Researchers at the University of Erlangen-Nürnberg are developing an oil magnet

An oil tanker or oil rig breakdown often has devastating consequences for the environment, fisheries and tourism. The classic methods of removing oil spills are not particularly efficient and are usually ecologically questionable. A method that researchers at the University of Erlangen-Nürnberg have developed could fundamentally change this problem: the “oil magnet”.

This blog was originally posted by Brunel Germany. See original post here.

On April 20, 2010, the Deepwater Horizon oil rig explosion triggered one of the largest man-made marine oil spills to date. 84 km off the coast of the US state Louisiana, up to 1 million tons of crude oil entered the Gulf of Mexico. The oil company BP paid more than $65 billion in fines to government agencies, damaged companies and private individuals, as well as for cleaning work. Many thousands of helpers were on duty to remove the oil slick, which grew to an area of almost 200,000 km² - about half the area of Germany. One of the measures was the controlled burning of the oil, which was not very effective due to the excessive swell and the large quantities of environmentally harmful combustion products released into the air and water.

Chemical dispersion, the breaking up of the oil slick into small droplets with the help of so-called dispersants, remained the method of choice. The finely-divided oil sinks below the surface of the water and is then - at least according to the theory - broken down by microorganisms faster than the dense oil film on the surface of the water. Critics complain, however, that the constituents of the dispersants - e.g. petroleum-like solvents and salts of organic sulfonic acids, such as those used in synthetic cleaning agents - are sometimes more toxic than the crude oil components themselves, and that the dispersion makes the oil less visible. In fact, research vessels later located huge plumes of oil in deep areas of the Gulf of Mexico that had hardly been attacked by microorganisms.

Almost 7 million liters of dispersants were used during the Deepwater Horizon oil spill. Experts estimate that a maximum of 20% of the leaked crude oil could still be removed. The rest sank to the sea floor or was distributed in large volumes in the deep sea. Newer methods for combating oil pollution such as oil-decomposing microbacteria and oil-absorbing adsorption sponges were not yet available in 2010 and are still predominantly at the testing stage. They are also controversial because of their toxic side effects on the marine ecosystem.
 

But new developments are bringing new hope: Under the direction of the materials scientist Prof. Marcus Halik, a process that a working group at the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) has been researching since 2015 is likely without any environmental hazard: collecting oil with the help of magnets. Halik is convinced: "With our process we extract substances such as crude oil, gasoline and diesel practically completely from water, without any auxiliary substances remaining in the water."

Of course, oil isn't magnetic. So the FAU researchers use a clever trick: They designed tiny magnetic particles to which oil adheres so tightly that an electromagnet with the particles also fishes the oil out of the water. Marco Sarcletti, who was doing his master's thesis on the subject, describes the process in more detail: “We use nanoparticles made of magnetite that are surrounded by self-assembling monolayers made of alkylphosphonic acids. The acid ends bind to the magnetite particles, while the alkyl chains point away from them. These chains are strongly oleophilic, which means that they bind oily substances with a high degree of effectiveness." The FAU researchers were able to show that each functionalized nanoparticle accumulates up to 14 times the volume of oil molecules.

The researchers optimized the process through computer simulations and various experiments. The mineral magnetite, an iron oxide with the composition Fe3O4, proved to be suitable as a magnetic material. It is non-toxic, relatively inexpensive and can be easily processed into nanoparticles. In this extremely fine distribution, it is particularly effective for two reasons, explains Sarcletti: “On the one hand, we use nano-scaling to increase the active surface enormously. On the other hand, in contrast to massive magnetite, the nanoparticles show a special magnetic behavior, becoming SPIONs (SuperParamagnetic Iron Oxide Nanoparticles)."