Researchers from the federal universities of São Paulo (Unifesp) and São Carlos (UFSCar) are developing magnetic materials that could help remove crude oil from the water surface in case of spills such as hit the beaches of the Brazilian coast this year.

In laboratory tests, these hybrid materials - composed of nanoscale ferromagnetic particles (one billionth of a meter) and biomass residues - have been shown to be able to remove crude oil and other types of oil, such as ship engine, with more than 80% effectiveness.

The results of the Unifesp project, developed with support from FAPESP, will be tested in field experiments in Ceará. The objective is to evaluate the efficiency of the material in the removal of oil present in the beaches of the northeastern state.

“These nanomagnetic particles allow not only the cleanliness of beaches but also the recovery of oil by companies in case of leaks. Another advantage is that they are environmentally friendly because they are made of compounds naturally found in nature, ”said Georgia Labuto, a professor at Unifesp, campus of Diadema, told FAPESP.

The particles developed by the Unifesp group gather in its composition magnetite (a magnetic mineral) and yeast biomass residue from fermentation processes in the ethanol industry. The association gives rise to bionanocomposites - nanoscale hybrid materials obtained from renewable sources - and, according to the researchers, allows to reduce the cost of production of the material and increase the amount of oil that can be removed.

This is because by depositing the magnetite particles on the biomass surface, it was possible to maintain the magnetic property and at the same time increase the surface contact area between the magnetic material and the oil.

“In addition to contributing to the economy, agro-industrial waste allows to produce a larger mass of magnetic material with fewer reagents. By applying a magnetic field in an aqueous medium where these particles are dispersed, it is possible to remove them together with a fluid attached to them, such as oil, ”said the researcher.

Removability 

In a study published in the Journal of Environmental Management, the researchers evaluated the ability of bionanocomposites to remove stains from new, used engine oil and API 28-grade oil from water - rated as a light-weight, high-grade commercial oil created to scale. by the American Petroleum Institute and the National Bureau of Standards (the higher the oil density, the lower the API grade).

The results indicated that the material was able to remove, after two minutes' contact, between 55% and 89% of the amount of new engine oil and 69% of the used engine oil present in the samples.

The researchers also found that the removal of these compounds from water by the material is a predominantly physical phenomenon, in which the force of attraction exerted by a magnetic field, such as that produced by a magnet, is so intense that it drags the particles and hence the oil adhered to its surface.

In the case of spills, the researchers' idea is to use the particles to remove crude oil after the oil has been removed from the surface of the water by skimmers - a kind of wake attached to the ship that carries oil spilled into the sea mixed with water and debris. into the vessel.

“Our goal is to use the material to collect the oil already collected and separate it from the water,” said Labuto.

The Unifesp research group has also been using cork powder to develop bionanocomposites.

In another study, also published in the Journal of Environmental Management, the effectiveness of the two particle types - one with yeast biomass and one with cork powder - in the removal of petroleum with different API grades including heavy oils (API 10) was evaluated. and light (API 45) of the freshwater and marine surface, with and without agitation of the aqueous surface.

Magnetic nanomaterials exposed to oil in water were removed by a neodymium magnet.

The results of the analyzes indicated that the yeast biomass magnetic nanocomposites had higher oil recovery rates. In addition, the removal of oil by this magnetic material increases as the API decreases. This way you can predict how much can be recovered according to the density.

“The higher the API grade, the lighter and higher the commercial value of oil,” Labuto explained.

By varying the mass of bionanocomposite, it was possible to remove 100% of all studied oil types, regardless of API grade.

"Magnetic composites can be used in various oil removal cycles before recovery and even after recovery as they retain their magnetic properties," said Labuto.

Other materials 

Another group of researchers from UFSCar has been developing, as part of a postdoctoral project supported by FAPESP, hybrid matrices in powder and membrane form, composed of cobalt ferrite also in nanometer scale.

The powders were synthesized using residues of coconut mesocarp, sugarcane bagasse, sawdust and water hyacinth. The membranes were prepared using polyethersulfone polymer.

In a study also published in the Journal of Environmental Management, in collaboration with colleagues at the Federal University of Sergipe (UFS), researchers evaluated in the laboratory the effectiveness of removing heavy crude oil from the water surface by magnetic attraction of these materials.

The results of the analyzes indicated that the material in the form of sugarcane bagasse-based powder had the highest oil removal efficiency, with 85% adsorption capacity, and that this can be attributed to the fibrous nature of the raw material used.

Already the membranes were able to remove an amount of oil equivalent to 35 times their mass.

When both materials were used simultaneously, it was possible to remove an amount of oil equivalent to 35 times their mass and increase the adsorption capacity of sugarcane bagasse-based powder by 23%.

This high adsorption capacity is related to a retention barrier formed by the powder material, which prevented the spread of the oil slick and allowed its homogeneous removal, the authors pointed out.

“We also observed that the distribution of cobalt ferrite nanoparticles in biomass residues increased the speed of oil removal,” said Caio Marcio Paranhos da Silva, UFSCar professor and project coordinator.

“The materials were able to remove oil from the water surface of the samples in just two seconds,” he said.

Through a research internship at the University of Aveiro, Portugal, also supported by FAPESP, postdoctoral student José Arnaldo Santana Costa, supervised by Paranhos, now intends to incorporate cobalt ferrite nanoparticles into a particle obtained from bark. rice he developed during his doctorate.

The goal is to produce a new membrane capable of removing not only crude oil from the water surface but also polycyclic aromatic hydrocarbons (HPAs). This would not only remove heavy oil from spills but also reduce its toxicity.

"These substances, which are present in heavy oil, are very toxic, have carcinogenic potential and pose a great risk to people who have volunteered to remove oil from the beaches of the Northeast without adequate protection," said Silva.

Published articles on theme: 

Oil spill cleanup employing magnetite nanoparticles and yeast-based magnetic bionanocomposite (DOI: 10.1016/j.jenvman.2018.09.094), de Karina B. Debs, Débora S. Cardona, Heron D.T. da Silva, Nashaat N. Nassar, Elma N.V.M. Carrilho, Paula S. Haddad and Geórgia Labuto, can be read at www.sciencedirect.com/science/article/pii/S0301479718311046;

A comparison study of cleanup techniques for oil spill treatment using magnetic nanomaterials (DOI: 10.1016/j.jenvman.2019.04.106), de D.S.Cardona, K.B.Debs, S.G.Lemos, G.Vitale, N.N.Nassar, E.N.V.M.Carrilho, D.Semensatto and G.Labuto, can be read at www.sciencedirect.com/science/article/pii/S0301479719305730;

And the article Removal of heavy crude oil from water surfaces using a magnetic inorganic-organic hybrid powder and membrane system (DOI: 10.1016/j.jenvman.2019.06.050), de Graziele da Costa Cunha, Nalbert C. Pinho, Iris Amanda Alves Silva, José Arnaldo Santana Costa, Caio M.P. da Silva and Luciane P.C. Romão, can be read at www.sciencedirect.com/science/article/pii/S0301479719308527.