溶液环境对陶瓷膜微滤微米级颗粒悬浮液的影响

本文研究了溶液环境对陶瓷微滤膜处理微米,亚微米级颗粒悬浮液过程的影响,通过测定电解质溶液种类,浓度对微滤过程渗透通量的影响,及溶液环境对微滤过程影响随颗粒粒径,膜孔径的变化,确定了溶液环境对微滤过程的影响主要是由于其引起了颗粒表面Ｚｅｔａ电位的变化,改变了颗粒在溶液中的分散情况,并引起了决定膜通量的颗粒粒径／膜孔径比值的变化,从而改变了微滤过程。     

陶瓷膜过滤细微颗粒悬浮体系的数学模拟

通过对陶瓷膜过滤悬浮液过程中单颗粒的受力分析,获得了可沉积颗粒临界粒径(xcrit)的计算公式.计算的xcrit值与实验测定的沉积层内的粒径分布一致:随颗粒粒径的增大, xcrit呈先增大后减小的趋势. 在讨论xcrit与颗粒粒径(dp)、膜孔径(dm)关系的基础上,将微滤过程按dp/dm的比值分为三种类型:dp/dm≤1, 颗粒迅速阻塞膜孔;1＜dp/dm≤10 ,颗粒在膜表面形成连续滤饼;dp/dm》10,颗粒对膜孔口覆盖,在膜表面形成不连续滤饼.并以此为基础建立了预测陶瓷膜过滤不同粒径和粒径分布的颗粒悬浮液渗透通量的数学模型.计算结果与实验结果的比较表明:本模型对文献模型的改进之处是适用范围从1＜dp/dm≤10扩展到0.48≤dp/dm≤120;在操作压力对渗透通量的影响计算中,假设滤饼层孔隙率不变的计算结果与实验结果一致,说明此体系的滤饼是不可压缩的;在错流速率对渗透通量的影响计算中,假定滤饼层孔隙率随错流速率成指数变化的计算结果比假定沉积层孔隙率随错流速率不变的计算结果好,说明错流速率的变化同时影响滤饼层内颗粒的粒径分布和其形成的滤饼层的结构.     

超声强化多通道陶瓷膜微滤超细TiO2悬浮液

针对超声强化膜分离过程能耗高的问题,提出并设计了一种新型超声强化膜分离操作方式,并进行了超声强化陶瓷膜微滤超细TiO₂颗粒悬浮液的研究。考察了超声场参数、操作时间及溶液环境对多通道陶瓷膜微滤过程的影响规律,并分析了此操作方式强化陶瓷膜微滤颗粒悬浮体系的机理。结果表明,该操作方式能够获得较高膜通量恢复率及平均膜通量,同时超声能量消耗减小了90.0%以上;降低超声频率及提高功率,有利于膜通量恢复,在超声参数45 kHz和0.33 W·cm^-2条件下,膜通量恢复到初始值的94.0%;控制超声辐射时间0.167 min,微滤时间8 min时,平均膜通量提高了61.5%;降低悬浮液颗粒浓度及提高料液温度都有利于超声场强化陶瓷膜微滤过程。     

面向过程的陶瓷膜材料设计理论与方法(Ⅰ)膜性能与微观结构关系模型的建立

提出了面向过程的陶瓷膜设计基本研究框架 ,分析了膜的孔径分布与悬浮液颗粒体系粒径分布对过滤过程的影响 ,提出采用堵塞因子来表征膜的初始堵塞污染情况 ,建立了颗粒体系微滤过程中的膜微观结构与性能关系新模型 ,不仅可以计算膜通量随时间的变化 ,且能预测陶瓷膜结构参数对膜通量的影响 .模拟结果与实验值有较好的一致性     

面向过程的陶瓷膜材料设计理论与方法(Ⅰ)膜性能与微观结构关系模型的建立

提出了面向过程的陶瓷膜设计基本研究框架,分析了膜的孔径分布与悬浮液颗粒体系粒径分布对过滤过程的影响,提出采用堵塞因子来表征膜的初始堵塞污染情况,建立了颗粒体系微滤过程中的膜微观结构与性能关系新模型,不仅可以计算膜通量随时间的变化,且能预测陶瓷膜结构参数对膜通量的影响.模拟结果与实验值有较好的一致性.     

