The treatment and recovery of pollutants in aquatic system is one of the greatest challenges for environmentalists throughout the world. In this study, solvent extraction of indium using phosphonium ionic liquid (Cyphos IL 104) as an extractant and its mathematical model was proposed for prediction of In(III) ion transport across a FSSLM (flat-sheet-supported liquid membrane). Solvent extraction experiments on indium have been carried out under various experimental conditions in order to assert some fundamental parameters using mathematical analysis for mass transfer process. Diffusion is the process which facilitates metal ion transport across liquid membrane, indicating the applicability of Fick's law of diffusion in model formulation. The influence of different parameters like composition of diluent, feed acidity, and ligand concentration on In(III) ion transport rate has been reported. At different extractant concentrations, the modeling outputs and experimental indium extraction were observed to be in reasonably good agreement.