The purpose of this work was to evaluate the influence of mode of
activation (heat and acid) on the ability/capacity of active carbons to adsorb
nitrite ions from solutions. Two samples of active carbons obtained from nut
shells (i) by chemical activation with phosphoric acid (CAN-7) and by
physical-chemical activation with water vapours (CAN); and, by
comparison, commercial active carbon (AG-5) have been used for
adsorption of nitrite ions from water.
The influence of various experimental parameters (pH value, amount of
adsorbent, initial concentration, temperature, contacting time and effect of
electrolytes) was evaluated in batch experiments. Adsorption equilibrium
data were fitted to Langmuir and Freundlich isotherms and to different
kinetic models. Nitrite ions diffusivities were calculated from the slopes of
Fick’s unsteady state mass plots. The equilibrium data of series of the nut
shells-based activated carbons (CAN-7, CAN, CAN-Cl) were best
represented by the Langmuir isotherm, while of samples of commercial
active carbon (AG-5, AG-5ox)- by the Freundlich isotherm. Obtained results
reveal that adsorption capacity of activated carbons decreases in order:
CAN-7 ˃ CAN-Cl ˃ AG-5ox ˃ AG-5 ˃ CAN.