Adsorption of Lead (II) Ions onto Diatomite From Aqueous Solutions: Mechanism, Isotherm and Kinetic Studies

Abstract

This study presents an evaluation of diatomite as a low cost adsorbent for Pb (II) removal from aqueous solutions under various conditions. The results demonstrate that adsorption of Pb (II) is strongly dependent on the pH of the solution. The effect of pH on adsorption of Pb (II) on diatomite was studied by varying pH from 2 to 12 at 20 °C. In the pH range of 2.0-4.0, the percentage of Pb (II) adsorbed increases slightly as the pH increases. At pH>4, the percentage of Pb (II) adsorbed decreases with increasing pH because hydrolysis and precipitation begin to play an important role in the sorption of Pb (II). At pH 4, the maximum adsorption capacity of diatomite was found to be 26 mg/g. The adsorption isotherms of Pb (II) on diatomite can be described well by the Freundlich model. The regression equation coefficients were calculated and the data fitted to a second-order kinetic equation for removal of Pb (II) ions. The high adsorption capacity of diatomite makes it a suitable low-cost material for the removal of Pb (II) from aqueous solutions. © 2015 Global NEST.