Recently, more studies have focused on enhancing the effectiveness of activated carbons
by modifying their specific properties using various techniques in order to develop their affinities
for certain contaminants. Acidic treatment to introduce acidic functional groups onto the surface
of activated carbon was the most studied technique, due to its simplicity, availability of oxidizing
agents and the established nature of this technique.
In the present research, hydrochloric acid treatment was applied on activated carbon
prepared from nut shells and the adsorption capacity of the chemically modified activated carbon
was evaluated. The adsorption capacity of the modified activated carbon (CAN-Cl) on nitrite and
nitrate ions was compared with the untreated activated carbon (CAN).
Physical-chemical characteristics of the studied active carbons have been evaluated by
using nitrogen adsorption isotherms, thermogravimetric analysis and FTIR spectral analysis.
Batch equilibrium tests were carried out on both the untreated activated carbon prepared
from nut shells and also the hydrochloric acid treated activated carbon, to compare their
adsorption capacity on nitrite and nitrate ions.
Adsorption equilibrium data were fitted to Langmuir and Freundlich isotherm models. The
equilibrium data for both the untreated nut shells-based activated carbon and the chloride ionstreated
activated carbon were best represented by the Langmuir isotherm.
The surface modification of the nut shells -based activated carbon using hydrochloric acid
has increased its adsorption capacity on nitrite ions from 0.05 to 2.50 mg/g (by about 50 times)
and nitrate ions from 0.22 to 4.30 mg/g (by about 20 times).