Zeta电位结合通量原检测中空纤维膜局部膜污染研究

发布时间：2018-01-01 19:25

本文关键词：Zeta电位结合通量原检测中空纤维膜局部膜污染研究　出处：《天津工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：如何深入分析膜过滤行为是有效控制中空纤维膜污染的核心问题,也是保障膜系统高效稳定运行的关键。本文以Zeta电位原位无损检测技术和局部通量结合表征的方法,来研究中空纤维膜局部膜污染特性。首先,优化了实验所选用的酵母标准溶液的预处理方式,分析了酵母溶液经过离心和干燥、磁力搅拌、超声、溶于缓冲溶液这四种预处理后对中空纤维膜过滤性能的影响。结果表明：经离心干燥预处理的酵母溶液的各项性能比较稳定,比较适合作为膜过滤溶液用来满足不同的实验需求,以深入分析膜污染的机理。其次,以Zeta电位原位无损检测技术和局部通量结合表征的方法,来研究膜过滤过程中Zeta电位的变化规律,探索Zeta电位和局部膜过滤行为之间相互作用关系,为深入理解局部膜污染的机理提供更详细的信息。研究发现：在整个中空纤维膜过滤酵母溶液过程中,Zeta电位的变化形式互不相同。当Zeta电位值快速降低时,是膜孔堵塞过程；在滤饼层形成过程中,Zeta电位的变化趋于平缓并呈现线性关系；当Zeta电位值趋于稳定表明处于滤饼层压阶段。在整个死端过滤过程中,Zeta电位值在洁净膜和酵母溶液的Zeta电位值之间变化。此外,纤维长度对局部Zeta电位的分布和局部膜污染行为有很大的影响。随着纤维长度的增加,三段进入滤饼层压实阶段的时间延长,并且三段Zeta电位的差值增加。最后,利用Zeta电位结合通量表征的技术来分析膜过滤实验中发现的污染再分布现象。在局部膜过滤实验中发现：在中空纤维膜过滤起始阶段,靠近泵出口处的局部通量最大,中段次之,尾段最小。局部通量沿着膜纤维长度不均匀分布是因为抽吸压力的不均匀分布,在死端过滤过程中,靠近泵出口处的抽吸压力最大,因此首段的膜通量最大,但是污染物首先在首段发生沉积,首段的污染也最为严重,通量下降速率最快；而尾段较小的抽吸压力而使其渗透通量的变化比较轻微,这就导致了局部通量的不均匀分布。随着膜过滤的进行,压降迅速下降,首段的滤饼层阻力与尾段滤饼层阻力的比值逐渐增大,因而尾段沉积的滤饼层更少,因此出现中段或尾段局部通量大于首段的情况。接着延长膜过滤行为,膜表面形成的滤饼层逐渐被压缩,由于滤饼层压缩系数的差异而再次出现首段局部通量最大的情况,进而出现一定程度的污染再分布现象。
[Abstract]:How to analyze the membrane filtration behavior is the key problem to effectively control the fouling of hollow fiber membrane. It is also the key to ensure the efficient and stable operation of the membrane system. In this paper, the characteristics of local membrane fouling of hollow fiber membrane are studied by Zeta potential in situ nondestructive testing and local flux characterization. The pretreatment method of yeast standard solution was optimized, and the yeast solution was analyzed by centrifugation and drying, magnetic stirring and ultrasonic. The effects of the four pretreatment methods dissolved in buffer solution on the filtration performance of hollow fiber membrane were studied. The results showed that the performance of yeast solution pretreated by centrifugal drying was relatively stable. It is suitable to be used as membrane filtration solution to meet different experimental requirements in order to deeply analyze the mechanism of membrane fouling. Secondly, Zeta potential in situ nondestructive testing technique and local flux combination characterization method. To study the change of Zeta potential in membrane filtration process and explore the interaction between Zeta potential and local membrane filtration behavior. In order to provide more detailed information for understanding the mechanism of local membrane fouling, it was found that: in the whole hollow fiber membrane filtration yeast solution process. The change of Zeta potential is different. When the Zeta potential value decreases rapidly, it is the membrane pore blocking process. The change of Zeta potential tends to be gentle and linear during the formation of filter cake layer. When the Zeta potential value tends to stabilize, it indicates that it is in the stage of cake lamination. During the whole dead end filtration process, the Zeta potential changes between the Zeta potential of the clean membrane and the yeast solution. Fiber length has a great influence on the distribution of local Zeta potential and the fouling behavior of local membrane. And the difference of three-segment Zeta potential increased. Finally. Zeta potential combined with flux characterization technique was used to analyze the phenomenon of contamination redistribution found in membrane filtration experiment. In the local membrane filtration experiment, it was found that: in the initial stage of hollow fiber membrane filtration. The local flux near the outlet of the pump is the largest, followed by the middle and the tail. The uneven distribution of the local flux along the membrane fiber length is due to the uneven distribution of suction pressure in the dead end filtration process. The suction pressure near the outlet of the pump is the largest, so the membrane flux in the first stage is the largest, but the pollutants are deposited in the first section first, the pollution in the first section is also the most serious, and the flux decline rate is the fastest. However, the small suction pressure in the tail resulted in a slight change in the permeation flux, which resulted in the uneven distribution of the local flux. With the membrane filtration, the pressure drop decreased rapidly. The ratio of cake resistance of the first section to the resistance of the filter cake layer of the tail section increases gradually, so the cake layer deposited in the tail section is less, so the local flux in the middle or tail section is larger than that in the first section, and then the membrane filtration behavior is prolonged. The filter cake layer formed on the membrane surface was gradually compressed. Due to the difference of the compression coefficient of the filter cake layer, the maximum local flux of the first section appeared again, and then the phenomenon of pollution redistribution occurred to a certain extent.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ342.8;TQ051.893

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