A solution chemistry approach to the study of rare earth element precipitation by oxalic acid

A solution chemistry approach is developed to study oxalic acid efficiency (OAE) in recovering rare earth (RE) elements from the leachates of weathere d clays. The optimal pH for precipitation (approximately 2) to obtain the h ighest RE recovery with the highest purity is identified experimentally and confirmed by solution chemistry calculations. Applying the solution chemis try approach to three case studies, the cause for a larger oxalic acid cons umption than that calculated from stoichiometry of RE oxalate precipitation is identified. A typical OAE of approximately 60 pct was determined with 4 0 pct of excess oxalic acid consumed by precipitating and complexing non-RE elements while maintaining a low residual RE element concentration. Both s olution chemistry calculations and experimental results showed that OAE can be improved by processing leachates of high initial RE concentrations.