Mercury Ions Removal from Aqueous Solution Using an Activated Composite Membrane

This work presents the results concerning the first use ofactivated composite membranes (ACMs) for the removalof Hg(II) ions from aqueous solution, using as the ligand di-(2-ethylhexyl)dithiophosphoric acid (DTPA). The effectson the removal percentage of Hg(II) of variables such aspH, the nature of the acid, the concentration of mercury (inthe feed solutions), and the ligand content (in themembrane) as well as the total surface membrane areaexposed to the Hg(II) aqueous solution were studied. Duringthe course of the removal experiments, the membranewas immersed in the Hg(II) aqueous solution in acid mediaand samples of the solution were taken at differenttimes to enable monitoring of the mercury concentrationchanges. It was found that when the ACM was prepared witha 1.0 M DTPA casting solution and the feed solutioncontained 2.49 10-4 M Hg(II) in HCl 0.1 M the amountof mercury extracted was higher than 93%. Straightforwardly,additional experiments were carried out with the free-DTPA composite membranes to make up a set of controlreference points to verify that removal of the investigatedheavy metal was a consequence of the presence of theorganic ligand; otherwise there was no Hg(II) concentrationvariation at all.