Advantages and Disadvantages of Air Purification Methods
First of all, according to the generation principle of air purifiers, traditional purification methods mainly include physical methods, electrostatic adsorption methods and chemical purification:
Weigh the pros and cons of various air purifiers. List of shortcomings
1. Physical purification method
1. Adsorptive filtration - activated carbon
Activated carbon is a porous carbon-containing substance, which has The highly developed pore structure and porous structure of activated carbon provide it with a large surface area and can fully contact gas (impurities), thus giving activated carbon its unique adsorption performance, making it very easy to absorb and collect impurities. Just like magnetism, all molecules have an attraction to each other. Such as the popular bamboo charcoal products on the market.
Disadvantages: Ordinary activated carbon cannot adsorb all toxic gases, has low efficiency and is easy to desorb.
2. Mechanical filtration—HEPA network
HEPA (HighefficiencyparticulateairFilter), which means high-efficiency air filter in Chinese, is a filter that meets HEPA standards and has an effective efficiency of 99.999 for 0.3 microns. %, the characteristic of HEPA net is that air can pass through, but fine particles cannot. The HEPA filter is composed of a stack of sub-glass fiber membranes that are continuously folded back and forth to form a wavy gasket to place and support the filter media.
Disadvantages: The filter needs to be cleaned or updated regularly, which has certain hidden costs.
2. Electrostatic purification method
Working principle: The tungsten wire of the electrostatic precipitator continuously releases high-voltage static electricity, so that the dust and bacteria that come in with the air are positively charged and then negatively charged. Electrode plate adsorption. It can filter dust and smoke smaller than cells. Comprehensively protect the respiratory system and greatly reduce the risk of cancer.
Advantages: It is simple to use. After one or two weeks of use, the black dirty water can be washed out, reducing secondary pollution. There is no need to replace expensive consumables. And it can be sterilized by static electricity. The electrostatic tungsten wire releases 6,000 volts of high-voltage static electricity to instantly kill bacteria, viruses and pollen. Extremely effective in eliminating colds and various infectious diseases.
Disadvantages: After a power outage, the dust adsorbed on the electrodes will be released and cause secondary pollution, so the electrode plates need to be cleaned regularly.
3. Chemical Purification Method
1 Photocatalytic Method
Working Principle: When the air passes through the photocatalytic air purification device, the photocatalyst itself does not change under the irradiation of light. Substances that change but can promote chemical reactions. Harmful substances in the air, such as formaldehyde and benzene, are degraded under the action of photocatalysis, producing non-toxic and harmless substances. Bacteria in the air are also removed by ultraviolet light, and the air Thus purified.
Disadvantages: Broad spectrum but requires low air flow rate, relatively slow purification speed and a certain amount of radiation to the human body. It is a purification method that has been eliminated in Europe and the United States.
2. Formaldehyde scavenger
Working principle: It uses chemical substances and formaldehyde to carry out chemical reactions to achieve the purpose of removing formaldehyde
1. Chemical reactions: Chemically reacts with formaldehyde to produce carbon dioxide and water, such as ammonia, etc.;
2. Biological: Made of biological agents that can react with formaldehyde, such as urea, soy protein, amino acids, etc.;
3. Plant type: made of plant extracts, such as aloe vera, tea extract, etc.;
4. Sealed type: made of film-forming substances, forming a thin film to prevent the release of formaldehyde. Such as chitosan, liquid paraffin, etc.
Disadvantages: 1. The substances generated after chemical reactions are likely to cause secondary pollution. In practice, secondary detection often exceeds the standard. The second method is to absorb formaldehyde and reduce the formaldehyde content in the air without changing the chemical composition. However, this method treats the symptoms but not the root cause, and formaldehyde is easily released again.
