Abstract
Catalytic NO2 removal by activated carbon loading Ag, Pt, Cu and CuO has been studied. In this experiment, activated carbon from coconut shells was used after washing with 1 mol dm−3 HCl and water. Activated carbon lording metals was prepared by adsorbing metal complexes (H2PtCl6, CuII-picolinate) or metal ion (Ag+), followed by heating the activated carbon at 700 °C in N2 atmosphere. Copper(II) oxide on activated carbon (CuO/AC) was prepared by heating the Cu/AC at 400 °C in air. Nitrogen dioxide was generated by decomposition of Pb(NO3)2 at 550 °C and circulated in a catalyst column packed with activated carbon (Fig. 1). Nitrogen dioxide was highly removed by Pt/AC, Cu/AC and CuO/AC in air or nitrogen atmosphere but less by Ag/AC (Fig. 3, 4). After the removal of NO2, very small amounts of HNO3, HNO2, NO and NH3 existed in the gas phase and the increase in N-contents on activeted carbon was small (Table 1). From the XRD patterns of activated carbon after removal of NO2, it was suggested that the oxidation state of Pt was not changed but the peak height decreased (Fig. 5). On the other hand, XRD patters of Cu/AC and CuO/AC indicated the presence of Cu, Cu2O and CuO in air and Cu and Cu2O in N2 atmosphere (Fig. 6, 7). These results indicate that activated carbon loading Pt or Cu is a good catalyst for removal of NO2 and NO2 may be reduced to N2 by catalysis of Pt, Cu or Cu2O.
