چكيده به لاتين
Nowadays, recovery of materials from secondary sources has received extensive attention for its added value and environmental provisions. Considering decadent sources of rare earth elements and economic considerations in Iran, recycling of these elements plays an important role in saving resources and protection of the environment. In this research, hydrometallurgical recovery of lanthanum and cerium from used catalysts of FCC process has been studied. The catalysts were first roasted at 750oC. DESIGN-EXPERT 7 commercial software was utilized to design procedure of experiment for leaching of catalysts by considering three major controlling factors, temperature, concentration of hydrochloric acid, and time in three different levels including temperature of 20-80oC, HCl concentration of 2-4M and leaching time of 2-4 hours. Efficiency of lanthanum, cerium, and aluminum recovery was severely influenced by leaching temperature. In 4M concentration of HCl, temperature of 80oC and leaching time of 4 hours, leaching efficiencies of %100, %100 and% 30 were obtained for lanthanum, cerium and aluminum, respectively. In order to separate lanthanum and cerium from aluminum as an impurity, D2EHPA was used as extractant. In the solvent extraction process, the experiments were performed in pH range of 0.5-2.5 and organic phase concentration in kerosene of 0.2-1M. The results showed that the best separation factors were obtained in pH=1.5-2 and concentration of organic phase equal to 0.8M. However, the best extraction efficiency of extraction of lanthanum and cerium was achieved in PH=2-2.5, and organic phase concentration of 1 mular. Finally, by studying lanthanum and cerium extraction reactions, it was found out that these two elements were extracted from the solution in their monovalent state and in the form of LaCl2+ and CeCl2+.
