Surface modification of pitch-based spherical activated carbon by CVD of NH3 to improve its adsorption to uric acid

Surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by chemical vapor deposition of NH(3) (NH(3)-CVD) to improve the adsorption properties of uric acid. The texture and surface chemistry of PSAC were studied by N(2) adsorption, pHPZC (point of zero charge), acid-base titration and Xray photoelectron spectroscopy (XPS). NH(3)-CVD has a limited effect on carbon textural characteristics but it significantly changed the surface chemical properties, resulting in positive effects on uric acid adsorption. After modi. cation by NH(3)-CVD, large numbers of nitrogen-containing groups (especially valley-N and center-N) are introduced on the surface of PSAC, which is responsible for the increase of pHPZC, surface basicity and uric acid adsorption capacity. Pseudo-second-order kinetic model can be used to describe the dynamic adsorption of uric acid on PSAC, and the thermodynamic parameters show that the adsorption of uric acid on PSAC is spontaneous, endothermic and irreversible process in nature. (C) 2008 Published by Elsevier B. V.