Abstract
In this study, the monitoring of reactive oxygen species and the regeneration of the ferrous ions catalyst were performed during electro-Fenton (EF) process to highlight the influence of operating parameters. The removal of metronidazole (MTZ) was implemented in an electrochemical mono-compartment batch reactor under various ranges of current densities, initial MTZ and ferrous ions concentrations, and pH values. It was found that under 0.07 mA cm−2, 0.1 mM of ferrous ions and pH = 3, the efficiency of 100 mg L−1 MTZ degradation and mineralization were 100% within 20 min and 40% within 135 min of electrolysis, respectively. The highest hydrogen peroxide and hydroxyl radical concentrations, 1.4 mM and 2.28 mM respectively, were obtained at 60 min electrolysis at 0.07 mA cm−2. Improvement of the biodegradability was reached from 60 min of electrolysis with a BOD5/COD ratio above 0.4, which was reinforced by a respirometric study, that supports the feasibility of coupling electro-Fenton and biological treatment for the metronidazole removal.
•MTZ electroreduction involved in its degradation not in its mineralization.•Good regeneration of ferrous ions up to 0.07 mA cm−2•Highest OH production for 0.07 mA cm−2, pH 3 and 0.1 mM of ferrous ions•Limit of biodegradability reached for 60 min of electrolysis according to BOD5 test.•Results from BOD5 reinforced by respirometric study implemented during 21 days.