Sorption studies of nitrate ion by a modified beet residue in the presence and absence of ultrasound.

Kinetic and thermodynamic studies were carried out for the adsorption of nitrate ion from aqueous solutions onto modified beet residue and for desorption from the sorbent to the solution in batch experiments. The beet residue was modified by epichlorohydrin in the presence of pyridine. The experiments were conducted in the presence and absence of ultrasound. The removal of this ion was examined by varying experimental conditions such as the amount of sorbent, contact time, concentration, and temperature. It was found that more than 90% of nitrate ion was removed in less than 2 min from the solution. Results indicate that the adsorption of nitrate in the presence of ultrasound was higher at lower temperature (10 degrees C) and it was lower at higher temperatures with respect to the control method (without ultrasound). In the case of desorption study, the amount of desorption was higher in the presence of ultrasound than its absence at different applied temperatures. The Langmuir isotherm model fits adequately the experimental data for adsorption and desorption studies. In point of kinetics, the second-order kinetic model describes the sorption process for this ion. The thermodynamic parameters such as DeltaG degrees , DeltaH degrees , and DeltaS degrees were determined for the sorption of NO(3)(-) from the temperature dependence of the sorption process. Copyright (c) 2009 Elsevier B.V. All rights reserved.