Structural and surface modification of highly ordered alumina for enhanced removal of Pb2+, Cd2+ and Ni2+ from aqueous solution

Abstract

The adsorption performance of three-dimensionally ordered macroporous (3DOM) alumina doped with iron oxide, and subsequently modified with (3-aminopropyl)triethoxysilane (APTES), FeAl2O3 and FeAl(2)O(3)APTES, was used for enhanced Pb2+, Cd2+ and Ni2+ removal. The phase composition and the structural and surface/textural properties of the obtained adsorbents were analyzed by X-ray diffraction analysis, field emission scanning electron microscope, energy dispersive X-ray analysis, thermogravimetry, Fourier-transfer infrared spectroscopy, specific surface area of the samples and point of zero charge determination. Adsorption of selected cations was examined in the batch conditions using different contact time, adsorbent dosage and temperatures. Different models of the adsorption isotherms were used for determination of the adsorption capacities, in which the best fit of Freundlich and Langmuir model was obtained for FeAl2O3, that is, Freundlich model for FeAl(2)O(3)APTES. A significant increase of adsorption capacities: from 44.21 to 51.66 mg g(-1) for Pb2+, 25.69 to 32.96 mg g(-1) for Cd2+ and 19.48 to 24.64 mg g(-1) for Ni2+ was obtained for FeAl2O3 and FeAl(2)O(3)APTES, respectively, which indicated the significance of the macroporous structure of 3DOM alumina and subsequent amino-terminal modification. The values of the correlation coefficient (R-2) suggested that pseudo-second kinetic model best describes Pb2+, Cd2+ and Ni2+ adsorption on FeAl(2)O(3)APTES, and Cd2+ and Ni2+ onto FeAl2O3, while second kinetic model gave the highest correlation coefficients for Pb2+ adsorption on FeAl2O3.