New soy-based air filter can capture toxic chemicals

Scientists have developed a natural, biodegradable and inexpensive soy-based air filter that can capture toxic chemicals, such as carbon monoxide and formaldehyde, which current air filters can not.
The research could lead to better air purifiers, particularly in regions of the world that suffer from very poor air quality, researchers said.
The engineers at Washington State University (WSU) in the US designed and tested the materials for the bio-based filter.
Working with researchers from the University of Science and Technology in China, the WSU team used a pure soy protein along with bacterial cellulose for an all-natural, biodegradable, inexpensive air filter.

Poor air quality causes health problems worldwide and is a factor in diseases such as asthma, heart disease and lung cancer.
Commercial air purifiers aim for removing the small particles that are present in soot, smoke or car exhaust because these damaging particles are inhaled directly into the lungs.

With many sources of pollution in some parts of the world, however, air pollution also can contain a mix of hazardous gaseous molecules, such as carbon monoxide, formaldehyde, sulphur dioxide and other volatile organic compounds.
Typical air filters, which are usually made of micron-sized fibres of synthetic plastics, physically filter the small particles but are not able to chemically capture gaseous molecules.

They are most often made of glass and petroleum products, which leads to secondary pollution, Zhong said.
The team developed a new kind of air filtering material that uses natural, purified soy protein and bacterial cellulose - an organic compound produced by bacteria.
The soy protein and cellulose are cost effective and already used in numerous applications, such as adhesives, plastic products, tissue regeneration materials and wound dressings.
Soy contains a large number of functional chemical groups - it includes 18 types of amino groups. Each of the chemical groups has the potential to capture passing pollution at the molecular level.

The researchers used an acrylic acid treatment to disentangle the very rigid soy protein, so that the chemical groups can be more exposed to the pollutants.
The resulting filter was able to remove nearly all of the small particles as well as chemical pollutants, said Zhong.
Especially in very polluted environments, people might be breathing an unknown mix of pollutants that could prove challenging to purify.
However, with its large number of functional groups, the soy protein is able to attract a wide variety of polluting molecules.
"We can take advantage from those chemical groups to grab the toxins in the air," Zhong said.

The research was published in the journal Composites Science and Technology.