Towards the Circular Economy of Rare Earth Elements: Lanthanum Leaching from Spent FCC Catalyst by Acids

Corradino Sposato,Assunta Romanelli,Marilena Forte,Alessandro Blasi,Enrico Catizzone,Massimo Migliori,Giacobbe Braccio,Massimo Morgana,Girolamo Giordano

doi:10.3390/pr9081369

Abstract

Rare earth elements (REEs) are strategic materials widely used in different applications from Information and Communication Technologies (ICT) to catalysis, which are expected to grow more in the future. In order to reduce the impact of market price and reduce the environmental effect from soil extraction, recovery/purification strategies should be exploited. This paper presents a combined acid-leaching/oxalate precipitation process to recover lanthanum from spent FCC catalyst using nitric acid. Preferred to hydrochloric and sulphuric acid (preliminary assessed), HNO3 showed a good capability to completely leach lanthanum. The combination with an oxalate precipitation step allowed demonstrating that a highly pure (>98% w/w) lanthanum solid can be recovered, with a neglectable amount of poisoning metals (Ni, V) contained into the spent catalyst. This could open a reliable industrial perspective to recover and purify REE in the view of a sustainable recycling strategy.

Highlights

In the last decades, different chemical elements have received wide attention, due to their use in specific applications such as battery, hybrid and electric engines, energy storage, electronic devices, high-tech devices and light emitting diodes, and some of the elements are not abundant on Earth
Rare earth metals and natural graphite reserves are more abundant than lithium and cobalt, and there are large reserves of rare earth metals in China [1]
China is recognised as the largest producer, consumer and exporter of rare earth elements (REEs) in the world [2,3]

Summary

Introduction

Different chemical elements have received wide attention, due to their use in specific applications such as battery, hybrid and electric engines, energy storage, electronic devices, high-tech devices and light emitting diodes, and some of the elements are not abundant on Earth. The presence of rare earths in the FCC catalyst is fundamental to obtain a catalyst with a significant activity, high selectivity and good stability [37,38,39] From these premises, it is important to develop technologies and processes able to recover strategic materials, such as REEs, from spent FCC catalysts. Several studies have been performed on the recovery of REEs from batteries, glass scarps and other high-tech devices [40,41,42], few studies have been published on their retrieval from spent FCC catalysts [43] In this concern, the aim of this study was to explore the possibility to recover REEs (mainly lanthanum) from fines of industrial FCC catalysts (waste from Petrobras refinery), by using acid leaching and selective separation (the oxalate precipitation method). Zeolite recovery is an interesting aspect that might be considered in future works

Materials and Methods

Findings

Metals Leaching by Acids