Separation of zinc from manganese, magnesium, calcium and cadmium using batch countercurrent extraction simulation followed by scrubbing and stripping

Abstract

A systematic study for the separation of zinc from solutions containing zinc, manganese, iron, cadmium and magnesium as sulfates was developed after a batch countercurrent extraction, followed by scrubbing and stripping. In the first step, batch countercurrent experiments were carried out on a synthetic solution containing 14.60g/L Zn(II), 6.4g/L Mn(II), 2g/L Mg(II), 819mg/L Ca(II) and 60mg/L Fe(II). The results of this step showed that at a three-stage extraction and six cycles under the conditions being O/A ratio of 1:1 and temperature of 40°C, 13.06g/L equal to 89.50% of zinc was extracted by D2EHPA whereas only 83mg/L of manganese was loaded by the extractant. As a result, the low extraction percentage of manganese is an attractive advantage of this process. In comparison to the literature, the high separation factor of zinc and manganese (i.e. 643.79) of this study was obtained without any pH adjustment or using any synergetic mixture. To remove the trace concentrations of cadmium, calcium, manganese and iron from the loaded organic solution, a series of scrubbing experiments was conducted. With regard to the scrubbing results, a solution with a composition containing 6g/L Zn and 18g/L H2SO4 could scrub trace concentrations of metals from the loaded organic solution. Finally, the McCabe–Thiele diagram of the stripping stage predicted that at an O/A phase ratio of 2:1, two countercurrent stages are sufficient to transfer zinc from the organic solution to the aqueous solution. The obtained aqueous solution contained 88.8g/L of Zn and the impurities were under the limited concentrations of electrowinning.