Degradation of anthracene, pyrene and benzo[a]-anthracene in aqueous solution by chlorine dioxide

Abstract

Polycyclic aromatic hydrocarbons (PAHs) constitute an important group of micropollutants, which are known to be mutagenic, carcinogenic and/or co-carcinogenic and relatively persistent in the environment. The effects of chlorine dioxide (ClO 2 ) on the degradation of anthracene (ANTH), pyrene (PYR) and benzo[a]anthracene (BaA) in aqueous solution were investigated using high performance liquid chromatography (HPLC). In preliminary experiments, it was observed that ClO 2 could remove these three PAHs effectively within a short time. Several factors including reaction time, the concentration of ClO 2 and pH of the reaction mixture influencing the degradation ratio of PAHs have been studied by batch experiments. The results showed that the degradation ratio of PAHs was af-fected by reaction time and the concentration of ClO 2 instead of pH. The degradation ratio of ANTH, PYR and BaA could reach their maximum as approximately 99.0%, 67.5% and 89.5%, respectively, under the condition as follows: reaction time 30, 60 and 120 min, the concentration of ClO 2 0.1, 0.4 and 0.5 mmol·L -1 , and pH 7.2. ANTH was selected as the representative to study the reaction mechanism with ClO 2 . The oxidation products formed in the reaction of ANTH with ClO 2 were tentatively identified by gas chromatography-mass spectrometry (GC-MS), and the results showed that the main product was 9, 10-anthraquinone, which could be biodegraded more easily and quickly than ANTH. Through analyzing the reaction properties of ANTH and ClO 2 , the possible pathway for the ANTH-ClO 2 reaction was proposed based on the theory of single electron transfer (SET).