Treatment Of Wastewater Containing Cadmium By MEUF-FF: Use Of Non-ionic Surfactant

Micellar enhanced ultrafiltration-foam fractionation(MEUF-FF)is a water treatment method which combines surfactant,ultrafiltration and foam fractionation.It utilizes the adsorption of surfactant micelles,the interception of ultrafiltration membrane and the entrainment of foam to realize the advanced treatment of heavy metal ions.Compared with the traditional MEUF,the surfactant utilization ratio of the whole process was greatly improved due to the subsequent increase of aeration.The combination of nonionic surfactants and ionic surfactants can effectively reduce the critical micelle concentration(CMC),which is the main method to reduce the amount of surfactant used by MEUF at present.Sodium dodecyl sulfate(SDS)was used as anionic surfactant and octylphenol polyoxyethylene ether(Triton X-100)was used as nonionic surfactant,wastewater containing cadmium ions was treated by "tangential flow ultrafiltration and foam fractionation".In this paper,the effects of compound ratio on cadmium ions removal at low SDS dosage were studied,and the removal ratio of cadmium ions,surfactant residual ratio,water production ratio,membrane fouling and foam properties of MEUF-FF before and after using Triton X-100 were compared.The results showed that when the total amount of surfactants was same,the MEUF-FF removal efficiency of MEUF-FF in SDS/Triton X-100 and SDS single systems were kept above 95%.This was because the use of nonionic surfactants,on the one hand,significantly reduced the CMC of anionic surfactants,prompted the surfactant monomers to form micelles at lower concentrations;on the other hand,the foaming properties and half-life of the surfactants were all improved,that was,the foam was easier to form and more stable after the compound.The micelles and foams had been used to remove cadmium ions efficiently.Although the use of Triton X-100 was increased slightly after blending,the dosage of SDS was reduced greatly compounded with no compounding,and the residual amount of SDS and the total amount of surfactant residue in effluent was lower than that in the control group.Therefore,the use of nonionic surfactants had achieved the goal of reducing the dosage of anionic surfactants,reduced the amount of anionic surfactant and the total amount of surfactant residues.In addition,both “using nonionic surfactants” and “combined foam fractionation” were considered in this study,which solved the problem of large dosage of anionic surfactants in the treatment of heavy metal wastewater by MEUF.At the same time,it provides a theoretical basis and application prospect for the further development of a new treatment method of heavy metal wastewater,“Micellar enhanced ultrafiltration and foam fractionation”,which is more efficient than MEUF and uses less surfactant.