What is the difference between membrane filtration and membrane concentration?

Membrane filtration and membrane concentration are two different processes. They both use membranes to separate and control particle molecules. When it comes to their different treatments, let us first understand their definitions:

Filtration refers to the process of passing a substance through a filter membrane or filter medium to separate or remove unwanted components, impurities or particles. The filter membrane here acts as a barrier, allowing certain components to pass through while retaining or capturing other components, thereby obtaining the required purified or clarified product; while the term "concentration" usually refers to a substance or solution with a high proportion of solutes or active ingredients relative to a solvent or carrier medium, indicating that the substance is processed or related to increase its concentration or strength. The concept of concentration here is a measure of the solute content in a given amount of solvent or solution. The concentrated solution contains a relatively large amount of solute compared to the solvent.

Then the membrane in membrane filtration is the medium in filtration. The pore size specification of the filter membrane can separate molecules or particles according to their size or molecular weight, allowing molecules below the pore size threshold to pass through. After the smaller molecules or particles pass through, the larger molecules or particles are retained at the same time. This separation mechanism is called size exclusion or screening. The separation efficiency of membrane filtration depends on the pore size and distribution of the membrane. The membrane with a smaller pore size can effectively retain smaller molecules, while the membrane with a larger pore size allows larger molecules to pass through.

Membrane filtration technology is widely used in various industries, including water treatment, air purification, chemical processing, pharmaceutical production, food and beverage processing, etc. The purpose of filtration includes particle removal, material separation, clarification, purification, etc. The selection of filtration membrane and filtration technology depends on the nature of the filtered substance, the required filtration level, and the specific requirements of the application.

Let's talk about membrane concentration. Membrane concentration uses membrane separation to control the concentration of solutes in the solution. This process is usually carried out using a semipermeable membrane. The semipermeable membrane selectively allows solvent molecules to pass through while restricting the movement of solute molecules. The solvent molecules (usually water) mentioned here can pass through the membrane through processes such as osmosis or diffusion. Due to the gradient change of concentration, the molecules can move from the low solute concentration area to the high solute concentration area, thereby concentrating the solutes in the remaining liquid. The solute molecules (dissolved substances) are retained or the permeability through the membrane is also limited.

Membrane concentration technology is usually used in related industries and fields such as juice, dairy products, pharmaceuticals, chemical solutions, industrial wastewater, and saline solutions. The membrane separation method combines evaporation, reverse osmosis, freeze concentration and other technologies to select the concentration method according to the liquid characteristics and desired results.

In short, membrane filtration focuses on separating molecules or particles according to their size, allowing smaller molecules to pass through while retaining larger molecules; while membrane concentration mainly controls the solute concentration by selectively allowing solvent molecules to pass through the membrane while restricting the movement of solute molecules. They belong to the same membrane separation method, but the purposes and results they achieve are completely different.