Selective flotation of zinc(II) and silver(I) ions from dilute aqueous solutions

An experimental investigation is presented of the batch competitive flotation of zinc(II) and silver(I) ions from dilute aqueous solutions with sodium dodecylsulfate and ammonium tetradecylsulfonate as anionic surfactants and with cetylpyridinium chloride as a cationic surfactant. The sequence of growing affinity of metal cations to anionic surfactants is the same as the sequence of ionic potential values of the studied cations: Ag(+) < Zn(2+). The presence of potassium sulfate in aqueous solution has a negative influence of Zn(2+) foam separation with a anionic surfactant which is due to competition for the surfactant between Zn(2+) and K(+) cations. Also, the effect of inorganic ligands (i.e., thiosulfates, thiocyanates, and cyanides) on the selectivity of ion flotation of Zn(II) and Ag(I) is established. Results are discussed in terms of the complex species of zinc(II) and silver(I). At a total S(2)O(2)(3-) concentration of 3 x 10(-6) M, the silver(I) is floated as a mixture of anions [Ag(S(2)O(3))](-) and [Ag(S(2)O(3))(2)](3-), whereas zinc(II) remains in the aqueous phase as Zn(2+). At total concentrations of SCN(-) from 1 x 10(-4) to 2 x 10(-3) M, silver(I) is floated as a mixture of [Ag(SCN)(2)](-) and AgSCN species. Partial separation of zinc(II) from silver(I) can be achieved in the presence of CN(-) ligands at total concentrations varying from 2.5 x 10(-4) to 1.0 x 10(-3) M. The affinity of the studied cyanide complexes to cetylpyridinium chloride follows the order [Ag(CN)(2)](-) < [Zn(CN)(4)](2-) + [Zn(CN)(3)](-).