Application of emulsion nanofluids membrane for the extraction of gadolinium using response surface methodology

In this work, an emulsion nanofluid membrane (ENM) was applied to effectively extract gadolinium. Simultaneous emulsification of nanoparticles and surfactant was performed to stabilize the ENM. Multi-walled carbon nanotubes (MWCNTs) nanofluid was employed as liquid membrane. The ENM composed of diisooctylphosphinic acid (CYANEX 272) as carrier, MWCNTs as nanoparticles, Span-85 (sorbitan triooleate) as surfactant, kerosene as organic diluent and nitric acid as internal phase. The effects of important operating variables i.e., carrier concentration, MWCNTs concentration, surfactant concentration, mixing speed, internal phase concentration and feed phase pH were investigated. Response surface methodology (RSM), according to central composite design (CCD), is used to optimize the process variables and a regression model for extraction percentage was developed. The 3D response surfaces of gadolinium (III) extraction efficiency were achieved and significance of six important variables and their interactions on extraction efficiency were found out. The desirability function was performed to simultaneously evaluate all the factors and determine the best possible goals for each response. The optimum condition for gadolinium extraction were: The optimum condition for gadolinium extraction were: 0.84 M of CYANEX 272, MWCNTs concentration of 318.05 ppm, 2.91% (v/v) of Span-85, mixing speed of 188.15 rpm, 1.27 M of HNO3 as internal phase reagent, feed phase pH of 3 and desirability value of 0.904. Under the optimized condition, the extraction of Gadolinium (III) reached the maximum of 92.05%.