Volatile organic compounds (VOCs) in everyday items like paints, adhesives, furniture, cosmetics, and deodorants offer convenience. However, prolonged exposure can lead to severe health issues like respiratory problems, headaches, dermatitis, and cancer.
Adsorption mechanism and adsorption performance graph of iron oxide graphene adsorbent for polar VOCs. Image Credit: Korea Institute of Science and Technology.
While natural ventilation remains the most efficient means to decrease indoor VOC levels, air purifiers have gained popularity to sustain indoor air quality, particularly under challenging outdoor conditions, such as elevated fine dust concentrations, heat waves, and extreme cold.
Typically, air purifiers employ activated carbon for VOC removal via adsorption, thanks to its non-polar carbon surface and substantial surface area. Although effective against non-polar substances like toluene and benzene, it falls short in removing polar substances like ketones and aldehydes.
The Korea Institute of Science and Technology (KIST, President Seok Jin Yoon) has revealed that Dr Jiwon Lee and Dr Youngtak Oh from the Center for Sustainable Environment Research have created an innovative adsorbent technology capable of effectively capturing amphiphilic VOCs. These compounds possess hydrophilic and hydrophobic characteristics, making them challenging to eliminate using traditional activated carbon methods.
The KIST research team achieved the synthesis of a graphene-iron oxide heterostructure through precise control of surface oxidation in graphite and iron. This led to a significantly enhanced adsorption capacity for amphiphilic VOCs, attributed to the increased presence of oxygen functional groups and iron oxide on the surface.
This novel adsorbent demonstrated an impressive adsorption efficiency, up to 15 times superior to that of conventional activated carbon adsorbents when it came to capturing amphiphilic VOCs.
Furthermore, the study revealed that precise control over oxygen functional groups and iron oxides in the adsorbent provides the flexibility to optimize the surface properties for specific pollutant characteristics.
In experiments involving four challenging ketones that are typically hard to manage with activated carbon adsorbents, the researchers identified a correlation between the length of carbon chains and the adsorption efficiency. By carefully adjusting the oxygen functional group and iron oxide content in the adsorbent, they maximized the removal efficiency for these ketones.
The research team also investigated sub-nanometer electron transfer phenomena occurring between the adsorbent and VOC molecules, establishing a novel connection between the geometric shape of pollutants and their adsorption behavior for the first time. This breakthrough is anticipated to pave the way for developing tailored detection and control technologies for various air pollutants in our environment.
Unlike previous studies that focused on mere improvement of the adsorption performance and regeneration efficiency of adsorbents, we succeeded in developing a breakthrough material that exceeds the limits of existing adsorbents using accessible materials such as graphite and iron, which have high commercialization potential.
Dr. Jiwon Lee, Center for Sustainable Environment Research, Korea Institute of Science and Technology
Journal Reference:
Lee, S., et al. (2023). Effect of adsorbate geometry and hydrogen bonding on the enhanced adsorption of VOCs by an interfacial Fe3O4–rGO heterostructure. Chemical Engineering Journal. doi.org/10.1016/j.cej.2023.145346.