基膜调控及其对复合膜结构和性能影响

发布时间：2018-04-18 22:01

本文选题：基膜 + 复合膜　；参考：《天津大学》2015年博士论文

【摘要】：通过使用具有不同组成和结构参数的基膜制备反渗透膜和CO2分离膜,研究基膜组成和结构对复合膜结构和性能的影响。考察浸没沉淀相转化过程中,非溶剂通过涂层底面入侵对膜中大空穴生成的影响,制备具有较好耐压性能的基膜。选用三种孔径不同的商品基膜,经过表面活性剂十二烷基硫酸钠(SDS)溶液浸泡这三种基膜后制备反渗透膜。基膜孔径和SDS溶液浸泡处理基膜影响反渗透膜皮层交联度、皮层厚度、表面粗糙度以及皮层高分子材料应变等,进而影响反渗透膜的性能。反渗透膜水通量和盐截留率均随着基膜孔径的增大先增大后减小,当基膜孔径较小时(9.8 nm),反渗透膜水通量随着SDS溶液浸泡处理基膜而减小,盐截留率随着SDS溶液浸泡处理基膜而增大,当基膜孔径较大时(14.2或20.3 nm),反渗透膜水通量和盐截留率均随SDS溶液浸泡处理基膜而增大。在基膜铸膜液中添加脱掺杂聚苯胺(PANI)纳米材料调控基膜的组成和结构,制备反渗透膜。随着PANI添加量的增大,基膜表面氨基含量增加,孔径减小,孔隙率增大。随着PANI添加量的增大,基膜水通量增大,即基膜对水阻力减小。表面氨基和孔径的共同作用使反渗透膜皮层交联度和表面粗糙度先增大后减小,皮层厚度先减小后增大。皮层交联度、厚度、表面粗糙度和基膜阻力的共同作用使得反渗透膜的水通量随基膜铸膜液中PANI含量的增加先增大后减小,基膜孔径减小使皮层高分子材料在压力下的应变减小,皮层交联度和皮层高分子材料应变的共同作用使得反渗透膜的盐截留率先增大后减小。通过在基膜铸膜液中添加聚乙烯吡咯烷酮(PVP)调控基膜的组成和结构,并制备CO2分离膜。随着PVP添加量的增大,基膜表面羰基含量增加,表面平均孔径、孔密度和孔隙率均先增大后减小。基膜表面羰基与皮层材料聚乙烯基胺(PVAm)形成氢键,使基膜和皮层界面处更加致密,渗透性能降低,扩散选择性能提高。基膜孔径较小时,皮层材料向孔内的渗漏程度小,有利于膜渗透性提高。基膜表面孔密度和孔隙率较高时,部分气体在基膜和皮层界面的扩散路径减短,有利于渗透性提高。氢键以及表面孔径、孔密度和孔隙率的共同作用使得复合膜的CO2渗透速率和CO2/N2分离因子均随着基膜铸膜液中PVP含量的增大先增大后减小。此外,使用乙醇溶液处理后基膜所制复合膜渗透性能提高。考察了非溶剂通过涂层底面入侵对膜中大空穴生成的影响。涂在玻璃板上的涂层边缘先从玻璃板上剥离,非溶剂进入涂层底面和玻璃板之间的缝隙并侵入涂层底面,形成大空穴。溶剂和非溶剂通过无纺布缝隙交换,使无纺布支撑的膜中产生大空穴。通过在凝固浴中加入溶剂,能够抑制无纺布支撑的膜中大空穴的生成,制备具有较好耐压性的基膜。
[Abstract]:Reverse osmosis membrane and CO2 separation membrane were prepared by using the base membrane with different composition and structure parameters. The effects of the composition and structure of the base membrane on the structure and properties of the composite membrane were studied.In the process of immersion precipitation phase transformation, the influence of non-solvent invasion on the formation of large holes in the film was investigated, and the substrate film with good pressure resistance was prepared.Three commercial base membranes with different pore sizes were used to prepare reverse osmosis membranes by soaking them in surfactant sodium dodecyl sulfate (SDS) solution.The pore diameter of the base membrane and the SDS solution soaking affect the cross-linking degree of the reverse osmosis membrane, the thickness of the cortex, the roughness of the surface and the strain of the polymer material in the cortex, and then affect the properties of the reverse osmosis membrane.The water flux and salt retention rate of reverse osmosis membrane first increased and then decreased with the increase of the pore size of the base membrane. When the pore diameter of the base membrane increased to 9.8 nm, the water flux of reverse osmosis membrane decreased with the treatment of SDS solution.The salt retention rate increased with the treatment of SDS solution, and the water flux and salt retention rate of reverse osmosis membrane increased with the treatment of SDS solution when the pore diameter of the membrane was larger.In order to prepare reverse osmosis membrane, the composition and structure of the base film were regulated by adding the dedoped Polyaniline (pani) nano-material to the casting solution of the base membrane.With the increase of PANI content, the surface amino content of the substrate increases, the pore size decreases and the porosity increases.With the increase of PANI, the water flux of the base membrane increases, that is, the resistance of the base membrane to water decreases.The cross-linking degree and surface roughness of the reverse osmosis membrane increased firstly and then decreased, and the thickness of the cortex decreased first and then increased due to the interaction of surface amino and pore size.The effects of cortical crosslinking degree, thickness, surface roughness and substrate resistance make the water flux of reverse osmosis membrane increase first and then decrease with the increase of PANI content in the casting solution of reverse osmosis membrane.The decrease of the pore size of the base membrane makes the strain of the cortical polymer material decrease under the pressure, and the joint action of the cortical crosslinking degree and the strain of the cortical polymer material makes the salt retention of the reverse osmosis membrane increase first and then decrease.The composition and structure of the base membrane were regulated by adding polyvinylpyrrolidone (PVP) into the casting solution of the base membrane and the CO2 separation membrane was prepared.With the increase of PVP content, the carbonyl content on the substrate surface increases, and the average surface pore size, pore density and porosity increase first and then decrease.The carbonyl group on the surface of the substrate formed a hydrogen bond with the cortical material polyvinylamine (PVA), which made the interface between the substrate and the cortex more compact, the permeability decreased, and the diffusion selectivity improved.When the pore diameter of the base membrane is small, the leakage of the cortical material to the pore is small, which is beneficial to the improvement of membrane permeability.When the pore density and porosity of the substrate surface are high, the diffusion path of some gases at the interface between the substrate and the cortex is reduced, which is beneficial to the improvement of permeability.The interaction of hydrogen bond, surface pore size, pore density and porosity makes the CO2 permeation rate and CO2/N2 separation factor of the composite membrane increase firstly and then decrease with the increase of PVP content in the casting solution of the composite membrane.In addition, the permeability of the composite membrane treated with ethanol solution was improved.The influence of non-solvent invasion on the formation of large holes in the film was investigated.The edge of the coating coated on the glass plate is removed from the glass plate at first. The non-solvent enters the gap between the coating bottom and the glass plate and invades the coating bottom to form a large hole.Solvent and non-solvent are exchanged through the gap of non-woven fabric, so that large holes are produced in the film supported by non-woven cloth.By adding solvent in the coagulation bath, the formation of large holes in the film supported by non-woven cloth can be inhibited, and the base film with good pressure resistance can be prepared.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ051.893

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