Emulsion ionic liquid membrane for recovery process of lead. Comparative study of experimental and response surface design

Abstract

The technique of emulsion ionic liquid membrane (EILM) was used as chemical process for Pb(II) recovery, from nitrate medium, using Aliquat336 as ionic liquid carrier. The Tween20 as a dispersive non-ionic surfactant was used for the emulsion formation. The optimization of the extraction and pre-concentration of Pb(II) was determined by optimizing one parameter at the time. So, several experimental parameters as: carrier concentration, surfactant concentration, time and stirring speed of feed phase, initial concentration and pH of feed phase, were studied. The results showed that the lead ions were extracted at 82.61% by Aliquat336 and recovered at 82.16%, in aqueous solution of the nitric acid, from a feed phase of lead(II) nitrate of 207.2ppm at pH equal to 5.5, in presence of 1% w/w Aliquat336 and 0.5% w/w of Tween20 under 30min of stirring at 210rpm. The tests of separation experiments of Pb(II) and Cu(II) were carried on the basis of the optimal conditions of lead (II) recovery. Thus, the separation factor of lead over copper was equal to 1.30, obtained from their equimolar synthetic mixture. Indeed, the recovery of Cu(II) can be advantageous towards of Pb(II) if the molar composition of Cu/Pb in mixture was of 0.65. Response surface methodology (RSM) using Box–Benheken Design (BBD) was used for the statistical study. So, the reduced cubic of the quadratic model showed that the predicted values were in good agreement with those found experimentally and the parameter of ionic liquid concentration has an important individual effect on the response. Therefore, the recovery of Pb(II) can be predicted at 82.14% with the best desirability of the chosen model under our experimental conditions.