过氧化物处理反渗透膜耐氧化机制研究

发布时间：2018-05-05 08:03

本文选题：反渗透复合膜 + 耐氧化　；参考：《浙江工业大学》2017年硕士论文

【摘要】：芳香聚酰胺复合反渗透(RO)膜中起分离作用的聚酰胺皮层易受活性氯的攻击发生结构降解,使膜性能下降,寿命衰减。为解决这一问题,本文将探究过硫酸盐改性商品芳香聚酰胺RO膜的方法,提高膜的分离性能和耐氧化性能,并对改性机理做出初步探讨。用过硫酸钾(K2S2O8)水溶液浸泡改性商品RO膜,控制以下五个影响因素:浸泡溶液的温度、K2S2O8浓度、浸泡时间以及热处理温度和热处理时间。对NaCl水溶液的分离性能结果表明,最佳的改性条件是浸泡温度为60℃,K2S2O8浓度为5 wt%,浸泡时间为100 min,热处理时间为5 min,热处理温度为120℃。此时通量提高43.2%,截留率提高0.2%。对小分子醇(乙醇、异丙醇,正丁醇)的分离实验表明在5 wt%,100 min下改性膜的截留性能最好。静态氧化实验表明改性膜具有更好的耐氧化性,其中耐氧化性能最佳的改性条件是5 wt%,100min。SEM、AFM结果表明,适当的改性条件不会破坏膜表面的“峰-谷结构”,只会降低膜表面粗糙度,而高强度的处理则破坏膜的表面形貌。由ATR-FTIR和XPS得出,改性膜的红外谱图变化不大,而O元素含量增加,这说明改性膜表面的羧基增多;Zeta电位表征得出改性膜表面负电荷相对含量增加,这与膜表面羧基增多的结果一致。改性后接触角降低,即亲水性增加。基于上述结果,提出“界面层交联-皮层表面氧化”机理,即商品RO膜经K2S2O8改性后,一方面,底膜的聚砜与皮层的聚酰胺分子交联,形成致密的界面层;另一方面,皮层受过硫酸盐的氧化作用,结构变得疏松、厚度变薄,失去对溶质的截留作用,此时界面层起截留作用。由于界面层结构更加致密,对溶质的截留能力更强,因此膜的截留率提高;同时,疏松、变薄的皮层将减小溶剂的透膜阻力,使通量增加。界面处交联之后稳定性增加,能够耐受更高强度的氧化,从而提高膜的耐氧化性能。
[Abstract]:The polyamide polyamide composite reverse osmosis (RO) membrane is separated from the polyamide cortex, which is vulnerable to the structural degradation of the active chlorine, which reduces the membrane performance and attenuates the life. In order to solve this problem, this paper will explore the method of sulphate modified aromatic polyamide RO film, the separation performance and oxidation resistance of the high film, and the modification machine. A preliminary discussion was made. The modified RO film was soaked with potassium persulfate (K2S2O8) water solution to control the following five factors: the temperature of the soaking solution, the concentration of K2S2O8, the soaking time, the heat treatment temperature and the heat treatment time. The results of the separation performance of the NaCl solution showed that the optimum modification condition was that the soaking temperature was 60, K2S2O8 concentration. For 5 wt%, the soaking time was 100 min, the heat treatment time was 5 min and the heat treatment temperature was 120 C. The flux increased by 43.2%. The separation rate of the retention rate increased by 0.2%. to the small molecular alcohols (ethanol, isopropanol and n-butanol). The experiment showed that the modified film was best retained under 5 wt% and 100 min. The static oxidation experiment showed that the modified membrane had better oxidation resistance. The best modification conditions of the oxidation resistance are 5 wt%, 100min.SEM, and AFM results show that the proper modification conditions will not destroy the "peak valley structure" on the surface of the membrane, only reduce the surface roughness of the membrane, while the high strength treatment destroys the surface morphology of the membrane. The infrared spectrum of the modified membrane is not changed little by the ATR-FTIR and XPS, and the O element contains the elements. The increase of the quantity indicates that the carboxyl group on the surface of the modified membrane increases, and the Zeta potential indicates that the relative content of the negative charge on the surface of the modified membrane increases, which is in accordance with the increase of the carboxyl group on the surface of the membrane. After the modification, the contact angle is reduced, that is, the hydrophilicity is increased. Based on the above results, the mechanism of "interface layer cross-linking - cortical surface oxidation" is proposed, that is, the commodity RO film via K2S2O8 After modification, on the one hand, the polysulfone of the base membrane is crosslinked with the polyamide molecules of the cortex to form a dense interface layer; on the other hand, the cortex has been oxidized by sulfate, the structure becomes loose, the thickness becomes thinner, and the intercepting action of the solute is lost. At this time the interface layer is intercepted. Because the structure of the interface layer is more compact, the ability to intercept the solute is more important. As a result, the retention rate of the membrane is improved; at the same time, the loose, thinner cortex will reduce the permeation resistance of the solvent and increase the flux. The stability increases after the crosslinking at the interface, and can withstand the oxidation of higher strength, thus improving the oxidation resistance of the membrane.

【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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