超滤膜界面性质和溶液环境对海藻酸钠膜污染行为的影响

发布时间：2018-03-27 06:18

本文选题：扩展DLVO理论　切入点：超滤膜　出处：《西安建筑科技大学》2015年硕士论文

【摘要】：城市污水是重要的潜在水资源,膜处理技术在城市污水处理中发挥了重要的作用。随着城市居民生活方式的变化,城市污水中多糖含量日益增加,论文选取海藻酸钠(SA)作为多糖代表物,通过纯水接触角、标准截留率,以及扫描电镜和原子力显微镜等分析技术,获取了以浸没沉淀相转化法制备的亲疏水性不同的聚偏氟乙烯(PVDF)超滤膜、醋酸纤维素(CA)以及聚醚砜(PES)超滤膜的界面特性参数。结合zeta电位仪对不同p H值及特定浓度的Ca2+、Na+及腐殖酸(HA)、牛血清蛋白(BSA)等溶液环境中,SA溶液的zeta电位和粒径等特性理化性质参数的测定分析数据。以扩展胶体空间理论(XDLVO)和宏观过滤过程的膜污染数学分析模型,探讨了特定溶液环境条件(p H、离子种类、共存有机物)下,SA在不同材质超滤膜界面上的膜污染行为。研究结果如下:1.溶液p H从4升高到11时,SA的zeta电位由-9.72m V下降到-21.4m V;Ca2+或Na+存在下,SA的zeta电位从-15.43m V分别增加到-7.61m V和-7.86m V,SA稳定性下降;Ca2+存在下,SA的粒径呈现较为明显的变化(从138.4nm增加到500.1nm),表明SA发生团聚行为。2.XDLVO理论分析显示:疏水自由能决定了界面粘附自由能值的大小和正负,溶液环境的改变影响了SA与膜的极性张力分项,从而导致SA与膜界面间疏水自由能的改变。超滤膜界面的亲水化程度增加,溶液p H提高,共存金属离子的引入,可以有效提高膜界面及SA表面的极性张力,增大膜与污染物间的粘附自由能,从而减小SA的膜污染趋势。腐殖酸HA和BSA溶液共存环境中,SA界面负电性和粒径增大,界面极性张力分项减小,导致膜与SA界面间的粘附自由能降低。在相同溶液环境下,SA与CA的粘附自由能高于PES膜和PVDF膜,且SA在亲水性PVDF/PVA膜上的粘附自由能高于疏水性PVDF膜。随着p H升高,SA的粘附自由能增大。在Na+和Ca2+存在时,SA+Na+和SA+Ca2+比单一SA与膜的粘附自由能增大。在HA和BSA存在下,SA+HA和SA+BSA比单一SA与膜的粘附自由能降低。SA+HA与三种超滤膜中CA膜的粘附自由能最高;SA+BSA的混合比例对粘附自由能影响不明显。3.宏观膜污染过滤实验数据显示:随着p H值增加,单一SA,SA+HA和SA+BSA混合体系的膜污染情况均有所降低。Na+存在下,SA的通量衰减曲线变化不明显,不可逆污染指数和堵孔阻力有所下降;Ca2+的存在使得SA的通量衰减速率和损失量均明显增加,滤饼阻力明显增加。HA和BSA的存在,均使得SA的不可逆和堵孔吸附阻力增加。SA在亲水性PVDF/PVA膜上的污染程度均小于疏水性PVDF膜污染。在CA超滤膜上,SA+HA的膜污染较PES和PVDF超滤膜污染程度轻。过滤过程的膜通量衰减和膜污染数学模型分析数据验证了XDLVO理论分析结果,为超滤膜改性和膜前预处理调控提供了基础研究依据。4.以膜污染数学分析模型的初期通量下降速率、不可逆污染指数(rir)及堵孔阻力(Rf),与XDLVO理论中粘附自由能的相关性,其中最佳相关系数分别为0.9435,0.8586和0.9548,表明实际膜污染与理论预测结果具有较好相关性,然而在Ca2+存在下,SA的粘附自由能结果与初期通量下降速率的相关系数较低,这可能是因为Ca2+的自身极性导致的。
[Abstract]:City sewage is an important water resource potential, membrane technology has played an important role in city sewage treatment. With the change of the life style of city residents, city sewage in the polysaccharide content increasing, the selection of sodium alginate (SA) as the representative of the polysaccharide, the pure water contact angle, standard interception rate and scanning electron microscopy and atomic force microscopy analysis techniques to obtain different immersion precipitation of hydrophobic polyvinylidene fluoride prepared by phase inversion (PVDF) ultrafiltration membrane, cellulose acetate (CA) and polyethersulfone (PES) ultrafiltration membrane interface parameters. With the zeta potential instrument of different H value and specific p the concentration of Ca2+, Na+ and humic acid (HA), bovine serum albumin (BSA) solution environment, analysis data of SA solution zeta potential and particle size characteristics of physicochemical parameters. In order to expand the colloid space theory (XDLVO) and macro filtration process The membrane fouling mathematical model, discusses the specific solution environment (P H, ion species, coexisting organic compounds), the membrane fouling behavior of SA in different material membrane interface. The results are as follows: 1. P H solution increased from 4 to 11, the zeta potential of SA decreased from -9.72m V to -21.4m V the presence of Ca2+ or Na+; and SA zeta from the -15.43m V potential was increased to -7.61m V and -7.86m V, the stability of SA decreased; the presence of Ca2+, the grain size of SA showed obvious changes (increased from 138.4nm to 500.1nm), SA showed that the aggregation behavior of.2.XDLVO analysis theory has shown