双层PEEK-WC界面聚合正渗透膜的制备及表征
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摘要
正渗透过程是近些年发展起来的一种新型渗透驱动膜分离过程,它具有低能耗、低膜污染、高分离性等优点,在水处理领域有很好的应用前景.通过调控铸膜液温度制得具有不同外孔径的酚酞型聚醚醚酮(PEEK-WC)双层中空纤维基膜,然后用硫酸对双层中空纤维基膜外表面进行亲水改性,得到亲水基膜.再用无水哌嗪(PIP)和均苯三甲酰氯(TMC)作为反应单体,通过界面聚合反应在亲水基膜上形成聚哌嗪酰胺复合层制备正渗透膜.研究表明,较高的铸膜液温度有利于形成外表面为较小孔径的PEEK-WC双层中空纤维基膜;用质量分数90%的硫酸亲水改性15 s时,得到润湿性最佳的亲水基膜;在进行界面聚合反应时,外表面为较小孔径的亲水基膜有利于形成更均匀致密、渗透性能更好、截留率更高的聚哌嗪酰胺复合层;与NaCl相比,使用Na_2SO_4做汲取液可以有效降低内浓差极化(ICP),提高正渗透膜水通量,降低反向盐通量.
As a new type of osmosis driven membrane separation process, forward osmosis developed rapidly in recent years. It has many advantages such as low power consumption, high separation, low membrane fouling and so on. It has a good application prospect in the field of water treatment. The PEEK-WC double-layer hollow fiber membranes with different outer pore diameters were prepared by adjusting the temperature of the casting solution, then the membrane outer surface was hydrophilically modified with sulfuric acid to obtain hydrophilic base membranes. Piperazine(PIP) and trimesoyl chloride(TMC) were used as reaction monomers. The forward osmosis membrane was prepared by forming a polypiperazine amide composite layer on a hydrophilic base membrane surface by interfacial polymerization. Studies have shown that a higher temperature of the casting solution is beneficial to the formation of a PEEK-WC double-layer hollow fiber base membrane with a smaller pore diameter on the outer surface; the best wettability is obtained by hydrophilic modification with 90% sulfuric acid for 15 second; when the interfacial polymerization reaction was carried out, the hydrophilic base membrane with a smaller pore diameter on the outer surface was favorable for forming a polypiperazinamide composite layer with more uniform, dense, better permeability and a higher rejection; compared with NaCl as a draw solution, Na_2SO_4 solution can effectively reduce ICP, increase forward osmosis flux, and reduce the reverse salt flux.
As a new type of osmosis driven membrane separation process, forward osmosis developed rapidly in recent years. It has many advantages such as low power consumption, high separation, low membrane fouling and so on. It has a good application prospect in the field of water treatment. The PEEK-WC double-layer hollow fiber membranes with different outer pore diameters were prepared by adjusting the temperature of the casting solution, then the membrane outer surface was hydrophilically modified with sulfuric acid to obtain hydrophilic base membranes. Piperazine(PIP) and trimesoyl chloride(TMC) were used as reaction monomers. The forward osmosis membrane was prepared by forming a polypiperazine amide composite layer on a hydrophilic base membrane surface by interfacial polymerization. Studies have shown that a higher temperature of the casting solution is beneficial to the formation of a PEEK-WC double-layer hollow fiber base membrane with a smaller pore diameter on the outer surface; the best wettability is obtained by hydrophilic modification with 90% sulfuric acid for 15 second; when the interfacial polymerization reaction was carried out, the hydrophilic base membrane with a smaller pore diameter on the outer surface was favorable for forming a polypiperazinamide composite layer with more uniform, dense, better permeability and a higher rejection; compared with NaCl as a draw solution, Na_2SO_4 solution can effectively reduce ICP, increase forward osmosis flux, and reduce the reverse salt flux.
