抄録
Activated carbon (AC) was treated by ammonia gas to introduce nitrogen element on the graphite sheets for enhancing adsorption amount of copper(II) ions in aqueous solution. The nitrogen content was increased with the rise in NH3 treatment temperature. Though any significant textural properties was not observed in the NH3 treatment up to 700 °C , BET and meso-pore specific surface areas were increased above 800 °C indicating that the NH3 etched and gasified carbons to produce CH4. AC was also out-gassed in He flow at 1000 °C to remove surface acidic oxygen for the comparison with the NH3 treatment. Successfully applying the Langmuir adsorption isotherms to the experimental results, the adsorption capacity of copper(II) ions onto the NH3 treated AC at 700 °C (7AG) was greater than the outgassed carbon (OG). The amount of copper(II) ions desorption from 7AG was smaller than that from OG. In contrast, adsorption amount of proton on 7AG was smaller than that of OG from the pH alternation, suggesting that π-electrons on the graphene layers might be withdrawn by nitrogen introduced, then π-electrons density would be decreased. Some amount of copper(II) ions adsorption onto 7AG could be observed even if the pH was less than 3, whereas it was hardly taken place for OG. Based on the experimental results, the introduced nitrogen atoms are estimated to become new strong adsorption sites for the copper(II) ions adsorption, probably transferring loan pair electrons of nitrogen on the graphite sheets to the copper(II) ions.
