By : Franyi Sarmiento, Ph.D., Inspenet, May 13, 2022
Researchers from the Faculty of Higher Studies (FES) Cuautitlán of the National Autonomous University of Mexico, led by Yolanda Marina Vargas Rodríguez, manage to adsorb contaminants from water through the development of halloysite nanotubes, a clay mineral, and magnetite, another mineral that generates magnetism.
Contaminants include: bacteria, radioactive substances, viruses, parasites, fertilizers, pesticides, drugs, nitrates, phosphates, plastics, and fecal waste. Sometimes it is difficult to detect them because these elements do not always stain the liquid.
Vargas Rodríguez, head of Laboratory 11 “Nanomaterials and Catalysis”, of the Multidisciplinary Research Unit (UIM), of that academic entity, has the responsibility of contributing to reducing the pollution of bodies of water.
More than eight years ago, the development of various strategies began. At first, he used halloysite nanotubes (NTHs) to attract and retain harmful substances from the waste, which carry out this process naturally.
This project arose with the idea of being applied in the textile industry, as a filter to clean large amounts of liquid. “It is placed directly in the cistern and then retrieved below it,” he explained. Due to its characteristics, this technology can also benefit the pharmacochemical industries and hospitals, since it is already ready for immediate use.
With the aim of exploiting the benefits of this mineral, the researcher recently oriented this development towards the recovery of oil from the sea: spills from platforms, ships or from an accident, among others. After extensive research, he discovered that the most suitable for this is to use magnetic materials, with the idea of making more benign components, such as magnetite that does not pollute. In this way, he decided to add it to the halloysite nanotubes, because it is added to the oil slick and recovers it.
Vargas Rodríguez explained that there are three options to rescue hydrocarbons: use surfactants (a detergent that dissolves, but bubbles remain in the sea); burn it (it would cause greater environmental pollution due to CO 2 particles, sulfur, etc.); and, the most viable, magnetic recovery.
For this purpose, he devised a support for the magnetite, since he did not want to mix it with the halloysite nanotubes because both adsorb; however, extracting it from the nanotubes would remain in the water, contaminating it. For this reason, he created a nanocomposite (material with unique properties) and evaluated it with the different types of oil in the country.
He added it as a powder, formed a ferrofluid, and then applied the magnetic field. The result was that with the most viscous hydrocarbons (the most difficult to recover) it worked better, “it allows the stain to be collected, the oil spreads a lot, it collects it and we can move it to where we are going to recover it,” explained the academic .
Initially, he evaluated magnetite with carbon nanotubes, but its synthesis turned out to be complex and expensive; In contrast, costs were reduced with halloysite, since both are natural. Magnetite is a superparamagnetic material, which means that once the magnet is removed it is no longer magnetic and, thanks to this characteristic, the fuel can be recovered.
It should be noted that when it is recovered it can be reused, since little magnetic material is used and, although some residues remain, they remain in the asphaltenes (organic chemical compounds of crude hydrocarbon); which generates changes. Therefore, it is feasible to process or distill it.
This line of research was developed to benefit the environment and provide a solution to some of the problems that arise with maritime fuel spills. Currently, it is common to add surfactants, which remain and have an impact on the food chain, since the fish ingest it and then it reaches human consumption.
Also, it harms or kills the life of animals that dive or come to the surface, because it adheres to them and obstructs their respiratory tract. In addition, it can also cause irreversible damage to flora and fauna.
Due to the important scope of this project, the academic worked for four years to obtain the patent, which she achieved in 2021 and was registered under the name “Magnetic nanocomposite, its synthesis process and oil recovery process or body oils of water using said nanocomposite”.
Also collaborating in this research are: Adolfo Obaya Valdivia and Guadalupe Iveth Vargas Rodríguez, academics from FES Cuautitlán; José Álvaro Chávez Carvayar, from the Materials Research Institute; and they also have the support of the Physics Institute of the National University.
Source and Photo : https://www.dgcs.unam.mx/boletin/bdboletin/2022_355.html
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