The removal of nickel ions from waste streams discharged from mining and metal plating industries has become a popular research topic over the past few decades. In this work, the emulsion liquid membrane (ELM) technique was used to remove nickel ions from synthetic aqueous solutions using bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as the extractant. Sulphuric acid was selected as the internal stripping agent. Central composite design methodology was used to obtain the optimum conditions, with the factors selected in the design being extractant concentration, stripping agent concentration, NiSO4 solution pH, and NiSO4 solution/emulsion volume ratio. It was found that the extractant concentration, stripping agent concentration, and NiSO4 solution/emulsion volume ratio had a significant effect on nickel removal. Optimum operating conditions achieved a maximum nickel removal of more than 99%. Validation tests confirmed the good agreement between the predicted and experimental data. The emulsion was successfully broken afterwards and the oil phase was re-tested. The effects of kinetics, loading capacity, and pH variation tests between the emulsion phase and organic phase were investigated. Zeta potential measurements suggest a final pH of around 2.0 is desirable for the post-reaction treatment of the emulsion droplets.