Abstract
The effect of biodegradable chelating agents on the recovery of rare earth elements (REE) from clay minerals via ion-exchange leaching was investigated, with the aim of proposing a cost-effective, enhanced procedure that is environmentally benign and allows high REE recovery while reducing/eliminating ammonium sulfate usage. A processing route employing a lixiviant system consisting of simulated sea water (equivalent to about 0.5 mol/L NaCl) in conjunction with chelating agents was also explored, in order to offer a process alternative for situations with restricted access to fresh water (either due to remote location or to lower the operating costs). Screening criteria for the selection of chelating agents were established and experiments were conducted to assess the efficiency of selected reagents in terms of REE recovery. The results were compared to extraction levels obtained during conventional ion-exchange leaching procedures with ammonium sulfate and simulated sea water only. It was found that stoichiometric addition of N,N′-ethylenediaminedisuccinic acid (EDDS) and nitrilotriacetic acid-trisodium form (NTA-Na3) resulted in 10–20% increased REE extraction when compared to lixiviant only, while achieving moderate Al co-desorption and maintaining neutral pH values in the final solution.
Highlights
The bulk chemical composition of the ion-adsorption ore presented in Table 2 is characteristic of the typical weathered ores containing mixed alumino-silicates, mainly kaolinite/halloysite (Al2 (Si2 O5 )(OH)4 ), quartz (SiO2 ) and mica (KAl3 Si3 O10 (OH)2 ), consistent with the overall compositions described in literature ([16,59,60]); the total rare earth elements (REE) (TREE)
The present study investigated the effect of chelating agents on the recovery of rare earth elements from clay minerals via ion-exchange leaching, in order to propose an enhanced procedure that is environmentally benign and allows high REE recovery while reducing or eliminating ammonium sulfate usage
The authors established screening criteria for the selection of optimal chelating agents, conducted experiments in order to evaluate the efficiency of the selected reagents and compared the results with REE extraction levels obtained during conventional ion-exchange leaching procedures with ammonium sulfate
Summary
Yttrium (Y) and scandium (Sc) are considered “rare earths”, as they occur alongside lanthanides in the same ore deposits and have similar properties [1] Due to their unique physical and chemical properties, REEs became progressively more indispensable to the modern industry, with increasing demand in specific fields such clean energy, aerospace, and sustainable technology sectors. It is estimated [2] that the demand for REEs from clean technologies will reach 51.9 thousand metric tons (kt) rare earth oxide REO in 2030, with Nd and Dy, respectively, comprising. Adamas Intelligence [3] forecasted that magnet rare earth oxide demand (Nd, Pr, Dy, and Tb) will increase at a compound annual growth rate of
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