Influence of Surface Modification by Nitric Acid on Activated Carbon's Adsorption of Nickel Ions

Abstract

Four kinds of commercial activated carbons were soaked in sodium hydroxide after modification with 10% nitric acid. Nickel adsorption isotherms for modified activated carbons before and after sodium hydroxide treatment were tested. The surface groups were characterized by the Fourier transform infrared spectroscopy and Boehm titration, the adsorption properties were determined by the iodine number and methylene blue number, the pHIEP were deduced by the Zeta potential analyzer. The results showed that nitric acid blocks the pore, while enhances the content of acid groups, especially carboxyl resulting in the decrease of nickel adsorption capacity. After sodium hydroxide treatment, the nickel capacity of activated carbon from anthracite, long flame coal, lignite and coconut increased by 21.5%, 116%, 78.9%, 89.1% comparing with the virgin activated carbon, respectively. The overall research indicated that nickel ion adsorption capacity of activated carbon can be improved only when the acid groups are transferred into anion, and the modification is more effective on the activated carbon prepared by low metamorphic grade coal.