2020 Water Purifier Filter Knowledge -1

As we know that the effective part of a water purifier is its filter element.

Today, we have sorted out the common water purifier filter elements and their functions on the market for your reference only.

It contains ◆Reverse osmosis membrane (RO) filter element,  ◆Nanofiltration membrane (NF) filter element, ◆Ceramic filter, ◆Resin filter element, ◆PP cotton filter, ◆Granular Activated Carbon, ◆UDF or GAC Activated Carbon, ◆Carbon Rod Filter Element (CTO), ◆Carbon Fiber Filter Element.

◆PP Cotton Filter

PP cotton filter element is mainly made of polypropylene, which is relatively unfamiliar to most people, but PP cotton (not PP cotton filter element) using polypropylene as raw material is widely used in daily life. The common filling of the pillows we use is PP cotton made of polypropylene. When we went to AliExpress to select plush toys, many of the fillers indicated in the product details included doll cotton and hollow cotton. In fact, they all refer to PP cotton made of polypropylene. Thinking this way, are you familiar with polypropylene? Oh, I forgot to mention that polypropylene itself is non-toxic, so it can be used as a raw material for filter elements. Although both PP cotton filter element and PP cotton as filling materials are made of polypropylene, there are still big differences between the two. PP cotton filter element refers to a polypropylene melt that is a blown filter element. Regarding the melt-blown filter element, the original statement is: the melt-blown filter element is made of non-toxic and odorless polypropylene particles, which are melted by heating, spinning, drawing, and forming. Manufactured tubular filter element. The filtration accuracy of the PP cotton filter element ranges from 0.5μm (micron) to 20μm. The diameter of a human hair ranges from 0.017 to 0.18 mm (17 to 18 microns, the data comes from Wikipedia).

PP cotton filter elements used in water purifiers include ordinary PP cotton filter elements and high-precision PP cotton filter elements, which are usually placed in the first and third layers of filter elements respectively. The melt-blown polypropylene indicated by some merchants on the promotion page sounds like a very high-end product, but it is actually a PP cotton filter element.

In my understanding, the difference between the high-precision PP cotton filter element and the ordinary PP cotton filter element mainly lies in the pore size. The pore size of high-precision PP cotton is smaller than that of ordinary PP cotton, which can filter out smaller impurities. When our drinking water flows through the first layer of PP cotton, it is like flowing through a screen, which usually traps large particles of sediment and other visible impurities. When water flows through the third layer of high-precision PP cotton, it will filter out finer substances than the first layer. (For the filtration accuracy, the promotional data of the merchants that can be found on Jingdong is 5μm. If the filtration accuracy of 5μm is calculated, it is far from enough to filter out bacteria and viruses.

◆Granular Activated Carbon

I believe everyone is no stranger to activated carbon. Activated carbon has strong adsorption properties.
Activated carbon is widely used because of its characteristics. Many people have activated carbon bags in their cars to remove odors, and some people in newly renovated houses will also put some activated carbon bags to remove formaldehyde.

We often see that many water purifiers use activated carbon as a filter element in the water purifier leaflet, including granular activated carbon, carbon fiber filter element, carbon rod filter element, etc. So how are they different?
The coconut shell activated carbon filter commonly used in water purifiers is a kind of granular (UDF/GAC) activated carbon. In addition, the main raw material of granular activated carbon can also be apricot shells, walnut shells, and other fruit shells or coal such as anthracite. Activated carbon formed by activating these as raw materials has formed many small pores, but the size distribution of these pores is not uniform. According to the diameter, they are divided into micropores below 2nm, macropores above 50nm, and mesopores in the middle ( Also called transition hole). Some pores can even reach 1000nm.

◆Carbon Rod Filter (CTO)
The more commonly used carbon rod filter elements are compressed activated carbon and sintered activated carbon (extruded activated carbon is also included in CTO, but due to the fact that the adsorption capacity is very small during the molding process). Compressed activated carbon is formed by mixing activated carbon powder and inorganic liquid binder under high pressure.
Sintered activated carbon is sintered at high temperature after mixing activated carbon powder and polymer hot-melt pore-forming material. Because the polymer hot-melt pore-forming material used in sintered activated carbon also forms pores at high temperatures, and the inorganic liquid binder in compressed activated carbon cannot form pores under high pressure, sintered activated carbon has better filtration and decolorization effects than compressed activated carbon better. As sintered activated carbon

◆Carbon Fiber Filter
The carbon fiber filter element refers to an activated carbon fiber filter element (ACF). Activated carbon fiber is no longer a common powdery or granular form of activated carbon, but fibrous. The fiber is a continuous or discontinuous filament. Activated carbon fiber is composed of A substance composed of activated carbon-containing silk. These filaments are covered with a large number of micropores and mesopores. Unlike granular activated carbon, it has no macropores and is relatively uniform. When water flows through the activated carbon fibers, the pores on the fine filaments are easier to contact with the substances in the water than the pores inside the granular activated carbon with the same volume, and the adsorption speed is of course faster than that of the granular activated carbon. Since the surface area in contact with water is larger than that of granular activated carbon, and when water flows through, most of the internal pores of granular activated carbon are not in contact with impurities in the water, so under the same conditions, the same volume of activated carbon fiber can absorb substances (such as It can accumulate carcinogenic trichloroethylene (TCE) and Escherichia coli that can induce gastrointestinal diseases or organ infections in the human body under certain conditions). Of course, carbon fiber also has shortcomings: the cost is high, and no data has been found to show that activated carbon fiber has the ability to decolorize.

In the performance of intercepting large particles, activated carbon fiber filter element>activated carbon rod>granular activated carbon