Effects of carbonyl group formation on ammonia adsorption of porous carbon surfaces

In this work, the effects of different surface functional groups on the ammonia adsorption of porous carbons modified by electrochemical treatment in acidic solution (HNO3) under different current densities were investigated. The surface properties of the treated carbons were observed by Boehm's titration and X-ray photoelectron spectroscopy (XPS). It was found that the oxygen content of the carbons increased with increasing current density from the XPS results. However, the pH and acid values of the treated carbons slightly decreased in a sample prepared in 0.8 A/m(2) of current density (ACs-0.8). This result indicated that the surface acidity could be reduced according to the characteristics of surface functional groups introduced. From the XPS results, it was found that the growth of C=O groups was predominant at ACs-0.8. This result was also supported by an ammonia gas removal test. The adsorption capacity increased to ACs-0.4, but then began to decrease at AC-0.8. (C) 2007 Elsevier Inc. All rights reserved.