Working Principle of Membrane Filter

A comparatively short definition of membrane filter could be just like this: membrane filter is something to separate and enrich solutes in solution, and separate colloidal suspensions. Let’s know the membrane filtration principle. Hawach provided Cellulose acetate membrane, Hydrophobic PTFE membrane filter, PVDF Filter, and so on.

Principle of membrane filtration

Microfiltration is also called a microporous filtration membrane. The principle of membrane filtration uses a membrane with selective permeability as a separation medium. The membrane wall is densely covered with micropores. The original liquid passes through one side of the membrane under a certain pressure. The solute is retained by the membrane to achieve the purpose of material separation and concentration. The membrane separation process is a dynamic cross-flow process. The macromolecular solute is blocked by the membrane wall and flows out of the membrane module with the concentrated liquid. The membrane is not easy to be blocked and can be used continuously for a long time. The filtration process can be operated at room temperature and low pressure, with no phase change, high efficiency, and energy-saving.

Microporous filtration membrane is a refined filter material that can retain large solid particles and other particles, microorganisms and some bacteria in the solution, and solvents and small molecular substances. These substances can be separated through the membrane mixture. The membrane filter principle is the screening process. The raw material liquid passes through a microporous membrane material to separate specific substances under the action of static pressure difference.

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Membrane filter is to uses the sieving mechanism of the microfiltration membrane, driven by pressure, to trap particles with a diameter between 0.1-1μm, such as suspended solids, bacteria, some viruses, and large-sized colloids.

In addition, the membrane with a thickness of less than 100um must have the ability to withstand high pressure, so we should try to make various kinds of pressure-resistant membranes.

Water flow through the membrane is not very fast, so in order to pass the required amount of water, the monomer area of the membrane device should be large, and many thin membrane tubes should be filled in a small space. Tube membranes also need porous materials. Raw water passes through the inner side of the pipe and seepage flows out of the pipe. This kind of membrane filter is commonly used for passengers, but also for externally pressurized ones. The outer diameter of the hollow system is several hundred um, and most fiber tubes are packed in the system.

There are five types of membrane filters: plate-frame type, spiral type, bridge type, tubular type, and hollow fiber type. Porous materials should be used for the plate-and-frame membranes. The spiral type is coiled, and the bridge type is to insert a large area of the membrane into a small folded volume.

Click here to know more about PVDF vs PTFE, Membrane Material And Performance Characteristics Of Filter Membrane, The Applications Of Membrane Filter.