Effect of cerium valence on As(V) adsorption by cerium-doped titanium dioxide adsorbents

In this study, three titanium dioxide (TiO(2)) adsorbents doped with Ce(III) (Ce(3)), Ce(IV) (Ce(4)) and H(2)O(2) oxidized Ce(III) (Ce(3)O), respectively, were prepared and the effect of cerium valence on arsenate (As(V)) adsorption was investigated. The Ce(3), Ce(4) and Ce(3)O adsorbents all existed in amorphous form and Ce(3) exhibited a higher micropore surface area and micropore volume than both Ce(4) and Ce(3)O. The adsorption capacity of As(V) on Ce(4) and Ce(3)O decreased significantly when the solution pH was increased, while the adsorption capacity of As(V) by Ce(3) was higher and more stable at pH values ranging between 3.7 and 7.0. The adsorption kinetics of As(V) on Ce(3) was better fit to pseudo-second order model while both the pseudo-second order and the pseudo-first order model described the adsorption of As(V) on Ce4 and Ce30 well. The equilibrium adsorption data for As(V) on Ce(3) was well fit by the Langmuir model, and the adsorption of As(V) on Ce(4) and Ce(3)O was described well by both the Langmuir and Freundlich models. FUR analysis indicated that the hydroxyl groups on the three adsorbents' surfaces were involved in As(V) adsorption. The results suggested that the dominant chemical state of cerium valence plays an important role in affecting the adsorption behavior of As(V) by cerium-doped TiO(2) adsorbents. (C) 2011 Elsevier B.V. All rights reserved.