Aminated N-doped graphene hydrogel for long-term catalytic oxidation in strong acidic environment

Highlights: • Aminated N-doped graphene hydrogel is synthesized with free-standing and porous structure. • The ANGH has high activity and long lifetime for PMS activation under strong-acidic condition. • The active sites of ANGH will transform from N containing groups into oxygenous groups. • ANGH can be reused for rhodamine B degradation on a large scale after phenol degradation. Metal-based catalysts in advanced oxidation processes (AOPs) are not stable under strong acidic condition due to the remarkable leaching, which will also lead to a secondary pollution. In this study, an aminated N-doped graphene hydrogel (ANGH) is synthesized from graphene oxide and ethylenediamine (EDA) via an in-situ hydrothermal process. The ANGH shows a free-standing structure and has high catalytic activity especially in phenol degradation under strong-acidic condition because of a non-radical dominated mechanism determined in this process. On the large scale, a longer lifetime of ∼1700 min for ANGH is obtained under strong-acidic condition on a dynamic amplifying device, 2.9 times longer than that at neutral condition. It is proposed that amine N can be protected by hydrogen ions from being oxidized, thus leading to the better stability. Meanwhile, the active sites of ANGH can transform from N containing groups into oxygenous groups, and the deactivated material can be reutilized 10 times for rhodamine B degradation on a large scale. The ANGH synthesized facilely and could be recycled repeatedly, which is also very stable in the strong acidic environment, thus should have great potential in wastewater remediation.