Nitrate removal by calcined hydrotalcite-typed compounds

Abstract

The sorption of nitrate ions on calcined hydrotalcite-type compounds at 550ºC (HT550), 650ºC (HT650), and 850ºC (HT850) from pure water solution at 25ºC has been studied. The influence of the temperature was also investigated for the sample calcined at 850ºC by studying the sorption process at 10 and 40ºC. The experimental sorption data points were fitted to the Langmuir equation in order to calculate the sorption capacities (Xm) of the samples; Xm values range from 61.7 g/kg (HT550 at 25ºC) to 147.0 g/kg (HT850 at 40ºC). The values for the removal efficiency (R) obtained ranged from 70.5% for HT550 at 25ºC to 99.5% for HT850 at 40ºC. The sorption experiments showed that the greater the calcination temperature (850ºC), the more effective the removal of nitrate. The increase in the temperature from 10 to 40ºC for sample HT850 also tends to increase the sorption of nitrate from 63.3 g/kg to 147 g/kg and the corresponding removal efficiency from 71.5 to 99.5%.