Magnetic Fe3O4-chitosan microspheres were prepared by co-precipitating of Fe2+ and Fe3+ ions with NaOH in the presence of chitosan. The saturated magnetization of the resulting material was 20.0 emu/g. Then these magnetic microspheres were employed to immobilize iron-reducing bacteria to improve the biological reduction of Fe(III)EDTA(-), which was one of the key steps in nitrogen oxides (NOx) removal by the integrated chemical absorption-biological reduction process. The immobilized bacteria performed well on Fe(III)EDTA(-) reduction than free bacteria, even under unfavorable pH and temperatures. Furthermore, the effects of NO2-, NO3-, SO3-, and S2-, the potential inhibition compounds in the scrubber solution, on the reduction of Fe(III)EDTA(-) by the immobilized and free bacteria were also studied. (c) 2011 Elsevier Ltd. All rights reserved.