Determination of the optimum conditions for the precipitation of REEs by oxalic acid from chloride s

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Mohsen Valizadeh Holagh, Davood Moradkhani, Behzad Sedaghat

Today, the production of rare earth elements is on the rise due to a variety of strategic applications.
The most important applications of rare-earth metals are in the fields of catalysts (60 %), electronics
and magnetism (10 %), ceramics and glass (10 %), metalworking (10 %) and others (10 %). Esfordi
phosphate ore is composed of rare earth elements including cerium (Ce), neodymium (Nd), lanthanide
(La), samarium (Sm), yttrium (Y) and praseodymium (Pr). In this paper, we tried to optimize
the precipitation of REEs in the presence of chloride environment using oxalic acid. The chloride
solution was obtained by alkali digestion process, leaching with hydrochloric acid and neutralization
of iron. The optimization experiments were performed using four parameters of oxalic acid
concentration, stirring speed, temperature and time in four levels by classical method. The maximum
precipitation of rare earth elements was found for oxalic acid concentration: four times stoichiometric,
stirrer speed: 700 rpm, temperature: 60 ° C and time: 60 minutes. In optimum conditions,
the precipitation efficiency of Ce, Nd, La, Sm, Y and Pr was 99.62 %, 99.52 %, 97.79 %,
96.77 %, 98.41 % and 90.74 %, respectively. The highest grade of rare earth elements in the produced
oxalate concentrate was 36.45 %. The grade of Ce, Nd, La, Sm, Y and Pr in the oxalate concentrate
was 18.8 %, 7.48 %, 4.87 %, 1.11 %, 2.26 % and 1.93 %, respectively.

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