The worldwide production of NdFeB magnets has outpaced
all other
types of magnets owing to their low cost and enhanced magnetic properties.
The critical elements required for the production of these magnets
are Nd, Pr, and Dy along with other metals. However, the rare earth
elements (REEs) come with substantial supply risk. Recycling of REEs
from obsolete NdFeB may be a promising alternative to address the
supply chain pressure. The purpose of this work is to optimize the
water leaching process for the selective recovery of Nd, Pr, Co, and
Al from chloride-roasted waste NdFeB magnets, using a statistical
approach, and to simultaneously study the effect of significant process
variables on the extraction of metals from end-of-life (EOL) magnets.
Process optimization was carried out by performing a minimum number
of bench scale operations specifically designed for leaching experiments.
It was observed that the temperature, time, and pulp density were
the most significant process parameters. Tuning of operational parameters
was carried out, and model equations were generated for all the response
variables with the help of Design Expert software. The response surface
methodology (RSM) was used to generate optimized conditions for the
leaching process (temperature: 95 °C; pulp density: 100 g/L;
time: 60 min), which were further validated by repeating the leaching
experiments in triplicate. The extraction efficiency of metal ions
was found to be maximum under the optimized leaching conditions.
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