Recovery of rare earth elements from spent fluid catalytic cracking catalysts using leaching and solvent extraction techniques

摘要

This paper investigates the recovery of rare earth elements (REEs, mainly lanthanum and cerium) from spent fluid catalytic cracking (FCC) catalysts via the hydrometallurgical processes of leaching and liquid-to-liquid extraction. The maximum leaching efficiency (99.3% for REEs) was achieved under the following conditions: 2 mol/L HCI, a solid-to-liquid (S/L) ratio of 1:10, leaching at 60 degrees C for 2 h, and 2 h of roasting at 750 degrees C prior to leaching. Because the main impurity element in the leachate was aluminum, the extractions of REEs and aluminum using di-2-ethylhexyl phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic mono-2-ethylhexyl ester (HEHEHP) under different conditions were compared. The results indicated that D2EHPA and HEHEHP exhibited large extraction differences for REEs but small extraction capacity differences for aluminum. Based on the analysis of the experiments, the optimum extraction conditions for REEs were determined to be 0.5 mol/L D2EHPA, equilibrium pH = 2.5, ambient temperature and then stripping with 2 mol/L HCI. The overall REEs recovery efficiency was 62.88%. (C) 2016 Elsevier B.V. All rights reserved.