H2O2 electrosynthesis in a reactor without forced aeration for the complete degradation of antibiotics by photoelectro-Fenton-like process at neutral pH

Abstract

Innovative systems for H2O2-based advanced wastewater treatment avoiding the need of external aeration are pursued with great interest, since they allow decreasing the capital expenses significantly. This work shows the good performance of a rotating cylinder electrode (RCE) reactor for continuous H2O2 electrosynthesis sustained by anodic oxygen, and its use in the degradation of the antibiotic enrofloxacin (ENR) by photoelectro-Fenton (PEF) process at pH 7 using Fe(III)-ethylenediamine-N,N´-disuccinic (EDDS) acid complex as catalyst. For H2O2 accumulation in different aqueous matrices, each peripheral velocity (U) was linked to a specific limiting current (IL) using a mass transport correlation. H2O2 concentrations in the range of 2.4–3.7 mM were attained after 60 min of electrolysis at U = 198.9 cm s−1 (1000 rpm, IL = 0.31 A). At that rotation rate, the elimination of 5 mg L−1 ENR was 100 % after 30 min in a 50 mM Na2SO4 + 0.1 mM Fe(III)-EDDS. Moreover, ENR removal over 95 % was reached at 60 min in actual urban wastewater. The main by-products were oxalic and oxamic acid, accompanied by nitrate, ammonium, and fluoride ions. The superiority of PEF process as decontamination process was verified from the lower toxicity of the treated ENR solutions.