Engineering Degree Program in China - Membrane Technology

1. Introduction

Membrane Technology, as a new separation technology, has been widely used in gas separation, material separation and water treatment, among which the water treatment area has the biggest demand for membrane products. Membrane is an inorganic or polymer material with selective separation function. Membrane separation is the process to realize the separation, purification and concentration of the different components of the material by selective separation of the membrane. It is different from the traditional filtering in that the membrane can be separated in the molecular range, and this process is a physical process, do not need to change the phase of the changes and the addition of additives. The pore size of the membrane is generally micron, according to the different pore size (or cut-off molecular weight), the film is divided into microfiltration membrane, ultrafiltration, nanofiltration and reverse osmosis membrane, according to the different materials, the membrane can be divided into inorganic membrane and organic membrane, inorganic membranes are mainly microfiltration membrane: ceramic membrane and metal membrane. Organic membrane is made of polymer material.

2. Membrane

The membrane can separate the fluid into two parts that are not linked, so that one or several substances can penetrate through, and the other substances can be separated. Membrane technology is the first choice for environmental protection and environmental management. It also plays an important role in the food industry.

Membrane is the core of membrane technology; the properties and chemical structure of the membrane material have a decisive influence on the membrane separation performance.

Classification:

1) According to the source of the material: natural membrane and synthetic membrane, synthetic membrane is divided into organic membrane and inorganic membrane.

2) According to the structure, the membrane can be divided into seven categories:

Homogeneous membrane or dense membrane, symmetric microporous membrane (nuclear pore film, control stretch film and sponge structure membrane), asymmetric membrane, composite membrane, ion exchange membrane, charged membrane, liquid membrane (supporting liquid membrane and emulsion liquid membrane)

3) According to the shape: flat membrane, tubular membrane, hollow fiber membrane and roll membrane.

3. Membrane Separation

1) Microfiltration

2) Ultrafiltration

3) Nanofiltration

4) Reverse osmosis

5) Technological principle

6) Technological process

4. Membrane Separation Characteristics

1) Membrane separation can be operated under ordinary temperature; there is no phase transition;

2) Concentration and separation proceed at the same time;

3) There is no need to add other substances, does not change the nature of the separation of substances;

4) Strong adaptability, stable operation.

5. Development

1) Low pollution membrane

2) Ultra-low voltage membrane

3) Reverse osmosis membrane with positive charge

4) High temperature resistant, food grade, sanitary reverse osmosis membrane

6. Electrodialysis

1) Principle

Under the action of direct current electric field, take advantage of the selective permeability of anion and cation exchange membrane to the anion and cation in the solution to separate solute and water. The anion exchange membrane only allows the anion to pass through; the cation exchange membrane only allows the cation to pass through.

2) Ion exchange resin: exchange reaction happens between resin and ion.

3) Ion exchange membrane: the characteristics of selective permeation to ions in the solution

According to its structure, it can be divided into: heterogeneous membrane, homogeneous membrane.

Heterogeneous membrane: ion exchange resin becomes powder, be added into adhesive, rolling on the fiber web.

Homogeneous membrane: ion exchange resin matrix material to be made into continuous membranous, serving as a base film, on which embedding active groups.

According to ion selectivity:

Cation exchange membrane and anion exchange membrane

4) Ion exchange membrane selective permeability

The pore structure of the membrane; the action of the active exchange group

5) Excellent electrodialysis

High ionic selectivity; poor permeability; good conductivity; chemical stability and mechanical strength

7. Application

1). Electric power;

2). Electronics;

3. Chemical industry and medicine;

4) Light industry;

5). Biology;

6). Food and beverage;

7). Municipal services;

8). Environmental protection and other industries.