LEAD(II) EXTRACTION FROM NITRATE SOLUTIONS WITH DI(2-ETHYLHEXYL)PHOSPHORIC ACID

In this paper, equilibrium studies were carried out on the extraction of trace amounts oflead(II) from 0.2 mol/dm(3) (Na,H)NO3 aqueous solutions with di(2-ethylhexyl)phosphoric acid (HR) dissolved in n-dodecane at 298 K. The composition of the extracted species was numerically found to be PbR(2)(HR) and PbR(2)(HR)(2). A chemical equilibrium model was developed to evaluate the thermodynamic constants for the formation of the two complexes, based on the law of mass action, which took into account the activity corrections of reactive species in the aqueous phase by employing the Bromley and the simplified Fitter equations and those of the extractant in the organic phase.