By Claire Shi
The WHO’s utmost recommended protective measure against the pandemic is to wash hands frequently (World Health Organization). Yet, in many communities, people do not have access to clean water. In Sub-Saharan Africa, 63% of people in urban areas have difficulty accessing water services and cannot cleanse their hands. To combat the COVID-19 emergency, governments have put in place rapid response plans. However, most of these plans focus on immediate healthcare responses rather than improving household access to clean water.
For many countries, managing wastewater is a critical way to meet water demand. In African countries, however, only 10% of wastewater is treated. An increase in the reuse of wastewater would fortify the region’s water security, improving the country’s response to pandemics. For this proposal, I have developed a novel method of wastewater purification: integrating zeolite with Ag-doped TiO2 to coat plastic surfaces. A layer of this metal-doped photocatalyst would coat the inside of a large, clear plastic container, which would be distributed to regions that lack access to clean water during pandemics. By using this container, households would be able to sanitize their hands by reusing water used for bathing, washing clothes, etc.
Current means of wastewater treatment utilize large treatment plants that are energy-intensive, expensive, and use harsh chemicals. There is a critical need for a household-friendly, sustainable, safe, and low-cost wastewater treatment method. Titanium dioxide (TiO2), a photocatalyst, is used widely in many environmental applications due to its efficient photoactivity, high stability, low cost, and safety to the environment/humans. As a means of
destruction of chemical and microbial contaminants, TiO2 is insoluble in water and is not consumed in reactions. Therefore, coating the plastic surface of a water container with this compound would allow for the safe reuse of wastewater to sanitize hands during pandemics. Furthermore, when the right amount of energy (~400 nm) is supplied to the semi-conductor, TiO2, its electrons become mobile.
However, a disadvantage of using solely TiO2 is that it is activated by UV-light, which is not widely accessible for households. To overcome this, my proposal utilizes Ag-doped TiO2, which lowers the bandgap energy of TiO2 from 3.32 eV to 3.15 eV, allowing the photocatalyst to operate efficiently under solar illumination. The Ag would be incorporated by direct calcination of the sol-gel material. A study showed that the addition of Ag to TiO2 allowed for a more effective photocatalytic material (6-50% improvement in catalytic efficiency) and significantly increased the rate of degradation of rhodamine 6G (Seery et al.). In another study, metal-doped
TiO2 achieved a 99% degradation of methylene blue in only ten hours (Murugan et al.). Both rhodamine 6G and methylene blue are prominent water pollutants. Moreover, synthesizing Agdoped TiO2 with zeolite enables photocatalysts to maintain their inherent surface active site and,
as shown in a study, markedly improves TiO2’s efficiency at absorbing humic acid (Liu et al.). The coating of this doped photocatalyst and zeolite onto the plastic surface would be done through the sol-gel process, which incorporates titanium-isopropoxide, isopropanol, and hydrochloric acid (Tjugito).
Acting as a barrier to viruses, water is an indispensable weapon for responding to future pandemics. I firmly believe that hope during a pandemic begins with access to clean water. We can achieve this hope by reusing and treating wastewater with a plastic container coated with
zeolite and Ag-doped TiO2.
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About the author:
Claire Shi is currently a senior at the International School of Beijing. She is really interested in science and entrepreneurship, which are tied together by a common theme of problem-solving, a process that really resonates with her. She appreciates opportunities to think critically and exercise her creative mind; and so, she entered in the Crown Education Challenge!