Magnetic detergents to attract pollution and clean up the environment? Recent experiments show that the theory is now a reality. New surfactant molecules with magnetic properties have been synthesized, according to a study published in Angewandte Chemie, International Edition in January 2012. Potentially, these molecules can be used to clean the environment, for instance for oil spills in the sea.
Detergents: Surfactants and Their Structure
Detergents, such as soaps or washing powders, are made from compounds called surfactants. A surfactant is a molecule which has both a hydrophilic and a hydrophobic part; it is called amphiphilic. The hydrophobic part is made by a long “chain” of carbon atoms (the tail); it is insoluble in water but soluble in organic liquids, such as oils. The hydrophilic part, soluble in water, is much smaller (the head).
Surfactants may have an ionic structure, with the head bearing a charge. Depending on the nature of the surfactants, the hydrophilic part can have either positive or negative charge. A surfactant compound with a positive charge is called cationic, while a negatively charged compound is known as anionic.
How Do Surfactants Work?
Surfactants act as detergents, as they facilitate the mixing of water and oily compounds. Normally oil and water are immiscible fluids; they do not form a solution, but can only form an emulsion. A surfactant, however, can affect the behavior at the interface of the two fluids; this is because the hydrophobic part dissolves in the oil while, at the same time, the hydrophilic one dissolves in water.
New Surfactants with Magnetic Properties
Researchers from the School of Chemistry of Bristol University (UK) recently synthesized new surfactants, which also showed magnetic properties. The study was performed in cooperation with the Chemistry Department of Koln University (Germany), the Wuhan College of Chemistry (China), the Institute Laue-Langevin of Grenoble (France) and the Rutherford Appleton Laboratory (UK).
In this research, scientists modified the structure of standard cationic surfactants, with the introduction of iron (Fe). The Figure to the left shows as an example the standard surfactant and the modified one: both have the same positively-charged ion, dodecyl trimetyl ammonium. The standard surfactant, however, has a bromide ion (Br-) as counter ion (a), while the modified one has the iron-containing ion FeCl3Br- (b).
A similar modification was performed with two other surfactants, 1-decyl-3-methyl imidazolium chloride and didodecyltrimethylammonium bromide, using FeCl4- andFeCl3Br- as counter ions respectively. These molecules are referred to as Magnetic Ionic Liquid Surfactants (MILSs).
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