Grantee Research Project Results
Final Report: A New Photo-catalyst Based Air Treatment System to Reduce the Risks from Transmission of Viruses and Bacteria
EPA Contract Number: 68HERC22C0015Title: A New Photo-catalyst Based Air Treatment System to Reduce the Risks from Transmission of Viruses and Bacteria
Investigators: Alptekin, Gokhan
Small Business: TDA Research Inc.
EPA Contact: Richards, April
Phase: I
Project Period: December 1, 2021 through May 31, 2022
Project Amount: $100,000
RFA: Small Business Innovation Research (SBIR) Phase I (2022) RFA Text | Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Homeland Security
Description:
Treating air in the common, high-traffic areas to eliminate biological contaminants (e.g., virus, bacteria, fungus) could reduce the transmission of airborne diseases. UV germicidal irradiation has been shown to inactivate all types of microorganisms including drug-sensitive and multi-drug-resistant bacteria and different viral strains. TDA Research has developed a high-performance air treatment system that will destroy biological contaminants via a photocatalytic process. The system uses an approach that has been previously proven successful in the photo-oxidation of organic molecules in water for treating biological matter in air. In our system, the photocatalyst is coated onto optical fibers which will be bundled and attached to low-cost, low-power UV LEDs. Careful design of the external catalyst coating allows the light to be transported through frustrated total internal reflection along the optical fibers without significant loss, while enabling penetration of light into the thin catalyst layer (the frustrated aspect of the total internal reflection) from inside the fiber optic material-activating the catalytic sites and promoting photo-oxidation on the surface of the catalyzed fibers. The UV light will interact with the photocatalyst to generate reactive oxygen species (ROS) including hydroxyl radicals (•OH) and superoxide anions (O2-•) which inactivate virus and bacteria. Our UV photocatalyst system will efficiently reduce the risks of virus or bacteria exposure in high risk enclosed or semi-enclosed environments, including concert halls, gyms, classrooms, bars, etc.
Summary/Accomplishments (Outputs/Outcomes):
In the Phase I project, we prepared 4 novel photocatalyst powders using TDA's proprietary coprecipitation method and 2 commercial TiO2 catalysts to provide a baseline comparison. 2 of TDA's proprietary photocatalysts demonstrated enhanced photocatalytic kill over commercial off-the-shelf UV TiO2 photocatalysts. TDA's proprietary photocatalyst was coated onto 4 different types of fiber optics. We excited these using 4 UV LEDS of differing wavelengths (280nm, 300nm, 340nm, and 395nm). To achieve the desired coating of the catalyst onto the optical fibers, we have developed a method for stripping and etching polymer and silica-based cladding used on the commercial fibers and solarization-resistant fiber optic materials. This technique consisted of using laser etching of the fibers that generated holes in the cladding on which the photocatalyst is deposited. These slits in the fiber generated the UV light to escape in controlled amounts in close contact with the photocatalyst which allowed the UV excitation.
The log kill reduction of E. coli was measured for fiber optic variables including different methods for surface damage/etching, fiber length and fiber type. These bench-scale experiments using single and/or multiple coated fibers showed that the approach provides the desired effect increasing the kill rate of E. Coli in water, as well as in the experiments where the E. Coli laden water was aerosolized using a nebulizer and passed over a photocatalyst loaded filter assembly. TDA coated a fiber optic fabric with photocatalyst and demonstrated a 1.98 log kill reduction in an aerosolized E. coli test. A solarization-resistant, laser etched fiber optic coated with TDA's photocatalyst showed no reduction in performance after 500 hours of operation, indicating long-life and stable operation of the new photocatalytic filter. In addition, a methylene blue dye test was developed to increase sample testing rate (due to the slow rate of bacteria tests).
A low cost, HVAC filter was designed using multiple layers of the photocatalyst coated fiber optic fabric.
Conclusions:
Throughout the Phase I work, TDA has made a number of advances to our proprietary UV photocatalyst for the destruction of pathogens. These advances include: 1) the identification of a proprietary UV photocatalyst that demonstrates enhanced photocatalytic kill over commercial/off-the-shelf UV photocatalysts such as rutile and/or anatase TiO2, 2) an improved mechanism for coating the material onto fiber optic cables, 3) improvements in the preparation and pre-treatment of optical fibers (prior to depositing the photocatalyst) for improved uniformity of the UV delivered to the photocatalyst, and 4) preliminary work to optimize the wavelength range for the activation of the photocatalyst material.
Beyond Phase I, TDA recommends to continue with the development of the new technology including the modification of the design of the photocatalyzed fabric by examining the impact of changing the diameter of the optical fiber (impacts leakage and surface area), the spacing of the optical fibers (impacts the gas permeability of the fabric), and the spacing and weight of the polyester cross weave material (also impacts gas permeability). Pending the impact of lifetime testing, it is also recommended to explore alternative optical fiber and/or cross-weave material if UV-induced degradation is observed. A potential Phase II work will determine the impact of gas permeability (which will also be measured) on the single-pass kill efficacy for a fabric sample. In the Phase II, it is also recommended to test the impact of stacking multiple fabric sections in series in order to determine the multi-pass kill efficacy and how it relates to changes in the overall system permeability and how the multi-pass efficacy compares to the single pass efficacy. These results will be combined with power draw estimates (based on the measured gas permeability) to develop an optimized fabric stack that can be incorporated directly into a commercial HVAC system without modifying the HVAC blowers (i.e., without a significant pressure drop).
TDA's prototype design focuses on creating a 3-dimensional module that can integrate into existing HVAC (Heating, Ventilation, and Air Conditioning) systems. Because a wide variety of indoor spaces already utilize HVAC systems for controlling indoor air and ventilation, this is a natural place to integrate an advanced air cleaning system that can target biological pathogens and other pollutants that negatively impact indoor air quality. TDA has experience in moving SBIR-funded research into commercial products. We have a strong commercial team for technology scale-up, hardware development and commercialization of the UV photocatalyst system with the help of our industrial partners. We are capable of ton-level scale up of the photocatalyst production and have a commercial partner that we've worked with in the past to produce the new catalyst in large volumes if the demand increases due to widespread use of the new technology. In Phase II, we will continue to work with the fiber optic fabric supplier to optimize the fabric for use as a UV photocatalytic filter.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.