Recovery of Zn(II), Mn(II) and Cu(II) in aqueous solutions by foam fractionation with sodium dodecyl sulphate in combination with chelating agents

Abstract

Adsorptive bubble separation was used to remove polyvalent ion colligends Zn(II), Mn(II) and Cu(II) from aqueous solutions, for which optimum parametrical values that influenced the recovery of these ions were scrutinized. Additionally, the effect of some auxiliary ligands (malic acid, maleic acid, and EDTA) on the recovery was investigated. Sodiumdodecylsulphate (SDS) was used as a collector. The pH was measured as 5.5 and 4.0 for the solutions, which include metalSDS and metalSDSauxiliary ligand, respectively. In the metal : SDS mixtures, SDS has retained metal ions at pH 5.5, which was exactly the value of the membrane filtered water. Therefore, no further pH adjustment was necessary throughout the experiments. The metal ions were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The optimum experimental conditions (run time, SDS concentration, and the concentration of feed solution) on the recovery and enrichment of metal ions were also discussed. The maximum recovery rate was reached within 60 min. The optimum molar ratio between metal and SDS was found to be 15, and it was shown that the recovery of metal ions increased with increasing concentration of SDS. The most suitable initial concentration of metal ions was 2x10(-5) M. The recovery rates for Zn(II), Mn(II) and Cu(II) in the presence of SDS was found to be 90.5, 99.8 and 73.4%, respectively. By adding malic acid, and maleic acid as auxiliary ligands, higher recovery rates were achieved, even in a shorter foaming time. For optimal recovery, the best molar ratio between metal:SDS:auxiliary ligand was 155.