Single-atom Mn anchored on N-doped graphene oxide for efficient adsorption-photocatalytic degradation of sulfanilamide in water: Electronic interaction and mineralization pathway

• Mn-NGO enhanced adsorption-photodegradation of SNM in lake, tap, and DI water. • Single-atom Mn anchored on N-GO with interactions of d electrons and π rings. • Removal mechanism was studied by electronic channels and active radios. • The degradation of SNM starts from two pathways of C6-S14 and C3-N11 cleavage. • SNM removal rate of Mn-NGO remained at 55.6% after six cycles of reaction. Synergy between adsorption and photocatalysis provides an ideal green technology to treat antibiotic pollution in water. In this study, single-atom Mn anchored on N-doped graphene oxide (Mn-NGO) was synthesized for enhanced adsorptive-photocatalytic removal of aqueous sulfanilamide (SNM) and the corresponding mechanisms were revealed. The Mn-NGO had better performance of SNM degradation and TOC removal than GO and NGO. Density functional theory (DFT) calculation showed that the electrons of d-orbital (Mn) and p-orbital (N) upgraded the electronic structures of GO of the Mn-NGO to interact with amino and aromatic rings of SNM, increasing the adsorption and polarizing of SNM. Furthermore, more hydroxyl and superoxide radicals were observed on Mn-NGO, leading to the generation of key reaction intermediates of 2-aminohydroquinone and benzenesulfonic and thus subsequently opening loops and mineralizing SNM. In addition, Mn-NGO effectively removed SNM in different types of water systems (e.g., lake water, tap water, and deionized water) through synergistic adsorption-photocatalytic degradation.