Application of N-Alkylethylenediamines to Ion Flotationi

Abstract

The object of this investigation is by the ion flotation method to remove Hg( II) from a dilute aqueous solution containing various metal salts, using N-alkylethylenediamines (R-en). The formation constants betreen metal ions and R-en were determined at 25°C. These values were similar, regardless of alkyl chain length, but the values of Hg(II) complexes were smaller than that of ethylenediamine-Hg(II) complex. The order for the formation of these R-enmetal complexes was as follows: Fe (III) > Cu(II) > Hg(II) > Pb( II ) > Zn (II) > Cd(II) > Ca (II) (Table 2).
The optimum pH region in the ion flotation was above 4.0 for Hg(II) and above 6.5 for Fe(M). Cu(II), Pb(II), Zn(II) Cd(II) and Ca(II) scarcely showed a flotation effect (Fig.2-4). From an aqueous solution containing Hg(II), Fe(III), Cu(II), Pb(II), Zn(II), Cd(II), and Ca(II), He(II) could be selectively floated at pH 4.5 by usig R14-en or Ri-en, and at pH 5.7 by R-en or 1: Z12-en, leaving other cations in a solution (Fig.6).
R16-en, containing the largest alkyl chain, was the most effective agent for the elimination of Hg(II) and the minimum amount of Hg(II) in a residual aqueous solution was 1.2 ppm at pH 4.6. The minimum amount of Hg(II) was lowered to 0.031 ppm at pH 8.0 by the addition of Pe(II) and by using R-en (Fig.7).