| With the rapid development of industry,heavy metal pollution problems in the global has increased seriously,which has caused great threat to people's health.Water shortage and water pollution has become the two major problems facing this century.In order to solve the problem completely,researchers has been working to find more effective ways to deal with heavy metal ion wastewater.Supported liquid membrane has drawn great attention by scientific research workers,which possesses good separation effect,low consumption,environmental friendly and energy saving,but the technology has the disadvantages of low selectivity and poor stability.In this paper,Zn(?)-MIM and Cd(?)-MIM were prepared by using PVDF membrane as support material.The surface morphology,microstructure and properties of MIM were characterized by FTIR,XRD,UV-Vis,SEM,XPS,TGA-DTA and CA.Transmission process of heavy metal ions in the supported liquid membrane were analyzed and discussed.The main research contents were as follows:(1)Zn(?)was extracted by TBP,P204 and P507,and the best extractant was P204.The optimum conditions for transport of zinc under the single factor experiment were as follows:the pH of the feed phase was 5.0,the initial concentration of Zn(?)was 2.0×10-4 mol/L,the concentration of HCl was 5mol/L,the solvent ratio was 75%.The migration rate of Zn(?)could reach 81.0%under these conditions.On the basis of single factor experiment,the main factors influencing the transmission of Zn(?)were optimized by response surface method and the quadratic polynomial mathematical model was established.The results showed that the secondary model had good fitting degree,highly significant and R2 was 0.9838.The optimum migration conditions were as follows:the pH of feed phase was 4.87,the concentration of Zn(?)was 2.21×10-4 mol/L,the ratio of solvent was 95.61%,and the concentration of HCl was 5.5 mol/L.The theoretical migration rate was 81.6%,the actual migration rate was 84.5%and the relative error was 3.6.This model could predict the actual migration rate of Zn(?).(2)Zn(?)-MIM was prepared by UV surface grafting and preparation of influencing factors of Zn(?)-MIM were discussed.The surface morphology,structure and properties of Zn(?)-MIM were studied by a variety of characterization methods.The results showed that the optimal preparation conditions were UV irradiation 3 h,nzn(?):n(MAA):n(EDMA)1:5:30.Zn(?)-MIM membrane pores were uniform and pore size were about 2 um.The contact angle changed from 114° to 86.6°,membrane hydrophilicity and chemical resistance became better.The crystallinity and regularity of membrane became low.Under the optimal migration conditions,the migration coefficient of Zn(?)in Zn(?)-MIM supported ionic liquid membrane was higher than PVDF membrane,the migration rate was about 80%,and Zn(?)-MIM had good selectivity to Zn(?).(3)Cd(?)-MIM was prepared by hot-initiated surface grafting method using Cd(?)as template,MAA as functional monomer,EDMA as crosslinking agent and PVDF membrane as base film.The preparation conditions of Cd(?)-MIM were discussed.The surface structure,morphology and properties of Cd(?)-MIM were studied.P507 as the carrier,Cd(NO3)2 solution as the feed phase,H2SO4 as the striping phase,kerosene as membrane solvent,PVDF membrane as a support,Cd(?)-MIM supported liquid membrane system was established.On the basis of single factor experiment,the second mathematical model was established by the response surface method,and the optimal migration conditions of Cd(?)in the supported liquid membrane system were optimized.The results showed that the optimal preparation conditions of Cd(?)-MIM were ncd(?):n(MAA):n(EDMA)=1:6:30,reaction temperature 60?,reaction time 24 h;Cd(?)-MIM had more small hole;Contact angle dropped from 112.9° to 108.5°,hydrophilic enhanced.Under the optimal migration conditions,the migration permeability coefficient of Cd(?)in Cd(?)-MIM supported liquid membrane was higher than that of PVDF membrane,the migration rate was up to 73.5%,and Cd(?)-MIM had good selectivity to Cd(?). |
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