New liquid-liquid extraction column with random packed agitation structure for heavy metal removal and hydrodynamic evaluation

Abstract

A new random packed agitation column was presented to enhance the evaluation of dispersed phase holdup and hydrodynamic velocities. The extraction of cobalt ions from an aqueous to organic phase was observed under operating conditions. The interaction and association between operating parameters (rotor speed, aqueous phase flow rate (Qc), and organic phase flow rate (Qd)) were investigated by designing response surface methodology (RSM). Quadratic models for three responses (holdup (φ), slip velocity (Vs), and extraction efficiency (%E)) were obtained by statistical analysis. The achieved optimal conditions included 203 rpm of rotor speed, 32 L/h of Qd and 28 L/h of Qc. The model outcomes were 0.094, 10.57 mm/s, and 99.91% for φ, Vs, and %E, respectively. Comparison between results obtained from the central composite design approach and artificial neural network (ANN) proved that both techniques had a high ability to predict the experimental data, but the ANN technique had a higher coefficient of determination (0.9999) and lower error. The cobalt recovery can be significantly increased using higher rotor speed and phase flow rates. The data clearly demonstrates that the column configuration can be applied with high efficiency for the recovery of cobalt ions or other elements from secondary sources.