Studies on europium separation from a middle rare earth concentrate by in situ zinc reduction technique

Abstract

The present work is directed to establish the laboratory conditions for europium separation from its lanthanide neighbors, which are derived from the Egyptian monazite middle rare earth concentrate. The laboratory separation procedure is oriented to be commercialized for large industrial scale application (utilizing the commercially available reagents in Egypt). The separation process is based on a combined reduction-precipitation process, in which the europium is reduced by commercial zinc metal to its bivalent state followed by the precipitation of its sparingly soluble europous sulphate. Factors affecting the efficiency of the reduction-precipitation process which include; zinc type and its stiochiometric amount, reduction time, nature of precipitating agent and its concentration, and precipitation time were studied and evaluated in details. The best resulted reduction precipitation conditions were attained with a commercial zinc metal (2.5 times the stiochiometric amount), reduction time of 60 min, sulphuric acid as the precipitating agent (3.0 M) and finally precipitation time of 2 h in a non-oxidizing atmosphere of nitrogen. Application of the resulted optimum laboratory conditions for the separation of europium on a middle rare earth concentrate containing 2.5 wt.% Nd, 10.13 wt.% Sm, 11.35 wt.% Eu, 2.6 wt.% Gd, and 2.7 wt.% Tb gave 95% recovery of europium (II) sulphate with a purity of 92%. In the second reduction-precipitation run, the purity was increased to 97% with a final recovery of 91%.