1685
Investigation of Process Intensification Role in
Solid–Liquid Separation Techniques for the Recyclable
Samarium-Cobalt Magnet
Zainab Nasrullah, Frank Agyemang, Oluwatosin Adeyebayo, John Dhuol
Department of Metallurgical and Materials Engineering, Montana Technological University, Butte, Montana. USA
Richard LaDouceur
Department of Mechanical Engineering, Montana Technological University, Butte, Montana, USA
ABSTRACT: To sustain the circular economy, defense applications, and other renewable technologies,
recycling rare earth elements (REEs) and other critical elements from their secondary resources is important.
This cause has resulted in rigorous research and development for viable extraction and separation of REEs.
Previously, Sm-Co recycling has been done with technologies, which fall under the categories of pyrometallurgy,
physical separation, and hydrometallurgy. All these methods have limitations associated with energy, cost, and
environment. Reportedly, the chemical leaching technology has successfully recovered and separated Sm-Co.
Still, it has limitations associated with slow mass transfer and leaching kinetics, and there is a need to intensify
the process to make it time efficient. This approach has also adversely impacted the environment by an extensive
use of toxic, corrosive, non-selective, and expensive reagents. In this research study, chemical leaching of Sm-Co
was performed using this new class of solvents, Deep Eutectic Solvents (DESs), which fall under the category
of ionometallurgy. Four different DESs were used, proven to be green, non-toxic, biodegradable, cheap, and
selective for cobalt over samarium by 82% leaching conversion. To improve the slow mass transfer and leaching
time, this new technology of resonant vibratory mixing (RVM) was also tested. RVM intensifies mixing by
establishing near instantaneous, low energy mixing conditions through resonance. It has been shown to improve
the adsorption kinetics and was tested for the leaching kinetics. Four combinations of DESs were prepared, which
are made up of two quaternary salts: Choline Chloride and Tetra Butyl Ammonium Chloride, and three organic
compounds: Oxalic Acid, Urea, and Ethylene Glycol. These combinations were used for chemical leaching of
Sm-Co with leaching factors of time, temperature, and type of DESs. After leaching, the samples were tested
with and without resonant vibratory mixing with conditions of time, intensity (%),and type of DESs. Samples
were analysed with Induced Coupled Plasma–Optical Spectroscopy (ICP–OES). Future work will involve a life-
cycle assessment to assess the RVM technology with other conventional mixers, and an extensive study of DES
properties to improve selective leaching.
INTRODUCTION
Together with yttrium (Y), scandium (Sc), and lanthanides,
the rare earth elements (REE) are a collection of 17 chemi-
cally related elements [1]. Due to their distinctive physical
and chemical characteristics, rare earth elements (REEs) are
valuable resources that are necessary for a wide range of
modern technological applications, including metallurgy,
machine building, radio electronics, instrument engineer-
ing, nuclear engineering, and manufacturing [1], [2], [3].
Investigation of Process Intensification Role in
Solid–Liquid Separation Techniques for the Recyclable
Samarium-Cobalt Magnet
Zainab Nasrullah, Frank Agyemang, Oluwatosin Adeyebayo, John Dhuol
Department of Metallurgical and Materials Engineering, Montana Technological University, Butte, Montana. USA
Richard LaDouceur
Department of Mechanical Engineering, Montana Technological University, Butte, Montana, USA
ABSTRACT: To sustain the circular economy, defense applications, and other renewable technologies,
recycling rare earth elements (REEs) and other critical elements from their secondary resources is important.
This cause has resulted in rigorous research and development for viable extraction and separation of REEs.
Previously, Sm-Co recycling has been done with technologies, which fall under the categories of pyrometallurgy,
physical separation, and hydrometallurgy. All these methods have limitations associated with energy, cost, and
environment. Reportedly, the chemical leaching technology has successfully recovered and separated Sm-Co.
Still, it has limitations associated with slow mass transfer and leaching kinetics, and there is a need to intensify
the process to make it time efficient. This approach has also adversely impacted the environment by an extensive
use of toxic, corrosive, non-selective, and expensive reagents. In this research study, chemical leaching of Sm-Co
was performed using this new class of solvents, Deep Eutectic Solvents (DESs), which fall under the category
of ionometallurgy. Four different DESs were used, proven to be green, non-toxic, biodegradable, cheap, and
selective for cobalt over samarium by 82% leaching conversion. To improve the slow mass transfer and leaching
time, this new technology of resonant vibratory mixing (RVM) was also tested. RVM intensifies mixing by
establishing near instantaneous, low energy mixing conditions through resonance. It has been shown to improve
the adsorption kinetics and was tested for the leaching kinetics. Four combinations of DESs were prepared, which
are made up of two quaternary salts: Choline Chloride and Tetra Butyl Ammonium Chloride, and three organic
compounds: Oxalic Acid, Urea, and Ethylene Glycol. These combinations were used for chemical leaching of
Sm-Co with leaching factors of time, temperature, and type of DESs. After leaching, the samples were tested
with and without resonant vibratory mixing with conditions of time, intensity (%),and type of DESs. Samples
were analysed with Induced Coupled Plasma–Optical Spectroscopy (ICP–OES). Future work will involve a life-
cycle assessment to assess the RVM technology with other conventional mixers, and an extensive study of DES
properties to improve selective leaching.
INTRODUCTION
Together with yttrium (Y), scandium (Sc), and lanthanides,
the rare earth elements (REE) are a collection of 17 chemi-
cally related elements [1]. Due to their distinctive physical
and chemical characteristics, rare earth elements (REEs) are
valuable resources that are necessary for a wide range of
modern technological applications, including metallurgy,
machine building, radio electronics, instrument engineer-
ing, nuclear engineering, and manufacturing [1], [2], [3].