Experimental Study on Aqueous Phase Entrainment in a Mixer-settler with Double Stirring Mode

The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efficiency during industrial production. Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clarification. In this paper, in order to improve the efficiency of clarification, a mixer-settler with double stirring mode was designed and manufactured by adding a stirring device in the settler after reducing the volume of the settler. The innovation of this research involves adopting the ultraviolet-visible spectrophotometer to investigate the quantity of aqueous phase entrainment at the settler outlet in order to measure the clarification degree. Experimental results show that the clarification effect with stirring is better than that without stirring. The clarification effect is ameliorated as the stirring speed increases. Generally, the clarification effect shows a best condition when the offset distance is 12.5 cm, making the phase entrainment reduced to less than 0.1%. When the clearance over the tank bottom is 7 cm and 10 cm, respectively, the quantity of aqueous phase entrainment is better than the case with a clearance of 4 cm. The results show that the stirring paddle close to the mixed phase zone can better promote the two-phase separation.