Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: A kinetic and equilibrium study

摘要

The removal of Zn(II) ions from aqueous solution was studied using natural and MnO_2 modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kj mol~(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH~0), Gibbs' free energy (ΔG~0) and entropy (ΔS~0) were calculated for natural and MnO_2 modified diatomite. These values showed that the adsorption of Zn(ll) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously.