The effect of feeding location on the continuous precipitation of Pu(IV) oxalate in a vortex precipitator

The effects of feeding location on crystals size and distribution, precipitation percentage of Pu(IV) oxalate were investigated in a vortex continuous precipitator when the apparent average residence time was 25 min at 50 degrees C. The results showed that when oxalic acid was into the free vortex zone and Pu(IV) nitrate solution was into the forced vortex one, the VMD of the particles near the outlet of the precipitator increased from 36.8 +/- 1.2 mu m to 45.8 +/- 2.1 mu m, the precipitation percentage of Pu(IV) oxalate from 97.90% +/- 1.0-99.79% +/- 0.05%, compared with another feeding location, both oxalic acid and Pu(IV) nitrate solution into the forced vortex zone. The two feeding methods could both prevent Pu(IV) oxalate nuclei contacting the inner wall of the precipitator during nucleation. The results showed agglomeration happened during crystals growth even under stirring. Both local supersaturations and agglomeration decided particles size distribution and the average size of Pu(IV) oxalate.