颗粒体系错流过滤过程的数学模拟

以流体力学理论为基础,通过颗粒在水溶液中的受力分析,结合早期的阻塞过滤模型和近期的滤层过滤模型,建立了一种新的颗粒体系错流过滤过程的数学模拟方法,在该模拟过程中同时考虑了膜孔径和颗粒大小两种分布,并对具有相同平均孔径而孔分布不同的情形对膜渗透通量的影响进行了模似,经实验验证,模拟结果与实验值能够较好地吻合。     

动态Monte Carlo模拟蛋白质与微滤膜相互作用及其对微滤过程影响

构建了二维晶格蛋白质-微滤膜疏水相互作用模型，采用动态Monte Carlo方法模拟了微滤膜污染过程及其受膜孔径、蛋白质浓度和蛋白质结构特性等因素的影响。模拟结果显示：微滤过程中膜通量的变化呈现快速下降、缓慢下降和平台期3个阶段。小孔径微滤膜的滤阻从以膜孔阻力为主转变为以饼层阻力为主;而大孔径微滤膜的滤阻则以膜孔阻力为主。提高蛋白质浓度会强化滤阻从膜孔阻力向饼层阻力的转变。在微滤过程中，蛋白质会因疏水相互作用在膜孔内发生构象转换，进而发生不可逆吸附并形成多层堆积，导致膜污染和通量下降，提高蛋白质的构象稳定性可以显著降低其对微滤膜的污染。分子模拟结果与文献报道的实验结果和理论模型相符，所提供的微观信息对于微滤过程优化和微滤膜设计具有参考作用。     

纳米与微米颗粒污垢沉积的表面特性及等效关系

目前对颗粒污垢的研究主要局限于实验研究,通过实验和模拟的手段分别对微米和纳米颗粒污垢沉积的内在关系研究较少。为了研究静止流体中纳米级颗粒污垢与微米颗粒污垢出现相似沉积特点的原因,分别在不同工况下进行纳米颗粒污垢和微米颗粒污垢的沉积实验,并应用扫描电镜对试片表面进行观测。通过模拟方式得出不同粒径微米颗粒污垢的沉积质量,由实验得出颗粒污垢沉积质量呈现出渐进增长趋势。随着浓度的增大其渐进沉积质量越来越大,达到渐进污垢沉积量的时间越来越短。由于颗粒间的团聚效应,使纳米颗粒污垢出现与微米颗粒污垢相似的沉积规律。基于这种规律,提出纳米颗粒污垢等效直径的概念。将实验结果与不同直径微米级颗粒沉积模拟结果相结合,得出浓度0.4g/L的纳米悬浮液团聚后的等效直径约为9.2μm;浓度0.6g/L的纳米颗粒悬浮液团聚后的等效直径约为11.2μm。     

面向应用过程的陶瓷膜设计方法

无机陶瓷膜以其优良的材料性能获得了广泛的应用。由于膜品种的定型化 ,使膜应用研究受到一定的限制。面向应用过程来设计最优性能陶瓷膜将会是一个重要的发展方向。在提出面向应用过程的陶瓷膜设计基本研究框架基础上 ,以颗粒体系为对象 ,建立起包含膜结构参数的微滤模型 ,考察膜孔径、厚度、孔隙率等结构参数对微滤性能的影响 ,从而从理论上建立颗粒体系微滤过程中最优膜的选择方法     

微滤,超滤过程中的膜污染与清洗

本文综述了在微滤和超滤过程中，膜污染的影响因素，防止膜污染的措施的清洗方法的选择，指出料液粒子或溶质尺寸，膜结构以及膜与溶质间的相互作用都和膜污染程度有关；通过膜孔径，膜材料，膜结构，组件结构，料液温度，流速和压力的控制可以减轻或控制污染。     

Effect of Pore Size and Particle Size Distribution on Granular Bed Filtration and Microfiltration

Abstract

The paper reviews the effect of particle size distribution and pore size distribution on granular bed filter and crossflow microfiltration performance. The experimental results of the granular bed filter with pollen particles in suspension showed that the presence of large particles improved the filter efficiency of smaller particles in suspension. Microfiltration results with bi and tri‐modal latex suspensions showed that the permeate flux and the quality were significantly affected by the particle size and its distribution, especially when the particle size was smaller than the pore size of the membrane. The mathematical model simulation results of granular bed filtration show that media pore size distribution is an important parameter of filtration for the particle removal and pressure drop across the filter.     

PROTEIN ADSORPTION AND FOULING OF CERAMIC MEMBRANES AS MEASURED BY SCANNING ELECTRON MICROSCOPY WITH DIGITAL X-RAY MAPPING

A technique for studying fouling in ceramic membranes using the energy dispersive x-ray spectroscopy capability of an electron microscope is described. The location and amount of foulant within the membrane are presented on a digital x-ray map showing elements constituent to or stained on the foulant.

Fouling of alumina membranes during filtration of the protein hemoglobin has been studied as a function of filtration time, pH, and membrane pore size. After each filtration run, the protein within a piece of the membrane was stained with phosphotungstic acid and located on a digital map of either phosphorus or tungsten.

