Isotherm and kinetic studies on the adsorption of nitrate onto nanoalumina and iron-modified pumice

The use of nanoalumina and iron-modified pumice (IMP) as adsorbents for removal of nitrate from aqueous solution was investigated. Adsorption experiments were carried out as a function of the pH, contact time, and concentration of nitrate. Both adsorbents were effective for the nitrate removal in a pH range of 4–6, and optimum removal of nitrate ions occurred in a pH 5.0. The adsorption of nitrate on both adsorbents reached equilibrium within 50 min. Nitrate sorption kinetics was well fitted by pseudo-second-order model. The maximum nitrate uptake capacities for nanoalumina and IMP were found to be 70.8 and 86.7 mg g−1, respectively. The kinetic results showed that the nitrate sorption to nanoalumina and IMP followed pseudo-second-order kinetics with a correlation coefficient greater than 0.99. The equilibrium data for both the adsorbents for nitrate removal were fitted to Langmuir and Freundlich isotherms, but the experimental data were found to be little better fitted by the Langmuir model. These results indicate that nanoalumina and IMP are interesting alternatives for nitrate removal from the aqueous solution