex anion with CN^- ion. |