Magnetic Separations for Environmentally Benign Processing

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AbstractProposal Number: CTS-9985489 Proposal type: Response to NSF 99-108, NSF/EPA Technology for a Sustainable Environment ProgramPrincipal Investigators: James A. Ritter and Harry J. PloehnInstitution: University of South Carolina at ColumbiaMAGNETIC SEPARATIONS FOR ENVIRONMENTALLY BENIGN PROCESSINGThis project is developing a sound theoretical foundation and operational understanding of a novel magnetic-field-enhanced separation process. The new high-gradient magnetic separation (HGMS) process is based on the use of a magnetic adsorbent such as magnetite supported on a fixed bed. Due to its ferromagnetic property, magnetite can be used not only as an adsorbent for removing metal ions from solution but also as a magnetically energizable element for attracting and retaining paramagnetic nanoparticles from suspension. In such a system, the magnetite serves as a metal ion adsorbent, a high-gradient magnetic filter, or both, depending on the characteristics of the stream to be treated. Specifically, this research describes, analyzes, and demonstrates the advantages of this new magnetic separation process over other magnetic-field-enhanced separations and conventional metal-ion adsorption processes.Applications for this new, magnetic-field-enhanced separation process abound. In the area of environmentally benign processing, applications include the recovery and recycling of metal species at the source in mining and metallurgical operations and for desulfurization of coal by removing FeS2, thereby avoiding the generation of pollutants at the source. Another promising application is the use of HGMS in biomagnetic separations, in which viruses and cells can be separated through selective tagging with functionalized magnetic oxides. Also, proteins and enzymes can be fractionated by coupling to magnetic particles bearing bio-selective functional groups. The primary advantage of the proposed HGMS process for these applications lies in the small magnetite particle size and the concomitant high local magnetic field gradients. This leads to order-of-magnitude reductions in the particle sizes that can be captured and in the applied magnetic fields required. It may even be possible to capture individual protein molecules complexed with parmagnetic ions. The reduction in the externally applied magnetic field required enables, for the first time, the use of permanent ceramic magnets with relatively high magnetic field strengths (up to 1 Tesla) in the HGMS operations. These kinds of magnets do not require an external power source and thus are truly benign to the environment. By establishing a sound theoretical and operational understanding of the proposed HGMS technology, this research opens up many different avenues for removing, concentrating, recovering, and recycling weakly paramagnetic metal species in chemical process streams.