Oil and water can mix after all...
It sounds almost too good to be true. Researchers at Queen's University in Canada have found an effective and environmentally friendly way to mix (and unmix) oil and water. This could help the oil industry to clean up oil spills and extract oil from tar sands. The 'surfactant' (surface active agent) used at Queen's provides several advantages over current methods. It's cheap, reversible, and doesn't require metals, acid, or light. In fact, it can be switched on and off by the respective presence of CO2 or air. But as the researchers don't give a clue about commercial availability for their 'surfactant,' I guess there are still some problems to solve. But read more...
Here is the introduction about this Queen's study.
[It] addresses the recurring problem of separating oil and water mixtures, and targets diverse applications including cleaning up oil spills, and extracting oil deposits from tar sands and reservoirs. Other potential beneficiaries are plastics manufacturers, chemical and pharmaceutical companies, mining companies and makers of cleaning products.
The new process can be used whenever industry requires an emulsion (the mixture of two liquids in which droplets of one are suspended evenly throughout the other), explains lead researcher and Queen's Chemistry Professor Philip Jessop. This might occur when cleaning spills, extracting oil from the ground, de-greasing metal equipment or metal surfaces, and manufacturing chemical products such as plastics.
So how does the 'surfactant' used by Jessop's group can help?
The surfactant developed by the Queen's team is also completely reversible and does not require metals, acid, or light. Exposure to carbon dioxide (CO2) activates it, while bubbling air through the liquid turns it off again. CO2 and air were chosen because they are cheap, non-toxic and environmentally benign: the CO2 can be recycled material from power plants.
"You can do this over and over, timing it for exactly when you want the switch to occur," Dr. Jessop notes. And when the surfactant is turned off, causing oil and water to separate, the now-clean water may be returned to its source or recycled.
Below is a photo of Jessop and one of his students demonstrating this new oil and water emulsion process (Credit: Stephen Wild/Queen's University).
In "Oil and water mix and un-mix on demand," New Scientist gives some details about the reversibility process and the kind of chemical products used by Jessop.
While it is easy to use a surfactant to bind oil and water into an emulsion -- so they can be transported more easily through a pipeline, for example -- it is difficult to re-separate the oil and water once they reach their destination.
To get around this, the team fashioned molecules called long-chain alkyl amidines which consist of a long, stringy alkyl chain of hydrocarbons that bind to oils. At the other end of the alkyl chain is an amidine group which also binds to oils.
Simply bubbling air through the liquid reforms the amidine, reversing the process -- the oil-water mixture separates again.
This research work has been published by Science under the short title "Switchable Surfactants" (Volume 313, No. 5789, Pages 958-960, August 18, 2006). Here is a link to the abstract which adds a few details to the New Scientist article.
Long-chain alkyl amidine compounds can be reversibly transformed into charged surfactants by exposure to an atmosphere of carbon dioxide, thereby stabilizing water/alkane emulsions or, for the purpose of microsuspension polymerization, styrene-in-water emulsions. Bubbling nitrogen, argon, or air through the amidinium bicarbonate solutions at 65°C reverses the reaction, releasing carbon dioxide and breaking the emulsion.
If you don't want to pay $10 for an access to the full paper, you still can find free valuable information in this other Jessop's paper, "Designing Smart Surfactants" (PDF format, 8 pages).
Still, I'm puzzled by the fact that the researchers don't say anything about the commercial availability of a product which obviously could help the powerful -- and rich -- oil industry. So is there something which is not disclosed in this news release? Please send me a message if you have relevant information.
Sources: Queen's University news release, August 18, 2006; Andy Coghlan, New Scientist, August 17, 2006; and various web sites
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