Application of Complexane-type Surfactants to Ion Flotation

The relationship between the HLB (hydrophile-lipophile balance) value of the scum (surfactant-metal complex) and the efficiency of ion flotation was investigated by using 15 kinds of synthetic complexane-type surfactants (Rc). The optimum pH region in the Cu(II) flotation shifted to a lower pH range with the increase of chain length of the alkyl group in N-alkyliminodiacetic acid (RidaH2), whereas, in the case of N-(1-carboxyalkyl)ethylenediaminetriacetic acid (RedtaH4), it shifted to a higher pH range with the increase of chain length of the alkyl group, and the decrease of numbers of the coordination sites in Rc (Figs. 1-3). The HLB values of Rc-Cu complexes were calculated according to the Davies or Oda equation on the base of postulated chemical formula. The effective HLB value of Rc-Cu complexes in the Cu(II) flotation ranged from 4 to 14 (Table 4). Hg(II) was floated selectively from an aqueous solution containing Hg(II), Fe(III), Cu(II), Pb(II), Cd(II), Zn(II) and Ca(II) at pH0.8 by using R10edtaH4, but, at pH2, the order of selectivities for these metal ions was found to be identical with the order of formation constants of R10edtaH4-metal complexes (Fe(III) > Hg(II) > Cu(II) > Pb(II) > Cd(II) > Zn(II) > Ca(II)) (Fig. 5). Selectivity in the ion flotation was interpreted from the formation constants and the HLB values of the scum (Rc-metal complexes). Rc could be easily recovered from the scum by treating with 2N H2SO4.