Assessment of 4-aminoantipyrine degradation and mineralization by photoelectro-Fenton with a boron-doped diamond anode: optimization, treatment in municipal secondary effluent, and toxicity

Abstract

4‐Aminoantipyrine (4‐AA), a persistent metabolite of dipyrone found in natural water, has been treated in 100 mL of aqueous 0.050 M Na2SO4 solutions at pH 3.0 by photoelectro‐Fenton (PEF) with a 4 W UVA lamp. The assays were performed in a cell equipped with a boron‐doped diamond (BDD) anode and an air‐diffusion cathode for H2O2 generation. The formation of an unstable Fe(III)‐4‐AA complex with 1 : 2 molar ratio was evidenced. A 24 central composite design was used to assess the effect of four independent variables on PEF performance. The optimized conditions for 62.5 mg L−1 4‐AA were: current density of 77.5 mA cm−2 and 47.75 mg L−1 Fe2+, yielding 99 % 4‐AA degradation at 7 min, and 45 % 4‐AA mineralization with 3.2 % mineralization current efficiency at 130 min. Slightly slower degradation and similar mineralization were obtained under these conditions when 4‐AA was spiked into a municipal secondary effluent, showing a low influence of natural organic matter on PEF. The initially high acute toxicity determined using Artemia salina was largely diminished upon PEF treatment.