【作者】 罗婧艺；

【导师】 徐铜文；

【作者基本信息】 中国科学技术大学 ， 应用化学， 2013， 博士

【摘要】 扩散渗析(DD)由于其能耗低,无污染,操作简单等,因而成为了一种极具前景的分离技术。近年来,环境问题日益严重,能源资源日益短缺,所以在钢铁生产,金属冶炼,电镀,非铁金属的熔炼,铝箔浸蚀等工业中,人们逐渐把目光投向了DD这一环保且节能的分离技术。而在DD实际应用过程往往会处于一种极端的应用环境,如高温,高酸碱度,高金属盐含量,强氧化性,以及有机溶剂氛围等,所以这就对膜材料的物化稳定性及分离性能等提出了很高的要求。正是因为DD对膜材料的要求如此苛刻,所以目前为止,能够用于DD过程的膜非常有限。此外,在这些金属加工相关行业的生产过程中,往往根据特定的应用背景会使用到不同的无机强酸,因而会产生各种不同的废酸液,同时,酸液中也会存在着不同的金属盐。在使用DD技术处理这些废酸液时,不同的酸及不同的金属盐也会对DD的分离回收性能产生巨大的影响。本文为了解决上述问题,设计制备了有机-无机杂化离子膜,并考察了该批膜的高温DD性能,而后从中选择性能优良的杂化膜,基于数学模型考察了不同的酸及不同的金属离子对DD性能的影响,具体内容包括：(1)对溴化后的poly(2,6-二甲基-1,4-次苯基氧化物)(PPO)聚合物羟基化,再用三甲胺季胺化,继而引入无机硅烷TEOS进行溶胶-凝胶反应,制得了BPPO-SiO2杂化膜。用三甲胺季胺化是为了保证膜有较强的离子交换基团,保证一定的IEC和WR；引入无机硅烷就是为了将无机成分和有机成分的优势完美结合起来,赋予膜优良的物理及化学稳定性。通过对该批膜基本性能表征后证明：该批膜的热稳定性和机械稳定性都得到了显著的提高,并具有较高的离子交换容量(IEC)和合适的水含量(WR)。(2)把这批杂化膜用于HCl+FeCl2体系的DD来回收HCl,测试温度的变化范围为15℃-65℃。研究高温DD具有重要的意义：首先,由于生产运行过程中的摩擦力等作用,从工厂里直接排出的废液温度都较高；其次,高温能够有利于促进离子的传递。结果表明：随着温度的变化,该杂化离子交换膜在高温下表现出了较好的DD性能,其分离因子(S)可达41；而商业用膜DF-120的S都在较低的水平且没有明显的变化。将膜结构与DD结果关联后发现：无机硅的网状结构对DD的选择性具有较大的影响,尤其在高温下,影响更为明显。(3)基于制备的杂化膜,对HCl+NaCl、H2SO4+Na2SO4和H3PO4+Na3PO4进行DD性能测试,来考察不同的酸根离子对DD性能的影响。由于实验过程中强力的搅拌,所以忽略了液膜的影响,并且为了简化,假设了该DD过程是一个拟稳态过程。进而建立了总阴离子浓度随时间变化的微分式,并附以优化条件。该项工作中,只需要测定不同时间点下两室中离子的浓度,进而进行拟合可以求出最优化的渗析系数P,以此来定量的比较考察不同酸根离子对DD的影响。最终拟合的渗析系数的顺序为：将cl-,SO42"-和PO43-离子的性质和P的变化趋势关联后发现：离子在膜内的吸附、扩散以及其在溶液中的初始浓度是影响渗析系数的重要因素。该模型简单易用,即使是不从事DD理论研究的人员也容易上手。只需要测得不同时间点下渗析液和扩散液中的离子浓度,而后即可快速的拟合出膜对特定体系的P,进而判断出膜的DD性能。(4)而后将该模型进行调整和拓展,进一步研究了不同价态的金属离子对HCl渗析过程的影响。选取的体系有：HCl+NaCl, HCl+FeCl2, HCl+NiCl2, HCl+CuCl2, HCl+ZnCl2或HCl+AlC13。最终拟合出的各体系的Cl-离子的渗析系数的大小顺序为：通过考察发现,金属离子对HCl的DD的影响主要是由于金属离子会和Cl-离子形成各种不同的络合离子导致的。归根究底,即Pcl-的大小,则取决于金属离子本身的性质,以及金属离子和Cl-离子形成络合离子的电荷、体积及稳定常数的大小等。更多还原

