Competitive Adsorption of Pb and Cd on Ferrihydrite Modified by Humic Acid

Abstract

Ferrihydrite modified by humic acid was prepared by coprecipitation. It was characterized by SEM, BET, XRD, FTIR and XPS techniques. Ferrihydrite modified by humic acid was studied as an adsorbent for the adsorption of Pb(II) and Cd(II) simultaneously in aqueous. Furthermore, the influencing factors of adsorption and the competitive adsorption mechanism of Pb(II) and Cd(II) were also researched in this paper. Ferrihydrite modified by humic acid showed the favorable adsorption behavior for Pb(II) and Cd(II), especially for Pb(II). Adsorption kinetics followed pseudo second order kinetic behavior. The R-2 value of pseudo second order for Pb(II) and Cd(II) was 0.97921 and 0.98981, respectively. The competitive adsorption mechanism of Pb(II) and Cd(II) were mainly the competition of oxygen-containing functional groups and complex site. Therefore, Ferrihydrite modified by humic acid was a feasible adsorbent for the removal of Pb(II) and Cd(II), especially Pb(II).