Low cost and locally available maize stems and rice stems as potential biosorbents were tested for their effectiveness in removing nitrobenzene (NB) from aqueous solution. The sorption capacities of the biosorbents were evaluated using isotherm tests and other factors such as solution pH and ionic strength, biosorbent loading and particle size, contact time and initial NB concentration were also investigated. The sorption equilibration time of NB at 25 degrees C was about 72 h, and the optimal NB removal efficiency was achieved with biosorbent particle size of 80-100 mesh, further decrease in biosorbent particle size contributed to little changes in NB removal efficiency. When the biosorbent dosage was 10 g L-1, the NB removal efficiency approached to the optimization. Both biosorbents performed similarly and NB was completely removed when treated at pH > 7. So the optimized biosorbent loading was 10 g L-1 with optimum particle size of 80-100 mesh. High pH conditions (pH > 7) were found to improve NB removal, while increasing the ionic strength in solution was found to decrease NB removal efficiency. Maize and rice stems were shown to be capable in removing NB from solution and have demonstrated their potential use as biosorbents. (C) 2010 Published by Elsevier B.V.