Hugo Olvera-Vargas

Bioelectro-Fenton: A sustainable integrated process for removal of organic pollutants from water: Application to mineralization of metoprolol

The relevant environmental hazard related to the presence of pharmaceuticals in water sources requires the development of high effective and suitable wastewater treatment technologies. In the present work, a hybrid process coupling electro-Fenton (EF) process and aerobic biological treatment (Bio-EF process) was implemented for the efficient and cost-effective mineralization of beta-blocker metoprolol (MPTL) aqueous solutions. Firstly, operating factors influencing EF process were assessed. MTPL solutions were completely mineralized after 4h-electrolysis under optimal operating conditions and BDD anode demonstrated its oxidation superiority. The absolute rate constant of MTPL oxidation byOH (kMTPL) was determined by the competition kinetics method and found to be (1.72±0.04)×10(9)M(-1)s(-1). A reaction pathway for the mineralization of the drug was proposed based on the identification of oxidation by-products. Secondly, EF process was used as pre-treatment. An increase of BOD5/COD ratio from 0.012 to 0.44 was obtained after 1h EF treatment, along with 47% TOC removal and a significant decrease of toxicity, demonstrating the feasibility of a post-biological treatment. Finally, biological treatment successfully oxidized 43% of the total TOC content. An overall 90% mineralization of MPTL solutions was achieved by the Bio-EF process, demonstrating its potentiality for treating wastewater containing pharmaceutical residues.

A coupled Bio-EF process for mineralization of the pharmaceuticals furosemide and ranitidine: Feasibility assessment

A coupled Bio-EF treatment has been applied as a reliable process for the degradation of the pharmaceuticals furosemide (FRSM) and ranitidine (RNTD) in aqueous medium, in order to reduce the high energy consumption related to electrochemical technology. In the first stage of this study, electrochemical degradation of the drugs was assessed by the electro-Fenton process (EF) using a BDD/carbon-felt cell. Biodegradability of the drugs solutions was enhanced reaching BOD5/COD ratios close to the biodegradability threshold of 0.4, evidencing the formation of bio-compatible by-products (mainly short-chain carboxylic acids) which are suitable for biological post-treatment. Moreover, toxicity evaluation by the Microtox(®) method revealed that EF pre-treatment was able of detoxifying both, FRSM and RNTD solutions, constituting another indicator of biodegradability of EF treated solutions. In the second stage, electrolyzed solutions were treated by means of an aerobic biological process. A significant part of the short-chain carboxylic acids formed during the electrochemical phase was satisfactorily removed by the used selected microorganisms. The results obtained demonstrate the efficiency and feasibility of the integrated Bio-EF process.

Heterogeneous Electro-Fenton Process: Principles and Applications

Electro-Fenton (EF) process has received much attention among the various advanced oxidation process, due to its higher contaminant removal and mineralization efficiencies, simplicity in operation, in situ generation of hydrogen peroxide, etc. Heterogeneous EF process rectifies some of the drawbacks of conventional EF process by using solid catalyst for the generation of reactive hydroxyl radicals in water medium. The efficiency of various heterogeneous EF catalysts such as iron oxides, pyrite, iron supported on zeolite, carbon, alginate beads, etc. was tested by various researchers. All of these catalysts are insoluble in water; and most of them are stable and reusable in nature. Depending on the iron leaching characteristics, hydroxyl radicals are generated either in the solution or over the catalyst surface. Catalysts with higher leaching characteristics exhibit the first radical generation mechanism, while the stable catalyst with insignificant leaching exhibits the second radical generation mechanism. Adsorption of the pollutant over the surface of the catalyst also enhances the pollutant degradation. Overall, heterogeneous EF process is very potent, powerful, and useful for the pollutant decontamination from the water medium.

Bio-electro-Fenton: A New Combined Process – Principles and Applications

Biological treatments show insufficient removal efficiency in the case of recalcitrant organic compounds. Therefore, the necessity of upgrading wastewater treatment plants (WWTPs) with advanced treatment steps is unequivocal. Advanced oxidation processes (AOPs) are the most effective technologies for the removal of a large range of organic pollutants from water due to the generation of strong oxidizing species like hydroxyl radicals (•OH). However, AOPs often involve high energy and/or reagent consumption and are considered as less cost-effective than biological processes. Hence, the combination of AOPs and biological treatments has been implemented aiming at maximizing efficient removal of recalcitrant organic pollutants while minimizing treatment costs. Among AOPs, electrochemical advanced oxidation processes (EAOPs) have been widely explored during coupled processes, since they possess remarkable advantages, such as high efficiencies, operability at mild conditions, economic feasibility, ease of automation, as well as eco-friendly character. The electro-Fenton process (EF) stands out as one of the most applied EAOPs and the present chapter is devoted to the advances and applications of EF process as a treatment step coupled with biological methods: the so-called bio-electro-Fenton (Bio-EF) process, which brings together the high oxidation power of EF and cost-effectiveness of biological methods.

The synergistic effect of nickel-iron-foam and tripolyphosphate for enhancing the electro-Fenton process at circum-neutral pH

A composite nickel-iron-foam (Ni-Fe-F) electrode was used as a cathode in the electro-Fenton (EF) process at circum-neutral pH in the presence of sodium tripolyphosphate (TPP) as supporting electrolyte. It was found that phenol degradation was dramatically improved by the synergistic effect of Ni-Fe-F and TPP, reaching 100% removal in 40 min, with kapp = (8.90 ± 0.12) × 10-2 min-1, which was about 18 times higher than that of Ni-Fe-F with sulfate as conventional electrolyte at pH 3.00 (kapp = (5.00 ± 0.14) × 10-3 min-1). A (75.00 ± 1.67)% mineralization yield was attained after 4-h treatment time. Ni-Fe-F proved capable of providing the Fe2+ ions necessary to catalyze the Fentons reaction via a controlled chemical/electrochemical redox process. In addition, Ni-Fe-F promoted the chemical and electrochemical generation of H2O2. With respect to TPP, its chelation with Fe ions prevented iron precipitation at neutral and higher pH values, extending the pH range of the Fentons reaction. Furthermore, the TPP ligand promoted the activation of molecular O2 for the chemical production of OH, enhancing the process efficiency. By overcoming these common limitations of conventional EF in K2SO4 electrolyte, the Ni-Fe-F/TPP system represents a more sustainable alternative for practical application of EF. A degradation pathway for phenol mineralization with homogeneous and heterogeneous OH produced by the EF Ni-Fe-F/TPP system is proposed based on the identification of the oxidation by-products.