Introduction
Water is the source of life. Drinking water safety is related to the physical health of residents. Many nutrition experts recommend drinking plain water, believing that it is the healthiest drinking water. However, the boiled tap water scale may also contain harmful substances such as heavy metals and bacterial corpses mixed in. How can I drink safe and healthy boiled water? A new technological achievement from the Institute of Nuclear Energy and New Energy Technology at Tsinghua University, the nuclear pore membrane water filtration technology, has brought hope for solving this problem.
So, what is nuclear pore membrane technology? How does it purify water quality?
Scale is a deposit of heavy metals, calcium salts, dust, bacteria, insect eggs, and corpses mixed in water, which should be removed as much as possible.
With people's increasing emphasis on quality of life, the purity and beneficial mineral content of drinking water have become higher pursuits, and water purification equipment has become a new favorite of household appliances. However, cleanliness does not equate to health. Expensive water purifiers and frequent filter replacement undoubtedly increase the cost of drinking water, but may not necessarily result in healthy drinking water.
Many nutrition experts recommend drinking plain water, and the tap water used by residents has passed the national third level inspection. After daily and hourly sampling testing, it is safe water that meets the national drinking water standards. In addition, after boiling, the water is clean and sterile. After boiling, the water quality and hardness are improved, and an appropriate amount of minerals are preserved.
Wang Yulan, Senior Engineer at the Institute of Nuclear Energy and New Energy Technology, Tsinghua University
According to research, when fresh boiled water is cooled to 20 ℃~25 ℃, its chemical structure changes and becomes small molecule water, which can easily enter the cell through the cell membrane. In addition, after boiling water, some organic pollutants, such as chlorine gas, are easily evaporated. After boiling water, it can also improve the hardness of water that is too high. Experiments have shown that hardness can be reduced from over 300 to over 200.
However, experts have analyzed that the transportation of tap water through pipelines and the pressurization of secondary water tanks can indeed pose a risk of secondary pollution and affect water quality. Although plain water sterilizes and disinfects water at high temperatures, it also increases a large amount of scale. The visible scale is mainly composed of calcium, magnesium, etc., which are not very harmful to the human body. People need to be wary of the invisible dirt that is mixed in with the scale.
Wang Yulan, Senior Engineer at the Institute of Nuclear Energy and New Energy Technology, Tsinghua University
Scale is a sediment composed of heavy metals, calcium salts, dust, bacteria, insect eggs, and corpses mixed in water. They once conducted an experiment using a nuclear pore membrane to filter 30 liters of boiling water, in which the arsenic content in the scale reached 10.8 micrograms and the cadmium content was 31.2 micrograms; The lead content is very high, reaching 270 micrograms.
If the scale in the water is not filtered, drinking water for half a month will result in the accumulation of heavy metals in the body. They hired the Beijing Physical and Chemical Analysis Center for testing, and several experiments have detected heavy metals.
One of the biggest benefits of boiling water is to kill any bacteria that may exist in the water. So, is there still a risk of bacteria in boiling water?
Wang Yulan, Senior Engineer at the Institute of Nuclear Energy and New Energy Technology, Tsinghua University
The bacteria in water mainly include Salmonella, Shigella dysentery, Escherichia coli, Vibrio cholerae, anthrax type B, and chlorine resistant Legionella. Although bacteria are inactivated during the process of boiling water, they release bacterial endotoxins during the process of death. Once these endotoxins enter the human body, they can cause certain harm.
Bacterial endotoxins are cell wall products of Gram negative bacteria. Bacteria do not release during their living state, and only exhibit toxicity when they die and self dissolve or adhere to other cells, mainly manifested as thermogenic, lethal toxicity, leukopenia, hypotension, activation of the coagulation system, induction of tolerance to endotoxins, induction of specific resistance to infections, and tumor cell necrosis. So bacterial endotoxins are definitely harmful to human health and should be removed.
The standards for healthy drinking water provided by the World Health Organization include the absence of any toxic or harmful substances to the human body, such as heavy metals, impurities, bacteria (pathogenic bacteria), radioactive substances, and fluorescent substances, which should be controlled within the range of national standards.
The selective filtration of nuclear pore membranes can effectively remove toxic and harmful substances, while retaining trace elements beneficial to the human body in open water.
Many people nowadays are troubled by the problem of water purifiers containing scale and even harmful substances. Installing a water purifier can even purify beneficial elements from the water. Why is it so difficult to drink clean and healthy water.
With the increasing emphasis on healthy drinking water, relevant institutions have also increased their investment in technical research to solve this problem, among which water purifiers have become a highly respected method of drinking water purification by the public. However, although water purifiers have to some extent solved the problem of drinking water safety, some purification methods are too extreme. While removing toxic and harmful substances, beneficial trace elements in the water are also filtered out.
Wang Ziqin, Chief Physician of Henan Armed Police Corps Hospital
Purified water is not suitable for long-term consumption because it lacks many essential minerals and trace elements for the human body, especially for pregnant women, the elderly, and children who have a high demand for trace elements. Long term consumption of purified water can be harmful to health.
