针对之前所述阳膜选择透过性低、抗氧化性差以及均相离子交换膜难以满足市场需求的特点，以PVDF为基材，采用化学接枝法制备均相阳膜，以碱液NaOH、接枝苯乙烯为代表，制备机理如图3.1所示，制备过程及步骤如下：
膜基材选择
均相离子交换膜的膜制备材料主要有无机材料和有机聚合物，而对于工业用膜来说，有机聚合物制膜主宰了现有的膜市场，用于制膜的有机聚合物材料主要有聚偏氟乙烯(PVDF)、聚砜(PSF)，聚醚砜(PES)，聚丙烯腈(PAN)，聚酰胺，聚酰亚胺，和聚四氟乙烯(PTFE)。其中，PVDF是应用最广泛的膜制备材料，也被相关领域研究者广泛关注。
PVDF是一种重复多单体-(CH2CF2)r的半晶体聚合物，外观为半透明或白色粉体或颗粒，分子链间排列紧密，又有较强的氢键，不燃，熔点为172°C，热变形温度112~145°C，长期使用温度为-40~150°C，其分子式如下:
PVDF主要是指偏氟乙烯均聚物或者偏氟乙烯与其他少量含氟乙烯基单体的共聚物，兼具氟树脂和通用树脂的特性，而且化学结构中以-C-F-化学键结合，这种具有短键性质的结构可与H形成最稳定最牢固的结合。因此PVDF具有良好的耐化学腐蚀、耐氧化性等优异性能，此外还具有特殊性能，如介电性等，这些性质对于离子交换膜的实际应用非常重要。而且，PVDF价格低廉，在常见的有机溶剂中溶解性好，如N,N-二甲基乙酰胺(DMAC)、二甲基甲酰胺(DMF) etc.，它还很容易与辐射引起的单体共聚、接枝聚合。
It can be seen from the above that the excellent properties of PVDF make it the most widely used in the preparation of homogeneous ion-exchange membranes, and there are countless studies on its modification. However, the use of ion-exchange membranes to treat heavy metal wastewater has a great impact on the resistance of the ion-exchange membrane itself. Oxidation requirements are high, so PVDF is used as the main material for ion exchange membrane preparation in this study.
Basement membrane preparation
Measure 100ml of N,N-dimethylformamide in a beaker in advance, then use an electronic analytical balance to weigh-quantitative PVDF powder into the solution, stir it evenly with a glass rod, put it into an ultrasonic cleaner for ultrasonic dispersion until Finally , place the mixed solution (hereinafter referred to as the casting solution) in a vacuum oven at a certain temperature and let it stand for a period of time .
Pour the fully defoamed casting solution on the glass plate of the automatic film coating machine, scrape the film according to the previously set thickness, and let it stand solution solidifies and put it together with the glass plate in a vacuum Drying Oven at a certain temperature to dry for a certain period of time . After drying, peel off the base film by rinsing with distilled water, named as PVDF base film, cut it and place it in ethanol solution to soak for several hours , then soak in pure water for later use.
