BACKGROUND: The objective of this study was to quaternize pine bark (PB) wood residues using green chemistry and to use the quaternized PB to remove nitrate (NO3) from water. The quaternization process was achieved by reacting the wood residues with an ionic liquid analogue comprised of a choline chloride derivative and urea. Batch adsorption tests were used to delineate the NO3 uptake by the modified pine bark (MPB). Fourier Transform Infrared Spectroscopy (FTIR) analysis and Zeta potential measurements were used to characterize the changes at the surface of the PB due to quaternization and NO3 uptake. RESULTS: The MPB has a maximum NO3 uptake capacity of 2.91 mmol g1. The NO3 uptake kinetics indicated that diffusion through the boundary layer of the MPB was the rate limiting step. The Langmuir adsorption model provided a better fit for the uptake data than the Freundlich model, indicating monolayer adsorption. The uptake process was found dependent on concentration, pH and ionic strength, and was also spontaneous and exothermic. The desorptionregeneration experimental results indicated a 95% efficiency after five consecutive regeneration cycles. CONCLUSIONS: The quaternization technique was found very effective for developing effective and green anion exchange resins to remove NO3 from water. (c) 2012 Society of Chemical Industry