Modification of adsorbent surface for removal of lead (II) ion from aqueous solution

Abstract

The objective of this work was to study the adsorption efficiency of natural clay and its surface modified with manganese oxide for removal of Pb( II) ion. The adsorption of Pb( II) from aqueous solution onto raw natural clay (NC) and manganese oxide-modified natural clay (MnO-NC) was evaluated based on batch experiment. The adsorption efficiency of MnO-NC onto Pb( II) was investigated as a function of the initial pH of 6, equilibrium time of 30 min, adsorbent concentration of 5 g/L and initial concentration of Pb(II) solution in the range of 50- 500 mg/L. The adsorption isotherms of Langmuir, Freundlich and Dubinin-Radushkevich were used to describe the equilibrium isotherm. It is observed that the data from MnO-NC adsorbents fitted well to the Langmuir isotherm. The maximum monolayer adsorption capacities of MnO-NC were estimated as 38. 76 mg/ g. By comparing with NC, the amount of Pb( II) adsorbed onto MnO-NC was more than NC by about 38 times under the optimized adsorption condition. According to Dubinin-Radushkevich isotherm, the adsorptive mechanism of Pb(II) onto MnO-NC was chemisorption, whereas the NC showed the mechanism as physical in nature. The kinetic studies of Pb( II) demonstrated that the adsorption of Pb( II) onto MnO- NC and NC adsorbents followed a pseudo second- order model with a good correlation. The adsorption mechanism was processed via chemical ion exchange between H+ and bonded MnO groups and Pb(II) ions in solution.