Abatement of the fluorinated antidepressant fluoxetine (Prozac) and its reaction by-products by electrochemical advanced methods, Applied Catalysis B, Environmental http://dx.GRAPHICAL ABSTRACT Fluoxetine hydrochloride (fluorinated antidepressant) 4 primary aromatics 1 chloroaromatic 4 carboxylic acids CO 2 F  NO 3  UVA light BDD(  OH)  OH Research Highlights Fluoxetine hydrochloride treated with Pt, RuO 2 -based or BDD anode and H 2 O 2 generation  Faster mineralization by PEF with a BDD anode due to BDD(  OH),  OH and UVA light  Pseudo-first-order decay by AO-H 2 O 2 , EF and, more rapidly, by PEF using a BDD anode  Degradation of fluoxetine with F  and NO 3  formation and partial Cl  oxidation to HClO  Detection of 4 primary aromatics, 1 chloroaromatic derivative and 4 carboxylic acids AbstractThe degradation of the fluorinated antidepressant fluoxetine, as hydrochloride, was comparatively studied in sulfate medium at pH 3.0 by anodic oxidation with electrogenerated H 2 O 2 (AO-H 2 O 2 ), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with 100 mL solutions in an undivided tank reactor equipped with a Pt, RuO 2 -based or boron-doped diamond (BDD) anode and an air-diffusion cathode for continuous H 2 O 2 production. The BDD anode showed higher mineralization rate due to the great production of physisorbed BDD(  OH), which has larger reactivity to oxidize the drug and intermediates. The degradation rate was enhanced by EF with 0.50 mM Fe 2+ due to the additional production of  OH in the bulk from Fenton's reaction. The degradation was even faster using PEF owing to the additional photolytic action of UVA radiation.The most effective process was PEF with a BDD anode achieving 94% mineralization at 300 min.The fluoxetine decay followed a pseudo-first-order kinetics, being quicker in the order: AO-H 2 O 2 < EF < PEF. The effect of the current density and drug concentration on the mineralization rate and fluoxetine decay was clarified. Oxidation of fluoxetine by hydroxyl radicals yielded four aromatic by-products, as found by GC-MS. Additionally, a chloroaromatic compound was identified as a result of the reaction of active chlorine, which was formed in situ from the oxidation of chloride ion at the BDD anode. Four short-chain linear carboxylic acids, being oxalic and formic acid more abundant, were identified. In PEF, fluorine atoms of fluoxetine were completely released as fluoride ion, whereas the initial nitrogen was converted to nitrate ion in all cases. A reaction pathway for fluoxetine mineralization by the electrochemical advanced methods is finally proposed.

The electrochemical degradation of tetracaine hydrochloride has been studied in urban wastewater. Treatments in simulated matrix with similar ionic composition as well as in 0.050 M NaSO were comparatively performed. The cell contained an air-diffusion cathode for HO electrogeneration and an anode selected among active Pt, IrO-based and RuO-based materials and non-active boron-doped diamond (BDD). Electrochemical oxidation with electrogenerated HO (EO-HO), electro-Fenton (EF) and photoelectro-Fenton (PEF) were comparatively assessed at pH 3.0 and constant current density. The pharmaceutical and its byproducts were oxidized by OH formed from water oxidation at the anode surface and in the bulk from Fenton's reaction, which occurred upon addition of 0.50 mM Fe in all media, along with active chlorine originated from the anodic oxidation of Cl contained in the simulated matrix and urban wastewater. The PEF process was the most powerful treatment regardless of the electrolyte composition, owing to the additional photolysis of intermediates by UVA radiation. The use of BDD led to greater mineralization compared to other anodes, being feasible the total removal of all organics from urban wastewater by PEF at long electrolysis time. Chlorinated products were largely recalcitrant when Pt, IrO-based or RuO-based anodes were used, whereas they were effectively destroyed by BDD(OH). Tetracaine decay always obeyed a pseudo-first-order kinetics, being slightly faster with the RuO-based anode in Cl media because of the higher amounts of active chlorine produced. Total nitrogen and concentrations of NH, NO, ClO, ClO and active chlorine were determined to clarify the behavior of the different electrodes in PEF. Eight intermediates were identified by GC-MS and fumaric and oxalic acids were quantified as final carboxylic acids by ion-exclusion HPLC, allowing the proposal of a plausible reaction sequence for tetracaine mineralization by PEF in Cl-containing medium.

This work reports, for the first time, the manufacture and use of an air-diffusion cathode containing CoS 2 nanoparticles to enhance the H 2 O 2 electrogeneration. Hydrothermal synthesis allowed the formation of crystalline CoS 2 with pyrite structure, either unsupported or supported on carbon nanotubes. Both kinds of catalysts were characterized by X-ray diffraction and FE-SEM combined with energy dispersive X-ray analysis. The use of carbon nanotubes as support led to a remarkable enhancement of the CoS 2 stability, as deduced from cyclic voltammetry analysis. The electrochemical activity of the CoS 2-based materials towards the oxygen reduction reaction (ORR) in acidic medium was examined by potentiodynamic techniques using a rotating disk electrode. Both catalysts showed activity towards the ORR, being predominant the twoelectron pathway to form H 2 O 2 as main product. A novel CoS 2-on-carbon nanotubes catalyzed air-diffusion cathode, as well as an uncatalyzed one made for comparison, was manufactured to electrogenerate H 2 O 2 under galvanostatic conditions in an undivided two-electrode cell. A concentration of 56.9 mM was found with the former cathode at 100 mA cm − 2 , much > 32.0 mM found with the uncatalyzed cathode. This informs about the high performance of the CoS 2 nanoparticles to promote the two-electron ORR. Finally, the treatment of aqueous solutions of the anaesthetic tetracaine at pH 3.0 and 100 mA cm − 2 by electro-oxidation and photoelectro-Fenton processes demonstrated the viability of the manufactured CoS 2-based cathode for water treatment.

The degradation of 150 mL of 0.561 mM tetracaine hydrochloride at pH 3.0 by electrochemical oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2) has been studied at a low current density of 33.3 mA cm −2 in three different matrices: 0.050 M Na 2 SO 4 , real urban wastewater and a simulated matrix mimicking its electrolyte composition. Comparative trials were performed in an undivided cell with a 3 cm 2 boron-doped diamond (BDD), Pt, IrO 2-based or RuO 2-based anode and a 3 cm 2 air-diffusion cathode that allowed continuous H 2 O 2 electrogeneration. In 0.050 M Na 2 SO 4 , much faster and overall removal of tetracaine occurred using BDD because of the large oxidation ability of BDD(OH) formed from anodic water oxidation. In either simulated matrix or real wastewater, the RuO 2-based anode yielded the quickest tetracaine decay due to a large production of active chlorine from anodic oxidation of Cl −. For the mineralization of the organic matter content, the BDD/air-diffusion cell was the best choice in all aqueous matrices, always reaching more than 50% of total organic carbon abatement after 360 min of electrolysis, as expected if BDD(OH) mineralizes more easily the chloroderivatives formed from tetracaine oxidation in the presence of active chlorine. The initial N of tetracaine was partly transformed into NO 3 − , although the total nitrogen of all solutions always decayed by the release of volatile by-products. In the Cl −-containing matrices, significant amounts of ClO 3 − and ClO 4 − were obtained using BDD, whereas active chlorine was much largely produced using the RuO 2-based anode. Five aromatic by-products, one of them being chlorinated, along with low concentrations of oxalic acid were identified. The change in toxicity during EO-H 2 O 2 with BDD in the sulfate and simulated matrices was also assessed.