Adsorption of Pb(II) from aqueous solution onto manganese oxide-modified laterite soil

The objective of this work was to study the adsorption efficiency of natural soil and its surface modified with manganese oxide for removal of Pb(II) ion. The adsorption of Pb(II) from aqueous solution onto raw laterite soil (LS) and manganese oxide-modified laterite soil (Mn-LS) was evaluated based on batch method. The adsorption efficiency of Pb(II) was investigated as a function of the initial pH, equilibrium time, adsorbent concentration and initial Pb(II) concentration and temperature. The maximum monolayer adsorption capacities of LS and Mn-LS were estimated as 1.053 and 38.76 mg g-1, respectively. The results show that the amount of Pb(II) adsorbed onto Mn-LS was more than LS by about 39-times under the optimized adsorption condition. The adsorption isotherms of Langmuir and Freundlich models was used to describe the equilibrium isotherm. It is observed that the data from both adsorbents fitted well to the Langmuir isotherm. The calculated adsorption energy (14.95 kJ mol-1) from the Dubinin-Radushkevich (D-R) model indicated that the adsorption process onto Mn-LS was taken place mainly by chemical ion exchange. The kinetic evaluation also suggested that the adsorption process of both adsorbents followed well the pseudo-second-order kinetic model. The calculated thermodynamic parameters showed that the adsorption of Pb(II) onto LS and Mn-LS process was feasible, spontaneous and endothermic.