引文
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[2] 李刚,李雪梅,柳越,等.正渗透原理及浓差极化现象[J].化学进展,2010,22(5):812-821.
[3] Yan F,Chen H,Lu Y,et al.Improving the water permeability and antifouling property of thin-film composite polyamide nanofiltration membrane by modifying the active layer with triethanolamine[J].J Membr Sci,2016,513:108-116.
[4] Cheng X Q,Zhang C,Wang Z X,et al.Tailoring nanofiltration membrane performance for highly-efficient antibiotics removal by mussel-inspired modification[J].J Membr Sci,2016,499:326-334.
[5] Emadzadeh D,Lau W J,Matsuura T,et al.Synthesis and characterization of thin film nanocomposite forward osmosis membrane with hydrophilic nanocomposite support to reduce internal concentration polarization[J].J Membr Sci,2014,449(1):74-85.
[6] Tian E L,Zhou H,Ren Y W,et al.Novel design of hydrophobic/hydrophilic interpenetrating network composite nanofibers for the support layer of forward osmosis membrane[J].Desalination,2014,347(17):207-214.
[7] Xiao P P,Nghiem L D,Yin Y,et al.A sacrificial-layer approach to fabricate polysulfone support for forward osmosis thin-film composite membranes with reduced internal concentration polarisation[J].J Membr Sci,2015,481:106-114.
[8] Morison K R.A comparison of liquid-liquid porosimetry equations for evaluation of pore size distribution[J].J Membr Sci,2008,325(1):301-310.
[9] Bonyadi S,Tai S C.Flux enhancement in membrane distillation by fabrication of dual layer hydrophilic-hydrophobic hollow fiber membranes[J].J Membr Sci,2007,306(1):134-146.
[10] Cath T Y,Childress A E,Elimelech M.Forward osmosis:Principles,applications,and recent developments[J].J Membr Sci,2006,281(1/2):70-87.
[11] Xie M,Price W E,Nghiem L D,et al.Effects of feed and draw solution temperature and transmembrane temperature difference on the rejection of trace organic contaminants by forward osmosis[J].J Membr Sci,2013,438(7):57-64.
[12] Lobo V M M.Mutual diffusion coefficients in aqueous electrolyte solutions (technical report)[J].Pure Appl Chem,1993,65(12):2613-2640.
[13] Huang L,Mccutcheon J R.Impact of support layer pore size on performance of thin film composite membranes for forward osmosis[J].J Membr Sci,2015,483:25-33.
[14] 王许云,张林,王新,等.铸膜液溶解温度对制备PVDF微孔膜结构的影响[J].高分子材料科学与工程,2009,25(10):87-90.
[15] Young T H,Cheng L P,Lin D J,et al.Mechanisms of PVDF membrane formation by immersion-precipitation in soft (1-octanol) and harsh (water) nonsolvents[J].Polymer,1999,40(19):5315-5323.
[16] Wenzel R N.Surface roughness and contact angle[J].J Phys Colloid Chem,1949,53(9):1466-1467.
[17] Wenzel R N.Resistance of solid surfaces to wetting by water[J].Ind Eng Chem Res,1936,28(8):988-994.
[18] Zou K,Wang L H,Zhang L,et al.Preparation of TMC/TMPIP nanofiltration composite membrane with ultra-thin skin layer[J].Ciesc J,2012,63(3):948-954.
[19] Veerababu P,Vyas B B,Singh P S,et al.Limiting thickness of polyamide-polysulfone thin-film-composite nanofiltration membrane[J].Desalination,2014,346:19-29.
[20] 马艳勋,任吉中,李恕广.气体分离复合膜的制备中材料匹配和孔渗现象的研究[J].膜科学与技术,2001,21(1):35-38.
[21] Tansel B,Sager J,Rector T,et al.Significance of hydrated radius and hydration shells on ionic permeability during nanofiltration in dead end and cross flow modes[J].Sep Purif Technol,2006,51(1):40-47.