Surface chemistry of wood-based phosphoric acid-activated carbons and its effects on adsorptivity

The surface oxygen content of selected wood-based phosphoric acid-activated carbons was quantified using X-ray photoelectron spectroscopy (XPS) and correlated with the residual bulk phosphate levels of the carbons and their adsorptivity in solution. The adsorption of Al³⁺, Cu²⁺, and parachlorophenol, respectively, from water decreased as a function of increasing surface oxygen content of the carbons. When the carbon of lowest surface oxygen content was oxidized with ozone to impart a surface oxygen content comparable to that of a carbon with a much higher phosphate level, adsorption of Al³⁺, Cu²⁺, and para-chlorophenol from water decreased proportionally. The increase in polarity of the carbon surface was accompanied by a decrease in pH and appeared to be the dominant factor with respect to the adsorption of the target species from water.