正渗透工艺特性及膜污染特征研究

发布时间：2018-05-05 09:07

本文选题：正渗透 + 膜污染　；参考：《哈尔滨工业大学》2013年硕士论文

【摘要】：正渗透作为新兴的绿色膜分离技术，不需要外加压力作为分离驱动力，而是靠选择性膜两侧溶液自身的渗透压差推动正渗透分离过程，是目前世界膜分离领域研究的热点之一。与其他所有膜分离技术一样，膜污染也是正渗透中一个重要的研究方向。低的膜污染意味着更多的产水，更少的膜清洗，更长的膜寿命，也因此降低了正渗透的运行及投资总成本。但是，与其他的压力驱动膜分离技术相比而言，正渗透的膜污染特性有很大不同。因此，有必要对正渗透的膜污染特性进行研究，以便为以后正渗透的应用以及制膜提供参考。考察了正渗透基本运行规律，并对基本实验条件进行了确定。本课题采用的是美国HTI公司提供的商用FO膜，对其提供的两种膜的结构、表面形貌、水通量及返混行为进行了对比。分别对正渗透运行模式、错流速度、渗透压驱动力等因素对正渗透运行过程中如水通量、返混通量、清洗效率等性能参数的影响规律进行了探索。并讨论了清洗时间和速度对膜清洗效率的影响。探讨了牛血清蛋白（BSA）、海藻酸钠（SA）、腐殖酸（HA）、富里酸（FA），和纳米二氧化钛（nano-TiO_2）的正渗透膜污染。FA使膜通量下降幅度最大，膜污染最严重，其次是BSA，HA和SA。nano-TiO_2使膜通量下降最少，膜污染最轻，几乎可以忽略。考察了钙离子存在与否时SA、BSA以及HA的污染程度以及有机物的两两复合污染。对于SA来说，由于钙离子具有架桥作用，因此，钙离子的加入加剧了膜污染。与SA不同，对于BSA，钙离子的存在反而对正渗透膜的污染有轻微的减弱。对于HA，与SA相同，，钙离子的存在也加剧了膜污染。当BSA和SA复合污染时，通量下降最多，膜污染最严重，其次是SA和HA的复合污染，而当BSA和HA复合污染时，通量下降最慢，污染最轻。对于复合污染时原料液的粒度分布来说，随着污染进行，小尺寸的物质含量逐渐降低，大尺寸物质的含量逐渐增多，溶液粒度逐渐增大。通过在含有BSA、SA和HA有机物的原料液中分别加入相同浓度的无机nano-TiO_2，考察了有机-无机复合污染。加入nano-TiO_2后的复合污染均使通量下降趋势有所减缓。当同时存在有机污染物和无机污染物时，加钙后的通量下降更快，说明钙离子的加入使膜的复合污染加剧。
[Abstract]:As a new green membrane separation technology, normal osmosis does not need external pressure as the driving force for separation, but promotes the process of forward osmotic separation by the osmotic pressure difference between the two sides of the selective membrane, which is one of the hot spots in the field of membrane separation in the world. As with all other membrane separation technologies, membrane fouling is also an important research direction in positive osmosis. Low membrane fouling means more water production, less membrane cleaning, and longer membrane life, thus reducing the total operating and investment costs of positive osmosis. However, compared with other pressure-driven membrane separation techniques, the membrane fouling characteristics of positive osmosis are quite different. Therefore, it is necessary to study the membrane fouling characteristics of normal osmotic membrane in order to provide reference for the application of normal osmotic membrane in the future and the preparation of membrane. The basic operating rules of normal osmosis were investigated and the basic experimental conditions were determined. The commercial FO membrane provided by HTI Company was used in this paper. The structure, surface morphology, water flux and backmixing behavior of the two membranes were compared. The effects of normal osmotic operation mode cross-flow velocity and osmotic pressure driving force on the performance parameters such as water flux backmixing flux and cleaning efficiency were explored respectively. The effects of cleaning time and speed on the cleaning efficiency were discussed. The positive osmotic membrane fouling of bovine serum protein (BSA), sodium alginate (SA), humic acid (HA), fulvic acid (FAA), and nano-TiO2 (nano-TiO2) were studied. The results showed that the membrane flux was the largest and the membrane fouling was the most serious, followed by BSAHA and SA.nano-TiO_2, the membrane flux was the least, and the membrane fouling was the least. Almost negligible. The pollution degree of BSA and HA and the compound pollution of organic matter in the presence of Ca ~ (2 +) were investigated. For SA, the addition of Ca ~ (2 +) increases membrane fouling due to the bridging effect of Ca ~ (2 +). Different from SA, for BSA, the presence of Ca ~ (2 +) weakens the fouling of positive osmotic membrane slightly. As with SA, the presence of Ca ~ (2 +) also contributes to membrane fouling. When BSA and SA were mixed polluted, the flux decreased the most, membrane fouling was the most serious, followed by SA and HA compound pollution, while when BSA and HA compound pollution, the flux decreased most slowly and the pollution was the least. As for the particle size distribution of the raw material solution, the content of the small size substance decreases gradually, the large size material content increases, and the solution size increases with the pollution. The organic-inorganic compound pollution was investigated by adding inorganic nano-TiO-2 at the same concentration into the raw material solution containing BSA-SA and HA respectively. After the addition of nano-TiO_2, the decrease trend of flux was slowed down by the compound pollution. When organic pollutants and inorganic pollutants exist at the same time, the flux decreases more quickly after adding calcium, which indicates that the composite fouling of membrane is aggravated by the addition of calcium ion.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU991.2

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