Treatment of fluid catalytic cracking spent catalysts to recover lanthanum and cerium: Comparison between selective precipitation and solvent extraction Valentina Innocenzi *, Francesco Ferella, Ida De Michelis, Francesco Veglio ` Department of Industrial Engineering, Information and Economy University of L’Aquila, Via Giovanni Gronchi 18 – Zona industriale di Pile, 67100 L’Aquila, Italy Introduction FCC waste catalysts have several uses once spent: for example, are reutilized in cement and ceramic industry, as a wastewater filtering agent and as a component in asphalt mixtures [1]. The demand of these catalysts will increase in the incoming years and consequently their production and wastes; in order to reduce the quantity and the catalyst cost it is necessary to limit the fraction discarded and improve the development of processes for recovery and reuse of them as raw material. Furthermore, FCC catalysts contain rare earths, in particular lanthanum and cerium, and as it is well known these elements are necessary for many technological sectors in the most industrialized countries. For these reasons it is important to develop processes for treating this type of catalysts at the end of their technical life in order to reduce the amount of waste and recover strategic materials, especially RE. The recovery of rare elements (Y, Eu, La, Ce, Tb.) awoke a great interest in the last years and many scientific works were focused on this field. The main researches were summarized in recent relevant reviews [2,3]. As regards lanthanum and cerium, they can be recovered from several industrial wastes. Some papers that describe the recovery of such rare earths from Ni-MH spent batteries [4–10] and glass scraps [11,12] are reported in the following. Pietrelli et al. [4] proposed a process that includes leaching with 2 M of H 2 SO 4 at 20 8C, 2 h, solid to liquid (S/L) ratio of 1:10, filtration and selective precipitation by addition of NaOH at pH lower than 1.5. At this pH range rare earths precipitated as NaRE(SO 4 ) 2 . The overall recovery of rare earths was 80%. Li et al. [5] described a method that includes leaching with 3 M of H 2 SO 4 at 95 8C, 4 h and S/L ratio of 1:7.5. About 95% of rare earths precipitated as Re 2 (SO 4 ) 3 , whereas the other 5% remained in the solution. The precipitated rare earths were dissolved by water with a S/L ratio of 1:5 and treated by 1 M NaOH solution to form RE(OH) 3 ; instead, rare earths in the solution were stripped with 2 M HCl. The final recovery of rare earths was 97.8%. Zhang et al. [6] developed a process consisting of a leaching stage by 3 M HCl at 95 8C, 3 h and S/L ratio of 1:9. Recovery of rare earths from the solution was obtained by solvent extraction using 25% v/v D2EHPA in kerosene, stripping with 2 M of HCl and precipitation by oxalic acid at pH 3. The recovery of La, Ce, Pr and Nd was around 98%. The same authors [7] proposed another process that includes leaching with 2 M H 2 SO 4 at 95 8C for 4 h. Rare earths were recovered by using solvent extraction with 25% v/v of D2EHPA in kerosene, followed by stripping with 1 M sulfuric acid solution, precipitation by oxalic acid and final calcination to oxides. In this treatment RE recovery was 93.6%. Journal of Industrial and Engineering Chemistry 24 (2015) 92–97 A R T I C L E I N F O Article history: Received 26 June 2014 Received in revised form 8 September 2014 Accepted 13 September 2014 Available online 22 September 2014 Keywords: Hydrometallurgical process FCC spent catalyst Lanthanum Cerium Precipitation Solvent extraction A B S T R A C T The paper is focused on the study of hydrometallurgical processes for recovery of rare earths (RE) from fluid catalytic cracking catalysts (FCCC). According to the experimental results two processes were proposed: in the first one RE were recovered as double sulfates by selective precipitation with sodium hydroxide after leaching with sulfuric acid. The second approach consisted of dissolution of powder by acids, solvent extraction by (2-ethylhexyl)phosphoric acid (D2EHPA), stripping and precipitation of RE oxalates using oxalic acid. Experiments showed that solvent extraction was found to be beneficial in terms of achieving improved final products quality with greater purity (98%). ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +39 0862434236. E-mail address: valentina.innocenzi1@univaq.it (V. Innocenzi). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec http://dx.doi.org/10.1016/j.jiec.2014.09.014 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.