【作者】 刘强；

【导师】 孟范平；

【作者基本信息】 中国海洋大学 ， 生态学， 2007， 硕士

【摘要】 首先通过正交试验对膜制备的主要工艺参数(A,壳聚糖浓度;B,添加剂聚乙二醇分子量;C,溶剂中的丙酮含量;D,干燥温度;E,凝固浴NaOH溶液浓度)对壳聚糖(CS)超滤膜渗水通量的影响进行了评价。结果表明,各因素对膜水通量影响的主次顺序为:B>A>D>E>C,以添加剂聚乙二醇(PEG)分子量影响最为显著。优化后的膜制备条件为:PEG分子量800;壳聚糖浓度为2.0%;溶剂中丙酮含量为40%(V/V);干燥温度50℃;凝固浴NaOH溶液浓度为0.25 mol·L-1。而后,重点研究了添加剂PEG的分子量和用量对CS超滤膜微观形态和膜性能的影响。在最佳制膜工艺的基础上,通过改变铸膜液中PEG的分子量和用量,制备了一系列CS膜,在0.2MPa的进水压力下测定了这些膜的渗透通量和截留率,同时对膜表面进行电镜扫描。结果发现,PEG分子量(M)、制膜体系中的PEG含量(C)的改变,显著地影响了膜表面的微观形态,随着M和C的不断增大,膜表面的粗糙程度逐渐提高,颗粒状结构越来越明显,颗粒粒径和微孔尺度也不断增大。当PEG800用量达到10%、PEG1000用量达到8%时,粒状增大突变为片状,表面孔密集成缝,当用量进一步增大时,由于水溶胀性过大,膜无法获取。随着M和C的不断增大,CS膜的性能表现为渗水通量逐渐增大和对BSA的截留率不断减小。统计分析发现,PEG分子量(M)与CS膜的截留率(R)之间有较好的线性相关,但是,PEG的用量(C)与水通量(F)之间并不存在线性关系,当PEG200、PEG400和PEG600的用量分别为10%、8%和10%时,F值达到最大;PEG分子量达到1000时,对膜的微观结构影响十分显著,相应的渗水通量急剧上升,而截留率则迅速降低。可以认为,PEG不是单纯的致孔剂,它通过改变铸膜液中聚合物的聚集态、溶液热力学行为和凝胶的动力学行为,对膜结构造成一定程度的影响,从而导致膜性能的改变。综合考虑膜的截留率和水通量两个指标,以PEG200(用量10%)或PEG400(用量8%)作为制备CS膜的添加剂比较适宜,既可得到90%以上的截留率,还能获得较高的水通量(12~13ml?h-1?cm-2)。利用PEG400(用量8%)作为添加剂制备的CS膜对蛋白质分子量的截留范围在60000~70000之间,且膜的孔径分布范围较窄。近年来,随着我国沿海水产品加工业的兴起,水产品加工废水成为环境污染的又一突出问题。本研究设计了粗滤+CS膜超滤的串联工艺,对三种水产品废水进行处理,CODcr的去除率分别达到82.6%、89.3%和90.0%,出水符合《污水排放综合标准》的一级标准(100mg·L-1)的要求。对于两种蛋白质浓度分别为111.32 mg·L-1和84.55 mg·L-1的鱼片加工废水,经过粗滤分别去除废水中32.9%和39.4%的蛋白质(颗粒蛋白)后,采用CS超滤膜对水溶性蛋白质进行截留,截流率分别达到52.9%和44.8%(相对于原废水蛋白含量),整个工艺对废水中蛋白质的总截留率可以达到85.8%和84.2%。废水pH值的优化会使颗粒状态的有机成分增加,较大幅度提高粗滤对CODcr和蛋白质的去除率,但对于整个工艺的CODcr和蛋白质去除效果影响并不大。与生物处理技术相比,利用CS超滤膜处理水产品加工废水,不仅可以在较短的时间内获得较好的废水处理效果,而且为废水中蛋白质等营养成分的回收利用创造了有利条件,因而具有较好的应用前景。更多还原

