Adsorption of lanthanum(III), samarium(III), europium(III) and gadolinium(III) on raw and modified diatomaceous earth: equilibrium, kinetic and thermodynamic study
Imad Hamadneh, Noor W. Al-Jundub, Alaa A. Al-Bshaish, Ammar H. Al-Dujiali
Abstract
ABSTRACT In the present work, naturally available diatomaceous earth (DE) was organically modified with hexadecyltrimethylammonium bromide (DE-HDTMA). The adsorption properties of DE and DE-HDTMA for lanthanum (La), samarium (Sm), europium (Eu) and gadolinium (Gd) ions in solution were studied. The effects of adsorbent dosages, ionic strength, and initial concentration of metal ions, adsorption time, pH value of solution and temperature on adsorption capacity were investigated. The results showed that the adsorption isotherms of DE and DE-HDTMA for metal ions satisfied the Langmuir, Freundlich and Dubinin–Radushkevich isotherms. By fitting the Langmuir equation, the saturated adsorption capacity of DE and DE-HDTMA for La(III), Sm(III), Eu(III) and Gd(III) ions can reach 185.185, 232.558, 117.647, 199.60, 111.048, 172.414, 92.593 and 156.250 mg g –1 , respectively. The mean free energy (E DR ) for adsorption of metal ions by DE and DE-HDTMA has been calculated from the Dubinin–Radushkevich equation and showed that the physisorption mechanism was operative. The adsorption kinetics confirmed to the pseudo- second-order kinetic equation. The calculated thermodynamic parameters revealed that the adsorption is a spontaneous and exothermic process.