Recycling of rare-earth elements (REEs) from NdFeB magnets is an important strategy to mitigate the risks associated with the REE supply chain. In this article, we propose an electrochemical process to recover REEs wherein all the reagents required for both leaching of REEs as well as the precipitation are generated in situ electrochemically. A three compartment electrochemical reactor was used in which a rare-earth containing salt along with an additive salt, ammonium sulfamate, was fed into the middle compartment. Upon electrolysis, the salts were split into acid and rare-earth hydroxides. The acid generated in the anolyte compartment was used to leach the NdFeB magnet waste. The rare-earth hydroxides were collected in the catholyte compartment and calcined to obtain rare-earth oxides. More than 95% of REEs and cobalt were extracted into the solution, and more than 85% of iron was removed as Fe(OH)₃precipitate in the same step. Subsequently, the leachate was oxidized and neutralized to remove more than 99% of iron. By using electrons as green reagents, this process combines leaching and precipitation in a single reactor enabling process intensification. The leachate produced at the end is rich in REEs and can be fed again into the middle compartment, forming a completely closed-loop process. Overall, the process consumes no acid, only electricity, ammonium hydroxide for neutralization, and an additive salt, ammonium sulfamate.

A hyphenated optical-electrochemical set-up was used to investigate the early-stage dissolution mechanism of NdFeB permanent magnets immersed in acetic, citric, and formic acids at concentrations of 0.01 and 0.1 M. This approach enabled a direct correlation between quantifiable surface changes and dissolution behaviour under open-circuit potential (OCP) conditions. Despite minimal OCP variation (180 mV) across all conditions and rapid stabilisation within approximately 300 s, significant optically-detectable surface changes continued throughout the measurement period (1 h). This emphasises that surface dissolution kinetics, rather than thermodynamics, predominantly control the early-stage dissolution of NdFeB. Kinetic parameters obtained by fitting mean activity-level curves with a sigmoidal model revealed that higher acid concentrations result in shorter induction periods and faster surface activation. In-situ optical analysis indicated a consistent dissolution mechanism characterised initially by localised activation, followed by the progressive expansion of active sites across the surface. Post-immersion analysis confirmed preferential dissolution of rare-earth-rich phases at grain boundaries and triple points, alongside intragranular dissolution observed in 0.01 M citric acid. Among the tested conditions, dilute citric acid (0.01 M) emerges as particularly suitable medium for practical control, as its relatively long induction period (∼1378 s) allows monitoring and controlling local dissolution before rapid surface activation begins. The combined optical-electrochemical approach also revealed that, while rare-earth-rich sites are preferentially activated, early signs of matrix activation are detectable, underscoring the value of in-situ optical analysis for advancing process control in NdFeB recycling.