The Research On Advanced Treatment Of Permeate From MEUF By Foam Fractionation With Surfactant Mixtures

The foam fractionation is a physical separation technique that can be used to separate soluble or insoluble materials from wastewater,and has many advantages such as simple operation and equipment,low energy consumption,and high separation efficienc y.In this paper,sodium dodecyl sulfate(SDS)was used as an anionic surfactant,and octylphenol polyoxyethylene ether(Triton X-100)was used as a nonionic surfactant.At a lower SDS concentration(300 mg/L),the advanced treatment of Cd(II)and surfactant in permeate from micellar enhanced ultrafiltration(MEUF)by foam fractionation with mixed anionic-nonionic surfactant were studied.And the effects of the molar ratio of anionic-nonionic surfactant,the initial Cd(II)concentration and pH on the surface tension of solution,the size of the bubbles formed,the foam properties and separation efficiency of the three matters were also investigated.The results show that the nonionic surfactant Triton X-100 can significantly reduce the surface tension of the solution and the size of the bubbles formed by bubbling in the solution,and can also significantly improve the foam properties.When the concentration of Cd(II)in the feed solution was 10 mg/L and the molar ratio of Triton X-100 /SDS was 0.1,the removal percentage of Cd(II)reached the optimal value of 99.1%,and the concentration of effluent was less than 0.1 mg/L,meeting the national comprehensive sewage discharge standard.In addition,the removal percentages of the two surfactants were also relatively high at this condition.The initial Cd(II)concentration and pH also have a significant effect on the surface tension of the solution,bubble size,foam properties,and foam fractionation process.By studying the influence of Triton X-100 on the critical micelle concentration of SDS solution,the measurement of zeta potential and the analysis of FT-IR spectrum,the influence mechanism of Triton X-100 on the removal of Cd(II)by foam fractionation was analyzed.Therefore,foam fractionation can efficiently remove Cd(II)and surfactant from micellar enhanced ultrafiltration permeate,and this technology is suitable for separation of pollutants with low concentration.A small amount of nonionic surfactant Triton X-100 can significantly improve the removal percentage of Cd(II)and surfactant by reducing the surface tension of the solution,the size of the bubbles formed,thereby improving the foaming properties of the anionic surfactant and reducing the amount of surfactant used.However,excessive nonionic surfactant Triton X-100 may lower the removal percentage due to its negative effect on adsorption of Cd(II)and surfactant at gas-liquid interface.