The filtration mechanism of nanofiltration water purifiers and their retention of different molecules

Nanofiltration water purifiers are advanced water purification equipment that uses nanofiltration technology to remove harmful substances in water through selective filtration while retaining beneficial minerals and trace elements for the human body. The principle of nanofiltration technology is to utilize the semi-permeability of nanofiltration membranes, that is, allowing small molecular substances to pass through while blocking the passage of macromolecular substances, thus achieving the purpose of purifying water quality.

Nanofiltration membranes are a type of hollow fiber membrane with pore sizes ranging from several nanometers to several tens of nanometers. The size of the pore of this membrane can be controlled, thus selectively retaining ions, organic matter, and some macromolecular substances in water. The selective retention ability of nanofiltration membranes mainly depends on the pore size of the membrane and the chemical properties of the membrane surface, while the pore size of the membrane and the chemical properties of the membrane surface will also affect the retention efficiency and stability of the membrane.

The retention of different molecules by nanofiltration membranes is as follows:

Retention of ions: Nanofiltration membranes have the ability to retain ions in water, but the type and retention rate of the retained ions depend on the pore size of the membrane. For example, when the membrane pore size is smaller than the radius of the ions, the membrane can retain these ions. For some smaller ions, such as sodium ions, potassium ions, calcium ions, and magnesium ions, nanofiltration membranes can effectively retain them, but for some larger ions, such as chloride ions, fluoride ions, and so on, the retention effect is poor. For some harmful heavy metal ions, such as lead, cadmium, and mercury, nanofiltration membranes can effectively retain them.

Retention of organic matter: The retention ability of nanofiltration membranes for organic matter is relatively weak, but it can retain some small molecular organic substances, such as certain pesticides, antibiotics, detergents, and so on. For macromolecular organic matter, the retention ability of nanofiltration membranes is weak, but it can reduce the content of macromolecular organic matter.

Retention of macromolecular substances: Nanofiltration membranes have strong retention ability for macromolecular substances, which can retain bacteria, viruses, colloids, proteins, and other macromolecular substances. For some specific organic substances, such as polycyclic aromatic hydrocarbons, phenolic compounds, and so on, nanofiltration membranes can effectively retain them.

In general, nanofiltration membranes have the selective retention ability for ions, organic matter, and some macromolecular substances in water, which can effectively remove harmful substances in water while retaining beneficial minerals and trace elements for the human body, thus achieving the purpose of purifying water quality. However, it is necessary to note that the retention efficiency of nanofiltration membranes is affected by various factors, such as the pore size of the membrane, the chemical properties of the membrane, the pH value of the water, and the water temperature. Therefore, when using nanofiltration water purifiers, it is necessary to select appropriate nanofiltration membranes and treatment conditions according to the actual situation to achieve the best water purification effect.