Efficient degradation of ciprofloxacin by 3D oxygen-doped MoS2/polyacrylamide/graphene oxide composite hydrogel co-catalytic Fenton reaction

In this work, we prepared a novel recyclable 3D oxygen-doped MoS2/polyacrylamide (PAM)/graphene oxide (GO) composite hydrogel (O-MoS2-CH) and constructed an O-MoS2-CH co-catalytic Fenton system (O-MoS2-CH/Fenton) to enhance ciprofloxacin (CIP) degradation. The degradation efficiency of CIP reached 92% in O-MoS2-CH/Fenton under suitable conditions ([FeSO4 center dot 7 H2O] = 10 mg/L, [H2O2] = 0.6 mM, pH = 4.21, one O-MoS2-CH), and the degradation rate constant of O-MoS2-CH/Fenton was 1.4 times that of MoS2-CH/Fenton. Additionally, the Fe2+ content of this system was 1.5 times higher than that of MoS2-CH/Fenton. Various instrumental characterizations and density functional theory (DFT) calculations proved that O-MoS2-CH contained 2 H/1 T mixed-phase MoS2, which had a stronger ability to transfer electrons and adsorb Fe3+. The Fe3+/Fe2+ cycle was driven by the exposed Mo4+ and S2- active sites on the O-MoS2-CH surface, which further enhanced the activation of H2O2. Electron paramagnetic resonance (EPR) tests and quenching experiments verified that center dot OH and O-1(2) were dominant ROS for CIP degradation. Notably, O-MoS2-CH/Fenton could tolerate high concentrations of Cl- and NO3- (even up to 3000 mg/L). O-MoS2-CH structure kept unchanged and the co-catalytic activity decreased slightly after five cycles, and the maximum leaching of Mo was less than 0.88 mg/L. This study provides a theoretical basis and technical support for 3D O-MoS2-CH co-catalytic Fenton technology and its application in degrading residual antibiotics in water.