A comparative study of experimental optimization and response surface methodology of Bi(III) extraction by emulsion organophosphorus liquid membrane

This paper considers a new approach in the study of bismuth extraction by di(2-ethylhexyl)phosphoric acid (D2EHPA) as an organophosphorus carrier. A comparative study on the optimization of process parameters of an emulsion organophosphorus liquid membrane (EOgLM) by experimental work and response surface methodology (RSM), according to a Box–Behnken design (BBD), was carried out. Emulsion stability was achieved by the TritonX-100 as biodegradable surfactant in a dichloromethane membrane. The transport of Bi(III) ions from the acidic nitrate medium was evaluated from yield of extraction as analytical response, and the optimum conditions were initially determined by optimizing one parameter at the time. The extraction of Bi(III) was found to be total. The comparison between the values, experimentally optimized and those RSM optimized, was accomplished by optimizing the following parameters: D2EHPA/TritonX-100 ratio, initial feed phase concentration and concentration of internal phase. The comparison showed that all the values were in good agreement and all interactions of the chosen variables are significant except for the internal phase concentration and initial feed phase concentration. It was observed that it is necessary to decrease the acidity of the stripping phase to make the Bi extraction by EOgLM process more efficient.