For a 0.2 μm pore size membrane, time dependent fouling was observed consistent with an observed flux decline within the first few minutes of filtration. A pH dependence was also observed indicating much greater fouling at pH 6.9 near the protein isoelectric point than at pH 8.5. This observation is consistent with pH dependent adsorption, flux, and rejection studies. No internal fouling was observed for a 40 Å pore size membrane, which is consistent with the size of hemoglobin in solution being larger than the 40 Å pores and with the fact that the 40 Å membrane can be more easily cleaned after use than can the 0.2 μm membrane.     

Effects of particle size on microstructure and mechanical strength of a fly ash based ceramic membrane

Recycling fly ash for ceramic membrane fabrication not only reduces solid waste discharge, but also decreases the membrane cost. Now, fly ash is becoming a promising substitute material for ceramic membrane preparation. A significant difference between fly ashes from different plants is the particle size, which makes performances of fly ash membranes unpredictable. The novelty of this work is to clarify the effects of the particle size of fly ash on ceramic membranes, thereby giving practical suggestions on fly ash selection for ceramic membrane preparation. Ceramic membranes were fabricated with different sizes of fly ashes. Effects of particle size on porosity, pore size, microstructure, mechanical strength and gas permeability of the membrane were investigated. Results indicate that a broader particle size distribution of fly ash leads to a denser structure of membrane with a lower porosity. Pore size and gas permeability of membrane increase while bending strength decreases with the particle size increasing. Bending strength of a fly ash membrane is largely determined by large particles in the fly ash because the large particles lead to cracks in the membrane. This work provides experimental bases for developing high performance ceramic membranes from fly ash.     

非均粒悬浮液的陶瓷膜错流深滤速度研究

根据使用陶瓷膜中存在的问题,并以非对称陶瓷膜结构特点为基础,提出了以陶瓷膜支撑层（深层）与膜层共同作为过滤介质的一种新的陶瓷膜错流深层过滤方式。用非均粒径高岭土悬浮液,经过自行设计的实验流程和错流过滤器,进行了陶瓷膜错流深层过滤等实验。对取得的实验数据进行分析对比,得到了在相同操作条件下新方式比传统错流膜过滤的过滤阻力...     

混凝耦合多孔陶瓷膜净化河水简

Membrane filtration technology combined with coagulation is widely used to purify river water. In this study, micro filtration （MF） and ultrafiltration （UF） ceramic membranes were combined with coagulation to treat local river water located at Xinghua, Jiangsu province, China. The operation parameters, fouling mechanism and pilot-scale tests were investigated. The results show that the pore size of membrane has small effect on the pseudo-steady flux for dead-end filtration, and the increase of flux in MF process is more than that in UF process for cross-flow filtration with the same increase of cross-flow velocity. The membrane pore size has little influence on the water quality. The analysis on membrane fouling mechanism shows that the cake filtrationhas significant in fluence on the pseudo-steady flux and water quality for the membrane with pore size of 50, 200 and 500 nm. For the membrane with pore size of 200 nm and backwashing employed in our pilot study, a constant flux of 150 L-m^-2-h^-1 was reached during stable operation, with the removal efficiency of turbidity, total organic carbon （TOC） and UV254 higher than 99%, 45% and 48%, respectively. The study demonstrates that coagulation-porous ceramic membrane hybrid process is a reliable method for river water purification.     

陶瓷膜澄清厚朴水提液膜污染机理的研究

采用一个经典模型描述了厚朴水提液过滤过程中的通量衰减,通过模型参数分析了膜的污染机理。分析结果表明孔径为50,200,500 nm的陶瓷膜主要由"完全孔堵塞"机理、"滤饼过滤"机理和"部分孔堵塞"机理控制;通过此污染机理的分析来指导膜清洗,孔径为50,200,500 nm的陶瓷膜清洗后分别恢复了84.5%,89.4%和90.0%左右;实验表明孔径为200 nm的陶瓷膜较适合厚朴水提液体系。     

Insight into fouling behavior of poly(vinylidene fluoride) (PVDF) hollow fiber membranes caused by dextran with different pore size distributions

Membrane fouling is the key problem that occurs in membrane process for water treatment. However, how membrane microstructure influences the fouling behavior is still not clear. In this study, fouling behavior caused by dextran was deeply and systematically investigated by employing four poly(vinylidene fluoride)(PVDF)membranes with different pore sizes, ranging from 24 to 94 nm. The extent of fouling by dextran was accurately characterized by pore reduction, flux decline, and the change of critical flux. The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent. As the membrane pore size increased, the critical flux ranges were 105-114, 63-73, 38-44 and 34-43 L·m~(-2)·h~(-1),respectively. The critical flux and fouling resistances indicated that the fouling propensity increases with the increase of membrane pore size. Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment. The results showed that serious irreversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of40.5 L·m~(-2)·h~(-1).On the other hand, membrane with pore size of 25 nm exhibited much better anti-fouling performance when permeate flux was set to 40.5,48 and 60 L·m~(-2)·h~(-1).