Sawdust, an available and renewable biomass, was investigated as a novel ammonium biosorbent. Biosorption occurred over a pH range of 6-10, reached an equilibrium state within only 20 min, and can be described by a pseudo-second-order model predicting a chemisorption process. Equilibrium data were very well represented by Langmuir isotherm and confirm monolayer coverage. FTIR analysis before and after biosorption of ammonium onto sawdust suggested that the main mechanisms involved in the removal of ammonium might be the ionic exchange and complexation. The use of sawdust presents an interesting option for both tertiary wastewater treatment (as a possible non-conventional biosorbent for the removal of ammonium), and waste recycling (as a fertilizer and compost). (C) 2010 Elsevier Ltd. All rights reserved.