Minute Cu2+ coupling with HCO3− for efficient degradation of acetaminophen via H2O2 activation

Homogeneous Cu2+-mediated activation of H2O2 has been widely applied for the removal of organic contaminants, but fairly high dosage of Cu2+ is generally required and may cause secondary pollution. In the present study, minute Cu2+ (2.5 μM) catalyzed H2O2 exhibited excellent efficiency in degradation of organic pollutants with the assistant of naturally occurring level HCO3− (1 mM). In a typical case, acetaminophen (ACE) was completely eliminated within 10 min which followed the pseudo-first-order kinetics. Singlet oxygen and superoxide radical rather than traditionally identified hydroxyl radical were the predominant reactive oxygen species (ROS) responsible for ACE degradation. Meanwhile, Cu3+ was deduced through Cu+ and p-hydroxybenzoic acid formation analysis. CuCO3(aq) was the main complex with high reactivity for the activation of H2O2 to form ROS and Cu3+. The removal efficiency of ACE depended on the operating parameters, such as Cu2+, HCO3− and H2O2 dosage, solution initial pH. The presence of Cl−, HPO42−, humic acid were found to retard ACE removal while other anions such as SO42− and NO3− had no obvious effect. ACE exhibited lower degradation efficiency in real water matrices than that in ultra-pure water. Nevertheless, 58–100% of ACE was removed from domestic wastewater, lake water and tap water within 60 min. Moreover, eight intermediate products were identified and the possible degradation pathways of ACE were proposed. Additionally, other typical organic pollutants including bisphenol A, norfloxacin, lomefloxacin hydrochloride and sulfadiazine, exhibited great removal efficiency in the Cu2+/H2O2/HCO3− system.