<p>One of the crucial problems in recovering precious metals from the zinc plant residue is the environmental effects and high energy consumption. Efficient and green solvents have a special place in the development of the recovery process for the critical ions. This paper presents the separation of Cd(II) ions from a hydrochloric acid solution, including zinc ions, achieved by applying of phosphonium ionic liquids (Cyphos IL 104). At first, the solvent extraction was examined experimentally in the batch tests, and it was observed that 0.1&#xa0;M HCl was a relative acidic solution to reach the maximum separation factor. Afterwards, the effects of certain crucial factors, such as time, the concentration of Cyphos IL 104 as the extractant, and the temperature, were examined to achieve the highest possible separation factor. Based on batch studies, an optimal feedstock was prepared to investigate the real-scale conditions in the multistage contactor. The ionic liquid was found to extract Cd(II) more efficiently in the continuous operation mode. The mass transfer performance of the column showed that the proposed correlations were not successful in predicting the results. Therefore, a new equation for the overall aqueous phase mass transfer was proposed by utilizing the obtained results from the extraction of both ions with ionic liquid. Thus, the utilization of Cyphos IL 104 as an alternate solvent to replace traditional organic solvents is one of the promising approaches as well as a green method for separating Cd(II) ions from the real leaching solution of zinc plant residue.</p>