Extraction separation of Co(Ⅱ) from Ni(Ⅱ) in H_2SO_4 solutions with carriers in hollow-fiber contactors

摘要

The separation of Co(Ⅱ) from Ni(Ⅱ) in H_2SO_4 solution across a hollow fiber membrane containing D_2EHPA carriers dissolved in kerosene was studied. The Co(Ⅱ) was simultaneously re-extracted to a strip phase containing H_2SO_4. Experiments were conducted to determine the effects of the feed pH (4-5), carrier concentration (0.1-0.5 mol/dm~3), strip acidity (0.1-2mol/dm~3), and flow rates of the three phases (200-600 cm~3/min). The extraction efficiency for each metal ion was found to increase with increasing flow rate of the feed phase, feed pH, and D_2EHPA concentration in the extraction module. Co(Ⅱ) was preferentially extracted over Ni(Ⅱ) by D_2EHPA under the same extraction conditions. In the extraction module, the separation factor β_(Co/Ni) increased with increasing flow rate of the feed phase and D_2EHPA concentration but decreased with increasing feed pH. In the re-extraction module, the recovery of Co(Ⅱ) increased with increasing the feed pH, D_2EHPA concentration, and flow rate of the strip phase but decreased with increasing the strip acidity. At a feed pH of 4, the percent extraction and recovery of Co(Ⅱ) were 81% and 26.4% (Ni/Co-11% in strip phase), respectively. The percent extraction and recovery for Co(Ⅱ) using one-stage HFMCs were better than those using two-stage HFMCs.