Interplay of bicarbonate and the oxygen-containing groups of carbon nanotubes dominated the metal-free activation of peroxymonosulfate

Abstract Revealing how different physicochemical/texture properties and water matrices affect the carbocatalysis-based oxidation processes (COPs) is critical to develop green remediation methods for wastewater detoxification. However, the interplay of oxygen-containing groups (OCGs) of carbocatalysts and alkalinity on the oxidation behavior of organic pollutants by COPs is rarely documented. In this study, we investigated the mutual effects of OCGs and bicarbonate on the catalytic activation of Peroxymonosulfate (PMS) by carbon nanotubes (CNTs) with respect to the formation of Reactive oxygen species (ROS) and oxidation behavior of ibuprofen. The profiles of the removal kinetics of ibuprofen, degradation products, and product toxicity highly rely on the OCGs and bicarbonate-regulated ROS. The C O groups within CNTs serve as an electron donor to cleave the O O bond of PMS for producing •OH. Increasing the amount of electron-rich C O/C OH groups can induce the formation of SO4•−. The electron-rich OCGs deprotonated by bicarbonate promote the PMS activation/decomposition to generate more •OH and/or SO4•−, while the deprotonated electron-deficient OCGs can activate PMS to form 1O2. The HCO3−/CO32− in the bicarbonate-containing CNTs/PMS system can partially quench •OH and SO4•− to produce CO3•−. Despite the diverse ROS controlled by OCGs and bicarbonate, •OH and/or SO4•−-initiated H-atom abstraction reactions are the first steps for the degradation of target contaminant.