Magnetic Soap Could Revolutionise Cleaning

A droplet containing the soap is attracted to the magnet at left.

Magnetic soap could help in oil spill clean-ups: An international team of scientists has demonstrated the first soap that responds to magnets. This means the soap and the materials that it dissolves can be removed easily by applying a magnetic field. Experts say that with further development, it could find applications in cleaning up oil spills and waste water.

Details of the new soap, which contains iron atoms, are reported in the chemistry journal Angewandte Chemie. It is similar to ordinary soap, but the atoms of iron help form tiny particles that are easily removed magnetically. "If you'd have said about 10 years ago to a chemist: 'Let's have some soap that responds to magnets', they'd have looked at you with a very blank face," said co-author Julian Eastoe of the University of Bristol. He told BBC News: "We were interested to see, if you went back to the chemical drawing board with the tool-kit of modern synthetic chemistry, if you could...design one."

Soap is made of long molecules with ends that behave differently: One end of the molecule is attracted to water and the other is repelled by it. The "detergent" action of soap comes from its ability to attach to oily, grimy surfaces, with the "water-hating" end breaking up molecules at that surface. The soap molecules then gather up into droplets in which all the "water-loving" ends face outward. Prof Eastoe and his team started with detergent molecules that he said were "very similar to what you'd find in your kitchen or bathroom" - one of which can be found in mouthwash. The team found a way to simply add iron atoms into the molecules. The droplets that the soap formed were attracted to a magnet, just as iron filings would be.

The soap could make for a far easier means of gathering oil from spills.

But single iron atoms would not behave as tiny individual magnets, so some other process had to be at work. To get a look at what was going on in the chemical process required a view at the molecular level. So the team sent their samples to the Institute Laue Langevin (ILL) in Grenoble, France, where an intense beam of the sub-atomic particles known as neutrons shed light on the matter. They saw that the iron particles were clumping neatly together into iron nanoparticles, tiny clumps of iron that could in fact respond to a magnetic field.

Prof Eastoe said the research was still at the laboratory stages but was already the subject of discussion. "The research at the University of Bristol in this field is about how we can take the ordinary and give it extraordinary properties by chemical design," he said. "We have uncovered the principle by which you can generate this kind of material and now it's back to the drawing board to make it better."

Scientists Produce World's First Magnetic Soap: Scientists from Bristol University have developed a soap, composed of iron rich salts dissolved in water, that responds to a magnetic field when placed in solution. The soap’s magnetic properties were shown with neutrons at the Institut Laue-Langevin to result from tiny iron-rich clumps that sit within the watery solution. The generation of this property in a fully functional soap could calm concerns over the use of soaps in oil-spill clean ups and revolutionise industrial cleaning products.

Scientists have long been searching for a way to control soaps (or surfactants as they are known in industry) once they are in solution to increase their ability to dissolve oils in water and then remove them from a system. The team at Bristol University have previously worked on soaps sensitive to light, carbon dioxide or changes in pH, temperature or pressure. Their latest breakthrough, reported in Angewandte Chemie, is the world’s first soap sensitive to a magnetic field.

Ionic liquid surfactants, composed mostly of water with some transition metal complexes (heavy metals like iron bound to halides such as bromine or chlorine) have been suggested as potentially controllable by magnets for some time, but it had always been assumed that their metallic centres were too isolated within the solution, preventing the long-range interactions required to be magnetically active.

The team at Bristol, lead by Professor Julian Eastoe produced their magnetic soap by dissolving iron in a range of inert surfactant materials composed of chloride and bromide ions, very similar to those found in everyday mouthwash or fabric conditioner. The addition of the iron creates metallic centres within the soap particles.

To test its properties, the team introduced a magnet to a test tube containing their new soap lying beneath a less dense organic solution. When the magnet was introduced the iron-rich soap overcame both gravity and surface tension between the water and oil, to levitate through the organic solvent and reach the source of the magnetic energy, proving its magnetic properties.

Once the surfactant was developed and shown to be magnetic, Prof Eastoe’s team took it to the Institut Laue-Langevin, the world’s flagship centre for neutron science, and home to the world’s most intense neutron source, to investigate the science behind its remarkable property.

When surfactants are added to water they are known to form tiny clumps (particles called micelles). Scientists at ILL used a technique called “small angle neutron scattering (SANS)” to confirm that it was this clumping of the iron-rich surfactant that brought about its magnetic properties.

Dr Isabelle Grillo, responsible of the Chemistry Laboratories at ILL: “The particles of surfactant in solution are small and thus difficult to see using light but are easily revealed by SANS which we use to investigate the structure and behaviour of all types of materials with typical sizes ranging from the nanometer to the tenth of micrometer.”

Up, up and away: This photo shows the magnetic soap rising up through the test tube.

The potential applications of magnetic surfactants are huge. Their responsiveness to external stimuli allows a range of properties, such as their electrical conductivity, melting point, the size and shape of aggregates and how readily its dissolves in water to be altered by a simple magnetic on and off switch. Traditionally these factors, which are key to the effective application of soaps in a variety of industrial settings, could only be controlled by adding an electric charge or changing the pH, temperature or pressure of the system, all changes that irreversibly alter the system composition and cost money to remediate.

Its magnetic properties also makes it easier to round up and remove from a system once it has been added, suggesting further applications in environmental clean ups and water treatment. Scientific experiments which require precise control of liquid droplets could also be made easier with the addition of this surfactant and a magnetic field.

Professor Julian Eastoe, University of Bristol: “As most magnets are metals, from a purely scientific point of view these ionic liquid surfactants are highly unusual, making them a particularly interesting discovery. From a commercial point of view, though these exact liquids aren’t yet ready to appear in any household product, by proving that magnetic soaps can be developed, future work can reproduce the same phenomenon in more commercially viable liquids for a range of applications from water treatment to industrial cleaning products.”

Peter Dowding an industrial chemist, not involved in the research: “Any systems which act only when responding to an outside stimulus that has no effect on its composition is a major breakthrough as you can create products which only work when they are needed to. Also the ability to remove the surfactant after it has been added widens the potential applications to environmentally sensitive areas like oil spill clean ups where in the past concerns have been raised.”