A Comparative Study of Experimental Optimization and Taguchi Design of Co(II) Recovery by Aliquat 336 as Ionic Liquid Carrier

Abstract

Experiments of extraction and stripping of cobalt(II) were carried out. The liquid–liquid extraction process was considered, in which the organic phase was constituted of Aliquat 336 extractant that is the quaternary ammonium salt, and oleyl alcohol modifier dissolved in dodecane where the aqueous phase contained the metal ion in a concentrated hydrochloric acid solution. The optimization of Co(II) recovery was determined by optimizing one parameter at the time. Therefore, several experimental parameters such as Aliquat 336 concentration, extraction time, hydrochloric acid concentration, and the initial concentration of metal ion were studied. The cobalt(II) ions were extracted at 62.5% and stripped from the metal-loaded organic phase at 41.0% by distilled water as stripping agent. The mass balances were checked for all the studied parameters with an average deviation percentage of 2%. In fact, the McCabe–Thiele showed six theoretical stages for total recovery of cobalt. The separation tests of Co(II) and Ni(II) were carried out on the basis of the optimal conditions of Co(II) recovery. It showed that the nickel ions were slightly extracted (< 10%) whatever the composition of mixture. A Taguchi design with a L4 orthogonal array was used for the statistical study to determine the influence and the contribution percentage of certain experimental parameters on the Co(II) extraction. Analysis of variance and analysis of means showed a total absence of the uncontrollable factors (noise), in which the chosen model has described our extraction process with accuracy. In fact, only the main effects without interaction of controllable factors (A, B, and C) contribute to the optimal extraction of cobalt as follows: A (50.10%), B (28.33%), and C (21.47%) at levels: 2/2/1 with high signals as 32.07, 28.38 and 25.13, respectively.