Abstract
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Foam fractionation is an effective separation technique in recovery of metal ions and surfactant from wastewater. In this paper, recovery of Cd(II) and surfactant in permeate from MEUF by foam fractionation with mixed anionic-nonionic surfactant were studied. Effects of the molar ratio of anionic-nonionic surfactant, Cd(II) concentration, pH on the foam properties and separation efficiency of the three matters were investigated. When the Cd(II) concentration of the feed solution was 10 mg/L, the molar ratio of Triton X-100/SDS was 0.1, the best Cd(II) removal percentage 99.1% was achieved. In addition, the removal percentages of the two surfactants were also relatively high at this condition. The mechanism of the effect of Triton X-100 on removal of Cd(II) by foam fractionation was also investigated by measurement of zeta potential and analysis of FTIR spectra. Results showed that a small amount of nonionic surfactant can significant enhance the removal percentage of Cd(II) by improvement of foam properties of anionic surfactant, while excessive nonionic surfactant may lower the removal percentage due to its negative effect on adsorption of Cd(II) at gas-liquid interface.