Performance of Nb/BDD material for the electrochemical advanced oxidation of prednisone in different water matrix.

Glucocorticoids are widely used to treat a variety of diseases. Consequently, these compounds have been found in water and wastewater matrix. Despite studies have proven its toxicity, just a few works investigate techniques to degrade and mineralize them. To solve this issue, this work presents the degradation and mineralization of prednisone (PRED) by electrochemical advanced oxidation (EAO) using a boron-doped diamond supported on niobium (Nb/BDD) anode in synthetic and real wastewater. Cyclic voltammetry (CV) was performed to investigate the PRED oxidation mechanisms. CV suggest that PRED will be oxidized via HO• and other oxidants generated from the ions present in the liquid matrix (S2O82-, SO4•-, HClO, ClO- etc.). Different EAO conditions as initial pH (3, 7 and 11) and applied current densities (5, 10 and 20 mA cm-2) were evaluated. The best result was obtained at alkaline pH (11) and a current density of 20 mA cm-2, achieving 78% of degradation and 42% of mineralization. Using the best conditions, the EAO was applied as a polishing treatment stage to remove PRED from a biological pre-treated municipal wastewater spiked with PRED. The results indicate that EAO applied in the real matrix provides better results than the synthetic solution, probably associated with the presence of ions that can be electrochemically converted into oxidant species, resulting in higher kinetic constant, mineralization current efficiency and lower energetic consumption. Therefore, the EAO process without the addition of chemicals has proven to be an effective alternative as a tertiary treatment of municipal wastewater contaminated with PRED.

Electrooxidation Using Nb/BDD as Post-Treatment of a Reverse Osmosis Concentrate in the Petrochemical Industry.

This work evaluated the performance of an electrochemical oxidation process (EOP), using boron-doped diamond on niobium substrate (Nb/BDD), for the treatment of a reverse osmosis concentrate (ROC) produced from a petrochemical wastewater. The effects of applied current density (5, 10, or 20 mA·cm-2) and oxidation time (0 to 5 h) were evaluated following changes in chemical oxygen demand (COD) and total organic carbon (TOC). Current efficiency and specific energy consumption were also evaluated. Besides, the organic byproducts generated by EOP were analyzed by gas chromatography coupled to mass spectrometry (GC⁻MS). The results show that current densities and oxidation time lead to a COD and TOC reduction. For the 20 mA·cm-2, changes in the kinetic regime were found at 3 h and associated to the oxidation of inorganic ions by chlorinated species. After 3 h, the oxidants act in the organic oxidation, leading to a TOC removal of 71%. Although, due to the evolution of parallel reactions (O2, H2O2, and O3), the specific energy consumption also increased, the resulting consumption value of 66.5 kW·h·kg-1 of COD is considered a low energy requirement representing lower treatment costs. These results encourage the applicability of EOP equipped with Nb/BDD as a treatment process for the ROC.