Enhanced antibiotic removal through a dual-reaction-center Fenton-like process in 3D graphene based hydrogels

Abstract

Considerable attention has been paid to water treatment using nanomaterials. In this study, ethylene glycol (EG) is used to control the formation of α-FeOOH/reduced graphene oxide (RGO) hydrogels in a facile way. The EG-promoted α-FeOOH/RGO hydrogels exhibit higher moisture content, more porous structure, lower agglomeration, larger swelling, higher specific area, more defects in graphene sheets, stronger Fe–O–C bonds, and higher roughness than those without modification. More importantly and interestingly, we found for the first time that the α-FeOOH/RGO hydrogels could generate reactive oxygen species (ROS) without the addition of H₂O₂, and this property is also enhanced in EG-promoted hydrogels due to (i) the increase in defects in graphene sheets leading to enhanced oxygen reduction reaction (ORR) and (ii) the strengthening of Fe–O–C bonds relating to dual reaction centers with stronger generation of ˙OH. In tetracycline degradation from water, the increase in electron density disparity in the material and the promoted role of tetracycline as an electron donor are proved to be the main reasons for the enhanced tetracycline removal from aqueous solution. Results obtained through density functional theory (DFT) indicate that the electrons could be transferred from the N area in tetracycline to the Fe area in the material, based on which we found a special π–π interaction (between tetracycline and graphene) coupled with π–Fe interactions (between graphene and α-FeOOH) as an efficient pollutant removal method. Our findings provide a simple strategy for the structure improvement of environmental nanomaterials and enrich their mechanism studies.