Adsorption of Europium on Al-substituted goethite

Europium (Eu(III)) has been extensively used as an analogue of trivalent lanthanide in the radioactive wastewater from nuclear industry. The adsorption of Eu(III) on the Al-substituted goethite was investigated by characteristic and batch techniques. The characteristic results illustrated that the Al-substituted goethite was synthesized successfully and the acicular-like structure goethite was transformed to multi-domain jagged crystal with the increase of Al content, respectively. The adsorption amount of Eu(III) on Al-substituted goethite was increased with an increase of pH from 4.0 to 8.0. The thermodynamic parameters revealed that the adsorption of Eu(III) on Al-substituted goethite was a spontaneous and endothermic process. The increase of Al content increased the adsorption capacity of Al-substituted goethite to Eu(III). The maximum Eu(III) adsorption capacity was determined to be 6.75 mg/g for α-(Fe_0.85Al_0.15)OOH at pH = 5.5 and T = 293 K using Langmuir model. Furthermore, XPS (X-ray photoelectron spectroscopy) analysis verified that oxygen-containing functional groups were responsible for the major adsorption mechanism and the effect of ionic strength on the adsorption displayed the inner-sphere surface complexation of Al-substituted goethite dominated the adsorption process.