Effect of pre-oxidation for introduction of nitrogen containing functional groups into the structure of activated carbons and its influence on Cu (II) adsorption

Abstract

Modification of surface structure of adsorbents in order to enhance their adsorption capacity toward special adsorbates has gained great interest in the recent years. Introduction of nitrogen functional groups such as amine, pyridinic, and pyrrolic onto the surface of adsorbents and replacing them with oxygen groups has been known as one of the modification methods for producing strong adsorbents toward heavy metals like Cu (II) ion. In the present work, a new procedure for nitrogenation of commercial activated carbon was proposed: heat treatment of adsorbent under the atmosphere of NH3 after pre-oxidation with HNO3; and the influence of this treatment on the characteristics and adsorption properties of activated carbon toward Cu (II) were investigated. Characterization of produced samples was performed by several analyses, including N2 adsorption/desorption, pH of zero point charge, elemental analysis and FTIR spectroscopy. Comparison of the foresaid sample with another one modified by NH3 without pre-treatment, showed that the pre-oxidation of adsorbent has a good influence on increasing of the amount of nitrogen functional groups introduced onto structure of adsorbent. Besides it was found that the introduction of nitrogen functional groups has negligible effect on the porous properties of activated carbon. The higher adsorption rate and capacity toward Cu (II) was obtained in the case of nitrogenated carbons.