New magnetically responsive yeast-based biosorbent for the efficient removal of water-soluble dyes

Fodder yeast (Kluyveromyces fragilis) cells were magnetically modified by a contact with the water-based magnetic fluid in order to prepare a new type of magnetically responsive biocomposite material. This procedure enabled a simple separation of modified cells by means of commercially available magnetic separators or strong permanent magnets. It allows using the prepared material as a new inexpensive magnetic affinity adsorbent for the removal of water-soluble dyes. Magnetically modified cells were characterized by means of magnetic and microscopy methods. Both isolated magnetic nanoparticles and aggregates of particles were present on the cell surface. The prepared material displayed a superparamagnetic behavior at room temperature, with a transition to a blocked state at TB ∼ 180 K for the applied magnetic field H= 50 Oe. Seven dyes (crystal violet, amido black 10B, congo red, Saturn blue LBRR, Bismarck brown, acridine orange and safranin O) were used to study the adsorption process. The dyes adsorption could be described with the Langmuir isotherm. The maximum adsorption capacities ranged between 29.9 (amido black 10B) and 138.2 (safranin O) mg of dye per g of dried magnetically modified cells. © 2006 Elsevier Inc. All rights reserved.