that hydrophobic free energy determined the value of free energy of adhesion and positive solution environment changes affecting the sub polar tension SA and membrane, resulting in the interface of SA and membrane between the hydrophobic free energy change. The hydrophilic degree of ultrafiltration membrane interface increased, H is applied to improve the solution P, metal ions can be saved. In order to effectively improve the polar membrane interface and SA surface, increase the adhesion between the film and the free of pollutants, thereby reducing the membrane fouling of SA. Humic acid HA and BSA solution in a coexistence environment, SA interface and negatively charged particle size increased, interfacial polar tension breakdown decreases, cause adhesion free film with SA interface the energy was decreased. In the same solution under the environment of SA and CA, adhesion free energy is higher than that of PES film and PVDF film, and the adhesive free SA in hydrophilic PVDF/PVA membrane can be higher than that of hydrophobic PVDF membrane with P. The increase of H, SA can increase the adhesion of freedom. In the presence of Na+ and Ca2+, SA +Na+ SA+Ca2+ and SA with single freedom than adhesion film can be increased. In the presence of HA and BSA, SA+HA and SA+BSA than single SA and membrane free adhesion can reduce.SA+HA and three kinds of membrane CA membrane adhesion free energy is highest; the mixed proportion of SA+BSA on the adhesion of free energy does not significantly influence the.3. macro view of membrane pollution Dye filtration experiment data: with P H increase in the value of a single SA, SA+HA and SA+BSA mixed system of membrane fouling was decreased by the presence of.Na+, SA flux attenuation curve did not change significantly, irreversible pollution index and the pore blocking resistance decreased; in the presence of Ca2+ SA flux decay rate and loss amount the cake resistance increased significantly, significantly increased.HA and BSA, the SA irreversible adsorption resistance and plugging holes increased.SA in hydrophilic PVDF/PVA membrane pollution levels were less than the hydrophobic PVDF membrane fouling. In CA ultrafiltration membrane, membrane pollution SA+HA staining is higher than that of PES and PVDF ultrafiltration membrane pollution light the flux of membrane filtration process. The attenuation and the membrane fouling mathematical model analysis data to verify the analytical results of XDLVO theory, which provides a basis for the research on the basis of.4. to membrane fouling mathematical analysis model for initial flux regulation of UF membrane modification and pretreatment Drop rate, irreversible pollution index (RIR) and pore block resistance (Rf), and the correlation between the adhesion of XDLVO free energy theory, the best correlation coefficients were 0.9435,0.8586 and 0.9548, showed that the actual membrane fouling and the predicted results have good correlation, however, in the presence of Ca2+, SA and the free energy of adhesion the initial flux decline rate of correlation coefficient is low, this may be because Ca2+ its polarity of lead.

【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ028.8;X703

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