The adsorption of nitrate from aqueous solution onto calcined Mg/Fe hydrotalcite

A laboratory study was conducted to investigate the use of Mg/Fe hydrotalcite-like compounds for the removal of nitrate from synthetic solution. A series of calcined hydrotalcites (CHTlcs) with different chemical composition were investigated to remove nitrate. The highest nitrate percentage of adsorption (about 95%) and adsorption capacity (about 70 mg/g) were obtained by using the CHTlcs with Mg/Fe molar ratio of 3. The adsorption experiments were carried out under various equilibration conditions, such as adsorbent dose, pH, temperature, and competitive ions. It was found that 1.5 g/L Mg/Fe CHTlcs could achieve ideal adsorption efficiencies of nitrate during the nitrate adsorption process with an initial nitrate concentration of 100 mg/L at pH 8 and at temperature 30 degrees C. Various co-existing anions interfered in the adsorption of nitrate. The inhibitory effect was in the order of phosphate > sulfate > chloride. Adsorption isotherms showed that the experimental equilibrium data was fitted better by the Langmuir isotherm model than the Freundlich. The adsorption kinetics was successfully fitted by pseudo-second-order kinetics. And the characterization of the Mg/Fe CHTlcs was also analyzed to validate adsorption process. Results showed promising utility of Mg/Fe CHTlcs that could be developed into a viable technology for nitrate removal from water.