Degradation potential of ofloxacin and its resulting transformation products during Fenton oxidation process

The degradation of ofloxacin(OFX)in the aqueous solution by Fenton oxidation process was investigated in the present study.The optimum operating conditions for the degradation of OFX in our system was determined.More importantly,the degradation pathways on a basis of the identification of transformation products during the degradation of OFX were proposed,which revealed that the initial degradation step could be associated with the decarboxylation at the quinolone moiety.Moreover,the detachment of the F element during the Fenton oxidation process has also been detected.Since the carboxylic group within OFX has been considered as an important bridge for binding quinolones with the DNA gyrase target,the decarboxylation process would offer insights into the reduction of antibacterial potentials.

Enhanced remediation of Cr(Ⅵ)-contaminated groundwater by coupling electrokinetics with ZVI/Fe_(3)O_(4)/AC-based permeable reactive barrier

Although widely used in permeation reaction barrier(PRB)for strengthening the removal of various heavy metals,zero-valent iron(ZVI)is limited by various inherent drawbacks,such as easy passivation and poor electron transfer.As a solution,a synergistic system with PRB and electrokinetics(PRB-EK)was established and applied for the efficient removal of Cr(Ⅵ)-contaminated groundwater.As the filling material of PRB,ZVI/Fe_(3)O_(4)/activated carbon(ZVI/Fe_(3)O_(4)/AC)composites were synthesized by ball milling and thermal treatment.A series of continuous flow column experiments and batch tests was conducted to evaluate the removal efficiency of Cr(Ⅵ).Results showed that the removal efficiency of Cr(Ⅵ)remained above 93%even when the bed volume(BV)reached 2000 under the operational parameters(iron/AC mass ratio,2:1;current,5 m A).The mechanism of Cr(Ⅵ)removal by the PRB-EK system was revealed through field emission scanning electron microscopy images,X-ray diffraction,X-ray photoelectron spectroscopy,Fe^(2+) concentration,and redox potential(E h)values.The key in Cr(Ⅵ)reduction was the Fe^(2+)/Fe^(3+) cycle driven by the surface microelectrolysis of the composites.The application of an externally supplied weak direct current maintained the redox process by enhancing the electron transfer capability of the system,thereby prolonging the column lifetime.Cr(Ⅵ)chemical speciation was determined through sequential extraction,verifying the stability and safety of the system.These findings provide a scientific basis for PRB design and the in-situ remediation of Cr(Ⅵ)-contaminated groundwater.