Highly active based iron-carbonaceous cathodes for heterogeneous electro-Fenton process: Application to degradation of parabens

Personal care products are known as endocrine-disrupting compounds and their degradation is a matter of concern to avoid their release into the environment. For this reason, the main objective of this study is to develop an effective advanced oxidation process able to degrade a paraben as methyl paraben (MePa). Initially, the efficiency of two electrodes, Graphite felt (GF) and Ruthenium (Ru), was compared on the degradation of MePa by anodic oxidation (AO) and electro-Fenton (EF). Near complete degradation was obtained after 1 h when Graphite felt (GF) was used as cathode in EF, showing the superiority of this treatment over AO. To improve this process, heterogeneous EF through inclusion of iron into the cathode was carried out. To do that, four iron-carbonaceous cathodes were prepared based on GF (raw or activated with H2SO4, named AGF-1) showing a significant iron content (25-30%) and attaining high degradation values (95-100%) in all of them. From preliminary experiments was determined that by the use of AGF-1 as cathode the electrode performance improved, reducing significantly the treatment time required and the total amount of MePa contained in the solution had disappeared after 30 min with a TOC reduction of 98.68% after 120 min. The profiles of MePa exhibit an exponential decay throughout time being satisfactorily described by pseudo-first order reaction kinetic showing a maximum degradation rate of around 0.143 min−1 at optimal conditions (100 mA and pH 3). In addition, the selected cathode showed high structural and catalytic stability after several reuses. Finally, key steps of a plausible degradation pathway were tailored in accordance with identified and quantified intermediate products of the degradation process.