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

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)-O-center dot. Increasing the amount of electron-rich C-O/C-OH groups can induce the formation of SO4 center dot-. 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 O-1(2). The HCO3-/CO32- in the bicarbonate-containing CNTs/PMS system can partially quench (OH)-O-center dot and SO4 center dot- to produce CO3 center dot- Despite the diverse ROS controlled by OCGs and bicarbonate, (OH)-O-center dot and/or SO4 center dot--initiated H-atom abstraction reactions are the first steps for the degradation of target contaminant.

Automated summary

Understanding the interplay of oxygen-containing groups (OCGs) and alkalinity on the oxidation behavior of organic pollutants by carbon-based oxidation processes is crucial for developing green remediation methods. The study found that electron-rich OCGs deprotonated by bicarbonate can promote the activation of Peroxymonosulfate (PMS) to generate more reactive oxygen species (ROS) for the degradation of target contaminants. Despite the diverse ROS controlled by OCGs and bicarbonate, (OH)-O-center dot and/or SO4 center dot--initiated H-atom abstraction reactions are identified as the first steps in the degradation process.