Removal of copper(II) and lead(II) from aqueous solution by manganese oxide coated sand: II. Equilibrium study and competitive adsorption

Abstract

The adsorption equilibrium of MOCS and the Cu(II) and Pb(II) ions removal capacity by MOCS in single-(non-competitive) and binary-(competitive) component sorption systems from aqueous solutions were investigated. The equilibrium data were analyzed using the Langmuir, Freundlich, Temkin and Redlich–Peterson isotherms. The characteristic parameters for each isotherm were determined. The Langmuir and Redlich–Peterson isotherms provided the best correlation for both Cu(II) and Pb(II) onto MOCS. From the Langmuir isotherms, maximum adsorption capacities of MOCS towards Cu(II) and Pb(II) are determined at different temperature. The maximum adsorption capacity of Cu(II) and Pb(II) per gram MOCS in single component sorption systems were from 5.91 and 7.71μmol to 7.56 and 9.22μmol for the temperature range of 288–318K, respectively. The order of affinity based on a weight uptake by MOCS was as follows: Pb(II)>Cu(II). The same behavior was observed during competitive adsorption that is in the case of adsorption from their binary solution. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) for Cu(II) and Pb(II) sorption on MOCS were also determined from the temperature dependence. This competitive adsorption showed that the uptake of each metal was considerably reduced with an increasing concentration of the other, the adsorption of Cu(II) being more strongly influenced by Pb(II) than vice versa due to the higher affinity of MOCS for the latter.