Using the Power of Ions to Create Materials That Absorb Oil!
Kazuki Sada , Professor
Faculty of Science/Graduate School of Chemical Sciences and Engineering (School of Science, Department of Chemistry)
High school : Rakunan Private High School (Kyoto Prefecture)
Academic background : Doctorate from Kyoto University
- Research areas
- supermolecular chemistry, polymer chemistry, science of soft matter
- Research keywords
- organic solvents, (crude) oil, absorbency (absorbent materials), ions, network (structure)
What are you aiming to achieve?
Fig. 1: Crude oil escaping from a grounded tanker off the coast of Alaska
“No use crying over spilt milk” is a proverb used to describe the fact that there is no making up for a failed situation. It uses the image that milk, once spilt, cannot be put back into a bottle. When factories or tankers spill vast quantities of oil or organic solvents into the environment, they not only cause significant damage to ecosystems and to the wild animals that inhabit them, but they are also believed to cause damage to human health. As such, the overall environmental damage is a cause for social concern. In fact, the methyl cyanate spill that occurred in Bhopal, India in 1984, and the crude oil spill that occurred in 1989 off the coast of Alaska (Fig. 1) and in the Bay of Mexico in 2010 have become global problems. Against this background, we are working towards the development of a simple collection and disposal system for large quantities of oil and organic solvents that have been released into the environment. We have been working on the development of a highly efficient material that can absorb this kind of liquid (an organic solvent absorbent).
Fig. 2 An experiment
What sort of experiments do you do?
The main flow of our experiments involves designing the structure of a material having the target properties, based on a unique concept, and synthesizing it. In fact, what we do is exactly what chemists have always done, in terms of mixing the chemicals that comprise our raw materials in flasks and beakers, then heating and cooling them to cause a reaction (Fig. 2). We use filtration, liquid separation, distilling and recrystallization to achieve the target product (referred to as the “mono” in Japanese). We identify the molecular structure using instrumental analysis to confirm whether our substance that we created has been made by humans before or not. Finally, we evaluate the function and feed the results back into our concept and design. Repeating this cycle of design, synthesis, and evaluation allows us to aim to develop even higher-functioning materials and discover new phenomena and principles.
Fig. 3 Molecular structure and attributes of organic solvent absorbent material
Fig. 4 Solvent absorption and structure of organic solvent absorbent
An actual organic solvent absorbent material that was developed through this process is illustrated in Fig. 3. This is a substance known as a polymer, in which long chain-shaped molecules are partially cross-linked, forming a three-dimensional network structure at the molecular level. Furthermore, 95% of it is formed from a long-chain group that is easily mixed with oil, with approximately 5% being a special type of ion. When this absorbent is soaked in an organic solvent, as illustrated in Fig. 4, we found that it absorbs between a hundred and several hundred times its own weight in solvent (weight in a dry state), and expands significantly. This absorption ability for organic solvents is the highest that has ever been produced, and the substance has now been publicized in the newspapers and on TV. The key to designing an organic solvent absorbent is to use special ions that are large in size, but also mix well with oil. These ions can be dissociated in many organic solvents, and since the fixed positive ions electrostatically repulse one another, and osmotic pressure occurs as a result of the difference in ion concentration between the inside and outside of the absorbent material, the network swells and expands significantly and it becomes possible to absorb large volumes of organic solvents.
Where do you get your research ideas?
We took a hint from highly water-absorbent polymers used in disposable diapers and contact lenses. These materials are the similar cross-linked polymers with ordinary ions, and can absorb between several hundred and several thousand times their own weight in water. Despite this, however, they do not swell at all if soaked in organic solvents. This is because ordinary ions do not blend with oil, and cannot dissociate. The introduction of ions in our absorbent, which can dissociate when placed in organic solvents, was our own original work.
What are you aiming for next?
We have successfully synthesized a range of materials that absorb organic solvents, but have not yet succeeded in our project to create a material that efficiently absorbs large quantities of crude oil or other oils. This is because no ions exist that can dissociate in oil. We are currently engaged in the development of ions that dissociate even within oil. If ions such as this can be developed, we would not only be able to develop an absorbent material that would “put spilt oil back in the bottle,” but also enable the transmission of electricity through oil, which is expected to change the history of chemistry. Blending new ideas in this way allows us to create more and more new materials that go beyond what is currently considered “common wisdom.”