The interaction between a cationic dye Methylene Blue(MB) and an anionic surfactant sodium dodecyl sulfate(SDS) with the presence of Cd2+ was investigated spectrophotometrically in a certain concentration range.The spectrophotometric measurements of dye-metal ion-surfactant system were carried out.The results indicated that the SDS concentration had a significant influence on the dye spectrum,while the addition of Cd2+ hardly caused change of the maximum value of absorbance.According to this observation,we concluded that electrostatic and hydrophobic interaction between dye and surfactant occurred up to a certain level,and the homo-ions Cd2+ almost exerted no effect on the dye-surfactant complexation,establishing a theoretical foundation for simultaneous removal of organic dye and heavy metal using foam fractionation.Meanwhile,the effects of their interaction on foam performance were investigated.The results showed that the addition of Cd2+ favored the tendency to ameliorate foam properties just contrary to MB.The feasibility of foam separation for dye and heavy metal removal from simulated wastewater was also confirmed using a continuous foam fractionator.In the simultaneous removal process,with the initial SDS concentration ranging from 0.5 to 5.0mmol/L,the maximum removal efficiencies of MB and Cd2+ were obtained as 99.69% and 99.61%,respectively.The enrichment ratios were reduced from24.34 to 7.65 for MB and from22.01 to 3.35 for Cd2+.
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