I.introduction

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I
Introduction
1.Separation processes 2. Introduction to membrane processes 3. The history of membrane technology 4. Definition of a membrane 5. Membrane processes 6. Problems
1.2. A classification of some separation processes
A classification of some separation processes in terms of the physical or chemical properties of the components to be separated is given in table I.1(far from complete) Table I.1 Separation processes based on physical/chemical properties property size separation process filtration, microfiltration, ultrafiltration, dialysis, gas separation, gel permeation chromatography vapour pressure distillation, membrane distillation freezing point crystallisation affinity extraction, adsorption, reverse osmosis, gas separation, pervaporation, affinity chromatography charge ion exchange, electrodialysis, electrophoresis, diffusion dialysis density centrifugation chemical nature complexation, carrier mediated transport
1.3. General criteria for the choose of a separation process
How can a separation process be selected to solve a given problem? Two general criteria apply to all separation processes: 1). The separation must be feasible technically (be capable of accomplishing the desired separation and achieve a quality product); 2). The separation must be feasible economically.
-energy consumption is generally low; -membrane processes can easily be combined with other separation processes (hybrid processing); -separation can be carried out under mild conditions; -up-scaling is easy; -membrane properties are variable and can be adjusted; -no additives are required.
module
permeate
1.5. Characters of membrane technology
The benefits of membrane technology can be summarized as follows:
- separation can be carried out continuously;
The production of fresh water from the sea, which is very practical problem, can be performed by several commercially available separation processes:
The performance of a given membrane is determined by two parameters: its selectivity and the flow through the membrane.
1). The flow(often denoted as the flux or permeation rate): is defined as the volume flowing through the membrane per units area and time. Volume flux may be readily converted to mass flux or mole flux by using the density and molecular weight.
1.Separation processes
1.1.Analysis of thermodynamics 1.2.A classification of some separation processes 1.3.General criteria for the choose of a separation process 1.4. The objectives of separation 1.5. Characters of membrane technology
The minimum amount of energy (Wmin) necessary to accomplish complete separation is at least equal to or larger than the free enthalpy of mixing: Wmin≥△Gm=△Hm - T△Sm In practice, the energy requirement for separation will be many times greater than Wmin. The basic principle of any separation process is that a certain amount of energy is required to accomplish the separation.
1.4. The objectives of separation --concentration: the desired component is present in a low concentration and solvent has to be removed. - purification: undesirable impurities have to be removed. - fractionation: a mixture must be separated into two or more desired components. -reaction mediation: combination of a chemical or biochemical reaction with a continuous removed of products will increase the reaction retentate rate. feed
本课程为双语教学国内外均在试行还没有统一的模式备课和教学均没有经验希望同学们提意见以便改进
Basic Principles of Membrane Technology
Second edition Marcel Mulder
膜技术基本原理
李琳译
教学计划与安排
中英文讲授，英文作业，中英文考试。 一定要听课，考试内容为讲解的内容，
1). Distillation: heated 2). Freezing: cooled 3). Reverse osmosis: pressurized 4). Electrodialysis: an electric field is applied 5). Membrane distillation: heated Separation processes consume more energy than this minimum amount. Reverse osmosis has the lowest energy consumption of those mentioned above.
1.1.Analysis of thermodynamics
C H H H C H C H C
(a)
C C C H H C C C H H H H
(b)
Fig.1 a random situation(a) is transformed into an ordered one (b) This course is against the second law of thermodynamics. The free enthalpy of the mixture is smaller than the sum of the free enthalpies of the pure substances.
membrane Phase 1 Phase 2
permeate
feed
Driving force △C,△P,△T,△E
Fig.I.4 Schematic representation of a two-phase system separated by a membrane
2.2. The paraFra biblioteketers of membrane performance
The following drawbacks should be mentioned:
-concentration polarization/membrane fouling;
-low membrane lifetime; -low selectivity or flux; -up-scaling factor is more or less linear.
2. Introduction to membrane processes
2.1.Introduction 2.2. The parameters of membrane performance
2.1.Introduction
From an economic point of view, the present time is intermediate between the development of first generation membrane processes such as microfiltration(MF), ultrafiltration(UF), nanofiltration(NF), reverse osmosis(RO), eletrodialysis(ED), diffusion dialysis(DD), and dialysis and second generation membrane processes such as gas separation(GS), vapour permeation(VP), pervaporation(PV), membrane distillation(MD), membrane contactors(MC) and carrier mediated processes. All membrane processes have one thing in common, the membrane.