Activated carbon surfaces were modified using molten KNO3 to introduce functional groups and form microtextures. Their surface treatment temperatures were 250—300 °C; the melting point of KNO3 is 337 °C. Microtextures formed on the surfaces of the activated carbons during the molten KNO3 treatment. Furthermore, various functional groups such as -COOH, -COO, and -CO, were observed clearly in XPS spectra of the surface-modified activated carbons. Their metal-ion adsorption ability increased in the order of activated carbon modified at 300 °C > activated carbon modified at 250 °C > original activated carbon.
