Recovery of lanthanides from hydrocarbon cracking spent catalyst through chemical and biotechnological strategies

Abstract

The aim of this work is to evaluate the rare earth elements (REEs) recovery from fluid catalytic cracking spent catalyst (FCC-SC) by chemical and biochemical strategies while also examining a route for the valorization of biodiesel-derived glycerin (RG), which is presently unprofitable to refine. Recovery tests for REEs were performed with no pretreatment of the FCC-SC. A chemical leaching investigation was carried out using HCl, HNO₃, NaOH, CaCl₂ and citric acid aqueous solutions (1 mol L⁻¹, at 30, 50, 60 or 70 ± 1 °C). The leaching tests carried out with 1 mol L⁻¹ citric acid at 50 °C provided the best recovery of La (27%). Subsequent bioleaching tests were carried out with four strains of Yarrowia lipolytica to evaluate their potential to produce organic acids using RG as the main carbon source. The FCC-SC contains some REEs, predominantly La. Remarkable biorecovery rates for REEs (namely, La (53%), Ce and Nd (both 99%)) were achieved using the Y. lipolytica IM-UFRJ 50678 fermented medium at 50 °C. Thus, here, a sustainable approach to recovering metals from spent cracking catalyst using RG under low-cost and non-energy-intensive processing conditions is reported.

Keywords:

• Rare earth elements
• chemical leaching
• biomining
• biorecovery
• FCC spent catalyst

Additional information

Funding

The authors are thankful to Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) and to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support. The authors assert no conflicts of interest.