In the prevention and control of the pneumonia epidemic caused by the new coronavirus infection, masks are the last “line of defense” for many citizens. Without masks, they cannot go out, pick up their children, or go to work. Although the domestic epidemic has been well controlled, we still need to pay attention to protection. After all, foreign epidemics are still spreading wildly.
Flying masks have become as necessary as mobile phones and keys. However, how should hundreds of millions of discarded masks be properly disposed of? How to reduce their pollution to the environment?
As people become accustomed to wearing masks, some environmentalists have raised various concerns: the plastic materials contained in disposable masks will pollute water sources; discarded masks will entangle wild animals and ingest disposable masks by mistake. The lives of wild animals wearing masks are also in danger. Some environmental groups have discovered that thousands of disposable masks are already being discarded outdoors, causing damage to towns and villages.
A British photographer captured a peregrine falcon “hunting” for a mask in the wild (source: bbc)
So, where will the disposable masks that protect people’s lives go after they are discarded? Will they cause new pollution problems? How should discarded disposable masks be disposed of scientifically? How can we balance public health and sustainable development?
How dirty are discarded masks?
First of all, let’s take a look at the velvet surface of the used mask under a microscope. There are obviously yellow particles attached to it. When magnified to 2000 times, you can see the moving bacteria.
Therefore, used masks must be disposed of promptly and correctly! Masks worn by the general population have no risk of virus transmission and can be disposed of according to the requirements for domestic waste classification. Masks discarded by patients, suspected patients and caregivers need to be collected and processed separately as medical waste.
How to deal with discarded masks?
my country is the world’s largest mask producer and exporter, accounting for about 50% of the world’s annual mask output. In 2018, China’s mask output was approximately 4.54 billion pieces, and in 2019, it exceeded 5 billion pieces. Affected by the epidemic, the total output of masks in 2020 is expected to double compared with 2019.
After the outbreak, relevant companies quickly tackled the production of special materials and built melt-blown cloth production lines (Source: Sinopec)
How many discarded masks were produced during the epidemic? Wang Dujin made a simple calculation for reporters: assuming that each person discards one mask (weighing about 5 grams) per day, 3,500 to 4,000 tons of discarded masks will be produced in China every day.
Disposable medical masks are mainly composed of waterproof layer (spunbond non-woven fabric), filter layer (melt-blown non-woven fabric), ear straps, nose bridge and other components. Among them, the waterproof layer and filter layer are made of polypropylene non-woven microfiber as the core material, which is the main material of disposable medical masks (accounting for more than 90%); the ear straps are commonly made of PET plastic and polyurethane (PU). Material; nose bridge strips are commonly made of polypropylene/galvanized iron wire, polyethylene/galvanized iron wire or aluminum strips.
Common mask filter layers are prepared using a melt-blown process. The diameter of the polypropylene microfibers is about 2 microns. When droplets containing bacteria or viruses are close to the microfibers, they will be absorbed by the surface of the microfibers. The electrostatic charge is firmly absorbed, thereby achieving the purpose of blocking bacteria or viruses. However, the adsorbed pathogens are not killed, which brings special inconvenience to the recycling of discarded masks.
So, what harm will happen if discarded disposable masks are not handled properly?
Liu Yijie told reporters that masks are easy to migrate with the wind. If they are randomly discarded in the environment, on the one hand, it will affect the landscape environment and increase the spread of bacterial viruses; on the other hand, after the masks enter the soil or water, they will Breakage occurs in conditions such as sunlight, heavy rain or strong wind, resulting in long-term microplastic pollution.
Environmentalists discovered a large number of discarded masks washed up on the beach (Source: oceansasia)
However, although plastic (polymer) Propylene) is the main component material of disposable masks, but masks are not the main use direction of plastic materials. Therefore, a large number of discarded disposable masks will not cause a significant increase in plastic waste.
Wang Dujin introduced that the current treatment of discarded disposable masks mainly uses centralized incineration. The advantage of this method is that it can solve the problem of disposal of discarded masks and other garbage at once, and can use the collected heat to generate electricity. The disadvantage is that it will produce some toxic by-products, which will pollute the environment to a certain extent.
In addition to incineration, possible disposal options for disposable masks include landfill degradation, mechanical processing and chemical recycling. Wang Dujin said that from the perspective of circular economy, these current methods are not ideal and cannot make full use of the treatment process to achieve added value, nor can they bring more energy and economic benefits.
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Optimize the material selection and design of masks
In view of the environmental challenges caused by discarded masks, in addition to efforts in classified collection and processing, value-added technologies should also be developed to strive to “turn waste into treasure” ” and sustainable development.
Wang Dujin said that it is usually difficult to achieve closed-loop and recycling of discarded masks because existing technology cannot selectively and efficiently decompose polymers into their original monomers. Therefore, if future disposable medical masks are designed into integrated materials, the recycling and recycling problems of discarded masks can be alleviated from the perspective of basic materials.
Common disposable masks are mainly made of non-woven fabrics made of polypropylene
He suggested that when selecting materials and The types of materials should be reduced during design, and polypropylene materials should be used as much as possible, other polymer materials should be used less, and metal should be avoided to achieve a single type of materials and diversified functions, and to provide maximum convenience for subsequent value-added recycling.
Masks made of a single material are simpler and more convenient in the value-added utilization process. They can be processed directly after recycling to achieve low-value utilization (melting processing to make daily necessities such as trash cans or flower pots), chemical transformation (pyrolysis into Monomers or small molecule compounds) and upcycling (melting processing to achieve functionalization and high performance).
In addition, Wang Dujin suggested that on the basis of integrating mask materials, new polymer functional materials should be developed as soon as possible so that in addition to blocking bacteria and viruses, masks can also kill bacteria and viruses and extend their use time. Function.
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