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Chinese scientists develop new filters to reduce air pollution


02-15-2017 08:41 BJT

A group of Chinese scientists have developed new air filters using special materials. Their breakthrough was recently picked up on by international scientific journal 'Nature', sparking a great deal of attention. The team has been working on this project for more than five years. Let's find out how their technology might potentially revolutionize air purifiers that are already a fixture in many Chinese homes.

The secret is all in these crystals called metal-organic frameworks, or MOFs.

Developed by American scientists in 1992, MOFs contain hard substances usually found in metal, ceramics and glass. They also incorporate malleable substances often found in plastic and rubber.

This compound is able to form a three-dimensional framework that can capture large amounts of tiny substances.

Microscopic images show that air pollutants like PM 2.5 particles can easily be trapped by MOF crystals.

Professor Wang Bo and his colleagues at the Beijing Institute of Technology have applied MOFs onto different fabrics to make air filters.

"I think our biggest breakthrough is that we have developed special MOFs that can selectively capture toxic air, liquids and solids and detoxify them. What's more, we have made MOFs into thin films that can stick to various types of surfaces. So, a very small amount of MOFs can play a big role in purifying the air," Professor Wang said.

In one experiment that simulates a closed room, a researcher placed an MOF filter in a simple air pump. This small equipment reduced the amount of hazardous air by almost 100 percent within just a few minutes.

In another experiment, the researcher placed a MOF filter in a glass box to mimic a fresh air unit. When hazardous air comes in, the filter also cleaned the smog effectively.

But just how many MOF crystals are needed to produce a single piece of filter?

Let's take one gram of metal organic frameworks, or MOF crystals, as an example. If we cut their pores and unfold their inner surface, their collective area is as large as this --- a standard soccer field. Their extensive pores are like an extremely dense and powerful net that captures toxicants in the air.

This makes it cheap to produce MOF filters. Wang says that most commercial air purifiers either have difficulties in letting enough air through while simultaneously catching toxicants, or their filters need to be frequently replaced. MOF filters, however, only need to be replaced once or twice a year.

"I think cost efficiency is always the fundamental question to be solved. Regardless of whether it is for industrial or domestic use, a technology has to be affordable. A second question is sustainability, which is also linked with cost. Only once these two questions are solved can a technology be widely used," Professor Wang said.

Wang says his lab has been working with various companies for more than two years, looking for ways to both protect individuals and reduce toxicants from factories and vehicles. But he declines to comment on the cost of MOF crystals.

Consumers can expect to find purifiers using MOF filters on general sale in just a few months' time.

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