反洗水组分对N0M超滤膜污染机理的研究

发布时间：2018-03-11 16:09

本文选题：反洗水组分　切入点：反洗效率　出处：《天津工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：反洗水组分对超滤膜污染进程有重要影响,以腐殖酸(Humic acid,HA)、Na+和Ca2+模拟反洗水中的小分子有机物、一价和二价金属阳离子,以腐殖酸、海藻酸钠(Sodium alginate,SA)和牛血清蛋白(bovine serum albumin,BSA)模拟真实微污染地表水中的天然有机物(natural organicmatter,NOM)主要组分,通过死端过滤的方式研究了反洗水中的不同组分对PVDF超滤膜通量和反洗后膜通量恢复情况的影响。同时借助质量守恒准确地对膜可逆污染物和不可逆污染物进行定量的分析。通过实验对比分析可得,NOM各污染物之间存在协同作用,小分子污染与大分子污染物共同生成更为致密的滤饼层,使得膜通量急剧下降。金属阳离子之间的与NOM污染物质之间的作用是影响膜通量变化的主导因素;NOM各组分对膜面的累积的不可逆污染存在一定规律,蛋白质类物质BSA对膜面不可逆污染贡献最大,多糖类物质SA次之,腐殖质类小分子有机物HA最小;通过质量守恒定律分析发现,经过反向水力清洗后,滤饼层变得膨松,膜通量得到一定恢复,污染物并未完全有效去除,随着过滤进程又重新被压实至膜面;超滤进水和反洗水中的二价金属阳离子Ca2+均能够与污染物或膜之间产生架桥作用、静电屏蔽作用,加固膜面和污染物之间的作用,产生较多的不可逆污染;Na+的放电能力较Ca2+强,能够获得较Ca2+多与NOM污染物结合的机会,减少了由于Ca2+"架桥作用"产生的污染物,减少了不可逆污染。反洗水中的Na+也能够和滤饼层中的Ca2+发生离子交换,破坏部分架桥,增加污染物的可逆性。反洗溶液中单独存在的小分子有机物HA对膜面污染存在一定的影响,但当存在Ca2+时,HA对膜面污染的作用明显增强,一方面Ca2+架桥作用强化了小分子有机物在膜面的吸附,另一方面HA分子和Ca2+共同形成较大的有机物聚集体,堵塞反洗通道,形成反洗无效孔,反洗通道的堵塞,使得产生较为明显的不可逆污染。
[Abstract]:The backwash water component has an important effect on the process of ultrafiltration membrane fouling. Humic acid humic acid (humic acid) and Ca2 are used to simulate the small molecule organic compounds, monovalent and divalent metal cations in the backwash water, which are used as humic acids. Sodium alginate (sodium alginate) and bovine serum albumin (BSAs) were used to simulate the main components of natural organic matter (NOM) in real micro-polluted surface water. The effects of different components in backwash water on the flux of PVDF ultrafiltration membrane and the recovery of membrane flux after backwash were studied by dead-end filtration. The reversible and irreversible pollutants of membrane were accurately and accurately treated with the help of mass conservation. Quantitative analysis. Through the comparative analysis of experiments, we can find that there is a synergistic effect among the pollutants of NOM. Small molecule pollution and macromolecular pollutants together form a denser filter cake layer. The interaction between metal cations and NOM pollutants is the main factor affecting membrane flux change. The protein substance BSA contributed the most to the irreversible fouling of the membrane surface, followed by the polysaccharide SA, and the humus small molecule organic matter HA was the smallest. Through the analysis of the law of conservation of mass, it was found that the filter cake layer became dilated after reverse hydraulic cleaning. The membrane flux was recovered, the pollutants were not completely removed, and the membrane surface was compacted again with the filtration process, and the bivalent metal cation Ca2 in the ultrafiltration and backwash water could bridge with the pollutants or the membrane. Because of the effect of electrostatic shielding, strengthening the film surface and the effect of pollutants, the discharge ability of Na produced more irreversible pollution is stronger than that of Ca2, and it can obtain more chances of combining with NOM pollutants than Ca2. The pollution caused by "bridging action" of Ca2 is reduced, and irreversible pollution is reduced. Na in backwash water can also exchange ions with Ca2 in filter cake layer and destroy some bridges. To increase the reversibility of pollutants, HA, which exists alone in backwash solution, has a certain effect on membrane surface fouling, but when Ca2 exists, the effect of HA on membrane surface fouling is obviously enhanced. On the one hand, the bridging effect of Ca2 enhances the adsorption of small molecular organic compounds on the membrane surface, on the other hand, HA molecules and Ca2 together form a larger organic aggregates, blocking backwash channels, forming ineffective pores for backwashing and blocking backwash channels. The result is more obvious irreversible pollution.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;TQ028.8

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