【Abstract】 Diffusion dialysis(DD) becomes one of the most promising separation techniques due to low energy consumption, no environmental pollution, easy operation and etc. Thus, the production industries, including steel production, metal refining, electroplating, non-ferrous metal refining and etc., start to focus on DD technique with increasing serious environmental pollution and resources shortage.In practical DD application, there is always a harsh operation condition, such as high temperature, high acid or alkali, heavy metal salts content, strong oxidization or organic solvents. So, the membrane materials with high physic-chemical stability and separation effect are strongly required. Accordingly, the membranes that can be used in DD processes are quite limited. Besides, in the metal production industries, different kinds of strong acids will be selected according to different application backgrounds. Thus, large quantities of different acidic wastes with all kinds of metal salts will be produced. If DD is employed to treat those wastes, the different acids and metal salts will affect DD performance significantly. In order to investigate and deal with the above scientific problems, organic-inorganic hybride ion exchange membranes for DD are designed. Then, high temperature DD performances for hybrid membranes are investigated in HCl+FeCl2solution. And the effects of different acids and metal salts on hybrid membranes DD are also discussed based on mathematical model. The main contents can be summarized as followings:(1) Poly(2,6-dimethyl-1,4-phenylene oxide)(PPO)-SiO2hybrid membranes, which are produced from hydroxylation with KOH, quatemization with Trimethyl-amine(TMA), sol-gel reaction with TEOS of brominated PPO, have been prepared. Among them, TMA is used to bring in strong ion exchange groups to assure IEC and WR; inorganic silica TEOS is to combine the merits of organic and inorganic materials, endowing excellent physic-chemical stabilities and mechanical stability to membranes. From the membranes characterizations, it’s demonstrated that the hybrid membranes’ stabilities have been enhanced obviously, and high IEC and proper Wr can be obtained.(2) High temperature DD for hybrid membranes has been tested, and the temperatures are ranged from15℃to65℃. Research on high temperature DD process is meaningful:first, the wastes discharged from factories are in high temperature due to continuous processing and friction forces; second, high temperature is advantageous to ion transport. With increasing temperatures, excellent DD performances can be obtained, and separation factor(S) can be as high as41, while commercial membrane DF-120shows low separation effect throughout. The excellent DD results, especially at high temperature, can be ascribed to the silica network formation.(3) The effect of different acids on DD effects are discussed based on a mathematical model. The following systems are selected:HCl+NaCl, H2SO4+Na2SO4, and H3PO4+Na3PO4. Due to intensive stirring, the effects of liquid films can be neglected and the preudo-steady state of DD process is supposed for simplification. Then, the basic differential equations describing the dependence of the total anion concentrations upon time can be obtained, combined with the optimized procedure. The optimized dialysis coefficient P can be further fitted based on the experimental ions concentrations at different times. And P is used to describe the acid effect on DD quantitively. The final fitted results are as following:PH2SO4total(2.50×10-6m/s)>PHCl (1.60×10-6m/s)>PH3PO4total(1.0×10-7m/s). After correlation Cl-, SO42-and PO43-charicters with P trends, it’s found ions adsorption and diffusivity in membrane and the ions initial concentrations in waste are the important factors to affect DD performance. This model is simple and easy to use, so it is readily available for users, including those who don’t engate in DD.(4) Then, the model is modified and expanded to investigate the effects of different metal salts on DD. The investigated systems are HCl+NaCl, HCl+FeCl2, HCl+NiCl2, HCl+CuCl2, HCl+ZnCl2and HCI+AICl3. The fitted results are PCl-(CuCl2)(6.1×10-6m/s)> PCl-(FeCl2)(3.1×10-6m/s)>PXCl-(NiCl2)(2.6×10-6m/s)>PCl-(NaCl-)(2.0×10-6m/s)>PCl-(NaCl-)(1.6×10-6m/s)>PCl-(ZnCl2)(3.4×10-7m/s). The metal ions effects on HC1DD are mainly resulted from the complexes formation between metal ions and Cl-. In summary, Pci-is highly related with metal ions charicters, and the charge, volume, stability coefficients of complexes.更多还原