Effect of ultrasonic time on adsorption of Eu(III) by nano structured hematite and its mechanism

Abstract

In this paper, the nanostructured hematite was prepared by heat treatment of siderite in air atmosphere. The influence of ultrasonic time on the physicochemical properties of nano structured hematite was studied. The effects of reaction time, pH, ionic strength and initial concentration on the adsorption of Eu(III) hematite with different ultrasonic time were investigated. The series of characterization showed that nanostructured hematite can be formed by heating siderite. The size and crystallinity of nanoscale hematite were further reduced by ultrasound, resulting in increasement of the specific surface area. Compared with the nanostructured hematite without ultrasound, nanostructured hematite (PCH-3) after ultrasound for 1 h obtained the biggest specific surface area (29.37 m2/g). Batch experiments results indicated that PCH-3 had the maximum rate constant ( K 2=3.49 g/(mg min)) and the maximum adsorption capacity (4.88 mg/g) for Eu(III) adsorption at T = 288 K, pH 5.5. X-ray photoelectron spectroscopy (XPS) analysis confirmed that oxygen-containing functional groups (especially hydroxyl groups) were the main adsorption sites of Eu(III) enriched by nano structured hematite. The results showed that proper ultrasound treatment can significantly improve the surface reactivity of the nano structured. This work is of great theoretical value for the adsorption of heavy metal ions by nanostructured mineral materials.