In this study, magnetite nanocomposites coated with bentonite were synthesized as adsorbent material and their effects in Cr (VI) adsorption were investigated. Magnetite nanomaterials (Bentonite-Fe3O4) were characterized by surface morphology (SEM-EDX) and elemental analyses (FTIR). RSM was used to investigate the optimum ambient conditions of parameters for the removal of Cr (VI) ions. Isotherm and kinetic models were calculated to determine the mechanism of adsorption, and obtained results showed that Cr (VI) adsorption by Bentonite-Fe3O4 was more suitable for Tempkin isotherm (R2:0.99) and second-order kinetic model (R2:1). The optimum adsorption efficiency (77.46%) of Cr (VI) ions in 6.5 mg/L concentration was obtained at contact time of 60 min, pH 2.0, adsorbent dosage of 2.5 g/L and at 35 oC.