Near‐neutral Electro‐Fenton Treatment of Pharmaceutical Pollutants: Effect of Using a Triphosphate Ligand and BDD Electrode

Abstract

In this work, a mixture of pharmaceutical pollutants was successfully treated by electro-Fenton (EF) at near-neutral pH using the inorganic ligand triphosphate (TPP). The effect of the ligand and the reactivity of its Fe complexes were thoroughly investigated under different conditions of TPP : Fe 2 + ratio, Fe 2 + and TPP concentrations, current density, and nature of the anode material (Ti/IrO 2 À RuO 2 and boron doped diamond, BDD). The mineralization of organics was mainly controlled by the EF reaction promoted by the continuous electrochemical formation of H 2 O 2 and regeneration of Fe 2 + (as Fe 2 + -TPP), while the main role of the ligand was to keep active Fe 2 + ions dissolved in solution to catalyze the Fenton's reaction at near-neutral pH. The results contrasted with previous works that reported the ability of Fe-TPP to enhance the oxidation performance of Fenton-like systems. Moreover, the remarkable oxidative properties of diamond electrodes enhanced the mineralization efficiency and TPP was not detrimental to oxidation with BDD. Finally, the degradation kinetics of all the compounds under investigation were determined, and a pathway for the antidepressant amitriptyline (ATTL) was proposed.* OH oxidation and thus, diminishing [a] Dr.

Electro-Fenton beyond the Degradation of Organics: Treatment of Thiosalts in Contaminated Mine Water

“…In fact, BDD is known to be a powerful anode material for the mineralization of organic contaminants and its use in EF has been reported to significantly enhance the overall efficiency of the process. 36 The increase of the S 2 O 3 2− degradation rate was much less pronounced when the current density rose further to 10.43 and 15.63 mA cm −2 . The simultaneous rise of the rate of parasitic reactions reducing H 2 O 2 and BDD( • OH) production as the applied current density increased might explain this effect (eqs 15 −17).…”

“…This behavior is attributed to an acceleration of the rate of reaction described in eq , producing H 2 O 2 at the cathode, and of the reaction described in eq , producing surface-adsorbed • OH radicals at the BDD anode (BDD­( • OH)). In fact, BDD is known to be a powerful anode material for the mineralization of organic contaminants and its use in EF has been reported to significantly enhance the overall efficiency of the process . The increase of the S 2 O 3 2– degradation rate was much less pronounced when the current density rose further to 10.43 and 15.63 mA cm –2 .…”

Critical Review on the Mechanisms of Fe2+ Regeneration in the Electro-Fenton Process: Fundamentals and Boosting Strategies

“…Following the pioneering work of Wang et al describing the chelating properties of tetrapolyphosphate, we used polyphosphates like tetrapolyphosphate (4-TPP), tripolyphosphate (3-TPP), and pyrophosphate (PP) as supporting electrolytes to circumvent the pH limitations in the EF process (see reactions –). , As an interesting result, it was found that the addition of TPP accelerated the cathodic cycle of Fe 3+ /Fe 2+ via decreasing the redox potential, also promoting the oxidation of Fe 2+ to form • OH. Figure shows that the • OH generation ability decreased in the order: Fe 2+ -4-TPP > Fe 2+ -3-TPP > Fe 2+ -PP ≈ Fe 2+ -PO 4 , which was in good agreement with charge transfer calculations by DFT and ultraviolet photoemission spectroscopy (UPS, Figure c). , The potential eutrophication concern derived from the presence of polyphosphate supporting electrolytes was addressed by CaCl 2 precipitation, and a promising high value-added compound was obtained after treatment …”

Recent advances in electro-Fenton process and its emerging applications

“…Peroxi-coagulation (PC), fered-Fenton (FF) and anodic-Fenton (AF) are the best examples of such modified processes. In PC process, sacrificial anodes such as iron or stainless steel are used (instead of stable anodes in EF process) to generate ferrous ions in the electrolytic system (Nidheesh & Gandhimathi, 2012;Olvera-Vargas et al, 2019b). However, controlling ferrous ion generation is quite difficult and ultimately PC process is considered as the combination of electrocoagulation and EF process Kumar et al, 2018).…”