Writer: Bonnie Chen
Anticipation of Obstacles
The main obstacle to the creation of an epoxy asphalt with significant photocatalytic effects is the limited amount of TiO2-graphene nanocomposite that can be dispersed within it without affecting the physical properties necessary for roads. Furthermore, for the widespread implementation of the technology, a greater amount of graphene might increase costs by a considerable amount, as the graphene oxide solution required costs around $440 for 400 mL from a supplier like Graphenea. For this reason, this study will create multiple epoxies in small amounts with different ratios of photocatalyst material to asphalt binder and conduct preliminary studies on NOx degradation to find any trend between the rate of pollutant degradation and photocatalyst concentration before moving on to larger studies on the effects of environmental conditions. This will help to pinpoint a ratio to optimize the cost and efficiency of the photocatalyst epoxy asphalt.
Because of limitations based on resources and convenience, there exists the obstacle of the testing and promotion of the epoxy. While TiO2 is thermally stable and safe for use on roads and buildings, as “up to a concentration of 220 μg/mL, [TiO2 nanoparticles] do not affect viability of human acute monocytic leukemia cell line THP-1 macrophages and human liver and kidney cells.”, verification of its ability to degrade NOx gases and other pollutants is required to provide sufficient reason to modify frequently used infrastructure. It would not be feasible to apply a photocatalytic epoxy or other binding materials and to conduct long-term studies on a long stretch of road or on a building in the residential sector, which is the target area of the research on the efficacy of photocatalysts, as doing so would disrupt the daily lives of many residents. Moreover, as, according to Maxwell-Boltzman’s speed distribution,vp=2RT/M, at a common temperature of 70℉ or 21.5℃, a NO2 molecule can move around 330 m/s, any change to the composition of the air around the photocatalytic site would be more difficult to measure with human interactions and the rate of diffusion in open air. Thus, a real trial of the asphalt epoxy would not allow for accurate measurements of its efficacy in catalyzing NOx reactions
The solution which grants the ability to study the rate of pollutant degradation would be to simulate a city environment, including the concentration of NOx, ozone, SO2, CO2, and CO in the air, the wear on the roads over time, and effects of the weather, like levels of sunlight, rain, or humidity in a closed testing facility. For the purpose of simulating sunlight levels as well as humidity, a greenhouse would be the best place to test the TiO2 and graphene nanocomposite epoxy. NOx, ozone, SO2, CO2, and CO levels can be simulated by bringing canisters of gas into the greenhouse, so data must first be taken over the course of the study by sampling the air in a large city (e.g. New York City) and using the data taken to adjust the particle levels in the greenhouse. Although the closed testing facility provides many advantages, it cannot account for unexpected results that may arise if the epoxy is implemented on a larger scale over the course of many years. Nevertheless, if pollutant degradation occurs at a significant rate, it would provide the rationale for a subsequent study in the intended city environment.
The final anticipated obstacle to the effective creation of a TiO2-GR epoxy asphalt is the possibility of deactivation of the catalyst in the process of pollutant degradation. In previous applications of TiO2 as a photocatalyst, the photocatalyst deactivated after a certain amount of reactions. In one instance concerning the degradation of volatile organic compounds (VOCs), this deactivation was due to the blockage of active sites by the “accumulation of sulfate on active sites.” In another study, the TiO2 deposited on glass was deactivated due to the “adsorption of nitrate ions produced from NO2 oxidation on the surface of substrates,” while the reaction rate of the NOx remained constant in the presence of a mortar substrate. It will be necessary to determine whether deactivation-resistant properties exist when TiO2-GR nanocomposite is mixed with epoxy asphalt binder in the process of testing the reaction rates. In the case that the epoxy asphalt is not deactivation-resistant, further study must be carried out to find appropriate materials that could modify the surface of the catalyst and prevent blockage.
The writer effectively organizes the obstacles into logical sections following the order of the procedure for creating the new technology. This helps the readers of the proposal to better follow the process and understand the steps taken to create the technology with more clarity, especially after the description of the team’s solution in the previous section (requirement 5). She also supports the obstacles and describes their significance using published sources like research journals. This is shown when she writes about catalyst deactivation in the last paragraph, which not only ensures the accuracy and importance of the issues raised but also shows the reader of the proposal that the author has considered difficult problems to solve and offered solutions instead of ignoring them, which is an integral part of showing the thought process and innovation behind any product.
One way she could improve her writing on the obstacles to the creation of the new technology is by being more specific in her hypothetical solutions to these obstacles, specifically in the last paragraph. The writer simply states, “further study must be carried out to find appropriate materials that could modify the surface of the catalyst and prevent blockage,” but the statement does not offer any ideas as to how this will be studied, such as which materials could be tested and the rationale behind them. While a cost estimate is not required for Envision proposals, in reality, this section would assist in a more accurate and effective cost estimate. Overall, this example component helps to convince readers of the proposal’s feasibility, but it could improve with more clarification.
Ângelo, J., Andrade, L., Madeira, L. M., & Mendes, A. (2013). An overview of photocatalysis phenomena applied to NOx abatement. Journal of Environmental Management, 129, 522–539. https://doi.org/10.1016/j.jenvman.2013.08.006
Brittain, H. G., Barbera, G., Devincentis, J., & Newman, A. W. (1992). Titanium Dioxide. Analytical Profiles of Drug Substances and Excipients, 659–691. https://doi.org/10.1016/s0099-5428(08)60404-9
Cui, G., Xin, Y., Jiang, X., Dong, M., Li, J., Wang, P., … Yan, B. (2015). Safety Profile of TiO2-Based Photocatalytic Nanofabrics for Indoor Formaldehyde Degradation. International Journal of Molecular Sciences, 16(11), 27721–27729. doi:10.3390/ijms161126055
Highly Concentrated Graphene Oxide (2.5 wt% Concentration). Graphenea. https://www.graphenea.com/collections/graphene-oxide/products/highly-concentrated-graphene-oxide-2-5-wt-concentration.
Weon, S., He, F., & Choi, W. (2019). Status and challenges in photocatalytic nanotechnology for cleaning air polluted with volatile organic compounds: visible light utilization and catalyst deactivation. Environmental Science: Nano, 6(11), 3185–3214. https://doi.org/10.1039/c9en00891h