Graphene oxide mediated Fe(III) reduction for enhancing Fe(III)/HO Fenton and photo-Fenton oxidation toward chloramphenicol degradation.

Slow reduction of Fe(III) in iron-mediated Fenton-like systems strongly limits the decomposition of HO to produce hydroxyl radicals (OH). Here, we report that graphene oxide (GO) possesses excellent reactivity to enhance the Fe(III)/HO Fenton and photo-Fenton oxidation for degrading chloramphenicol (CAP). EPR analysis and quenching tests reveal that OH is the primary oxidant for CAP degradation. The characterization analysis and iron species transformation experiments demonstrate that Fe(III) can combine with the functional groups on the GO surface to form GO-Fe(III) complexes. The chronopotentiometry and cyclic voltammogram suggest that GO can donate electrons to Fe(III) via intramolecular electron transfer and promote HO induced Fe(III) reduction by increasing the oxidation capability of Fe(III) due to the formation of GO-Fe(III) complexes, resulting in the strong promotion of the Fe(III)/Fe(II) cycle for producing OH. Moreover, the dark- and vis-GO/Fe(III)/HO systems can effectively degrade CAP at initial pH ranging from 2.0 to 4.7. The reusability and stability of GO were evaluated by performing the cyclic degradation experiments of CAP. The OH induced degradation pathway of CAP was proposed involving three stages, based on intermediates analysis of UPLC-QTOF-MS/MS system. Therefore, the GO/Fe(III)/HO system with or without visible light shows high potential for application in environmental remediation.