Nitrate removal from water by quaternized pine bark using choline based ionic liquid analogue

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 (NO 3 − ) 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 NO 3 − 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 NO 3 − uptake. RESULTS: The MPB has a maximum NO 3 − uptake capacity of 2.91 mmol g −1 . The NO 3 − 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 desorption–regeneration 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 NO 3 − from water. © 2012 Society of Chemical Industry