Adsorption of model naphthenic acids in water with granular activated carbon

Abstract

This work evaluated the adsorption performance of a commercial granular activated carbon (GAC) for three naphthenic acids (NAs) model compounds. In single-compound adsorption, the saturation capacity (qm) at pH 4 was 452.6 mg/g (1,4-cyclohexanedicarboxylic acid) > 357.9 mg/g (2-naphthoic acid) > 317.7 mg/g (diphenylacetic acid). Of all model NAs, adsorption of 1,4-cyclohexanedicarboxylic acid was the most negatively affected in multi-component adsorption at pH 4. The qm decreased significantly with increasing pH due to its effect on both carbon surface charge and dissociation of the NAs. An important finding was that the total amount of NAs adsorbed in multi-component adsorption at pH 4 (326 mg/g) was almost the same as that adsorbed at pH 8 (324 mg/g), indicating the potential of activated carbon adsorption for removal of mixture of NAs from the real oil sand process water, which is basic (pH~8) in nature.