Innovative wastewater treatment based on electrodeposited thin film: Systematic studies of interfacial processes between birnessite and Mn(II) for a better efficiency

Abstract Electrodeposited birnessite thin films have remarkable properties for spontaneous degradation of organic pollutants until mineralization via a complex mechanism of charge transfer reactions. But, birnessite may be transformed into passivated material by reaction with Mn(II) species generated during the reduction of birnessite due to oxidation of organic pollutants. Such modification could imply a possible inhibition of the degradation process, a depreciated condition for future applications. This paper focuses on the determination of the real robustness of electrodeposited birnessite thin films and their quality for innovative wastewater treatment. Systematical studies were performed with solutions containing different Mn(II) concentrations in presence and in absence of oxygen to have unfavorable conditions. Samples were characterized at macroscopic scales (SEM and XRD) in addition to a focused study on the chemical modification at the extreme near surface by XPS. Open circuit potential (OCP) was also followed to complete the study. Similar characterizations were performed after interaction with organic pollutants solutions. As a result, nature and structure of the bulk and the near surface of birnessite stay unchanged after long times even in absence of oxygen or in presence of organic pollutants at high concentrations, proving their very good robustness and real interests for future applications.