Concomitant Leaching and Electrochemical Extraction of Rare Earth Elements from Monazite

Abstract

Rare earth elements (REEs) have become increasingly important in modern day technologies. Unfortunately, their recycling is currently limited, and the conventional technologies for their extraction and purification are exceedingly energy and chemical intensive. New sustainable technologies for REE extraction from both primary and secondary resources would be extremely beneficial. This research investigated a two-stage recovery strategy focused on the recovery of neodymium (Nd) and lanthanum (La) from monazite ore that combines microbially based leaching (using citric acid and spent fungal supernatant) with electrochemical extraction. Pretreating the phosphate-based monazite rock (via roasting) dramatically increased the microbial REE leaching efficiency. Batch experiments demonstrated the effective and continued leaching of REEs by recycled citric acid, with up to 392 mg of Nd L and 281 mg of La L leached during seven consecutive 24 h cycles. Neodymium was further extracted in the catholyte of a three-compartment electrochemical system, with up to 880 mg of Nd L achieved within 4 days (at 40 A m). Meanwhile, the radioactive element thorium and counterions phosphate and citrate were separated effectively from the REEs in the anolyte, favoring REE extraction and allowing sustainable reuse of the leaching agent. This study shows a promising technology that is suitable for primary ores and can further be optimized for secondary resources.

Geochemistry of Monazite within Carbonatite Related REE Deposits

“…Except for the extremely high Th-monazite, rarely-identified in carbonatite, most REE extraction from monazite in carbonatite-related deposits follow the processing described by Aly et al [59]. Furthermore, Maes et al [65] proposed a two-stage recovery strategy focused on the recovery of Nd and La from monazite that combined microbially based leaching with electro-chemical extraction. The radioactive element thorium and counter-ions phosphate and citrate were proven to effectively separate from REEs in the anolyte, which allows for the sustainable reuse of the leaching agent [41].…”

“…Currently, REEs have a low price in the global market, especially the LREEs. The price for Nd 2 O 3 (USD$38-40 kg −1 ) is much higher than La 2 O 3 and Ce 2 O 3 (US$2 kg −1 ), and, even for Nd, it is currently not sufficient to balance the power costs ($314 kg −1 for Nd) using environmentally-friendly technology to recover the REEs [65].…”

Design and optimization of a fused‐silica microfluidic device for separation of trivalent lanthanides by isotachophoresis

“…Furthermore, high lanthanide concentrations can be found in leachates from potentially recyclable materials, such as landfilled materials [62], neodymium magnet waste [63], fluorescent lamp waste [64], and fluid catalytic cracking catalysts [65]. This MFD could provide fast analysis of lanthanide content in these leachate materials, particularly in processes where consecutive leaching steps occur, as employed by Maes et al [61], providing measurement of the lanthanide content of the leachate throughout consecutive processing cycles. Furthermore, chemicals employed in this electrophoretic system, such as ammonium [66,67] and acetate [55], are present in the leaching processes of some environmental samples.…”

Selective electrochemical extraction of REEs from NdFeB magnet waste at room temperature

“…Membrane electrolysis has been successfully employed in various fields including metal recovery. [26][27][28] For all the electrolysis experiments, 3 grams of magnet waste was first partially leached with HCl at (nHCl/nREE = 3.5). In this study, a membrane electrochemical reactor with two chambers separated by an anion exchange membrane was used to treat the magnet waste (Fig.1).…”