Extract showed properties similar to aluminum sulfate in the coagulation process that precedes water filtration for consumption
Study developed at ICT-Unesp (Institute of Science and Technology of the Universidade Estadual Paulista), in São José dos Campos, shows that moringa or white acacia (Moringa oleifera) has for removing microplastics from water. The work was in the magazine ACS Omegaof the American Chemical Society.
Originally from India, moringa is well adapted to different tropical countries and is used for various purposes, such as food, by consuming its leaves and seeds with nutritional value. For some years now, the seeds have been for their potential in water treatment.
“We showed that the saline extract from the seeds has a similar performance to aluminum sulfate, used in treatment plants to coagulate water with microplastics. In more alkaline waters, it performed even better than the chemical product”says Gabrielle Batista, first author of the study, carried out as part of her master’s degree in the Postgraduate Program in Civil and Environmental Engineering at the Faculty of Engineering of Bauru at Unesp.
The work is coordinated by , professor at ICT-Unesp and the postgraduate program, who also coordinates the project “”supported by Fapesp.
“The only disadvantage found so far in relation to aluminum sulfate was the increase in dissolved organic matter, the removal of which could make the process more expensive. However, on small scales such as rural properties and small communities, the method could be used with low cost and efficiency.”, says Reis.
The focus was on water treatment via in-line filtration, in which the water is coagulated, destabilizing the particles, and goes to a sand filter. This type of treatment is recommended for water with low turbidity, which is clearer and does not require as much filtration.
Coagulation is essential because pollutants such as microplastics, which have a negative electrical charge on their surface, repel each other, just as they repel the sand contained in water treatment filters. Coagulants such as moringa saline extract, which can be made at home, and aluminum sulfate neutralize this charge, causing pollutants to unite and be filtered.
Previously, the group showed the effectiveness of moringa seeds for coagulation in a complete water treatment cycle, which also involves flocculation, sedimentation and filtration. The work’s first author was a master’s degree with Fapesp at FEB-Unesp.
Jar Test simulates, on a small scale, water treatment: experiments showed good efficiency of moringa seeds for microplastic coagulation
Experiments
To test the effectiveness of the water treatment method, the researchers used tap water, which they experimentally contaminated with polyvinyl chloride, better known by its acronym PVC.
Microplastics from this specific source were chosen because they are among the most dangerous to human health, given the documented mutagenic and carcinogenic potential of PVC, in addition to their prevalence both on the surface of bodies of water and in water treated by traditional processes.
The PVC was artificially aged using ultraviolet rays, which mimics the action of natural processes and reproduces the properties of naturally aged microplastics.
Water contaminated by microplastics went through the coagulation and filtration process in the so-called Jar Testequipment that reproduces water treatment processes on a small scale. The results were compared to those of the same tests carried out in water with aluminum sulfate, a compound used in traditional treatments.
The counting of microplastic particles, before and after treatment, was carried out using scanning electron microscopy (SEM). The size of the flakes formed by the different treatments was measured using a high-speed camera and a laser beam, without finding significant differences in particle removal.
The group is now testing the moringa seed extract using water directly collected from the Paraíba do Sul river, which supplies São José dos Campos. In experiments carried out so far, the product has proven to be quite efficient in treating natural water.
“There is increasing regulatory scrutiny and health concerns about the use of coagulants based on aluminum and iron, due to the fact that they are not biodegradable, in addition to leaving residual toxicity and presenting a risk of disease. Therefore, the search for sustainable alternatives has intensified”, concludes Reis.
With information from .
