A study conducted at the Institute of Science and Technology of São Paulo State University (ICT-UNESP) in São José dos Campos, Brazil, shows that Moringa oleifera, also known as moringa or white acacia, has the potential to remove microplastics from water.
The study was published in the journal ACS Omega, published by the American Chemical Society.
Moringa is native to India and well-adapted to various tropical countries. It is used for a variety of purposes, such as food, through the consumption of its leaves and seeds, which are nutritious. For several years, researchers have studied the potential of the seeds in water treatment.
"We showed that the saline extract from the seeds performs similarly to aluminum sulfate, which is used in treatment plants to coagulate water containing microplastics. In more alkaline waters, it performed even better than the chemical product," says Gabrielle Batista, the first author of the study. She conducted the research as part of her master's degree in the Post-Graduate Program in Civil and Environmental Engineering (PPGECA) at the Bauru School of Engineering (FEB) at UNESP.
Adriano Gonçalves dos Reis , a professor at ICT-UNESP and in the PPGECA at FEB-UNESP, coordinated the research and also leads the project "Direct and In-Line Filtration for the Removal of Microplastics from Drinking Water" , which is supported by FAPESP.
"The only drawback found so far regarding aluminum sulfate was the increase in dissolved organic matter, the removal of which could make the process more expensive. However, on a small scale, such as on rural properties and in small communities, the method could be used cost-effectively and efficiently," says Reis.
The study focused on water treatment via in-line filtration. In this process, the water is coagulated, which destabilizes the particles, and then it passes through a sand filter. This treatment method is suitable for water with low turbidity, meaning it is clearer and does not require as many preliminary processes.
Coagulation is essential because pollutants, such as microplastics, have a negative electrical charge on their surface and repel each other and the sand in water treatment filters. Coagulants, such as moringa salt extract (which can be made at home) and aluminum sulfate, neutralize this charge. This causes the pollutants to clump together so they can be filtered out.
In a previous study , the group demonstrated the effectiveness of moringa seeds for coagulation in a complete water treatment cycle, which also involves flocculation, sedimentation, and filtration. Luiz Gustavo Rodrigues Godoy , the first author of the study, completed his master's degree with a scholarship from FAPESP at FEB-UNESP.
Experiments
To test the effectiveness of the water treatment method, the researchers used tap water that they contaminated with polyvinyl chloride (PVC).
Microplastics from this source were chosen because PVC is one of the most dangerous plastics for human health due to its documented mutagenic and carcinogenic potential. PVC is also prevalent on the surfaces of water bodies and in water treated by traditional processes.
They artificially aged the PVC using ultraviolet radiation to mimic natural processes and reproduce the properties of naturally aged microplastics.
The microplastic-contaminated water underwent coagulation and filtration in a Jar Test, a device that replicates water treatment processes on a small scale. The results were then compared to those of the same tests performed on water treated with aluminum sulfate, a compound used in traditional treatments.
Scanning electron microscopy (SEM) was used to count the microplastic particles before and after treatment. The size of the flocs formed by the different treatments was measured using a high-speed camera and a laser beam; no significant differences in particle removal were found.
The group is now testing moringa seed extract using water collected directly from the Paraíba do Sul River, which supplies São José dos Campos. In the experiments conducted thus far, the product has proven quite effective in treating natural water.
"There's increasing regulatory scrutiny and health concerns regarding the use of aluminum- and iron-based coagulants, as they aren't biodegradable, leave residual toxicity, and pose a risk of disease. For that reason, the search for sustainable alternatives has intensified," Reis concludes.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