A recent research achievement has brought hope for solving the problem of healthy drinking water. The research and development team led by Wang Yulan has improved traditional nuclear pore membrane technology and developed a new nuclear pore membrane filter cartridge that can be directly used for boiling water filtration.
According to Wang Yulan, multiple experiments have shown that using a certain parameter nuclear pore membrane to filter boiled water significantly reduces the total hardness, fluoride, and total organic carbon (TOC) indicators of the filtered water; The filter cake trapped on the membrane surface contains heavy metals that are significantly harmful to human health, such as aluminum, lead, barium, manganese, mercury, cadmium, chromium, etc., which have been detected several times; After filtration, the water still contains trace elements that are beneficial to the human body, and the proportion has not changed significantly.
The experimental data of nuclear pore membrane filtration shows that after filtering 30 liters of boiled underground drinking water in a certain area of Beijing, the filter element obtained 3.0 grams of scale. Water scale contains 0.27 milligrams of lead, 0.7 micrograms of silver, 10.8 micrograms of arsenic, 31.2 micrograms of cadmium, 0.12 milligrams of nickel, 40.8 micrograms of manganese, and elements such as chromium and aluminum that are harmful to human health. The filtered water not only removes harmful heavy metal elements, but also shows no significant change in the proportion of beneficial trace elements for the human body compared to before filtration, achieving maximum retention and making it very suitable for drinking.
Wang Yulan said that nuclear pore membrane technology will bring new opportunities to the water purification industry with a new way of water purification. According to the needs of the human body, boiling tap water can be directly "selectively filtered" without the need for other expensive water purification equipment, making drinking water not only clean but also healthier, and more affordable for the public to use.
It is reported that this technology has already collaborated with domestic enterprises to develop various forms of portable water purification cups, allowing the public to drink clean and healthy water anytime and anywhere.
The following is the dialogue between China Environment News and expert Wang Yulan:
Why can nuclear pore membranes filter harmful substances?
The development and research of nuclear pore membranes were first developed with the aim of membrane separation applications. Due to the uniform pore size of the nuclear pore membrane and the fact that the membrane itself is a dielectric film, there is no contamination of the filtrate by the membrane itself, making it an ideal tool for precision filtration and particle sieving.
What are the characteristics of nuclear pore membrane?
The nuclear pore membrane microfiltration material is different from other mesh structure filtration materials in that it has a very dense and uniform distribution of micropores. In addition, it has the advantages of high pore density, good chemical stability, mild mechanical strength, as well as acid resistance, weak alkali resistance, and good thermal stability. It also has various pore structures in cylindrical, single cone, or double cone shapes. This unique and unique pore structure cannot be compared with other filter materials and can be used for precision filtration according to different technical requirements. Therefore, it has a wide range of applications and can intercept particles larger than the pore size 100%, making it the most ideal material for precision filtration.
What are the main applications of this film?
The application fields include chemical separation, isotope separation, radiation metrology, biotechnology, medicine, mass spectrometry technology, insulation technology, purification technology, vacuum technology, electronics industry, pharmaceutical industry, food industry, materials science, etc. We have conducted experiments on vegetable preservation and found that the preservation effect is similar to that of a refrigerator, with some indicators even better than a refrigerator.
Is this high-tech suitable for civilian use?
We have conducted some experiments to demonstrate that nuclear pore membranes have high water filtration flux, high retention efficiency, strong pollutant carrying capacity, and a very simple filter structure. In addition, this membrane is easy to regenerate. With a gentle rinse of water on the surface of the membrane, all dirt is washed away. Therefore, nuclear pore membranes can be fully used for civilian products and can be made into very small filters to cover different purposes.
Is there a similar technology abroad now?
At present, this is the only precision filtration material that can be used for boiling water filtration. This technology does not use conventional nuclear pore membrane technology. It can be proudly said that only China can make nuclear pore membranes that can be used on very simple water filters and have achieved industrialization. There is no such technology abroad.
Besides being used for water filtration, are there any other applications of nuclear porous membranes in people's livelihoods?
We have made a type of screen window using nuclear pore membrane and placed it on the window for haze protection. There is also a breakthrough in technology, which is the special treatment of the membrane surface and pore wall, making it have the function of efficiently capturing and blocking PM2.5, that is, blocking outdoor PM2.5.
How to effectively block PM2.5?
The most critical material for this type of window screen is nuclear pore membrane, which has a large number of micro pores on a thin layer of plastic film. These micropores have a high distribution density, with hundreds of thousands of micropores per square centimeter, which is the size of a fingernail cover. Moreover, these micropores are all through holes that penetrate the membrane material.
Some special chemical properties of the pore wall result in static electricity on the pore wall and membrane surface. When PM2.5 is suspended in the air and passes through the membrane material, it will be adsorbed on the pore wall under static electricity.
In addition, the membrane has a large number of micropores, which are very thin, only 10 microns, making it highly breathable and capable of efficient indoor and outdoor gas exchange. Harmful gases such as formaldehyde and carbon dioxide, due to their high indoor concentration, can also pass through small holes to create a fresh indoor air environment.
