Investigating the original activity of amino group over carbon in peroxymonosulfate-based advanced oxidation processes

Metal-free catalysts featuring nitrogen defects have been developed rapidly in peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) for treating the organic wastewater. While a great deal of research has been conducted on the doped N sites such as pyridinic N, pyrrolic N and graphitic N, less attention has been paid to the role of modified N site (amino group) due to the low catalytic activity. To investigate the original activity of amino group over carbon, in this work, we selected two typical supports including a carbon support (graphene oxide) and a non-carbon support (silica), and subsequently functionalized both with amino groups. The phenol degradation performances in PMS-AOPs revealed that only amino-functionalized reduced graphene oxide could activate PMS, thus achieving the pollutant removal. To better understand the structure–activity relationship between amino groups and carbon supports, we enhanced the degree of reduction of graphene oxide by raising the synthesis temperature during amino group modification. Activity evaluation, reactive oxygen species analysis and density functional theory simulations demonstrated that as the content of hydroxyl groups decreased, both the adsorption and electron transfer of reactants were enhanced, thereby enhancing the contribution of non-radical pathway. Through this facile regulation of synthesis temperatures, the reaction rate constant for phenol degradation in PMS-AOPs using aminated graphene increased by approximately 4.8 times. This work provides a new insight into designing the efficient catalyst with amino sites for PMS-AOPs.