Surface properties of activated carbons in relation to their ability to adsorb nonylphenol aqueous contaminant

Abstract

Nonylphenol is a compound with estrogenic activity that is found in aquatic environments as a consequence of the biodegradation of nonylphenyl polyethoxylates discharged by many industries. The adsorption capacity for nonylphenol from aqueous solutions has been studied for four commercial microporous carbons. The texture and properties of the activated carbons were studied by means of N₂ adsorption at 77 K and CO₂ adsorption at 273 K, X-ray diffraction, immersion calorimetry and chemical analyses. Two-step isotherms have been determined for all carbons. The first isotherm plateau of the adsorbed nonylphenol is related to the mean pore width of the activated carbons. The second plateau seems to be related to the presence of inorganic impurities (carbonates and SiO₂). Depending on the type of inorganic carbonate impurity, different behaviour was found for the nonylphenol adsorption. These differences are attributed to the type of inorganic components present in the carbon, as well as their particle sizes and locations in the porous framework. Finally, the introduction of acidic oxygen surface groups on the activated carbon surface enhances nonylphenol adsorption.