Adsorption characteristics of U(VI) on Fe(III)-Cr(III) (oxy)hydroxides synthesized at different temperatures

Abstract

In this study, the adsorption behavior of U(VI) on (oxy)hydroxides synthesized at different temperatures (25 and 75 degrees C) was investigated. Four (oxy)hydroxides were synthesized by drying slurries of Fe(III) and (oxy)hydroxide in a vacuum desiccator (25 degrees C) or in an oven (75 degrees C). Batch adsorption tests were conducted using the (oxy)hydroxides thus synthesized and groundwater containing uranium ions. In general, the U(VI) removal fraction significantly increased with increasing pH from 3 to 5, remained constant with increasing pH from 5 to 9, and decreased at pH greater than 9, regardless of the type of (oxy)hydroxides and solid-to-liquid ratio. The effect of pH on the U(VI) removal fraction was more significant at a low solid-to-liquid ratio. The oven-dried Fe(III) (oxy)hydroxide exhibited a U(VI) removal fraction lower than that of the vacuum-dried one, whereas the oven-dried Fe(III)-Cr(III) (oxy)hydroxide exhibited a U(VI) removal fraction higher than that exhibited by the vacuum-dried one. X-ray photoelectron spectroscopy (XPS) analysis results indicated that the difference in the U(VI) removal fraction is attributed to the dissolution and precipitation of the Fe(III)-(oxy)hydroxide during oven drying and dehydration of the Fe(III) Cr(III)-(oxy)hydroxide during oven drying. (C) 2016 Elsevier Ltd. All rights reserved.