Plastic Beads Acting As Molecular Sponges

02 Aug


Fundamental Scientific Principles and Bioreactors

Andrew Daugulis is not only a leading researcher in his field, but also Queen’s Research Chair in Biochemical and Cell Culture Engineering, and a well respected professor and supervisor in Chemical Engineering and Biology. Andrew’s passion and love for his work is reflected in the enthusiasm of his graduate students towards their research, and in his exceptional publication record.

Andrew has three PhD students and two Masters students currently working under his supervision. While designing projects for his students, Andrew puts a great deal of emphasis on whether the project will be interesting to the student, whether the project is tailored to the student’s strengths, and whether the project will be successful. Though Andrew provides guidance when it is necessary, he firmly believes in helping his graduate students determine the direction of their research. At present, one of his PhD students, who has a very strong biosciences background and is interested in bioremediation, is working on degrading PCBs FROM contaminated soil. Another PhD student, due to his interest in a combination of lab work and modeling, is working on degrading gaseous benzene, and in developing a dynamic mathematical model to predict the performance of the bioreactor system. Both the students are dealing with different molecules, different environments and completely different scientific challenges.

The main focus of Andrew’s research involves the use of environmental and green technology for degrading toxic and difficult [to degrade] contaminants such as phenol, pentachlorophenol, PAHs, and PCBs. In Andrew’s lab, Two-Phase Partitioning Bioreactors (TPPBs) are used to achieve degradation. Andrew believes that the novelty of using TPPBs lies in the fact that it does not matter what the contaminant is (i.e. how toxic it is) or where it is located (air, water, gas streams or as stored material). While the use of standard bioreactors is limited to contaminants or contaminant concentrations which are not toxic to the degrading organisms, in TPPBs, the toxicity can be reduced to a level that microorganisms can handle. Andrew explains this by giving the example of benzene degradation in a TPPB. At the start of the process, an aqueous phase concentration of benzene of 1000mg/L is provided, which is well above the toxic threshold of microorganisms. When an immiscible organic solvent with high affinity for benzene  is added to the reactor (TPPB), the benzene partitions INTO the solvent, bringing its concentration down to 50mg/L in the aqueous phase, which the microorganisms can handle (microorganisms stay exclusively in the aqueous phase).

Then, as benzene is degraded, a thermodynamic disequilibrium between the benzene concentration in the aqueous phase and in the solvent occurs. To re-establish the equilibrium, thermodynamics force benzene FROM the solvent to partition INTO the aqueous phase. The benzene delivery to the system is based on the fundamental scientific principles of thermodynamic equilibrium and cell metabolism. The system relies on nature’s need to achieve equilibrium, and on the fact that cell metabolism is a property of all living things.

Both public and private sector groups have expressed interest in this research.  Andrew’s Fermentation Pilot Plant has been used to demonstrate that a scaled-up version of the system works – this technology can be implemented on a large scale and not just laboratory scale.

Research INTO the use of small plastic beads rather than organic solvents acting as molecular sponges is currently underway. These polymer beads can be made FROM very cheap sources (e.g. the material in running shoe treads) and even recycled polymers such as automobile tires. Rational selection, and modification, of these plastic beads allows control over the chemistry, and thus control over the molecular affinity. The possible use of these beads in TPPBs is being investigated in Andrew’s laboratory by his third PhD student, and future application could involve using these polymers at contaminated sites. Andrew exclaims, “When we are finished at a site, we would gather up the beads, go to a different contaminated site, and use the beads again!”


Posted by on August 2, 2007 in General Knowledge, R&D, Recylcing


3 responses to “Plastic Beads Acting As Molecular Sponges

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