The magnetic baker's yeast biomass (MB) was prepared by combining baker's yeast and nano-Fe3O4 using glutaraldehyde as a cross link agent. The MB was successfully used for the biosorption of methyl violet (MV) and was easily recycled by using an applied magnetic field. The mechanism of MV biosorption by MB was investigated by SEM, XRD, MR, zeta potential and potentiometric titration. The results revealed that nano-Fe3O4, with spherical and granular morphology, were distributed on the surface of baker's yeast biomass. The functional groups such as carboxyl, hydroxyl and amino groups found on the surface of MB may be responsible for MV biosorption. The optimal biosorption conditions were determined as pH 6.0, MV concentration 300 mg/L and contact time 30 min. The biosorption capacity in the optimal conditions was 60.84 mg/g. The biosorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm equation. The thermodynamic parameters Delta G degrees, Delta H degrees and Delta S degrees showed that the biosorption was feasible, spontaneous and endothermic. The desorption and regeneration experiments were investigated and the biosorption/desorption cycles of MV were repeated three times. The MB regeneration efficiency and the MV recovery efficiency were 82.64% and 84.54% respectively in the third cycle by using HAc as an eluent solution. (C) 2010 Elsevier B.V. All rights reserved.