Removal of As(V) and Cr(VI) Ions from Aqueous Solution using a Continuous, Hybrid Field-Gradient Magnetic Separation Device Ashish K. Jha and Arijit Bose Department of Chemical Engineering, University of Rhode Island, Kingston, RI, USA Jerome P. Downey Hazen Research, Golden, CO, USA Abstract: A continuous flow colloidal affinity magnetic separation device is used for the removal of As(V) and Cr(VI) from aqueous solutions. Langmuir isotherms fit the adsorp- tion behavior of the individual ions on Orica MIEX w ion exchange particles. In a mixture of equal weight percent As(V) and Cr(VI), the adsorption of As(V) begins only above a critical cut-off concentration, implying preferential adsorption of the higher valence ion at the available sites. Cr(VI) is removed selectively from the mixture in the continuous flow device, consistent with the presence of a higher concentration of the higher valence ion in the proximity of a charged (anion-exchange) surface. Keywords: Magnetic separation, ion-exchange INTRODUCTION Magnetic separation methods rely on labeling target material with magnetic particles and mobilizing these particles to specific locations using magnetic field gradients. This process is versatile and can be used for a wide variety Received 30 January 2006, Accepted 22 June 2006 Address correspondence to Arijit Bose, Department of Chemical Engineering, University of Rhode Island, Kingston, RI 02881, USA. Tel.: 401-874-2804; E-mail: bosea@egr.uri.edu Separation Science and Technology, 41: 3297–3312, 2006 Copyright # Taylor & Francis Group, LLC ISSN 0149-6395 print/1520-5754 online DOI: 10.1080/01496390600915007 3297