羧甲基壳聚糖和磷酸酯化聚乙烯醇复合纳滤膜的制备和表征

发布时间：2018-04-09 23:26

  本文选题：复合纳滤膜　切入点：羧甲基壳聚糖　出处：《湘潭大学》2017年硕士论文

【摘要】：纳滤(NF)膜的截留分子量(MWCO)介于200-1000 Da,它可以有选择性地高效截留水体中的无机盐离子、有机小分子、细菌和病菌等。目前主流商品化的NF膜是荷电的复合NF膜,按所带电性可分为荷正电、荷负电及两性复合NF膜。羧甲基壳聚糖(CMCS)是壳聚糖的一种水溶性两性衍生物,其分子结构上含有大量的COO-。磷酸酯化聚乙烯醇(PPVA)是聚乙烯醇的磷酸酯化后的产物。其分子结构上含有大量的PO3-4。在本研究中以CMCS和PPVA作为复合NF膜的表面活性材料,以乙二醇二缩水甘油醚(EGDE)作为交联剂,30000 Da聚砜超滤膜(PSF UF)为基膜,利用涂覆交联的方法,在一定的制备工艺下制备了CMCS/PSF和PPVA/PSF两种新型NF膜。利用衰减全反射红外光谱(ATR-IR)、环境扫描电子显微镜(ESEM)、静态接触角测量仪等仪器对其结构、形貌和膜表面的亲水性进行了表征,并研究了其最佳的制备条件及各种外界操作因素对最佳条件制备的膜的分离性能的影响。以5 mmol/L的Na_2SO_4作为料液。研究发现,CMCS/PSF系列复合NF膜最佳的制备工艺条件为:铸膜液的浓度为2 wt%,交联剂的浓度为5 vol%,交联反应的温度为70℃,交联反应的时间为25 min。最佳制备条件下,随着压力的升高,CMCS/PSF复合NF膜的截留率先升高,后降低,通量则几乎呈线性递增。随着料液流量的增大,CMCS/PSF复合NF膜的截留率和通量均先降低后升高。CMCS/PSF复合NF膜对不同盐截留率按从大到小的顺序为:Na_2SO_4、NaCl、KCl、MgSO4、MgCl2,且对Na_2SO_4和NaCl的截留率和通量均会随着盐浓度的升高而降低。随着甘油质量分数的提高,CMCS/PSF复合NF膜的截留率先下降后升高,通量表现和截留率相反,先升高后下降。研究发现,PPVA/PSF系列复合NF膜的最佳制备条件为:铸膜液浓度为1wt%,交联剂浓度为20 vol%,交联反应温度为75℃,交联反应时间为30 min。随着压力的升高,最佳制备条件下制备的PPVA/PSF复合NF膜的截留率先升高,后降低,通量则几乎呈线性递增。随着料液通量的增大,最佳条件下制备的PPVA/PSF复合NF膜的截留率和通量均先降低后升高。PPVA/PSF复合NF膜对不同盐截留率从大到小的顺序为:Na_2SO_4、NaCl、KCl、MgSO4、MgCl2,且对Na_2SO_4和NaCl的截留率和通量均会随着盐浓度的升高而降低。随着甘油质量分数的提高,PPVA/PSF复合NF膜的截留率呈线性下降,通量线性增长。在外界操作压力为0.4 MPa,料液通量为0.9 L/min和室温的条件下PPVA/PSF复合NF膜对仿真海水的截留率能达到75%以上,通量达到7.6kg·m-2·h-1以上。表明在分离海水的过程中可以将海水看作为一种“综合性的无机盐”。PPVA/PSF复合NF膜对三种典型的有机染料也具有较好的分离性能。其中对3 mg/L的碱性品红的截留率和通量分别为93.4%和13.2 kg·m~(-2)·h~(-1)。
[Abstract]:Nanofiltration (NFN) membrane has a molecular weight of MWCO between 200-1000 Da.It can selectively and efficiently intercept inorganic salt ions, organic small molecules, bacteria and bacteria in water.At present, the main commercial NF films are charged composite NF films, which can be divided into positive charged, negative charged and amphoteric composite NF films according to their electrical properties.Carboxymethyl chitosan (CMCS) is a water-soluble amphoteric derivative of chitosan.Phosphate polyvinyl alcohol (PPVA) is the product of polyvinyl alcohol phosphate.Its molecular structure contains a large amount of PO3-4.In this study, CMCS and PPVA were used as the surface active materials of NF composite membrane, and ethylene glycol diglycidyl ether (EGDE) as crosslinking agent, 30 000 Da polysulfone ultrafiltration membrane was used as the base membrane, and the method of coating crosslinking was used.Two new NF membranes, CMCS/PSF and PPVA/PSF, were prepared under certain preparation conditions.The structure, morphology and hydrophilicity of the films were characterized by means of attenuated total reflectance infrared spectroscopy (ATR-IRN), environmental scanning electron microscopy (ESM) and static contact angle measuring instrument.The optimum preparation conditions and the effects of various external operating factors on the separation properties of the membranes prepared under the optimum conditions were studied.5 mmol/L Na_2SO_4 was used as feed liquid.It was found that the optimum preparation conditions of CMCS / PSF composite NF membrane were as follows: the concentration of casting solution was 2 wts, the concentration of crosslinking agent was 5 vols, the temperature of crosslinking reaction was 70 鈩，

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