Experimental and modeling studies of Eu(III) sorption on TiO2

Abstract

Sorption / Eu(III) / TiO 2 / Surface complexation / ModelingSummary. Eu(III) sorption on TiO 2 (anatase) was investigated as functions of pH, ionic strength and Eu(III) concentration by using a batch experimental method. It was found that Eu(III) sorption on anatase is strongly pH-dependent, but insensitive to ionic strength. A constant capacitance model with three inner-sphere surface complexes, ≡SOEu 2+ , ≡SOEuOH + and ≡SOEu(OH) 3 − , was used to interpret Eu(III) sorption on anatase in the absence and presence of carbonate ( p CO 2 = 10 −3.58 atm).

Eu(III) adsorption on rutile: Batch experiments and modeling

“…The proton excess of a sorbent is usually obtained from the difference between the titration data of the suspension and blank solution [2,19]:…”

“…As shown in Figure 4, the adsorption of Eu(III) increases from about 5% at pH 4 to about 100% at pH 5.6. As Eu 3+ is the dominant Eu(III) species in aqueous phase up to pH 7.5 [2] and the rutile surface is positively charged at pH < pH nzpc (5.64), Eu(III) adsorption on rutile must be a chemical process because the positively charged rutile surface is unfavorable to Eu 3+ via physical binding. Thus the formation of inner-sphere surface complexes of Eu(III) on rutile can be reasonable proposed.…”

“…In this case, all of the main Eu(III) species in aqueous phase need to be considered in modeling calculations. Therefore, surface complexation reactions of Eu 3+ , EuOH 2+ , Eu(OH) 2 and Eu(OH) 3 0 were proposed because these species are the main Eu(III) species in aqueous phase at pH < 10 [2]. From modeling exercises, it was found that surface complexation reactions with Eu 3+ and Eu(OH) 3 0 are adequate to describe Eu(III) adsorption on rutile:…”

“…In our previous paper, both acid-base chemistry of anatase and Eu(III) adsorption were studied [2]. The potentiometric titration data of anatase at variable ionic strengths were fitted with a CCM model because the anatase titration data are relatively insensitive to ionic strength.…”

“…Europium(III), as an analogue of trivalent actinides, is usually used to predict the adsorption behavior of other trivalent lanthanides and Am(III) [1], thus the adsorption of Eu(III) on the metal oxides and clay minerals has been extensively studied [1][2][3][4]. TiO 2 is an excellent model adsorbent due to its low solubility in water over a wide pH range [2,[5][6][7]. A number of studies on the interactions between TiO 2 and heavy metals and/or anionic pollutants have been reported [5,[8][9][10][11].…”