【作者】 张旭；

【导师】 徐铜文；

【作者基本信息】 中国科学技术大学 ， 应用化学， 2014， 博士

【摘要】 扩散渗析作为一种以浓度差为推动力的膜分离技术,由于其具有操作简单、低能耗、无二次污染等优势,广泛地应用于各种产生废酸碱的领域：钢铁工业、钛材加工、稀土工业、钨矿工业等。同时由于易与其他过程集成,扩散渗析与其他过程集成处理废液的应用实例也很多,它们之间相互取长补短,达到比较理想的处理效果。另外,由于社会经济的快速发展和人们环保意识的日益强烈,扩散渗析在废酸废碱的处理中越来越受到人们的关注。然而,虽然扩散渗析目前已经得到了大规模的应用,但是扩散渗析的不足之处也随之显现出来。针对这些不足,本文对扩散渗析过程进行了相关理论与应用方面的研究。论文共分七章：第一章首先对化工产业、膜分离技术等进行了简单的概述,对扩散渗析过程进行了基本的文献综述,主要包括：扩散渗析原理、扩散渗析膜、扩散渗析膜组件、扩散渗析理论模型、扩散渗析的发展趋势、扩散渗析的应用领域等,然后引出扩散渗析的不足之处进而展开本论文的研究内容。第二章对扩散渗析进行基础研究,主要是使用扩散渗析处理模拟化成箔废酸液。结果表明：酸回收率和铝离子泄漏率随着流速的增加而降低；扩散液与渗析液流速比控制在1.0左右时,综合考虑酸回收率、铝离子泄漏率和回收酸浓度等因素,发现卷式扩散渗析膜组件的性能是最佳的：原料液中的盐酸浓度对扩散渗析的性能影响不是很明显,然而随着原料液中的氯化铝浓度的增高,酸回收率和铝离子泄漏率也相应地增高；当渗析液与扩散液流速均为0.48L/(m2·h)、原料液中盐酸浓度为2.12mol/L、氯化铝浓度为0.8mol/L时,盐酸的回收率能达到95%；将卷式扩散渗析膜组件与板框式膜组件的处理结果相比较,可以看出卷式膜组件的酸回收率较高、金属离子泄漏率较低、装填密度较高,但是两者达到回收平衡的时间相似：经济衡算显示卷式膜组件的投资-回报期只有16.5个月。第三章为了提高扩散渗析回收酸的浓度、降低扩散渗析过程水的消耗量,将传统电渗析膜过程与扩散渗析膜过程集成用于处理模拟化成箔废酸液。结果显示：这种集成膜过程是一种从无机酸盐中回收无机酸的有效可行的方法；扩散渗析过程的扩散液流速与传统电渗析电流大小可以调节两者的处理能力大小关系；当扩散液流速为0.60L/(m2·h),扩散渗析先于电渗析运行10分钟,电渗析电流为2A时,酸回收率和铝离子泄漏率分别为74.9%和12.2%,能耗仅为0.41kw·h；将集成膜过程与单一的扩散渗析过程的处理结果比较可以看出集成膜过程的水消耗量较低、回收酸浓度较高,尤其是在扩散液流速较大和回收时间较长的情况下,这种优势更为明显。第四章是在扩散渗析膜组件两端施加一个微电场(电辅助扩散渗析),考察微电场是否能够提高扩散渗析过程的处理效率,结果显示：扩散液隔室与电源正极相连接这种加电方式对扩散渗析的进程比较有利,并且从能斯特-普朗克方程的角度对其做出了解释；微电场对装配奇数张膜的扩散渗析过程比较有效,并且膜的张数越多,微电场的作用越不明显；微电场对装配偶数张膜的扩散渗析过程作用不是很明显；并且从根本上解释了电辅助扩散渗析与电解电渗析的区别。目前在工业应用中,一般而言,扩散渗析膜堆包含了很多重复单元,因此电辅助扩散渗析在实际应用中还是存在一定的限制因素和瓶颈。第五章是针对扩散渗析过程中的水渗透现象,以单一的氯化钠溶液作为考察对象,考察了扩散液体积随时间的变化曲线,并使用一元二次方程对其进行拟合,结果发现拟合结果比较令人满意；同时,以膜两侧溶液的化学势差作为传质推动力推导传质方程、建立数学模型,使用气。、P’2。和PNaCl、P’NaCl量化扩散渗析过程,结果显示随着氯化钠浓度的增加,PNCl和硫cl下降,20和P’H2O增加。进一步研究发现,当修正因子λ=3.30和θ=2.37时,比较扩散渗析的理论计算浓度的实际测量浓度发现P’H2O和P’NaCl,是用来量化扩散渗析过程时比较令人满意的参数。第六章是针对扩散渗析过程中的水渗透现象,以单一的盐酸溶液作为考察对象,考察了渗析液体积随时间的变化曲线,并将变化曲线分为两段分别使用一元二次方程对其进行拟合；同时,以膜两侧溶液的化学势差作为传质推动力推导传质方程、建立数学模型,结果显示随着盐酸浓度的增加,PHCI和PH2O数值都有所上升,也即膜对氯化氢和水的渗析能力均升高。第七章对全文进行总结,并且展望扩散渗析技术的未来。总之,本论文的研究都为基础性研究,如果想真正实现工业化生产,还需要做实际料液成分的大规模试验,同时还需要凝聚政府、工业界、学术界的力量,开发性能优异的离子交换膜和膜组件用于扩散渗析的应用开发,提高扩散渗析的回收性能与处理效率,减少扩散渗析过程的水渗透量等。鉴于扩散渗析过程本身的固有特点,我们相信该技术一定会发展得更好。更多还原