【Abstract】 In this research, the effects of main processing parameters involved in the preparation of chitosan(CS) membrane, including concentration of chitosan in membrane casting solution(A), molecular weight of PEG as an additive(B), dosage of acetone in solvent(C), torrefaction temperature(D) as well as the concentration of NaOH solution as coagulation bath(E), on the permeation flux of membrane were evaluated by orthogonal experiments. The results showed that, the degree order that the five factors influence permeation flux(F) of membrane was listed as follows: B>A>D>E>C. Among them, molecular weight of PEG has the most significant effect on F value. The CS membrane had a maximum F value at the following conditions: A was 2.0%, B was 800, C was 40% (V/V), D was 50℃, E was 0.25 mol·L-1.Then, the effect of molecular weight(M)and dosage(C) of PEG on the microcosmic surface texture and properties of CS membranes were studied specially. A series of CS membranes were prepared by changing the values of M and C of PEG in membrane casting solution. The permeate flux(F) and rejection ratio(R) of these membranes were tested under a pressure of 0.2MPa, the microcosmic surface texture of CS membranes was also observed with scanning electron microscope(SEM). It showed that, the microcosmic texture of membrane surface was evidently affected by M and C. With the increase of M or C, microcosmic surface texture became more and more rough, granulation degree of membrane became larger, size of micropore increased unceasingly as granule radius became larger, which resulted in that F ascend and R descend. It had been observed that granule on the membrane surface became patch when the dosage of PEG800 and PEG1000 were 10% and 8% respectively, at the same time, slot appeared as pores connected. With the further increase in dosage of PEG800 and PEG1000, CS membrane cannot be obtained for water swelling augmenting.For the properties of CS membranes, water permeate flux (F) raised gradually with the increase of M and C, while rejection ratio (R) became smaller and smaller. There was a better linear relationship statistically between M and R, but F value had non-linear relationship with C growth. For PEG200, PEG400 and PEG600, the maximum value of F were obtained when their dosage reached 10%, 8% and 10% respectively. In comparison with PEG800, the addition of PEG1000 lead to a distinct change in membrane micro-surface, accompanied by a sharp rise in F and a rapid decrease in R. It is concluded that PEG was not only a sort of pore-causing reagent, but also influence the structure and performance of membrane through interfering the aggregation state of polymer, thermodynamics action of solution and dynamic behaviors of coagulation.Generally, the additive PEG200 of 10% or PEG400 of 8% in membrane casting solution may obtained the better performance of CS membrane, with a R value aboved 90% and a F value of 12~13ml·h-1·cm-2. When PEG400 of 8% was added, the CS membrane had a retention range from 60000 to 70000 in molecular weight, and a smaller range in pore size of membrane.In recent years, wastewater from aquatic product processing has become a new pollution source in the coastal areas. Therefore, serial processes consisted of rough filtration with filter paper and ultrafiltration with CS membrane was designed to deal with three kinds of aquatic product processing wastewater. The removal rate of CODcr reached to 82.6%, 89.3% and 90.0% respectively.The CODcr of outflow could fit for the Intergrated Wastewater Discharge Standard of China (100mg·L-1). For two kinds of wastewater from fish slice production containing protein of 111.32 mg·L-1 and 84.55 mg·L-1 respectively, the total protein rejection of 85.8% and 84.2% were obtained respectively during the whole process, in which protein(granulated) of 32.9% and 39.4% were rejected by rough filtration, and deliquescent protein of 52.9% and 44.8%(relate to concentration of protein in raw wastewater)was rejected by CS membrane ultrafiltration. Optimization of pH value in wastewater raised the removal of CODcr and protein by rough filtration through the formation of organic detritus, but the total rejection ratio was not improved clearly in the whole treatment process.In comparison with biological treatment, ultrafiltration with CS membrane not only had a better purification to wastewater from aquatic product processing, but also create suitable conditions for the reuse of nutrimental components in wastewater.更多还原