PREPARATION AND CHARACTERIZATION OF SOME METAL OXIDE NANOCATALYSTS FOR REMOVAL OF HEAVY METALS FROM AQUEOUS SOLUTION

Abstract

Heavy metals pollution has become one of the most serious environmental problems today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. In this study metal oxide adsorbents were synthesized by three methods (precipitation, organic solvent and microwave) and were used for the removal of lead, manganese and zinc ions from aqueous solutions. The prepared adsorbents were characterized by X-ray diffraction (XRD) analysis,infrared spectroscopy(IR), transmission electron microscopy (TEM) and surface area measurements (BET). Adsorption experiments were carried out to investigate the influence of different sorption parameters on the removal of Pb(II), Mn(II) and Zn(II) from aqueous solutions, such as different contact times, variation of the initial concentration of Pb(II),Mn(II) and Zn(II)and the weight of metal oxide catalysts and compare adsorption efficiencies of the oxides. It was found that the metal oxides prepared by organic solvent method has a markedly higher efficiency for removal Pb(II), Mn(II) and Zn(II) from aqueous solutions, than those prepared by precipitation and microwave methods. The adsorption data were analyzed in terms of Langmuir and Freundlish isotherms models.From isotherms and regression coefficients, it was found thatthe regression coefficient (R) obtained from Langmuir model is much higher than that obtained from Freundlish model, suggesting the Langmuir model is better than Freundlish model, and could well interpret the studied adsorption process. The two adsorption kinetic models (first-order and second-order equations)were studied. From regression coefficients,the fit is better with thesecond-orderequation than that with first-order equation. So the kinetics of heavy metals adsorption on to these adsorbent can be described well by second-order equation.