【Abstract】 Diffusion dialysis is a spontaneous membrane separation process drivern by concentration gradient. Due to its simple operation, low energy consumption, without secondary pollution and so on, diffusion dialysis has been exploited to extract various acids and alkalies from waste solutios in steel production, titanium white, rare earth industry, as well as tungsten industry. In addition, because it is easily to be integrated with other processes, there are many application examples of the integration, and they learn from other’s strong points to offset one’s weakness to achieve better effect. What is more, due to the rapid development of social economy and the stong environmental protection consciousness, diffusion dialysis has been paid more and more attention. Although, diffusion dialysis has been widely used and developed, but with the increased application, some shortages appeared. Aiming at the shortages, this paper will study on the relevant theory and application of diffusion dialysis process.This dissertation consists of seven chapters.The1st chapter carrys on the brief overview of chemical industry, membrane separation technology and so on, also summarizes the diffusion dialysis process, mainly including:the principle, ion exchange membrane, membrane module, theoretical model and application field as well. Then leads to the deficiency of diffusion dialysis and starts this paper.The2nd chapter treats of the application of diffusion dialysis to deal with simulated chemosynthesis aluminum foil wastewater. The results show that the acid recovery ratio and aluminum leakage ratio decreased with an increase in the flow rate intensity, and an appropriate flow rate intensity ratio (diffusate:dialysate) is found to be approximately1.0. The HC1concentration in feed is observed to have little influence on the diffusion performance, while the acid recovery ratio and aluminum leakage ratio increase as the AlCl3concentration in feed increases. More than95%HCl are recovered from the simulated wastewater which contains2.12mol/L HCI and0.8mol/L AlCl3at the flow rate intensity of0.48L/(m2·h). When compares with plate-and-frame diffusion dialysis membrane module, the sprial wound diffusion dialysis membrane module has a higher acid recovery ratio, lower metal leakage ratio, higher loading density, and similar time to reach the equilibrium. Preliminary economic evaluation reveals that an investment in this process could be recovered within16.5months.Chapter3deals with the integration of diffusion dialysis and conventional electrodialysis to recover hydrochloric acid from simulated chemosynthesis aluminum foils. Results shows that the integration of diffusion dialysis and conventional electrodialysis is a feasible and effective approach to recover the hydrochloric acid. The dialysate flow rate and conventional electrodialysis current are adjustable to achieve a compatibility and operational uniformity between diffusion dialysis and conventional electrodialysis. When the dialysate flow rate is0.60L/(m2·h), ti is10min, and conventional electrodialysis current is2A, the average acid recovery ratio and average aluminum leakage ratio are74.9%and12.2%respectively, while the energy consumption is only0.41kw·h. The results confirm that such integration process is not only a cost-effective process compared with an individual diffusion dialysis process, but also an environment friendly process with little water consumption. Especially, due to the concentrating by conventional electrodialysis, the recovered acid can be reused in the productive cycle directly.The focus of the4th chapter is adopting the additional weak-electric field to improve the performance of diffusion dialysis process. Firstly, mode of applying electric field is discussed, results show that the mode that anode contacted with dialysate compartment is more effective, and results are explained through Nernst-Plank equation. Secondly, effect of electric field on odd pieces of membranes DD is studied, results illustrate that the more the pieces of membranes, the weaker the effect of electric field on DD performance. Thirdly, effect of electric field on even pieces of membranes DD is investigated, results reveal that overall dialysis coefficient has almost nothing to do with electric field. At last, energy consumption and current efficiency are investigated, and differences between electrically assisted diffusion dialysis and electro-electrodialysis are stated. But in industrial production, DD membrane stack usually contains many repeating units composed of many pieces of membranes, so it can come to a conclusion that EADD has some limiting factors and bottlenecks in practical application. However, EADD, with novel functions, has good prospects for development. And more efforts need to be contributed to bring this process to sustainable practice.The5th chapter disposes the quantification of diffusion dialysis process with single NaCl solution. Firstly, the volume of water which permeates from water side to feed side is quantified detailedly, and results show that diffusate solution volume changes over time according with the characteristics of quadratic polynomial (y＝ax2+bx+c). Secondly, Permeability coefficients of membrane to H2O (PH2O、P’H2O) and NaCl (PNaCl P’NaCl) are used to quantify diffusion dialysis process. Results show that with the increase of feed concentration, P’NaCl and PNaCl decrease, while P’H2o and PH2O increase. Furthermore, when modifying factor λ=3.30and0=2.37, comparisons of theoretical and experimental concentrations of NaCl in diffusate solution illustrate that both P’NaCl and P’H2O are satisfactory coefficients for characterizing the diffusion dialysis process. In addition, the mathematical model discussed in this study can provide an effective method to deal with the mass transfer process of diffusion dialysis easily and conveniently, especially, is helpful to select an optimum ion exchange membrane to operate diffusion dialysis.The6th chapter handles the quantification of diffusion dialysis process with the single HCl solution. Firstly, the volume of water which permeates from water side to feed side is quantified detailedly, and relevant equation is used to fit the variation curve of water volume; chemical potential difference of solution is used as the mass transfer driving force in the transformative Fick’s laws, results show that as the HCl concentration increases, PHCl and PH2O increase.The7th chapter summarizes the chapters above and hopes for prosperity of diffusion dialysis.In conclusion, this paper is basic research, and there is much to do before putting diffusion dialysis to industrialization. Other than scaling up the experiments of practical feed, more efforts have to be taken to collect the strength from the government, academia and industry. It is necessary to improve the recovery performance and treatment effeciency by developing the new excellent ion exchange membranes and membrane modules. In view of the inherent characteristics of diffusion dialysis process, we believe that the technology will be developed better.更多还原