3. Agent and catalytic method—cold catalyst essence
Working principle: Cold catalyst, also known as natural catalyst, is another new type of air purification material after photocatalyst deodorizing air purification materials Purification materials can catalyze reactions under normal temperature conditions, decomposing a variety of harmful odorous gases into harmless and odorless substances under normal temperature and pressure, changing from simple physical adsorption to chemical adsorption, decomposing while adsorbing, and removing formaldehyde and benzene. , xylene, toluene, TVOV and other harmful gases to generate water and carbon dioxide. During the catalytic reaction, the cold catalyst itself does not directly participate in the reaction. After the reaction, the cold catalyst does not change or be lost, and it plays a long-term role. The cold catalyst itself is non-toxic, non-corrosive and does not burn. The reaction products are water and carbon dioxide, which does not produce secondary pollution and greatly extends the service life of the adsorption material.
Other purification methods
1. Water washing method
Using the siphon and centrifugal principles, the purification agent mixed with water is sucked into the motor base through the siphon principle. In the straw at the bottom of the shaft centrifugal turbine, the AC shaded pole motor rotates at high speed, and then uses the centrifugal principle to spray the purifier mixed with water into the bottle to form a layer of water film, which absorbs dust and bacteria in the air into the water. Blow purified air into the room to quickly and effectively remove toxins, dust, smoke, odor, viruses, etc. indoors, and generate a large amount of fresh oxygen.
2. Negative ion method
After hydroxyl negative ions come into contact with harmful gases floating in the air, they can reduce pollutants from the atmosphere, nitrogen oxides, reactive oxygen species (oxygen) produced by cigarettes, etc. Free radicals), reduce the harm of excessive reactive oxygen species to the human body; neutralize positively charged airborne dust and then settle without charge, so that the air can be purified.
The basic method of air purification with negative ion technology
Using a certain concentration of air negative ions to purify and disinfect the air, because negative ions can easily adsorb to tiny pollution particles in the air and become charged Large ions settle on surfaces such as the ground, thereby purifying the air. Negative ions can reverse the electrical properties of the bacterial protein surface, causing the bacteria to die and achieve the purpose of disinfection and sterilization. The high-voltage electric field will produce a large number of negative ions, which will diffuse into the air with the air flow, allowing people to feel the fresh air of negative ions in the clean air. Li Changlian's research shows that under experimental conditions, the bactericidal effect of negative ions exceeds the bactericidal effect of peracetic acid with a concentration of 3/100. Jiang Yaoting and others reported that when artificial negative ions were used indoors for 2 hours, the concentrations of suspended particles, total bacteria, and formaldehyde in the indoor air were significantly reduced. This technology can effectively remove bacteria and dust in the air, but it makes the dust easily adsorbed on wallpaper and glass and cannot be removed from the room. The removal of gaseous pollutants, such as VOCs, needs further research. At the same time, the commonly used ion generators are often accompanied by the generation of ozone.
Ultraviolet sterilization type: Ultraviolet sterilization air purifiers and sterilizers also use the method of forcing indoor air to flow, so that the air passes through an isolation container equipped with ultraviolet disinfection lamps that does not directly irradiate the human body. The purpose of killing all kinds of bacteria, viruses and fungi in indoor air. Ultraviolet rays are divided into A-wave, B-wave, C-wave and vacuum ultraviolet rays. The ultraviolet rays used for disinfection and sterilization should be C-band. Its wavelength range is 200-275nm (nanometers). The band with the strongest sterilization effect is 250-275nm (nanometers). ). The irradiation dose of ultraviolet disinfection lamps used to kill bacteria, viruses and fungi should reach more than 20000 μW.s/cm2.
Disadvantages: It takes a certain period of time for ultraviolet irradiation to have obvious sterilization effect, and the effect of short-term irradiation with flowing air is limited.
Comprehensive:
Integrated air purifiers, as the name suggests, combine individual air purification methods to achieve the purpose of purifying a variety of indoor air pollutants. Common comprehensive air purifiers include: (1) electrostatic dust collection + ordinary filter type; (2) electrostatic dust collection + electronic dust collection type; (3) negative ion + electronic dust collection + ordinary filter type; (4) negative ion +HEPA filter element; (5) Ordinary filter element + HEPA filter element + activated carbon; (6) Ordinary filter element + HEPA filter element + activated carbon + UV sterilization, etc.
Disadvantages: Comprehensive air purifier is the method used by most brands on the market. However, due to different HEPA filter materials, filtration levels, and negative ion technology, the actual purification effects of air purifiers of various brands are also different.