REACTION OF CARBONS WITH AMMONIA - EFFECTS ON THE SURFACE-CHARGE AND MOLYBDENUM ADSORPTION

Previous research has shown that pretreatment of certain carbons in ammonia enhanced the activities of molybdenum-based catalysts for coal asphaltene hydrogenation. The current study examines the influence of the ammonia reaction on the surface electrical properties of the carbons with the aid. of electrophoretic mobility and adsorption experiments. The results showed that, in aqueous solution, the parent carbon was negatively charged over the range of pH investigated (about pH 3-12) and had an isoelectric point (i.e.p) of pH 2.O. Treatment of the carbon in ammonia raised the i.e.p. to pH 5.7, the carbon being positively charged below this pH value. The higher positive charge density on the ammonia-treated carbon enhanced its molybdenum adsorption capacity. © 1990.