Deciphering co-catalytic mechanisms of potassium doped g-C3N4 in Fenton process

Abstract

Conventional Fenton reaction for the pollutant removal is restricted by incomplete H2O2 decomposition due to the low efficient Fe(III)/Fe(II) cycle. In this study, the co-catalytic Fenton processes with g-C3N4 and the roles of potassium doping in the diverse mechanisms were comprehensively investigated. The degradation rate of enrofloxacin (ENR) in g-CN-3.9 %K/Fe(III)/H2O2 was 204 times higher than that in conventional Fenton reaction. This significant enhancement was ascribed to the readily formed complex between Fe(III) and K doped g-C3N4. The K doping facilitated the transfer of photoexcited e− from g-CN-3.9 %K surface to Fe(III), leading to an accelerated Fe(III) reduction to Fe(II). In addition, this complex was coordinated and oxidized by H2O2, resulting in the formation of Fe(V) which quickly degraded ENR. Without K doping, on the other hand, only O2 dominated the degradation of ENR in g-CN/Fe(III)/H2O2 due to the lack of Fe(III) complexation. This study provides a new perspective for regulating the transfer directions of the photoexcited e− with K doping in g-C3N4/Fenton coupled catalytic system for water purification.