Preparation of Sm2O3 and Co3O4 from SmCo magnet swarf by hydrometallurgical processing in chloride media

Abstract

The recycling of rare earth elements (REE) from end-of-life REE based products is an environment friendly proposition. Waste Sm-Co based permanent magnet generated during machining is a good source for both Sm and Co. In the present study a simpler process of acid leaching at 80 degrees C followed by solvent extraction, oxalate precipitation and calcination is described for producing pure Sm2O3 and Co3O4. With either 10 vol% H2SO4 or 15 vol% HCl at 80 degrees C more than 95% Sm and Co are leached in 1 h. Extraction of Sm from sulphate leach liquor with TBP or Aliquat 336 was poor. Although extraction with TOPS-99 is quantitative but Sm from sulphate leach liquor precipitated as Sm-2(SO4)(3).8H(2)O. The chloride leach liquor at an initial pH of 2.5 and with 1.2 mol/L TOPS-99 shows requirement of 4-stages at A:O = 3:2. Stripping with oxalic acid precipitates Sm-oxalate which is calcined at 800 degrees C to produce Sm2O3. Co3O4 is recovered from the raffinate through oxalate precipitation followed by calcination at 450 degrees C. (C) 2018 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.