Selective and fast recovery of neodymium from seawater by magnetic iron oxide Fe3O4

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 262; pp. 966 - 972
• Main Authors: Tu, Yao-Jen, Lo, Sheng-Chung, You, Chen-Feng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2015
• Subjects: Kinetics; Magnetic iron oxide; Neodymium; Recovery; Thermodynamics; Thermodynamics; Kinetics; Neodymium; Recovery; Magnetic iron oxide
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2014.10.025

•The synthesized Fe3O4 is fast and effective in recovering Nd from seawater.•A rapid increase of Nd recovery was observed when the pH increased from 2.0 to 8.2.•The inner-sphere mechanism is involved with Nd adsorption onto Fe3O4.•The adsorbent could be fast recovered by a magnet in 20s.•The data indicates that 0.05N HNO3 is sufficient for Nd desorption from Fe3O4. Neodymium (Nd) is a key element that widely applied in high-tech industries; therefore, to recover it efficiently from aqueous solutions is rather important. This work examines the recovery of spiked Nd from seawater media by magnetic iron oxide (Fe3O4). A rapid increase of Nd recovery from 0.04 to 22.27mgg−1 was observed when the solution pH adjusted from 1.98 to 8.22 at 298K. A maxima Nd adsorption capacity was estimated to be 24.88mgg−1 at 308K and 8.22 pH. A negative change in standard free energy (ΔG°=−5.87, −6.69, −7.68kJmol−1 at 288, 298, and 308K, respectively) suggests that Nd adsorption is spontaneous. The positive ΔH° value (2.42kJmol−1) supports its endothermic nature of the adsorption and agrees with the observed enhanced Nd adsorption at high temperatures. Besides, the positive ΔS° (10.84Jmol−1K−1) displays that the randomness increase at the solid-solution interface during Nd adsorption. More importantly, we observed that the Nd adsorption only decreased slightly while the NaCl ionic strength increased from 0.001 to 1.0N, implying the involvement of inner-sphere mechanism. These data indicated that the adsorbent of ferrite has a great potential in selective and fast recovery of spiked Nd from seawater matrix.